Analyzing log files

[Rich Z]

I'm spending a lot of time (relatively speaking, of course) just reviewing the log files I've been accumulating while getting my toes wet with EFILive. I figure that unless I understand what I am actually SEEING during a logging session, then trying to jump right in with tuning will be a fruitless and frustrating experience. But quite honestly, I don't have any sort of yardstick to go by to compare my logs with to try to figure out if what I am seeing is good, OK, or just plain awful.

For instance, I don't see any signals from the PIDs for long term fuel trims. Do I have something set up incorrectly in the setup for data capture?

My O2 sensors seem to be working OK, I think, which surprised me since I thought the harness on at least the passenger side one had been butchered. But is the signal I see during acceleration and deceleration normal? It looks like pretty much a nice sine wave during constant speed cruising.

The AFR from my wideband seems to be a low amplitude sine wave centered around the commanded AFR. But there are spikes and dips with RPM and TP changes. How much variation is "normal"?

My SAE.MAF signal doesn't seem to climb past the half way mark in my dashpage display. Is that normal?

My MAP inHg signal is hitting over 100 in spots. Is this normal for a 2 BAR MAP with FI? Am I really seeing vacuum or seeing pressure?

The MAX I have seen on my injector duty cycles is 15 percent during normal driving. Is that OK?

With my foot off of the gas pedal, I see a throttle position of 17.3 percent. Does that sound right?

While crusing down my dirt road at 10 mph, my SPARK Deg trace looks like a snake trying to dodge getting run over. Should it be this way or be a fairly stable line?

Referring to above, my RPM jumps around quite a bit, from around 885 to 1030 at low speed with no pressure on the gas pedal. Is that normal?

In other words, can someone point me to some yardsticks I can compare to what I am seeing? Or maybe look at my own log files to perhaps point out some things that just seem odd to you?

Oh yeah, and what is this CALC.POWER_RW value? I see a max value of 867 when the max RPM I hit that trip was only 3354. So that certainly can't be correct. I would think my rear tires would be shredding off of the wheels if that were true.

Anyway, thanks for any guidance you all can give me on this.

[joecar]

Rich,

Post some log files.

[Rich Z]

OK, done. Bear in mind that I live on a dirt road, so the first log should be of my driving under 10 mph. The odd thing about that log is how the RPMs jump all around, and the jagged trace that the timing makes. Also, I think it's in the third log that you will see the 6 seconds where my IAT reading went bonkers.

I'm using the serial interface from my LC-1 wideband, btw.

Thanks....

[swingtan]

LTFT PIDs appear to be there so I guess you have not selected them for the charts you are viewing. If you "Right click" on a PID label on the sides of a chart, you get an option to select a new PID. Look under the "Other PIDs" listing for the LTFT's.
The O2 voltages indicate that one of the sensors may have a damaged heater feed. It looks like it takes longer to become active and when it does, it's slightly lazy. It may be wiring or it may just be a bad sensor.
Variation for the O2 sensor is arbitrary. A good check is to compare both O2's to see how similar that look. They shouldn't be "identical" when viewed over a time period, but should appear similar.
The MAF signal is just a measurement displayed on the chart. The total air flow is what ever the motor is using, the level on the graph can be adjusted by right clicking on the chart and selecting "chart properties". Read the help files for adjusting chart properties.
100 inHg, I'm not sure where you are measuring that. 100kPa is normal barometric pressure, are you mixing up inHg and kPa?
Injector Duty Cycle peaks only really come into play at peak engine torque. As long as you are at a reasonable level here (80% to 90%) then other load points should be fine.
Is this a cable throttle or electronic? The ETC will hold the throttle open on declaration.
Spark at low RPM could just be a steep ramp in the spark map. It may be nothing and if the car drives OK, Then it's not a huge issue. It could also just be torque management in the auto.


It's probably worth you reading through the tutorials and help files. Even better, get on to one of the EFILive courses.

Simon.

[Rich Z]

LTFT PIDs appear to be there so I guess you have not selected them for the charts you are viewing. If you "Right click" on a PID label on the sides of a chart, you get an option to select a new PID. Look under the "Other PIDs" listing for the LTFT's.

The PIDs I have selected are

Long Term Fuel Trim - Bank 1 (SAE.LONGFT1)
Long Term Fuel Trim - Bank 2 (SAE.LONGFT2)


The O2 voltages indicate that one of the sensors may have a damaged heater feed. It looks like it takes longer to become active and when it does, it's slightly lazy. It may be wiring or it may just be a bad sensor.

Could be wiring, as there appear to be wires in the harness for the passenger side O2 sensor that look like they were cut off, and possibly others spliced in place.

When I got my car back from the shop that worked on it, this is what I saw for the O2 sensor wiring:

http://www.corvetteflorida.com/pics/o2_01.jpg

Notice the trailer hitch wire on one side, and the radio shack wire on the other.

Then I replaced both O2 sensors when I noticed them looking like this:

http://www.corvetteflorida.com/pics/old_o2sensors_02.jpg

So yeah, ANYTHING is possible.


Variation for the O2 sensor is arbitrary. A good check is to compare both O2's to see how similar that look. They shouldn't be "identical" when viewed over a time period, but should appear similar.

Well, I'm guessing they are basically OK then. Except for the possible slow heat-up you mentioned. I'm assuming "bank 1" refers to the engine side where cylinder number 1 resides?

The MAF signal is just a measurement displayed on the chart. The total air flow is what ever the motor is using, the level on the graph can be adjusted by right clicking on the chart and selecting "chart properties". Read the help files for adjusting chart properties.

Well the chart says MAF Lbs/min (SAE.MAF). I'm pretty much just using a very slightly modified DEFAULT dashboard and PID selection. I do have twin rear mounted turbos on the car, but I don't think I went into boost during this drive. So I guess the question is how accurate the MAF signal will be under full boost? And does the air flow characteristics change substantially even when under full boost as I would think the turbos would change things somewhat even during normal driving.

100 inHg, I'm not sure where you are measuring that. 100kPa is normal barometric pressure, are you mixing up inHg and kPa?

Heck if I know. I'm looking at the data tab and seeing "Intake Manifold Absolute Pressure" with the Units showing as "PSI" (SAE.MAP). But that surely can't be the units being displayed in the dashboards. The PID itself shows units in "kPa,PSI" so beats the heck out of me what I might have done wrong here.

Injector Duty Cycle peaks only really come into play at peak engine torque. As long as you are at a reasonable level here (80% to 90%) then other load points should be fine.

I guess what caught my attention is how LOW those readings are. Granted I really didn't "get on it" during this run, but they showed a max of just 15 percent. I'll have to see if I have a log where I ran the engine up to 5,000 rpm or so to see what that shows.

Is this a cable throttle or electronic? The ETC will hold the throttle open on declaration.

Electronic. This is a 2002 Corvette Z06 with a custom 427 in it. STS twin turbos, F.A.S.T. 102 intake, C6 Z06 throttle body (silver blade), long tube headers.

Spark at low RPM could just be a steep ramp in the spark map. It may be nothing and if the car drives OK, Then it's not a huge issue. It could also just be torque management in the auto.

At low RPMs driving down my dirt road the spark advance looks like a saw blade. Granted I know my tuner didn't really spend much time at all on the low RPM stuff, but I think it is something that does need some work. The car does often surge while driving at under 10 mph.



It's probably worth you reading through the tutorials and help files. Even better, get on to one of the EFILive courses.

Yeah, been doing that. And reading through old threads here as well. I know I'm a raw newbie, but everyone says I just need to ask questions. So here I am. :)

Simon.

Thank you for your help with this.

[Rich Z]

BTW, to give you a REAL good idea about why I don't trust anythign in the wiring for my O2 sensors, get a load of this:

http://www.corvetteflorida.com/pics/old_o2sensors_01.jpg

When I asked the guy about this, he says that's the way he does all the wiring for O2 sensors on cars that come into his shop. Obviously his shop will never see my cars in there again.

