Why am I running rich during PE?

[n8dogg]

After performing Calc.VET tuning (a few times) I feel I have an accurate VE table and the car runs very smooth. The only issue is my AFR at WOT is around 11.9-12.2 when I am asking for 12.5-12.7.

I know my MAF freq has always been a bit jumpy, especially at higher RPMs. BUT I have recently installed an airflow straightener from Halltech, didn't seem to help much.

Here is my latest log: 11444

My guess is the MAF is causing this since the PCM looks at MAF freq during WOT (right?).

Any help is appreciated. I'd really like to see what she does when it's running at optimal AFR.

[joecar]

Hi n8, I'll look at it tonite/tomorrow.

[Taz]

Post your tune if you are able ... will take a look for any additional enrichment in the tune itself - to rule out this possibility .... many eyes often find a solution.


Regards,
Taz

[n8dogg]

Thanks guys

Here is my current tune:11445

[Taz]

Took a quick look at the tune ... nothing jumps out as being causal. No extraneous fuel adders that I could find. Stoich at 14.68:1, PE from 1.15 (12.75:1) to 1.17 (12.54:1). MAF has a smooth consistent curve, VE shape is also well done - some of the transitions could be smoothed a little more (but that's just the old man being picky !).

Also took a quick look at the log - WBO does jump around a fair bit (even when not in OL / PE). Hopefully Joecar's keen eye will spot something.


Regards,
Taz

[SSpdDmon]

MAF needs to be redone with the addition of a screen. It makes sense that it would be off by a larger delta at higher airflow. It's altering the path of air right in front of the sensor. I guess it's possible that the VE would need a touch up as well, but I doubt it.

[joecar]

Some background info:

we previously noted that the MAF has large swings at WOT as rpm increases (MAF waveform would jump down 60 g/s and then back up);

n8 had installed an aftermarket duct, we're not sure if this is causing the MAF swings;
n8 installed a honeycomb screen on the MAF to see if this makes any difference and it appears not;

we know the PCM is able to filter out some of the MAF waveform swings, but we're not sure how large a swing it can handle.

[n8dogg]

I do have the stock intake, I could install it and log to see if things smooth out.

[Taz]

Hello N8,

Haven't logged an OL MAF only tune in a while - these work well for certain applications - if memory serves I think that is what Jeff (SSpdDmon) is using in his Camaro. Truck tunes use B4206 (O2 trim in OL) by default. Corvettes do not. Can't recall if B4206 trims in OL only, or in OL and PE modes. Enabling B4206 may assist (if it trims in PE) with promoting safe AFR until you find a more permanent tuning solution.


Regards,
Taz

[n8dogg]

Halltech has a newer style intake kit that utilizes a card type MAF found in newer Corvettes. Do you think I would see a more accurate reading by retrofitting a card style MAF? It's too bad I'm a perfectionist otherwise I'd leave it be. Not sure how much power I'm really sacrificing. Do you think the 90+ ambient temp could cause any of this?

[SSpdDmon]

If you're still seeing large swings after installing the MAF screen, my next step would be to make sure the MAF is thoroughly clean (can get MAF cleaner at Autozone type stores) and maybe try "clocking" it if there's room to do so. Depending on the path of the airflow, you may get better readings if the bar in the middle of the MAF is verticle instead of horizontal (or vice versa). Give those sugesstions a shot before throwing money/parts at it.

[joecar]

Yes, try those things, clock the MAF position, and with the screen redo the MAF table.

Also try the stock duct to see if it makes any difference, try it with and without the screen.

[n8dogg]

Ok I'll clean and clock it. What do you mean redo the MAF table?

[joecar]

With the MAF clocked/screened, redo the BEN correction on the MAF table B5001...

i.e. anything that changes how the MAF reads will require the MAF table B5001 to be corrected again.

