OK, Stoich AFR in PCM is 14.63, Stoich for new NGK AFX is 14.57 and...

Stoich for the actual fuel in the tank is what? 14.52ish maybe for E-10 (if it's actually E-10)? :banghead:

Along with playing with SoundEngineers advice on tuning the Cylinder Charge Bias and trying to retune MAF and VE, I'm starting to feel a quart low here! :o

So I have questions regarding Commanded AFR and AFR error.

After logging with my new wideband my Avg. Wideband AFR Error does not match the STFT AFR Error when re-enabling the trims, the wideband will be -2 or -3, STFT's going + and the car starts running bad. And yes I've read here it's best to tune the low end with only STFT's anyway. I see why.

Can I simply change the PCM's stoich from 14.62857 to say 14.3 to lower the closed or open loop Commanded AFR to try to match E-10 fuel so I can use the wideband exclusively?

AND more importantly is there a way to maybe alter the voltage range/afr range or something in a custom "user defined" wideband pid to match (or hopefully get close) to the mystery E-10 fuel? If so could one of you super experienced guys explain how I could set that up and do calc's for a desired stoich AFR for my wideband?

I really do appreciate any help on this. Anyone who finds this tuning thing easy must be a genius!

Thanks, Bob

I'm still learning this stuff myself but have come across quite a bit of info on what you're dealing with. The Sept GM High-tech Performance mag there is an article about tuning with diff fuels. They use 14.2 as stoich for Sunoco 93 as it is supposed to be E10. I also watched the Greg Banish dvd a couple months ago and it makes sense why he tunes using Lambda because 1.0 is always stoich regardless of what the number is. See if you can set your wideband to output Lambda and then it may make life easier.

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Originally Posted by bseitz

Stoich for the actual fuel in the tank is what? 14.52ish maybe for E-10 (if it's actually E-10)? :banghead:

Along with playing with SoundEngineers advice on tuning the Cylinder Charge Bias and trying to retune MAF and VE, I'm starting to feel a quart low here! :o

So I have questions regarding Commanded AFR and AFR error.

After logging with my new wideband my Avg. Wideband AFR Error does not match the STFT AFR Error when re-enabling the trims, the wideband will be -2 or -3, STFT's going + and the car starts running bad. And yes I've read here it's best to tune the low end with only STFT's anyway. I see why.

Can I simply change the PCM's stoich from 14.62857 to say 14.3 to lower the closed or open loop Commanded AFR to try to match E-10 fuel so I can use the wideband exclusively?

AND more importantly is there a way to maybe alter the voltage range/afr range or something in a custom "user defined" wideband pid to match (or hopefully get close) to the mystery E-10 fuel? If so could one of you super experienced guys explain how I could set that up and do calc's for a desired stoich AFR for my wideband?

I really do appreciate any help on this. Anyone who finds this tuning thing easy must be a genius!

Thanks, Bob

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1) Don't worry about the bias unless you are running open loop 100% of the time. I wrestled with it for 2 months and it didn't make really any difference. Not worth it. If you use closed loop, it's def. not worth it.

2) tune your maf and ve tables with stft's. it's def better than the wideband. use your wideband for open loop items only (like WOT). Don't use the wideband exclusively.

3) Keep stoich at the factory setting for now while you are tuning VE and MAF. Change it to 14.2 or so (E10 is 14.1) when you have it all tuned. The factory narrowbands will get you to stoich (not a preset AFR ike 14.X). they will get you to the stoich for the fuel in your tank. so try to tune in one tank.

4) Depending on your wideband it will show stoich at 14.6 or 8 or whatever. That is still stoich for the fuel in your tank, it is just displaying AFR based on its own preset. So stoich in your tank might be 14.1 and it displays 14.6.....you can just say, ok 14.6 means 14.1 in your head or you can scale it like you asked about....

the best way i found to figure out what your wideband thinks is stoich is to create an AFR AVG Histogram. Log only AFR output from your wideband into a single histo. cell (so no RPM range) over steady throttle over maybe 5 minutes. Don't go into PE or decel (DFCO) so it doesn't skew. Just keep it steady. See what it says.
As an example, mine said 15....!! or maybe like 14.9. So you take 14.2/14.9=.95. Go into your User Defined Section and with the formula provided with your wideband (maybe something like .625 + 10)...multiply the 10 by .95 and get 9.5 and put that in place of 10. leave .625 alone. i was changing it for a long time and it wouldn't scale right. only change the 10.

Now it should avg to 14.2 in your histograms.

Use your wideband. STFT's are ok for some fine tuning when done.

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Originally Posted by flame

See if you can set your wideband to output Lambda and then it may make life easier.

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I really appreciate all the replies and suggestions, thanks guys.

I would be open to Lambda or AFR. However I would think one target number would be the same as the other?
I would love to have my wideband readout match the stoich of the fuel in the tank. I need some input on theory and with the math on how to configure a new custom enhanced IO for my NGK wideband instead of the predefined inputs already set up by HPT. Question is that is this possible to do and make work?