[joecar]

Rich, you should buy a pair of new NBO2 sensors (they come with the correct wiring/shielding all the way up to and including the plug).

[joecar]

From swintangs comments and your replies:

1. did you select the pids LONGFT1/2...? did you place these on a chart...?

2. that O2 wiring is not acceptable.

5. use the units kPa (scantool: PIDs tab, on MAP do rightclick->Metric; tunetool: Edit->Configure Display Units, look at B0101).

7. for electronic throttle, look at the pid GM.ETCTP.

When selecting pids, make sure the pid channel count is no greater than 24.

I'm on the Mac so I can't view the log files right now, I'll view them later tonite.

[Rich Z]

Rich, you should buy a pair of new NBO2 sensors (they come with the correct wiring/shielding all the way up to and including the plug).

Putting in new O2 sensors was one of the first things I did when I brought my car back home over a year ago. I am using rear sensors because the cable harness is longer, with adaptors to mate up with the front harness connectors.

Cats are gone, so no actual rear sensors are installed, only the fronts.

[ScarabEpic22]

Putting in new O2 sensors was one of the first things I did when I brought my car back home over a year ago. I am using rear sensors because the cable harness is longer, with adaptors to mate up with the front harness connectors.

Cats are gone, so no actual rear sensors are installed, only the fronts.

Quick question, are the front and rear O2s the same on your year Vette? I know on both of my TrailBlazers the front and rear O2s are different part numbers...

And yes, that wiring is a hack job. I would be embarrassed if I did anything like that for a customer (or myself), good call not going back to that shop.

[Rich Z]

From swintangs comments and your replies:

1. did you select the pids LONGFT1/2...? did you place these on a chart...?

Yes, as best I can tell. I went though all of my logs and looked at the PIDS, DATA, and dashpages, and they are there.

2. that O2 wiring is not acceptable.

You don't know a tenth of what my car went through. Well, maybe you do if you have looked over that thread I pointed you to.

5. use the units kPa (scantool: PIDs tab, on MAP do rightclick->Metric; tunetool: Edit->Configure Display Units, look at B0101).

I'll be honest, I really don't remember how I may have set this up or changed it. kPa just doesn't compute quite yet with my old SAE brain.

7. for electronic throttle, look at the pid GM.ETCTP.

I'm using Absolute Throttle Position (%) as far as I can tell. SHOULD throttle position be ZERO when my foot is off of the gas pedal?

When selecting pids, make sure the pid channel count is no greater than 24.

It looks like I have 22 PIDS selected in my log files.

I'm on the Mac so I can't view the log files right now, I'll view them later tonite.

Going to be a few days before I will have my car back on the street again. I'm putting in PTFE fuel lines and replacing those stinking rubber lined ss braided lines that were put on my car. Those rubber lines seep gasoline through them like it's no body's business. You can actually see the gasoline stains with UV light.

Thanks for your help.

[Rich Z]

Quick question, are the front and rear O2s the same on your year Vette? I know on both of my TrailBlazers the front and rear O2s are different part numbers...

And yes, that wiring is a hack job. I would be embarrassed if I did anything like that for a customer (or myself), good call not going back to that shop.

They would have to have different part numbers, since the harness ends are different. The front O2s have a 4 wire flat connector, and the rear O2s have a 4 wire square connector, if I remember correctly. I forget who it was that suggested that I use the rear O2s as the fronts with an adapter. I've gotten a lot of advice from a lot of people once I had to do my own wrenching on my car. If I need to actually put FRONT O2s in place, this would be a great time to do that. I have my exhaust off of the car and the tunnel plate removed so I can get to the funky fuel lines to replace them.

Yeah, my car was in two shops for two and a half years, and I honestly can't see which shop screwed me over the worst. I must be extremely gullible, I guess. That really put a hurting on the finances for what was supposed to be a retirement spent doing fun stuff. Amazingly enough my wife has been behind me the entire way. I was ready to just give up MANY times and just part the car out.

So heck, I've been crash coursing my way through learning the mechanics of this Corvette, so it stands to reason that I might as well learn the tuning while I am at it.

[ScarabEpic22]

IMHO, Id get front O2s then buy some O2 extensions that are plug n play. That way you KNOW they're the right sensors and the wiring is done right.

Something like this: http://www.casperselectronics.com/store2/product_info.php?cPath=61_27_42_51&products_id=1161 $26 and Caspers has them in lots of different lengths and square or flat connectors. Interesting about your wiring, I thought the fronts were usually square with the rears being flat. Then again, my TBSS uses square fronts and rears so who knows how GM determines it.

[Blacky]

I'm using Absolute Throttle Position (%) as far as I can tell. SHOULD throttle position be ZERO when my foot is off of the gas pedal?


The corvette, with its ETC (electronic throttle controller), holds the throttle blade open to control idle air flow. So even when there is no pedal input the throttle blade will be slightly open to allow enough air to enter the engine to keep it idling.
For vehicles with a cable throttle, the throttle body usually has a bypass called the IAC (Idle Air Control) which the PCM uses to control the idle air flow while the throttle blade is shut.

Regards
Paul

[Rich Z]

IMHO, Id get front O2s then buy some O2 extensions that are plug n play. That way you KNOW they're the right sensors and the wiring is done right.

Something like this: http://www.casperselectronics.com/store2/product_info.php?cPath=61_27_42_51&products_id=1161 $26 and Caspers has them in lots of different lengths and square or flat connectors. Interesting about your wiring, I thought the fronts were usually square with the rears being flat. Then again, my TBSS uses square fronts and rears so who knows how GM determines it.

Actually I wasn't clear on the wiring problem. If there is a problem with the wiring, it will be on the PCM side of the connectors. Quite honestly, I don't know where exactly those cut wires went to that I saw in the harness. Now that I am thinking about it, those wires MAY have been for the alarm buzzer for the STS scavenge pump, as I have not yet found that little bugger. As it is, I had to buy a new after-run timer and re-wire that into my system. The wiring for the STS turbo scavenge pump was COMPLETELY wrong.

The photo earlier in this thread of those butchered O2 sensors shows that the fronts have the flat connectors. What the guy did was to splice extension wire into the O2 harnesses (which is a NO-NO according to GM) instead of putting the extensions on the end of the existing harness. And according to him, that's how he does ALL of his O2 modifications when he installs headers for customers.

As for operationally, I really don't know if there is any difference in the signals coming from the front or rear O2 sensors themselves. Wouldn't be the first time I was given bum advice, though.

[Rich Z]

The corvette, with its ETC (electronic throttle controller), holds the throttle blade open to control idle air flow. So even when there is no pedal input the throttle blade will be slightly open to allow enough air to enter the engine to keep it idling.
For vehicles with a cable throttle, the throttle body usually has a bypass called the IAC (Idle Air Control) which the PCM uses to control the idle air flow while the throttle blade is shut.

Regards
Paul

Ah, I see. That's why it is called the "absolute" throttle position, rather than the "relative" throttle position. That makes sense.

[ScarabEpic22]

Actually I wasn't clear on the wiring problem. If there is a problem with the wiring, it will be on the PCM side of the connectors. Quite honestly, I don't know where exactly those cut wires went to that I saw in the harness. Now that I am thinking about it, those wires MAY have been for the alarm buzzer for the STS scavenge pump, as I have not yet found that little bugger. As it is, I had to buy a new after-run timer and re-wire that into my system. The wiring for the STS turbo scavenge pump was COMPLETELY wrong.

The photo earlier in this thread of those butchered O2 sensors shows that the fronts have the flat connectors. What the guy did was to splice extension wire into the O2 harnesses (which is a NO-NO according to GM) instead of putting the extensions on the end of the existing harness. And according to him, that's how he does ALL of his O2 modifications when he installs headers for customers.