[n8dogg]

Something weird is going on. Almost like something in the tune itself that's hidden. I played around last night with the tune by adding 2% to the MAF calibration and the AFR is identical at WOT. I then took the MAF back by adding -2%. Took it to work this morning and my LTFTs are averaged at -3.5%, AFR is the same at WOT (11.6-12.0). I did reset fuel trims a few nights ago and it's hot and humid outside. Would resetting fuel trims and hot and humid air have a negative effect on my tune? Do I need to do more work now that my fuel trims are off or do I need more seat time to allow the fuel trims to adjust after being reset?

[SSpdDmon]

Is there a chance catalytic overtemp protection is still enabled?

You will see some swings in FTs as weather conditions change. So, I wouldn't be too concerned about a 2~3% swing.

Please list all mods and post up a copy of your current & factory stock tune. I'll take a look and see if anything stands out.

[n8dogg]

It's disabled, just checked. I did a search on the corvette forum and people are saying to turn fuel trims off and that they are applied during PE. So are they MAF only OL PE mode? Or are trims applied? If trims were applied I think I'd run lean wouldn't I? I'll have to find wifi on lunch and upload the logs from last night and this morning.

[joecar]

OL: trims are not applied.

CL: last positive trims are applied in PE mode (on top of PE table).

When trims are applied in PE mode, they will never remove fuel, they will add only.

Yes, post logs and tune file.


More info: Summary-Notes -> post #4 (http://forum.efilive.com/showthread.php?14188-Summary-Notes&p=127353&viewfull=1#post127353)

[n8dogg]

Thanks guys, I will get my logs and tune up asap. I will read more through the summary notes when I am not on the clock ;).

Here is a reply I got on the Corvette Forum, what do you guys think?


just cause you set your PE@ 13.0 or whatever doesnt mean it w ill do that. Not until you actually tune the MAF table.

when you go WOT your LTFT a STFT are not being used any more. You have to adjust your HZ to make your afr correct. so do a WOT run
put 1.129 in your PE table.
log WOT

if at 8600HZ you are 12.3 the take the 8600 hz cell and multiply by aprox .94 that should get it really close to the 13.0 you are commanding

[Mr. P.]

...Stoich at 14.68:1...

You sure that you're running 100% gasoline?? It is common here for stations to water down their gasoline with 5-15% ethanol; also due to Obama EPA laws, ALL pump fuel in the US will be at least 10% ethanol (E10) by 2012, so I would just change the stoich value to 14.17 now IMO. Either way, make sure the fuel you are using matches the stoich value in your tune.

Mr. P.

[n8dogg]

You sure that you're running 100% gasoline?? It is common here for stations to water down their gasoline with 5-15% ethanol; also due to Obama EPA laws, ALL pump fuel in the US will be at least 10% ethanol (E10) by 2012, so I would just change the stoich value to 14.17 now IMO. Either way, make sure the fuel you are using matches the stoich value in your tune.

Mr. P.

10% ethanol is in all gasoline around here. :/.

[Taz]

Nice catch Mr. P .... often forget this is a global Forum ... zero ethanol in "premium" gasoline here .... there is 10% ethanol in our "regular" gasoline. I had assumed N8 was running premium gasoline, and that the 14.68:1 setting for stoich was therefore accurate.

I use 14.12:1 for 10% ethanol gasoline. That would loosely equate the PE values to - EQ 1.17 (12.07:1 AFR) and EQ 1.15 (12.28:1 AFR). That is much closer to the WBO readings N8 had observed - 11.9 to 12.2 AFR.

That may explain some of the variance.


Regards,
Taz

[n8dogg]

Nice catch Mr. P .... often forget this is a global Forum ... zero ethanol in "premium" gasoline here .... there is 10% ethanol in our "regular" gasoline. I had assumed N8 was running premium gasoline, and that the 14.68:1 setting for stoich was therefore accurate.

I use 14.12:1 for 10% ethanol gasoline. That would loosely equate the PE values to - EQ 1.17 (12.07:1 AFR) and EQ 1.15 (12.28:1 AFR). That is much closer to the WBO readings N8 had observed - 11.9 to 12.2 AFR.

