Tuning questions w/cam/header mods..

[Redline Motorsports]

Just finished a cam/header install on a 00' C5 MN6. I started with the idle and got it working great. We pulled the motor on the dyno with the stock timing table and had zero knock retard. The A/F was a bit rich but damn near matched the values in table {B3618} PE Modifier based on rpm. Can I assume that the IFR (which was stock) and the VE table values are pretty close? After seeing that they where close, I leaned down the PE table and got the AF where I wanted it. My main question is back to the stock timing table. If the motor didn't mind the stock timing table, should I call it quits?? The timing ended up around 28 degrees at full advance for most the WOT range. The car made 388 RWHP and 370 RWFT which I felt was pretty good with the stock heads, cats and stock LS1 intake.

What do you guys think? As a newbie I finally felt like I got a grip on this tune as it only took me 4 flashes for the idle and 3 for the WOT! LOL!! :lol:

Howard

[foff667]

its hard to tell if a ve is spot on doing the work on a dyno & I would more or less go on the #'s you see in the real world on the street...so to say the ifr & ve are on just because on the dyno your pe is close to matching doesnt mean too much in my eyes imo.

[Redline Motorsports]

I thought I remember reading somewhere on this forum that the values in the PE modified (commanded AF) should match the actual WB readings. Isn't that parameter based upon a ratio off of 14.7 which the NB reads to determine WOT AFR?? EQ ratio of 1.00= 14.7 AFR if the tuning is close to be accurate?

[Dirk Diggler]

PE is a multiplier that represents a Commanded AFR. If you set your pe for 1.13 or 12.96 (samething) thru tuning your WB needs to read those values at WOT

[Redline Motorsports]

PE is a multiplier that represents a Commanded AFR. If you set your pe for 1.13 or 12.96 (samething) thru tuning your WB needs to read those values at WOT

I thought that is what I was saying. :roll:

I like use the AFR value vs. the EQ ratio as it is easier for me to compare to the WB on the dyno. My point was that the commanded AFR was with .1 of the actual WB reading! How can that not represent an commanded vs. actual perfect condition??

[Blacky]

I thought I remember reading somewhere on this forum that the values in the PE modified (commanded AF) should match the actual WB readings. Isn't that parameter based upon a ratio off of 14.7 which the NB reads to determine WOT AFR?? EQ ratio of 1.00= 14.7 AFR if the tuning is close to be accurate?

Yes, the commanded value in the PE table(s) should match what you see on your WO2.

The narrow band O2's are not used to determine AFR at WOT. The commanded fuel in PE mode may be *way* off and the PCM would never know since it cannot and does not monitor any AFR's in PE mode. That's why you need a wide band.

The PE table(s) command the PCM to calculate the appropriate injector pulse width for the measured air mass in the cylinder. If the underlying values that the PCM uses to determine the air mass in the cylinder (i.e. VE, MAF, IAT ect), or the injector pulse width (i.e. IFR) then the actual WOT AFR will not match the commanded AFR.

There is one exception, if the long term fuel trims are positive when PE mode is activated, then the PCM (assuming that the engine is running lean due to +ve trims) will add extra fuel to the WOT commanded PE values. that's why people shoot for LTFT that are slightly negative - that will prevent the PCM from "compensating" for a lean condition.

Regards
Paul

[Dirk Diggler]

PE is a multiplier that represents a Commanded AFR. If you set your pe for 1.13 or 12.96 (samething) thru tuning your WB needs to read those values at WOT

I thought that is what I was saying. :roll:

I like use the AFR value vs. the EQ ratio as it is easier for me to compare to the WB on the dyno. My point was that the commanded AFR was with .1 of the actual WB reading! How can that not represent an commanded vs. actual perfect condition??

You're asking a question and you arent satisfied with my answer. When i read your post it seemed to me you were kinda confused about the functions of the pe table, so i answered the best way i felt fit. Sorry if it wasnt to your liking or redundant :roll: oh and i wouldnt be worried about .1

[jfpilla]

I thought I remember reading somewhere on this forum that the values in the PE modified (commanded AF) should match the actual WB readings. Isn't that parameter based upon a ratio off of 14.7 which the NB reads to determine WOT AFR?? EQ ratio of 1.00= 14.7 AFR if the tuning is close to be accurate?

Yes, the commanded value in the PE table(s) should match what you see on your WO2.

The narrow band O2's are not used to determine AFR at WOT. The commanded fuel in PE mode may be *way* off and the PCM would never know since it cannot and does not monitor any AFR's in PE mode. That's why you need a wide band.

The PE table(s) command the PCM to calculate the appropriate injector pulse width for the measured air mass in the cylinder. If the underlying values that the PCM uses to determine the air mass in the cylinder (i.e. VE, MAF, IAT ect), or the injector pulse width (i.e. IFR) then the actual WOT AFR will not match the commanded AFR.