As for operationally, I really don't know if there is any difference in the signals coming from the front or rear O2 sensors themselves. Wouldn't be the first time I was given bum advice, though.

Ah I see, Ive been looking at possible header O2 extensions and GM states do not splice wires so I was going to buy an extension. I was only referring to any butchered wiring for the O2s, I didnt know you had other wiring problems (joy).

I have no idea if the signals from the front/rear sensors are different either.

[Mr. P.]

OK trying to help here:

The O2 sensor debacle - there is a big difference between front and rear O2 sensors, they ARE NOT interchangeable, even if you pull a Tim Tooltime Taylor and "rewire" them. If you are NOT running the PCM in strictly speed-density mode, then the O2s are a critical component. I agree with Scarab, the RIGHT thing to do is to get O2 extension harnesses, they're like $20 each (in my truck, I only needed one!). As you stated earlier, one never hacks-up the main harness of the car; what a bunch of gorillaz...

kPa - yes I know in the old days we measured manifold vacuum in SAE, but take it from me it's mentally easier to think in terms of kPa; 0 kPa is a perfect vacuum, 100kPa is "wide open" aka 0-inches of manifold vacuum, anything over 100 kPa is "boost". Since each 100kPa is "an atmosphere" then 200 kPa is saying you are at 15-lbs of boost. The reason to switch to kPa is because the PCM itself thinks in kPa!

Injector Duty Cycle - I looked at the logs, those INJ DC figures look just fine.

"At low RPMs driving down my dirt road the spark advance looks like a saw blade." - yeah this is "normal", I already have an active post on this topic, the spark is being manipulated when the vehicle is either coasting or standing still; it's totally ok because it's not costing you power or MPG (the spark lines right out under power) but looks erratic. I personally think that it has something to do with the "stall saver logic" in the PCM; it has nothing to do with your cam or heads or tune etc, my bone stock truck does it too, it's a "feature" of the PCM.

"The car does often surge while driving at under 10 mph." - then it's not tuned right. Period, end of story. The sucky part is, idle/low-speed tuning is the *last* thing you dial-in, one of the most difficult to get right, and one of the easiest to make harder on yourself when aftermarket injectors and intake plumbing is concerned.

CALC.POWER_RW - yeah the formula for that PID is not accurate IMO.

- Steve.

[Mr. P.]

What operating system is in the car's PCM?

Is the PCM tune in speed-density mode? If you are making over 8-psi boost I SERIOUSLY suggest you consider it.

I would make sure you are using an EFILive custom operating system (maybe COS-3?).

If the turbos are large enough, the MAF may be useless! Meaning you should just ditch it and go speed-density COS3 anyways!

I looked at your log - your tune is assuming that the stoich for fuel is 14.63:1; that was true 10-years ago, with E10 fuels now (in all 50-states) this needs to be changed to 14.17:1 or else you're gonna run WAY LEAN under EWP.

When Logging, I would ditch the PIDS for injector duty cycle & injector pulse width for Bank-2; it's redundant unless you are troubleshooting a specific fueling discrepancy between the left & right side of the motor. I don't think you need to monitor FUELSYS-B either.

DON'T DESPAIR - from what I read you are making progress now and are closer than you think!!

- Steve.

[Rich Z]

I have a 2 bar MAP sensor and I believe my tuner did a 2 bar map tune, as nearly everyone recommended what they were calling a "2 bar MAP speed density tune". I could attach the original tune for you to look at if you wouldn't mind reviewing it to tell me what you think. The tuner did send me a later tune, that I think he re-enabled the O2 sensors with. But heck, I'm not sure. I still don't know what to look for to be able to determine such things.

So stoich should be 14.17:1? I did a log using my newly installed wideband and during cruising it appeared that the actual AFR was sine waving around the commanded AFR rather nicely. I thought that was a good sign. :(

Yeah, I think the mechanical stuff is pretty much straightened away now. The only thing that is left that I haven't torn apart, fixed, changed, or puzzled over in aggravation is the internals of the engine itself. So I'm HOPING that is OK.

As for the tuning, heck the tuner did me a world of good just showing me that my car COULD be tuned. And he has invited me to bring the car up to his shop so he could do a REAL tune on the dyno and get things all up to snuff. So it's not at all like he just did a quick and dirty tune to grab the money and run. I'm thinking I should take this opportunity to learn EFILive and tuning. After I would have the car tuned to perfection (if there really is such a thing), I would lose much of the incentive to dive into this myself. When I get to the point where I need a dyno, then that would likely be the time to drive the car up to him (he's about 5 hours away). Plus, to be honest, I just don't TRUST the car yet to drive that far with it.

Oh yeah, I just read back over your earlier post. So my using the rear O2 sensors in place of the fronts is a no-no? If that is the case, NOW sure would be the time for me to do that while I've got the car torn down with the exhaust out, and fuel lines disconnected. But what symptoms would I be seeing to support the case that they ARE wrong? Not disputing what you are telling me, just trying to understand the "what" and "why" of all this.

Thanks..

[joecar]

The rear O2S are the same as the front O2S (other than the plug maybe)...

you can run them in the front O2S location (front harness sockets, and ahead of the cats if present).

Beware: on Corvettes it may be possible to inadvertently swap left/right O2S connections.

Yes, accord to GM training material and the Bosch Automotive Handbook, the O2S obtain reference air thru the attached pigtail, so you can't solder/splice wiring nor use alternate wiring.

[joecar]

You could run any of these:
- 2-bar speed density with/without CL (MAF is removed);
- 2-bar MAF/VE tune with/without CL (MAF/VE/IFR tables have to be scaled to avoid PCM's MAF 512 g/s limit, and all tables referencing airmass/airflow have to be shifted).

BUT: in any case, the IFR must match the FPR (your FPR is MAP-referenced, but your IFR is sloped which does not match the FPR).

[joecar]

Mechanical stuff:

it is important to perform various diagnostics (compression and leakdown tests, checking pushrods for straightness, checking lift of each cam lobe, checking for airleaks, coolant leaks, oil leaks, checking oil consumption, etc...);

it is also important to check electrical (power/ground voltage drops, checking secondary (spark tester, oscilloscope if available));

these are imperative before performing any tuning.

[Rich Z]

So stoich should be 14.17:1? I did a log using my newly installed wideband and during cruising it appeared that the actual AFR was sine waving around the commanded AFR rather nicely. I thought that was a good sign. :(


BTW, I am using 93 octane non-ethanol gasoline in my car. There is a local Sunoco that carries it. :)

[Rich Z]

The rear O2S are the same as the front O2S (other than the plug maybe)...

you can run them in the front O2S location (front harness sockets, and ahead of the cats if present).

Beware: on Corvettes it may be possible to inadvertently swap left/right O2S connections.

Yes, accord to GM training material and the Bosch Automotive Handbook, the O2S obtain reference air thru the attached pigtail, so you can't solder/splice wiring nor use alternate wiring.

Interesting... How should those front O2s be connected? I have the sensor on the passenger side header running to the right side connector to the PCM, and of course the driver side O2 sensor running to the left side connector. I'm assuming that the guys who thrashed my car didn't switch the harnesses.

Also, about the pigtail, does this mean that the pigtail itself has to be exposed to open air? I believe I covered them to keep them from being exposed to the header pipes that are pretty close to them.

Did I post my most recent logs somewhere? If so how did the O2 signals look? If not, heck I can post them again....

[Rich Z]

You could run any of these:
- 2-bar speed density with/without CL (MAF is removed);
- 2-bar MAF/VE tune with/without CL (MAF/VE/IFR tables have to be scaled to avoid PCM's MAF 512 g/s limit, and all tables referencing airmass/airflow have to be shifted).

BUT: in any case, the IFR must match the FPR (your FPR is MAP-referenced, but your IFR is sloped which does not match the FPR).