That may explain some of the variance.


Regards,
Taz

So the stoich setting directly effects PE AFR?

[SSpdDmon]

...also due to Obama EPA laws, ALL pump fuel in the US will be at least 10% ethanol (E10) by 2012....

WTF?!?!? When did this happen??? :bad:

[Taz]

So the stoich setting directly effects PE AFR?


No matter what AFR you set as stoich, EQ at stoich will always be "1.00". This why tuning in EQ or Lambda (rather than AFR) negates the effect of the ethanol content in the fuel.

If you configured your WBO to produce a result in EQ (directly or via a CALC PID) it should be in good agreement with your commanded PE (EQ of 1.17 to 1.15) - however the corresponding AFR will always be fuel dependent. Again, this why using EQ (or Lambda) output from your WBO will make tuning easier, and more accurate.


Regards,
Taz

[joecar]

Yes, you must set B3601 to the stoich AFR of the fuel you're running.

[n8dogg]

OK this is getting a little confusing for me. I just got back from logging on my lunch break. I changed the B3601 stoich AFR as 14.17. The car ran further rich, I'm guessing based on what you just said Taz, I did this incorrectly. The car also skipped at slow speed parking lot maneuvers afterwards, although its hot as hell outside and the A/C was running and fans blowing.

Here is the latest log with AFR at 14.17:
11462
This is the tune:
11463
Maybe you can help walk me through the proper way to change the stoich AFR. And what's the answer to the AFR during PE?

[n8dogg]

Here's what I am gathering:

I need to log showing EQ instead of AFR and recalibrate my MAF.
-Is following the Calc.VET tuturial a good way to do this?
-What about the missing FREQ. data in the new map, do I apply the average % to the entire table?

14.17 is stoich for premium gasoline with 10% alcohol, does this require the VE table to be reworked?

[joecar]

Yes, follow Calc.VET tutorial if you're running CLMAF.

The Calc.VET tutorial has info regarding the map.

Changing stoich does not require VE table to be redone. Changing engine's air breathing ability requires VE table to be redone.

[slows10]

You have B3601 set at 14.17 and then B3618 set at 1.17-1.16 . That is 12.11 afr at wot. Thats roughly what the wideband is saying. Why are you using 14.17? What someone is using for fuel in one state does not mean it is correct for you. I wouldnt think B3601 should be changed until it is confirmed by testing thet it is E10.

[n8dogg]

You have B3601 set at 14.17 and then B3618 set at 1.17-1.16 . That is 12.11 afr at wot. Thats roughly what the wideband is saying. Why are you using 14.17? What someone is using for fuel in one state does not mean it is correct for you. I wouldnt think B3601 should be changed until it is confirmed by testing thet it is E10.

My WB is showing as low as 11.6 when I'm asking for 12.5. The 14.7 was just a recommendation from the other members. I will try some things this weekend. Hope it cools down a bit.

[slows10]

I did nt see your post #21 where you said you have E10. Im not to far from you in ct. It really is unreal with the heat here. Hit 101 today in the shade.

[n8dogg]

Here's an update. I did the Calc.VET tutorial and adjusted my MAF. The AFR seems to be much closer now at WOT. One thing I noticed is that the previous commanded AFR during PE has been dropped from 12.5-12.7 to 12.0-12.2. Is this due to the change of stoich from 14.68 to 14.17?

Where is the sweet spot AFR for power with 10% Ethanol?