Yes we would be guessing what the stoich of the fuel being used is but when reactivating the trims I could see how close I'm getting.

When doing MAF my wideband says -2,-3's. Then activating the STFT's shows I,m going in the +"s and the car is running poorly.

It's possible and fairly easy to do, setting up a custom one that is. I have mine setup to display Lambda when logging thru the scanner, have been using Lambda for quite sometime now it's just alot easier to me. I really really wish the AFX wideband had a switch to choose between Lambda and AFR but I guess it really doesnt matter too much since ultimately I am using the data in the scanner in hpt anyways and I rarely even look at the display on the wideband itself except to make sure that I dont have any offset issues.

Setting it up isn't too difficult at all, I think their a couple of good threads floating around here on how to do it if you do a search.

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Originally Posted by Higgs Boson

1) Don't worry about the bias unless you are running open loop 100% of the time. I wrestled with it for 2 months and it didn't make really any difference. Not worth it. If you use closed loop, it's def. not worth it.

4) Depending on your wideband it will show stoich at 14.6 or 8 or whatever. That is still stoich for the fuel in your tank, it is just displaying AFR based on its own preset. So stoich in your tank might be 14.1 and it displays 14.6.....you can just say, ok 14.6 means 14.1 in your head or you can scale it like you asked about....

the best way i found to figure out what your wideband thinks is stoich is to create an AFR AVG Histogram. Log only AFR output from your wideband into a single histo. cell (so no RPM range) over steady throttle over maybe 5 minutes. Don't go into PE or decel (DFCO) so it doesn't skew. Just keep it steady. See what it says.
As an example, mine said 15....!! or maybe like 14.9. So you take 14.2/14.9=.95. Go into your User Defined Section and with the formula provided with your wideband (maybe something like .625 + 10)...multiply the 10 by .95 and get 9.5 and put that in place of 10. leave .625 alone. i was changing it for a long time and it wouldn't scale right. only change the 10.

Now it should avg to 14.2 in your histograms.

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Thanks Higgs, I will try that.
Two more questions: How can this be changed to lambda?
and What consequences are there when you change the stioch in the pcm?

This is my reason for looking into the CCT Bias table.
Ever since the cam and heads when the original tuner tuned the car I have had trouble. One problem was the car would'nt run right with the extreme seasonal swings in temperature. Another problem was the car was on "cruise control" at 30mph and below. I brought the car back and asked him to fix it a second time and he said he could do nothing more. At this point I knew I got ripped off by this tuner at this Corvette shop in town. Not knowing anything about modern car tuning I still asked him what adjustments he made and what do you need to do this? He said with tuning software he cut the Throttle Cracker Table in half and he can't go any further with it. I said "What the hell is a Throttle Cracker Table?

After learning about HPT's forum I started doing some investigating on there. After finally buying the software and playing around I found he did indeed half the Cracker table. Also my RAF"s were in the 11's at running temp! And I just have a little baby cam! I fixed the cruise control thing. But I'm just now finding that the CCT Bias table could be the answer to my seasonal temp. swing issue so I would like to continue to pursue this for a bit. So yes I'm back at messing with VE and MAF again. This summer my 2nd LC1 and 3rd sensor crapped out again so I bought the NGK AFX. Now i'm starting all over again!

When your NGK afx reads 14.57 it is Lambda = 1 or 14.68 stoich AFR. If you want your custom PID to display 14.68 as stoich you need to use this formula ([PID.2811]/.7095)+9.102 I use PID.2811 for logging through EGR but you can edit that part. Keep in mind afx will display 14.57 while your scanner should display 14.68.

try this config. its what i use with my ngk. and remember save it in configs then open it. it's set up for e10 in lambda. histogram 8 is afr error. you can just copy and then paste special into your ve provided the data is sane.

Thank you N383 and robbyredneck. Good info. here. I hope others see this thread and find it helpfull as well.

I've got my AFX tucked away with velcro into a place where I can't see it. It's not important to me to read what AFR it displays anyway. It's the data thats collected logging with HPT that's important.

robby, I couldn't open your config. I've got to upload the new beta software first. I might try to do that tonight if I get a chance, thanks!

For now I've been logging AFR only and using that info to make baby step adjustments into each cell by hand. What a pain but when getting close before I ended up doing just that anyway. The car likes no more than 14.20 in this warm weather we are having. 90* again today. 14.28+ any I can really feel the car running worse.

A few days ago I received and installed an IAT breakout harness and sensor from Caspers. For now I placed the sensor in the front facia just above the large screened opening. Wow, no more heatsoak problems anymore. Got to find a permanent waterproof location even though this car has yet to be driven in the rain. I was actually thinking of bringing the sensor into the cars cabin. Then it would always be in a controled temperature range! Problems solved! :D