Yeah, that issue with the IFR/FPR does bother me, I have to admit. My tuner didn't seem concerned about it when I called his attention to it. But I'm guessing that if I go about messing with that, then I've got zip for a tune. I'm not prepared to tackle that yet. And certainly in no position to argue with my tuner about it, neither. But yeah, I do know it is a bridge that I will need to cross sometime.

[joecar]

( the front and rear O2S are the same device, the fronts are used for bank trimming, the rears are used for measuring cat efficiency )

[Rich Z]

( the front and rear O2S are the same device, the fronts are used for bank trimming, the rears are used for measuring cat efficiency )

I've been scouring the net looking up info on this. Results are inconclusive simply because all the info seems to be based on opinion. Some say that the rear O2s will heat up faster, or slower, than the front O2s. Seems to be related to the resistance of the heating element affecting how quickly the sensor heats up. Some say wrapping the headers will help, which I have actually done recently. And some will claim that Denso, Bosch, NTK (pick one) is the only brand to use.

I think for now, I'm going to stick with the O2s I have. They are rear sensors with adaptors to mate the rear square connector of the sensor with the front straight connector in the PCM harness. I do know the sensor itself looks different, and I've been meaning to take pics to illustrate this. Since I have the exhaust off of the car, I can look right up the header collector pipes and see those O2 sensor ends.

But if I NEED to buy new O2s I will. But ONLY if I NEED to. I hope to hell I never screw up and tell my wife how much this has actually cost me. I haven't figured it out myself, just so if she asks, I can honestly say that I don't really know. But I have a good inkling. And it ain't pretty. :(

[joecar]

In your logs, MAP shows you might have an airleak, or valve timing/compression problems.

[Rich Z]

In your logs, MAP shows you might have an airleak, or valve timing/compression problems.

Well, coincidentally when I was pulling off the exhaust, I found that one of the vacuum lines on the turbo wastegates wasn't threaded in tightly. Actually it was barely threaded in at all. So that certainly would have been a vacuum leak there. But what is it in the MAP trace that tells you that, if you don't mind explaining it to me?

[Rich Z]

BTW, I took photos of the oxygen sensors looking for the differences between the fronts and the rear sensors.

Here's what the rear sensors look like:
http://www.corvetteflorida.com/pics/o2_sensor_rear_01.jpg

And here's what the front sensor looks like:
http://www.corvetteflorida.com/pics/o2_sensor_front_01.jpg

Looks like the rears are more open to allow gases to more easily reach the sensor itself. In any event, there is definitely a difference.

[joecar]

Well, coincidentally when I was pulling off the exhaust, I found that one of the vacuum lines on the turbo wastegates wasn't threaded in tightly. Actually it was barely threaded in at all. So that certainly would have been a vacuum leak there. But what is it in the MAP trace that tells you that, if you don't mind explaining it to me?It looked very wobbly when there was no reason for it to wobble.

[joecar]

I looked at all 4 sensors on my F-body and they are the same as your second pic.

Are yours all the same brand...?

[Rich Z]

I looked at all 4 sensors on my F-body and they are the same as your second pic.

Are yours all the same brand...?

Beats me. Interestingly enough, I found another rear sensor in a box of old parts off of my car that is the same style as the second pic, but with more slits for openings. The impression I am getting is that the rear sensors must need more airflow than the fronts for some reason.

[Mr. P.]

In my truck (2003 Silverado SS) the 'perforated' ones are the fronts... just be sure you are using the correct sensor!

As you KNOW you are running 93-octane E0 gasoline, the stoich of 14.63 you are running how is correct. If you are forced to use 'federal' gasoline E10, then your tune may be seriously off at high power levels IMO. The rest of us are forced to run crappy gas!

[Rich Z]

The sensor harnesses themselves attached to the sensors will tell me whether they are fronts or rears. The fronts have a flat 4 pin connector, whereas the rears have a square 4 pin connector. So when putting oxygen sensors on long tube headers, the choice offered to me was either front sensors with extension cables, or rear sensors with an adaptor to convert square 4 pin to flat 4 pin.

Once I get the issues straightened out on my car I will probably have to go with E10, since taking the car on any long trips out of town will certainly have me using the E10. I only know of one area locally that has the E0 93 octane fuel. The main reason I was using E0 was because I used UV lighting and could actually SEE the rubber lined SS braided hoses on my car weeping the E10 gasoline through them. The gasoline noticeably fluoresces under UV. And I could certainly smell gasoline whenever I walked into the garage, obviously coming from this car. Made me nervous, to say the least. I just got done yesterday putting all new PTFE ss braided fuel lines in, so to simplify things I will likely go back to the E10 pretty shortly.

Hopefully I'll have my car back on the street by the weekend. Assuming the weather clears up, that is.

This brings up a question. What about the stock tunes on cars prior to E10 being prevalent at the gas pumps? Are their tunes "seriously off" at WOT?

[Mr. P.]

...What about the stock tunes on cars prior to E10 being prevalent at the gas pumps? Are their tunes "seriously off" at WOT?
Yup; but stock vehicles aren't trying to make >600 forced-induction hp!!! In other words, stock power outputs do not require the huge amounts of enrichment fuel needed to cool the combustion chambers at the high power levels we enthusiasts are demanding now. The risk of damage is low if your AFRs are in the high-12s instead of the low-12s making only 275-325 natually aspirated horsepower, that is a whole different operating reality than delivering 800+hp at any extended period of time at 12.0:1 AFR instead of 11.5:1 AFR! Also remember that in older stock forced induction tunes (think like, Buick Regal V6 supercharged or turbo 3.8L motor) the calibrations were very fat at the top-end of the commanded AFR table just for a little insurance. The Delphi guys weren't stupid, in their time they had to deal with crappy California gasoline (which is now since 2012 federally mandated).

- Steve.

[ScarabEpic22]

And GM DUMPs fuel, at least in the truck cals. My TBSS commands between 12.1-13:1 during PE yet I actually get closer to 11.5-12..5:1.

Here's a pic of my last dyno day with my TBSS, run 1 was stock tune + efans patch + speed limiter removed. Run 3 was a spark-only tune to see what the power difference was going to be (ie completely stock VVE and MAF tables). Run 4 was with a 4" fenderwell intake that pulls air from behind the front bumper and the same tune as Run 3 except with a stock Z06 MAF curve so it would run. (not the best indication of stock fueling but the first 2 runs are.)

http://i32.photobucket.com/albums/d40/ScarabEpic22/Mobile%20Uploads/2012-11-25_13-58-19_599.jpg

[Rich Z]

Yup; but stock vehicles aren't trying to make >600 forced-induction hp!!! In other words, stock power outputs do not require the huge amounts of enrichment fuel needed to cool the combustion chambers at the high power levels we enthusiasts are demanding now. The risk of damage is low if your AFRs are in the high-12s instead of the low-12s making only 275-325 natually aspirated horsepower, that is a whole different operating reality than delivering 800+hp at any extended period of time at 12.0:1 AFR instead of 11.5:1 AFR! Also remember that in older stock forced induction tunes (think like, Buick Regal V6 supercharged or turbo 3.8L motor) the calibrations were very fat at the top-end of the commanded AFR table just for a little insurance. The Delphi guys weren't stupid, in their time they had to deal with crappy California gasoline (which is now since 2012 federally mandated).

- Steve.

OK, I'm not shy about admitting I'm confused. :)

So if my car is tuned for stoich (does that word sound like it is spelled?) at 14.63 for E0 fuel and I put E10 in the gas tank, which if I understand correctly has stoich of 14.13, then am I not running (assuming I'm in OL without the O2 sensors making any changes) a half a point LEANER than I should be? In other words, E10 requires a richer AFR than E0 does? Meaning it takes more fuel using E10 to reach the proper air/fuel mix than it does with E0?

So, again, what was E10 supposed to gain for us? Looks to me that gas mileage will take a hit. And I hear they want to go to E15 now?

