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What is the best A/F ratio for best power. Thanks guys
Lambda @ .85 to .87 at WOT. Today's premium fuels are ~E10 so the old 12.8 to 13.0 A/F numbers do not do much good. Tune for lambda and you make life much easier.
Lambda @ .85 to .87 at WOT. Today's premium fuels are ~E10 so the old 12.8 to 13.0 A/F numbers do not do much good. Tune for lambda and you make life much easier.
Thank very much guys. Yes i am using a dyno and wide band o2 sensor. Which brings another question to mind , which ex. pipe do you put it in , left or right. In other word what side might be the lean one. Thanks again
These new DI engines have a much leaner AFR than ever before---even the stock tune is in the 13's below 4000
Also---the Stoich AFR at P/T has always been 14.68 in the past---However on the LT1--it is now a richer 14.1 !!!! so confusing------
From what I've learned--- The new E92 computer changes the timing and AFR in PE completely by what's been "asked for in TQ" via the TQ response tables--If you ask for more power the ECM will try to achieve it by changing the AFR and timing---
It's not un common to see 30* actual timing in a data log even though in your tune you've only asked for 22 * same goes for the AFR---above 4000 the AFR in the stock tune is 12.40---however on a wideband the AFR can show a 12.9 AFR----
So the E92 ECM makes adjustments to power based on the TQ response table--it's the only reasonable conclusion
I have tuned and dyno's about a dozen C7's----and although I did by habit change the fuel slightly and the timing---the ECM still is in control of the actual #'s regardless
Seems 6 of one, half dozen of the other to me? But, I'm old and senility is gaining...
Elmer
this is the problem.....your conversion numbers are good for ethanol free fuel only. E10 stoich (1.0) is 14.1, not 14.7.....C12 vp race fuel is 15. E85 is 9.7......
this is the problem.....your conversion numbers are good for ethanol free fuel only. E10 stoich (1.0) is 14.1, not 14.7.....C12 vp race fuel is 15. E85 is 9.7......
lambda 1.0 is always lambda 1.0
That makes sense. I told you I was old! Why the hell pollute gasoline with ethanol! Idiots!
Lambda for gas 1.0 or 14.68----AFR
The C7 is NOT a flex fuel car it runs on gas which should be 14.68---
What I'm saying is that ONLY on the Corvette the closed loop AFR is now richer than lambda--at 14.10------A Silverado that has basically the same DI engine the AFR is still 14.68---Why would a DI engine using gas be different on a trk than on a C7?If anything you would think a truck that tows or carries a load would have a richer AFR
Lambda for gas 1.0 or 14.68----AFR
The C7 is NOT a flex fuel car it runs on gas which should be 14.68---
What I'm saying is that ONLY on the Corvette the closed loop AFR is now richer than lambda--at 14.10------A Silverado that has basically the same DI engine the AFR is still 14.68---Why would a DI engine using gas be different on a trk than on a C7?If anything you would think a truck that tows or carries a load would have a richer AFR
wrong again.
and yes, I personally own a 2015 silverado and a 2014 C7.
the truck doesn't "run at 14.68." O2 sensors switch at stoich for whatever is in the tank....if it's E10 they switch at lambda 1.0 which is 14.1.
seriously stop giving advice, you are always wrong.
and at least do some research before you reply with even more wrong info in an emotionally distraught tone.
This is the stoich table for a 2014 Flex Fuel truck with direct injection (and it is the same for any flex fuel vehicle no matter DI or port):
This is the stoich table from the C7, which is not a flex fuel vehicle:
The stoich table only gives reference for fuel trims and contributes to calculating PE AFR. When you are running closed loop you want this to match the fuel in your tank so you can see accurate fuel trims. This does not mean the oxygen sensors switch at whatever is in this table, it means the fuel trims will be bigger or smaller if it doesn't match stoich for whats in the tank.
Clearly, the flex fuel table is variable based on alcohol composition....If you run E0 or E85, the alcohol sensor will reference the appropriate cell and keep fuel trims low, but also reference the other alcohol tables in the tune and adjust spark, fuel, etc accordingly.
The point is the silverado is NOT "still at 14.68." The O2 sensors always switch (try to maintain) lambda 1.0 and lambda 1.0 is always accurate....lambda 1.0 is NOT 14.68 unless you have pure ethanol free fuel in your tank, which I am willing to bet 99.9% of us do not. There are only a few pumps in the state of Texas that offer it and they are all in rural areas. E10 is what is out there and that is why, not only the DI C7, but all new OS's from GM (that are not flex fuel) reflect 14.108 as the stoich value in the tune. If they still used 14.68 then it would only trim 4% to achieve 14.108.
Last edited by Higgs Boson; Dec 23, 2014 at 08:14 AM.
Reason: typo
Perhaps a "recall" on the cars he has tuned would be in order.
A Silverado that is a NON flex fuel car has a closed loop AFR of 14.68
A Silverado that has a flex fuel sensor can adjust the AFR to the 10% ethanol content that most gas is these days---At 10% the AFR is 14.10
I'm looking at 2 2014 tune files on both a flex fuel truck and a non flex fuel truck as we speak- They both read 14.68 at 0% ethanol
A non flex fuel truck CANNOT adjust the AFR to 14.10
A C7 is entirely different----It is NON flex sensor equipped--however the stock tune shows a closed loop AFR of 14.10 regardless of ethanol content--
I can't take the amount of stupid you post. There is not another user on on this forum that confidently posts such complete and utterly WRONG information so often.
This has absolutely nothing to do with a flex fuel sensor or flex fuel capabilities.
I'm looking at a 2015 C7 stock tune and it has the stoich AFR set to 14.1. Straight from GM. Not 14.7
NO oxygen sensor, narrowband or wideband, has ANY idea what AFR they're seeing. They read lambda. Lambda only. Nothing else. Only lambda. The narrowband O2's, while in closed loop, ALWAYS drive fueling towards lambda = 1. It doesn't matter whether stoich is 14.7, 14.1 or 9:1. All they know is lambda.
Stoich AFR values in the tune are used for BASE fuel calculations. It says hey, there is x amount of air going in. x / stoich = how much fuel you should need to get to stoich. This is a starting point. Based on oxygen sensor feedback, fuel is then added or subtracted from that base fueling calculation to make the NB O2 sensors cycle between leaner and richer than LAMBDA=1. What are these corrections called you might ask? FUEL TRIMS! Changing the stoich values changes the base fueling calculations but FUEL TRIMS will correct it back to +/- stoich regardless while in closed loop.
They don't give a rats *** what stoich value fuel you're using or what stoich value the tune has.
I think I just need to block you. You're the only person on here that makes my blood pressure go through the roof. Even with posts that are a year old.