There is one exception, if the long term fuel trims are positive when PE mode is activated, then the PCM (assuming that the engine is running lean due to +ve trims) will add extra fuel to the WOT commanded PE values. that's why people shoot for LTFT that are slightly negative - that will prevent the PCM from "compensating" for a lean condition.

Regards
Paul


Paul,
"If the underlying values that the PCM uses to determine the air mass in the cylinder (i.e. VE, MAF, IAT ect), or the injector pulse width (i.e. IFR) then the actual WOT AFR will not match the commanded AFR."

Did you leave out part of your point?
I think it should be pointed out that IFRs must be calculated properly. If the trims are set using IFRs then the commanded AFR will not match actual. Even after a well done tune the AFR will change based on weather.
So, how can .1 be measured and worried about. Also, I can't get my WB to measure that smoothly that I can tell .1.
It would be nice if posters would say whether they are running with or without an MAF, when asking about tuning questions. :P
Joe

[GMPX]

It would be nice if posters would say whether they are running with or without an MAF, when asking about tuning questions. :P
Joe

^^ You beat me to it.

Cheers,
Ross

[Blacky]

Paul,
"If the underlying values that the PCM uses to determine the air mass in the cylinder (i.e. VE, MAF, IAT ect), or the injector pulse width (i.e. IFR) then the actual WOT AFR will not match the commanded AFR."

Did you leave out part of your point?


No, I don't think so. I was just trying to say that the PE commanded AFR is based on calculations only (no feedback). So if the inputs that the calculations are based on (VE, MAF, IAT, IFR etc) are wrong then the final calculation will be wrong and always wrong. There is no trimming or learning based on any measured feedback.



I think it should be pointed out that IFRs must be calculated properly. If the trims are set using IFRs then the commanded AFR will not match actual. Even after a well done tune the AFR will change based on weather.
So, how can .1 be measured and worried about. Also, I can't get my WB to measure that smoothly that I can tell .1.
It would be nice if posters would say whether they are running with or without an MAF, when asking about tuning questions. :P
Joe

I agree with that 100%.

Paul

[Redline Motorsports]

Thanks for the clarifications and explainations. Sorry if I offended anyone...I was just trying to make sure I understood. I guess thats the problem with forums because sometimes its is misunderstood!

That particular car was still running the MAF. Very lightly modified motor. The .1 was only because the dyno reads to .1 and records the AF at every 100 rpms. I was surprised how close the commanded was to the actual WB numbers at there respective rpms.

If the PE commanded values did not match the actual and the IFR values where stock with there appropriate matched injectors, the MAF calibration was untouched with no changes to the intake tract can we then assume the VE table is initially off??

I have had a few cars at the shop that where tuned prior where the commanded wasn't even close to the actual. All and all in the end should that cause alarm even though the final WOT AF is good? I would think other functions of the tuning would suffer...??

[jfpilla]

"If the PE commanded values did not match the actual and the IFR values were stock with their appropriate matched injectors, the MAF calibration was untouched with no changes to the intake tract can we then assume the VE table is initially off??"
Is this a real situation?

No. The VE's are not used at WOT over 4000RPM's.


I have had a few cars at the shop that were tuned prior where the commanded wasn't even close to the actual. All and all in the end should that cause alarm even though the final WOT AF is good? I would think other functions of the tuning would suffer...??

No cause for alarm. That's a work around, but is not ideal since a WB would always be needed to set AFR and overall tuning is more difficult.

[Redline Motorsports]

I never knew that the base VE table had no effect on WOT AFR after 4000 rpms. What is the ultimate controller over 4000?? I know the PE table makes changes but I though the VE being correct over 4000 still played a role combined with the MAF, IAT and IFR.

Based on this, I would think that tuning VE under 4000 is more critical..

[dfe1]

" The VE's are not used at WOT over 4000RPM's.


If the VE table isn't used over 4,000 rpm and you're running speed density, how is fuel flow determined??? Divine intervention?

[Black02SS]

I never knew that the base VE table had no effect on WOT AFR after 4000 rpms. What is the ultimate controller over 4000?? I know the PE table makes changes but I though the VE being correct over 4000 still played a role combined with the MAF, IAT and IFR.

Based on this, I would think that tuning VE under 4000 is more critical..

This is only if you have the MAF plugged in. If you are in SD then the car will use the stoich AFR and a factor of that. Weather it be the VE table or PE vs RPM. If you have the Commanded Fuel while in open loop table and PE vs. RPM table set to the same, then the ve table is used to get the fueling in order. After you have the AFR where you like it at WOT, you can fine tune it by the PE vs. RPM table.

[jfpilla]

" The VE's are not used at WOT over 4000RPM's.


If the VE table isn't used over 4,000 rpm and you're running speed density, how is fuel flow determined??? Divine intervention?

Go back and read his question before you make SA comments. He references the MAF.