[mr.prick]

You're compounding the problem if the WBO2's stoich AFR value does not match {B3601} .
If {B3601} = 14.17 & WBO2 Stoich AFR = 14.7 then BEN is worthless. :sly:

Using {GM.EQUIVRATIO} & {EXT.WO2EQ1} for BEN instead of {GM.AFR}, {EXT.WO2AFR1} & {CALC.BEN1} will eliminate this. :angel_innocent:

The serial BEN pid should be replaced with "({GM.EQIVRATIO}/{EXT.WO2EQR1})" or "({GM.EQIVRATIO}*{EXT.WO2LAM1})"
And for AFR reference use "({B3601}/{EXT.WO2EQR1})"or "({B3601}*{EXT.WO2LAM1})"

The easy fix is to return {B3601} to 14.68 and proceed as you were,
filtering out LTFTs, MAP/TP transients, KR ect. during PE before using BEN. :blahblah:

[Taz]

+1 on Mr. Prick's comments ...

Moving away from AFR use, and learning how to tune using EQ (or Lambda) really does simplify the process.


Regards,
Taz

[n8dogg]

You're compounding the problem if the WBO2's stoich AFR value does not match {B3601} .
If {B3601} = 14.17 & WBO2 Stoich AFR = 14.7 then BEN is worthless. :sly:

Using {GM.EQUIVRATIO} & {EXT.WO2EQ1} for BEN instead of {GM.AFR}, {EXT.WO2AFR1} & {CALC.BEN1} will eliminate this. :angel_innocent:

The serial BEN pid should be replaced with "({GM.EQIVRATIO}/{EXT.WO2EQR1})" or "({GM.EQIVRATIO}*{EXT.WO2LAM1})"
And for AFR reference use "({B3601}/{EXT.WO2EQR1})"or "({B3601}*{EXT.WO2LAM1})"

The easy fix is to return {B3601} to 14.68 and proceed as you were,
filtering out LTFTs, MAP/TP transients, KR ect. during PE before using BEN. :blahblah:


+1 on Mr. Prick's comments ...

Moving away from AFR use, and learning how to tune using EQ (or Lambda) really does simplify the process.


Regards,
Taz

Thanks for the info. From what I have seen by pulling tunes from cars around here 14.68 is still used as stoich even though 10% Ethanol is in all the fuel here. From what it sounds like, using 14.68 (for now) as stoich doesn't really hurt anything. Is that accurate? Maybe if laws change and they start putting more than 10% in, it's going to be almost necessary to change tunes.

[Taz]

Hello N8,

If you transition to an EQ or Lambda readout from your WBO, the value in your tune set as stoich (14.68 / 14.12 / etc.) will have no real effect (or very little) on tuning. Your NBO, just like your WBO simply measures residual oxygen in the exhaust stream. Hang a WBO in free air, and the reading will be the maximum lean value.

An EQ or Lambda value of "1.00" relates to stoich, or loosely, complete combustion. Stoich for gasoline is generally around 14.7:1, while for E85 closer to 9.0:1 - but the EQ or Lambda value of theses remains as "1.00". This principle applies for PE values - guessing that is why the OEM used EQ for PE tables, so the values would be consistent across fuels.


Regards,
Taz

[joecar]

The Calc.VET tutorial has a calc_pids.txt file that computes BEN as mr.prick said above in post #34...

i.e. WO2BEN = {GM.EQIVRATIO}*{EXT.WO2LAM1}

Use GM.EQIVRATIO and either EXT.WO2LAM1 or EXT.WO2EQR1, and avoid GM.AFR and EXT.WO2AFR

( note that WO2LAM = 1/WO2EQR )

[n8dogg]

The Calc.VET tutorial has a calc_pids.txt file that computes BEN as mr.prick said above in post #34...

i.e. WO2BEN = {GM.EQIVRATIO}*{EXT.WO2LAM1}

Use GM.EQIVRATIO and either EXT.WO2LAM1 or EXT.WO2EQR1, and avoid GM.AFR and EXT.WO2AFR

( note that WO2LAM = 1/WO2EQR )

I have done the Calc.VET tutorial with stoich set as 14.68. If I were to tune the car for E10, is it as simple as changing the stoich value as 14.17 and completing the Calc.VET again?

[joecar]

If you already did the VE table then it should already be good...Yes, set stoich to 14.17 and redo Calc.VET, you should end up with the same results.