Hmm, well the guy who tuned my car tuned it for a commanded AFR of 14.63. So basically unless you find some non traditional source of E0 then the tune should actually be for 14.13?

I'm presuming that this is one of the constant values you need to have correct before you even start with the tuning? Like the IFR table?

[joecar]

Yes, half a point leaner.

Alcohol has a lower energy density BTU so yes you will see reduced MPG (edit: and a lower stoich means more fuel is used).

Yes, 14.13 (or something between 14.1 and 14.2).

If you don't initially set the correct stoich AFR, then tuning will bake in the difference.

[Mr. P.]

Elaborating on everything Joecar said -

In forced-induction applications, you'll learn that ultimatelty it's all about the capability of the fuel you choose to run; you are fuel-limited. Even guys that want *insane* torque levels figure out that it's dang near impossible to make 1500-hp on a forced-induction 6.0-litre motor with pump gas (because pump fuel will not tolerate cylinder pressure i.e. dynamic compression ratio levels that high), and they upsize to 7.0-litres because the increased chamber size/displacement allows them to achieve those power levels via a lower, more manageable dynamic compression ratio, one that pump fuel will tolerate. The fuel you run dictates everything, IMO.

From EFI-101 class:

"Stoich" (pronounced 'Sto-Ick') is slang for "stoichiometric ratio" (pronounced 'Sto-kee-oh-metric'), which from high school chemistry class is defined as the exact amount of fuel, plus the exact amount of oxidizer (air) needed to have chemically perfect combustion, i.e. no leftover emissions, there is exactly present the correct amount of fuel for each molecule of oxygen.

All fuels are chemically different, and will have different stochiometric ratios; in high school autoshop I was taught that gasoline has a stochiometric ratio of 14.63:1, meaning that for every 1 "part" of gasoline you must provide 14.63 "parts" of air to achieve a chemically perfect combustion. Fuels are VERY forgiving, gasoline especially - it will burn anywhere from 10:1 all the way to over 16:1, if the proportions are anywhere near close it will ignite/explode; but at 10:1 ratio, there will be a lot of leftover unburned fuel, because not enough oxygen molecules were provided!

Fuel refineries work very hard to make sure the products they sell meet these ratios, and different fuel blends will have differing ratios - for education purposes check out VP Fuels website, they publish the stoichiometric ratios on all their custom blends and you will see that C16 not only has a different octane rating but also a different stoich, meaning that a carburator jetting change -OR- change to the PCM's "stoich ratio" setting {B3601} is required. This same adjustment is necessary if you were to change to methanol, or E85, or E10... you gotta know the fuel you are running and it's stoichiometric ratio and plug that number into the {B3601} cell in your tune.


...In other words, E10 requires a richer AFR than E0 does? ... Meaning it takes more fuel using E10 to reach the proper air/fuel mix than it does with E0? ...
YES; significantly so. There is a vocabulary lesson required, the difference between "gasoline" and "fuel" - 40-years ago what came out of the service station nozzle was one-and-the-same, but today you are not purchasing "gasoline", rather you are technically purchasing a "fuel product" of which only 90% of that product is actual gasoline and the rest is 'something else'. This is the explaination I share, it's waaayyy oversimplified but.... Imagine two pie tins, fill one with an inch of mid-1960s "pre-emissions" gasoline and the other with today's E10 pump fuel, then light them both on fire, and feel the warmth from each fire with your hands - what you will observe is that the mid-1960s gasoline gives a MUCH HOTTER fire than today's fuel! After 30-years of EPA laws, fuel refiners have been forced to blend fuels having less and less heat energy, meaning that engine power outputs go down because the chemical energy just isn't there in the fuel to begin with; not only has the fuel octane gone down (that's been very obvious to the general public for decades) but more importantly the actual potential energy IN the fuel has been weakened over time. A large part of why 80's vehicle performance sucked so bad has a lot to do with the OEM's struggling to deal with the fuels available on the market -in addition to- congressional emissions laws, CAFE requirements, etc. E10 pump fuel is only 90% gasoline, and 10% FILLER! IMO, if the EPA could have realistically gotten away with mandating 10% water in pump fuel they would have happily done that instead (ethanol is the next safest thing, in their minds)!!! What this means for us throttle junkies is: fortunately there still remains "gasoline" in E10 pump fuel, you just gotta squirt a lot more of it into the engine than you would have 40-years ago to make power, because 10% of today's fuel is just "filler" - it has no combustion benefit that I can see.

Another common misconception: that E10 is related to E85, or simply just "E85 light" - as a fuel you cannot compare E10 to E85, they're totally different animals with totally different combustion characteristics. E85 fuel has an attractively high octane, but it burns very cool (remember the pie tins?) and you have to squirt a sh!t-ton of it down the intake port to make power. Meaning: purchasing a bigger fuel pump, bigger fuel injectors, bigger fuel plumbing, bigger fuel comsumption = MORE COST. These are my opinions and impressions of E85 fuel, do your own research, I came to the conclusion that yes a guy can make big power with E85 but the costs are prohibitive (compared to achieving the same power potential with E10 pump fuel, or E0 gasoline).


... I'm presuming that this is one of the constant values you need to have correct before you even start with the tuning? Like the IFR table?
YES; table {B3601}.


... the guy who tuned my car tuned it for a commanded AFR of 14.63. So basically unless you find some non traditional source of E0 then the tune should actually be for 14.13? ...
I've seen a few different fueling strategies, and at the end of the day as long as the engine gets what it needs then I guess all is well enough; some guys calibrate like Dephi does, they keep the stoich unchanged at 14.63:1 while increasing the commanded AFR under high load conditions, and they make it work. Personally, my philosophy is to not "lie" to the PCM, or it will not know how to accurately fuel the motor! It is my suggestion that whatever value is input into {B3601} matches the fuel you are actually injecting through the rails; make the computer work FOR you, rather than adopting a mindset of "workaround tuning".


... So, again, what was E10 supposed to gain for us? Looks to me that gas mileage will take a hit. And I hear they want to go to E15 now? ...
It's a California thang - 30-years ago, vehicle makers by themselves could not make engines running clean enough for the State of California; as a result, the California Air Resources Board (CARB) figured that they could immediately get a 10% improvement in air quality by geting all the cars in the entire state to burn 10% less gasoline by simply watering that gasoline down 10% with ethanol - the 10% figure was determined as the most amount of ethanol they could get into the fuel without citizens popping motors everywhere! CARB knew that everyone's cars would run lean on this new emissions fuel blend, that was not important to them - their goal was to get citizens to burn 10% less gas, hence putting 10% less crap into the air. So laws were passed in California requiring all fuel sold to contain 10% ethanol, and the result is that the fleet of vehicles in the state burned 10% less gasoline (because 10% of the fuel wasn't gasoline!) and air quality emissions DID improve. However the costs were increased fuel prices at the pump (California fuel is unique, and expensive), loss of MPG, and loss of torque.

Because of the success of California fuels in fighting emissions, the EPA now mandates E10 at the pump in all 50-states (as of last year). The OEMs have adapted to the problem with FlexFuel systems, so running lean isn't an issue now because the fuel line tells the PCM in real-time exactly the ethanol content in the fuel and the stoich value is now always varying according to what's in the tank - regardless of whether it's E0, E10, E50, E85, or even E100. But, you still cannot get away from the physics that ethanol burns much cooler than gasoline (ie has less energy density, as a fuel) so MPG takes a hit. And torque still suffers unless one uses their right foot to increase the amount of both air & fuel going into the combustion chamber... at the end of the day, it's cylinder pressure that makes the piston go down the hole, turn the crank, and make burnout marks - and that comes from MORE HEAT.

E15 - all I can offer there is... government forcing the market to invent a need for more ethanol, to the benefit of ethanol producers? I dunno...

- Steve.

[Rich Z]

Thanks for the informative reply. I have yet to run into any REAL person who wanted their gasoline watered down with ethanol. And quite frankly, using corn, which comes directly out of OUR food chain, is about as dumb of a move as I can imagine our government doing.

But back to the tuning stuff.

So what do the oxygen sensors do with all this? Aren't they still determining the correct ratio of air to fuel based on what they detect in the exhaust? So regardless of what we TELL the PCM the AFR ratio should be, aren't the O2 sensors compensating for what is REALLY being burned in the cylinders? Meaning that as long as the car is running in closed loop, isn't everything just ducky as far as the AFR is concerned? And OK, I'm a bit hazy about this, but does the PCM go into open loop during WOT? Which would mean that this is where the AFR tuning needs to be done to compensate because the O2 sensors are no longer running the show?

So given a choice of tuning at either 14.63 or 14.13 knowing that you may have either E0 or E10 gasoline in your gas tank at any given time, which would be the BEST AFR to tune for?

I plan on using E0 whenever I can, as long as I can find it in 93 octane. But once I stray away from home, this may not be possible to find, so I would HAVE to use the E10 blend. Obviously I don't want to have to carry my laptop and V2 everywhere I go and make a tuning change at the gas station. Of course, neither am I planning to be making WOT runs up and down the streets, neither, so perhaps the oxygen sensors will handle the difference and it will be completely transparent to the operation of the engine?

Thanks for your insight with this. I feel like I just spent the night at a Holiday Inn Express now. :)

[Rich Z]

In your logs, MAP shows you might have an airleak, or valve timing/compression problems.


It looked very wobbly when there was no reason for it to wobble.

Joe, I scanned through the log files, and darn if I can figure out what you were seeing to figure this out. I watched these variables:

RPM, TP, MAF, and MAP and they all seemed to be playing well together. But as I have mentioned before, I really don't have a clue as to what is really NORMAL in these displays yet. I'm only able to go by what SEEMS normal to me, which might be completely WAY off base.

My engine was build by LME so I'm fairly confident it was put together correctly. That would leave the shops that worked on my car botching up something. Early on I did spray starting fluid around every possible vacuum leak area, and got no signs at all of a vacuum leak. Of course, I never though to check at the wastegates, and no telling how long that vacuum line was loose. So if there is an identifiable and repeatable method to show that I might have a vacuum leak, then I would have something to use as a target knowing that I have to fix whatever it is that is making that display anomaly.

[joecar]

I thought MAP looked too wobbly in Log_0002 the other night, but today it looks more reasonable (lol, I wasn't drinking on either days).

[joecar]

...

So what do the oxygen sensors do with all this? Aren't they still determining the correct ratio of air to fuel based on what they detect in the exhaust? So regardless of what we TELL the PCM the AFR ratio should be, aren't the O2 sensors compensating for what is REALLY being burned in the cylinders? Meaning that as long as the car is running in closed loop, isn't everything just ducky as far as the AFR is concerned? And OK, I'm a bit hazy about this, but does the PCM go into open loop during WOT? Which would mean that this is where the AFR tuning needs to be done to compensate because the O2 sensors are no longer running the show?

So given a choice of tuning at either 14.63 or 14.13 knowing that you may have either E0 or E10 gasoline in your gas tank at any given time, which would be the BEST AFR to tune for?

I plan on using E0 whenever I can, as long as I can find it in 93 octane. But once I stray away from home, this may not be possible to find, so I would HAVE to use the E10 blend. Obviously I don't want to have to carry my laptop and V2 everywhere I go and make a tuning change at the gas station. Of course, neither am I planning to be making WOT runs up and down the streets, neither, so perhaps the oxygen sensors will handle the difference and it will be completely transparent to the operation of the engine?

Thanks for your insight with this. I feel like I just spent the night at a Holiday Inn Express now. :)The oxygen sensors report the difference between actual combustion and stoich, which the PCM uses to trim future combustion.

Yes, in closed loop the PCM is trimming to the fuel's stoich, but when you go WOT the PCM adds any positive trims on top of PE fueling... this is why you want to achieve CL trims close to zero... setting the correct value of stoich in the tune allows the PCM to calculate the correct initial fuel (before trimming).

When you got WOT, the PCM does not technically go OL... it still applies the last positive trims, i.e. it is in a partial CL mode where it applying the [positive] trims but is not updating the trims themselves; we did some experiments with intersecting PE and OLFA tables (and the protection modes disabled and/or given gorssly identifiable AFR's), we saw the following:
- OL: going to WOT -> the active tables was PE and OLFA, the PCM selects the richer of those (I saw the AFR jumping between PE and OLFA);
- CL: going to WOT -> the active table was PE only (i.e. OLFA never came active, I saw AFR from PE only);
[ remember that I had the PE and OLFA tables intersecting each other (i.e. to show the richer one coming thru ].


Also note that setting the correct value of stoich in the tune allows the PCM to get OL fueling correct (by allowing it to calculate the correct initial fuel).

[Mr. P.]

...So what do the oxygen sensors do with all this? Aren't they still determining the correct ratio of air to fuel based on what they detect in the exhaust? So regardless of what we TELL the PCM the AFR ratio should be, aren't the O2 sensors compensating for what is REALLY being burned in the cylinders? Meaning that as long as the car is running in closed loop, isn't everything just ducky as far as the AFR is concerned? ...

I view the O2 sensors as a Delphi "workaround", or add-on.

The O2 sensors DO NOT have any DIRECT bearing on fueling calculations; if the PCM calibration/tune is perfect, you don't need O2 sensors at all (!) in fact in my own truck I've been daily driving for YEARS without using the O2s (called "open-loop speed-density" mode) and lately my truck is getting its best MPG ever because I've been repeating the AutoVE process daily for about 4-weeks now and my main VE table is starting to get really dialed-in.

The process basically is:
1. get a current sit-rep by scanning the 'important' engine sensors (IAT, ECT, TPS, MAP, RPM, etc)
2. lookup values from the tables in the tune, and calculate how much fuel to inject into the engine
3. inject fuel, then ignite the air/fuel in the combustion chamber
4. see what the O2s have to say about what just happened

All the O2s do is provide feedback; under the right circumstances, the PCM will consider that accumulated feedback and derive from it an error percentage (called fuel trimming) which it will use the next time it must repeat Step #2. On the surface, this explaination may sound like somehow the O2s are "driving" fueling, but that isn't so - the various tables in the tune drive the fueling, and the O2s are simply there to tell the PCM after-the-fact how good or bad a job it's doing. Also remember, the O2 sensors themselves can only report 1 of 3 "answers" (1) the last combustion event was fueled correctly, (2) the last combustion event was rich, (3) the last combustion event was lean. It's like hooking up your truck to a trailer with your spouse helping you - "...you're too far left... no, now you're too far right... ok drive straight... no, now you're left again..." you really have no idea if your are off an inch or a yard, and no idea how far to countersteer. This is the same sort of hindsight feedback the PCM gets, so the PCM has no idea how FAR off it is with it's fueling, all the PCM knows is that it's last "guess" wasn't right, and to try again next time... (this is why we buy widebands!).

The O2 sensor feedback system was never intended or designed to "drive" the fueling math in the PCM; the reason O2 sensors are present is because after the brand new perfect vehicle rolls off the assembly line, parts begin to wear and the engine will mechanically not be "perfect" anymore which affects volumetric efficiency anywhere from 1-5% (or more?!) - the O2 sensor system is provided because by law the vehicle needs to still run cleanly at 100K-miles, and it's a lot cheaper to fit this workaround on a vehicle than to provide free ongoing dealer service for every car until it is 100K-miles old just so it can pass smog inspection!

O2s are a feedback loop only, the tune/calibration in the PCM still has to be reasonably accurate!!! O2s will NOT take a mediocre tune and "learn" how to cope and make it a badass, race-winning, fully-researched engine calibration.

Another thought - when in closed loop, the PCM purposely fuels the engine "rich-lean-rich-lean-rich-lean........." so it can SEE the O2's reporting this behavior a split-second later; meaning, that in my own truck when in closed loop my city MPG goes from high-14s to mid-12s! In open-loop operation, the PCM keeps fueling steady, the PCM isn't making every other squirt of the injector purposely a tiny bit rich (wasting fuel).



...So given a choice of tuning at either 14.63 or 14.13 knowing that you may have either E0 or E10 gasoline in your gas tank at any given time, which would be the BEST AFR to tune for? ... perhaps the oxygen sensors will handle the difference and it will be completely transparent to the operation of the engine?
OK. Dose of reality here: if the engine runs lean while you are only wanting 65-hp (say, cruising down a flat freeway) and it DOES ping or have some form of 'mal-combustion' there is so little energy involved that you will likely not be harming any engine internals. OTOH, if you are making 750-hp and you have a detonation event, you will likely be snapping a top ring land or driving over your own crankshaft! Add to that the fact that when you put your foot down past a certain point, the PCM will abandon the O2's completely and go on a hope & prayer that the PCM tune is right and fuel the motor completely on math; there is no O2 feedback during WOT, this by definition is going from closed-loop to open-loop. And even if the PCM were to stay in closed-loop during WOT, by the time the O2 sensors had anything important to say about what has just happened in the combustion chamber the damage will already have been done (remember, they are consulted on step #4!). Point being, the math (i.e. your tune!) needs to be as correct as possible.

Typically I suggest that people cave-in to the reality that E10 is now a fact of life, and use a stoich of 14.17; in your case however since you will be running the car 90% of the time E0 then I would go ahead and keep the stoich set at 14.63, and before taking a road trip of any kind I would prepare and change the stoich value to 14.17 the night before (then change it back again after you've returned home and refilled with E0). PITA I know, but it's better than carrying a laptop in the car. Whatcha gonna do... :/

- Steve.

[Rich Z]

I thought MAP looked too wobbly in Log_0002 the other night, but today it looks more reasonable (lol, I wasn't drinking on either days).

Well, THAT is encouraging to hear! I did have to do a lot of vacuum re-plumbing on my car, so certainly anything is possible. I had to install a manifold block so I could hook everything I needed to vaccum. Seems to be working, because I can see fuel pressure changing with manifold vacuum. But the few times I kicked it slightly into boost, I don't remember hearing the blowoff valve at all between shifts. But honestly I've been babying the car while trying to fix all the problems. Now that I've got the wideband hooked up (or will again when I put the exhaust back together on the car) I want to kick a little boost into the engine so I can see what the log files look like. Of course, I still don't have a clue how to set up the PIDs for this custom operating 2 bar MAP I've got. I thought I read somewhere that there are one or more additional tables involved. When my tuner was street tuning the car, he couldn't do much in boost because I had some older tires on the car (after being in shops for a couple of years, they just got hard and not able to hold much traction), and they just broke loose WAY too easily when boost kicked in. He told me he erred on the site of fatness, to be safe, but I would still like to see what the WB is actually seeing.

Oh well, all in due time, I guess.

And Joe, in case I need to do my tune over from SCRATCH, since the fuel pressure regulator is mapped to vaccum AND the IFR table is controlling fueling, is there some sort of a getting started tutorial to let me know how to actually set up the injector info? I do have an Excel spreadsheet that I got from the guy who worked up the injectors, but I don't even have a hint of a clue about how to turn that spreadsheet into something EFILive can digest.

And before anyone asks, no, I don't have access to a dyno. There are a couple around town that I know of, but I don't trust any of them to have my car in their shop. So I'm pretty much going to have to do this literally by the seat of my pants.

Thanks....

[joecar]

Pids: use the calc_pid.txt from the Calc.VET thread.


IFR/FPR technical: Calculating-Injector-Flow-rate (http://forum.efilive.com/showthread.php?4821-Calculating-Injector-Flow-rate)


IFR spreadsheet: enter rail pressure (measured with reference removed), injector rated flowrate, injector rated pressure.

[Rich Z]

Pids: use the calc_pid.txt from the Calc.VET thread.


IFR/FPR technical: Calculating-Injector-Flow-rate (http://forum.efilive.com/showthread.php?4821-Calculating-Injector-Flow-rate)


IFR spreadsheet: enter rail pressure (measured with reference removed), injector rated flowrate, injector rated pressure.

OK, thanks. I'll have to check my notes. I can't remember what I set the fuel pressure at with the vacuum hose disconnected. And I've got that info on the injectors somewhere....

[Rich Z]

Also, I think it's in the third log that you will see the 6 seconds where my IAT reading went bonkers.


I was planning on taking the car out for a drive today after fixing a bunch of minor exhaust leaks, and I had the laptop on, running EFILive, and was logging the warm up cycle to note how it goes from open loop to closed loop. I noticed immediately that the IAT signal was pegged at 284 degrees and staying there. So I apparently had a SOLID failure to track down. The main reason I was going to take the car out today was to do some logging specifically for this IAT problem. I had cleaned the contacts on the connector thoroughly, so I wanted to see if maybe that corrected the problem. Apparently not. Turns out I was barking up the wrong tree anyway.

So I shut off the car and set up the laptop where I could watch it while I was poking around under the hood with that harness. Connie was actually monitoring the screen for me, and she called out when the signal dropped from 284 to 90 degrees or so while I was jiggling a particular section of the IAT/MAF cable harness. So it looked like we had zeroed in to the problem. Hard failures are SO much easier to find than intermittent crap.

So I pulled the insulation sleeve off of the harness to take a look. And here we go:

http://www.corvetteflorida.com/pics/IAT_wire_01.jpg

http://www.corvetteflorida.com/pics/IAT_wire_02.jpg

http://www.corvetteflorida.com/pics/IAT_wire_03.jpg

http://www.corvetteflorida.com/pics/IAT_wire_04.jpg

Whoever did this piss poor soldering job left jagged ends sticking out from the soldered joints, and didn't bother to even cover the purple wire individually. Just plain laziness. So what happened was that a sharp point on the purple wire's joint had cut right through the insulation on the yellow wire and was shorting the two of them together. There were a couple of other sharp points on the other wires, so they may have been poking through the insulation as well. If not now, certainly sometime in the future.

Two things really wrong with this solder job. (1) Before putting the shrink wrap on the solder joints, smooth the sharp solder points down. This can easily be done with no more than needle nose pliers by crimping them down flat against the wire. Actually wrap the two wire ends together properly, and you rarely have sharp points sticking out every which way. (2) With multiple wires being soldered in a harness, stagger the cuts on the wires so the joints aren't right next to a neighboring joint. This not only helps to prevent this kind of problem with shorts, but also keeps you from having a big LUMP in a harness when you try to put a cover over the entire wiring. You know, looks like a snake that ate a big rat or something.

So I crimped the sharp ends in the solder joints, then rewrapped them all with silicon tape. Double checked the signal to make sure the short was gone, then rewrapped the entire harness with insulation and wire wrapped it back in place along the air bridge.

So I believe the intermittent IAT problem has been solved now as well.

Maybe tomorrow I can take the car out for a spin. I didn't hook the wideband controller up again, as I want to burn off any anti-seize compound that might be in the exhaust pipes above the sensor first.

[ScarabEpic22]

Wow Rich, that looks horrible. I tend to use the needle nose method of flattening sharp soldering edges but usually I try to solder in such a way that there arent any in the first place. Im an amateur at soldering by far, but I do know that much!

Hopefully you've got it sorted out!

[swingtan]

Those jagged points look like poorly twisted wires before the soldering was done. You can't do neat soldering if the wires themselves are all over the place.... To ensure you don't get solder spikes, you need to get plenty of heat into the solder and not go overboard with the amount of solder used. Plenty of heat and just enough solder will give excellent results.

Just be careful with the silicon tape as well. If the joins are in the O2 sensor leads ( not the main loom ) you might get silicon migrating down to the sensor. The O2 sensor uses the leads to reference free air and it is possible to get silicon contamination that way. For the same reason, you shouldn't use silicon spray on the O2 sensor plugs.

[joecar]

Hmmm, wow...

also looks like the heat shrink has been done wrong (won't keep moisture out).

[Rich Z]

Hmmm, wow...

also looks like the heat shrink has been done wrong (won't keep moisture out).

Yeah, no doubt. Believe me this is just the smallest tip of the iceberg in relation to what I have been through with the people who worked on this car, and what I have been trying to correct when I figured out that I need to do the wrenching myself or just scrap it.

One day when I have everything else done on the car and I'm bored, I'll just cut the connector and either resolder all the wires correctly, or just replace the connector itself. I'm sure each time I see it it's going to bug me. I do have a new connector in the box of parts I bought to troubleshoot this IAT problem. But it's sealed up pretty good with the silicon tape now, plus where the harness is located (running alongside my airbridge) it's highly unlikely to be exposed to moisture. I've got a dehumidifier running 24/7 in the garage. I live on a dirt road, so I try like hell to not drive when rain is in the forecast. I don't care about the car getting wet, but trying to flush mud out from underneath the car is not all that much fun to do.

[Rich Z]

Those jagged points look like poorly twisted wires before the soldering was done. You can't do neat soldering if the wires themselves are all over the place.... To ensure you don't get solder spikes, you need to get plenty of heat into the solder and not go overboard with the amount of solder used. Plenty of heat and just enough solder will give excellent results.

Just be careful with the silicon tape as well. If the joins are in the O2 sensor leads ( not the main loom ) you might get silicon migrating down to the sensor. The O2 sensor uses the leads to reference free air and it is possible to get silicon contamination that way. For the same reason, you shouldn't use silicon spray on the O2 sensor plugs.

Yeah, I learned to solder by repairing computer circuit boards at the component level. I've seen a lot of people who really don't have a clue about how to do this correctly. Nine times out of ten they wind up having cold solder joints that eventually plague them with intermittent electrical problems. They treat solder like it is some sort of glue that just needs to be splashed onto the joined wires instead of melted and flowed ONTO the wires. Most will use a soldering iron way too hot for the application that starts to melt the nearby insulation before they can even apply the solder to the joint, so they hurry it through before the rosin can clean the surface for the solder to melt and flow properly.

And no, this isn't on the O2 sensors. GM specifically states that O2 sensor harnesses are NOT to be spliced to be lengthened or repaired. But honestly, I've heard this said before about the O2 sensor leads being used to reference free air. So I've looked at oxygen sensor harness wiring, and darn if I can figure out how those wires would do that. All the wires I saw are insulated like any other wire I have seen, and there are no bare wires at all. So unless I missed something in the harnesses I looked at, I just don't understand how this free air stuff is done by the harness. The reason I've looked is because I like to insulate as much as possible against heat degradation, and those O2 harnesses are directly above the header collectors. So I've not covered them with additional insulation because of this issue with them determining free air. But I sure would like to know HOW this takes place.

[swingtan]

FWIW, the O2 sensors draws minuscule amounts of free air along the gaps between the individual copper conductors in the wire, they don't need much. This is why cutting and splicing will upset the flow of air from the connector end to the element.

I have tio admit that fixing other peoples mess ups is a pet hate of mine.

[slows10]

I view the O2 sensors as a Delphi "workaround", or add-on.

The O2 sensors DO NOT have any DIRECT bearing on fueling calculations; if the PCM calibration/tune is perfect, you don't need O2 sensors at all (!) in fact in my own truck I've been daily driving for YEARS without using the O2s (called "open-loop speed-density" mode) and lately my truck is getting its best MPG ever because I've been repeating the AutoVE process daily for about 4-weeks now and my main VE table is starting to get really dialed-in.

The process basically is:
1. get a current sit-rep by scanning the 'important' engine sensors (IAT, ECT, TPS, MAP, RPM, etc)
2. lookup values from the tables in the tune, and calculate how much fuel to inject into the engine
3. inject fuel, then ignite the air/fuel in the combustion chamber
4. see what the O2s have to say about what just happened

All the O2s do is provide feedback; under the right circumstances, the PCM will consider that accumulated feedback and derive from it an error percentage (called fuel trimming) which it will use the next time it must repeat Step #2. On the surface, this explaination may sound like somehow the O2s are "driving" fueling, but that isn't so - the various tables in the tune drive the fueling, and the O2s are simply there to tell the PCM after-the-fact how good or bad a job it's doing. Also remember, the O2 sensors themselves can only report 1 of 3 "answers" (1) the last combustion event was fueled correctly, (2) the last combustion event was rich, (3) the last combustion event was lean. It's like hooking up your truck to a trailer with your spouse helping you - "...you're too far left... no, now you're too far right... ok drive straight... no, now you're left again..." you really have no idea if your are off an inch or a yard, and no idea how far to countersteer. This is the same sort of hindsight feedback the PCM gets, so the PCM has no idea how FAR off it is with it's fueling, all the PCM knows is that it's last "guess" wasn't right, and to try again next time... (this is why we buy widebands!).

The O2 sensor feedback system was never intended or designed to "drive" the fueling math in the PCM; the reason O2 sensors are present is because after the brand new perfect vehicle rolls off the assembly line, parts begin to wear and the engine will mechanically not be "perfect" anymore which affects volumetric efficiency anywhere from 1-5% (or more?!) - the O2 sensor system is provided because by law the vehicle needs to still run cleanly at 100K-miles, and it's a lot cheaper to fit this workaround on a vehicle than to provide free ongoing dealer service for every car until it is 100K-miles old just so it can pass smog inspection!

O2s are a feedback loop only, the tune/calibration in the PCM still has to be reasonably accurate!!! O2s will NOT take a mediocre tune and "learn" how to cope and make it a badass, race-winning, fully-researched engine calibration.

Another thought - when in closed loop, the PCM purposely fuels the engine "rich-lean-rich-lean-rich-lean........." so it can SEE the O2's reporting this behavior a split-second later; meaning, that in my own truck when in closed loop my city MPG goes from high-14s to mid-12s! In open-loop operation, the PCM keeps fueling steady, the PCM isn't making every other squirt of the injector purposely a tiny bit rich (wasting fuel).



OK. Dose of reality here: if the engine runs lean while you are only wanting 65-hp (say, cruising down a flat freeway) and it DOES ping or have some form of 'mal-combustion' there is so little energy involved that you will likely not be harming any engine internals. OTOH, if you are making 750-hp and you have a detonation event, you will likely be snapping a top ring land or driving over your own crankshaft! Add to that the fact that when you put your foot down past a certain point, the PCM will abandon the O2's completely and go on a hope & prayer that the PCM tune is right and fuel the motor completely on math; there is no O2 feedback during WOT, this by definition is going from closed-loop to open-loop. And even if the PCM were to stay in closed-loop during WOT, by the time the O2 sensors had anything important to say about what has just happened in the combustion chamber the damage will already have been done (remember, they are consulted on step #4!). Point being, the math (i.e. your tune!) needs to be as correct as possible.

Typically I suggest that people cave-in to the reality that E10 is now a fact of life, and use a stoich of 14.17; in your case however since you will be running the car 90% of the time E0 then I would go ahead and keep the stoich set at 14.63, and before taking a road trip of any kind I would prepare and change the stoich value to 14.17 the night before (then change it back again after you've returned home and refilled with E0). PITA I know, but it's better than carrying a laptop in the car. Whatcha gonna do... :/

- Steve.

Great post Mr.P

[joecar]

...

O2s are a feedback loop only, the tune/calibration in the PCM still has to be reasonably accurate!!! O2s will NOT take a mediocre tune and "learn" how to cope and make it a badass, race-winning, fully-researched engine calibration.

...This is a very good point to keep in mind... this is the motivation for getting the VE and MAF tables correct.