Tripintaz

ok i have been tuning my 01 Z06 vette M6 with LS1 _edit and my LM1 wideband.( on the street)
I got a great tune in it with no knock. But I noticed that in 1st and 2nd gear my AF ratio is 13:1 but when i hit 3rd gear and the AF ratio is 12.2:1. Why is this and which gear should i use as a reference for AF ratio?

Would it be safe to tune my 3rd and 4th gear to show 13:1 AF ratio regaurdless of what 1st and 2nd gear AF ratio's are? I assume since the dyno's use 4th gear most of the time to get #'s and AF ratio's I should be using those same gears to dial in the Air Fuel Ratio.

Any one have some input?
thanks

ringram

Dude, AFR ratio is affected by loads of tables. Its affected by Manifold pressure, throttle position and RPM plus other stuff like spark, engine and intake temps etc. So unless you can tell us these things are fixed (not likely) and your afr still differs in different gears then I think you probably need to do some searching and reading.

There are a few good tutorials about which will talk you though the process of tuning. Id start on one of them and work your way through. I think that will answer all of your questions.

Sorry if I sound heavy, but I think you need to get the basics sorted first.

SSpdDmon

iTrader: (10)

Sounds like COT (cat over-temp) protection to me. It will dump in more fuel to keep the cats cooler during high load scenarios (aka WOT). If anything, the car should lean out as the load increases in the higher gears. Tune in your 1:1 if you can (4th gear).....that's why people like dynos - especially mustang dynos.

dynocar

I'm surprised that today's PCM technology does not take which gear is being used as a modifier for fuel and spark. As the combustion process encounters more difficulty accelerating the piston do to increased loads, such as caused by selecting different gears, timing and fuel requirements change. When I observed this decades ago on engine and manual load controlled chassis dynos, I realized that when we ordered our new chassis dyno for tuning, it had to be able to simulate actual engine loads. Part of our tuning proceedure is applying an extra load and testing in case the customer decides to take, as an example, a 5th or 6th gear WOT long sustained pull down the interstate, especially important on boost applications.

muncie21

iTrader: (14)

At good place to start is to log your 'Commanded AFR' versus you LM-1 'Actual AFR'. Once commanded=actual it's a simply matter of changing what is commanded.

Tripintaz

yup I noticed last night after I posted this thread that somehow I still had COT enabled. I loaded an older tune to edit and forgot i didnt turn off COT yet with that tune and I had uploaded it to my PCM.

It wasnt having this problem be4 yesterday when i changed the tune. Thats when it dawned on me that I had read about CAT overtemp be4 and I double checked my tune....sure enough! OOPS.


lol as far as me getting back to the basics..........
MAP,Timing,TPS,MAF - all the same in all gears, none are out of the ordinary for my setup.

Im an advanced LS1/LT1 edit tuner, Ive been at this for a while and was just looking for some IDEAS from you guys. IF I wouldnt have been so sure I had COT off already I would have never made this thread But I had a few tunes post header install and COT wasnt disabled until the 2nd tune after the headers. I forgot that and used the 1st tune to edit the PE tables totally overlooking the fact COT was still enabled in that tune.

Thanks for the help guys

brad8266

iTrader: (23)

brad8266

iTrader: (23)

If you tune 3rd or 4th to 13.1 that means 1st and second will be leaner than that. I would not do that, but then again i spray so i dont want to be lean at all. I personally would tune my leanest gear to target AFR or slightly leaner so that the richer gears will be a bit richer than target AFR. I would rather be slightly rich than lean.

RedHardSupra

iTrader: (1)

you have to realize (or better yet graph) that effective AFR barely ever is on the target AFR. think about it: you have air to measure ( a task hard enough by itself) and then proportion fuel delivery to it. all the usual errors in airflow measurement are gonna be only amplified by fuel delivery errors. ie: you have 5% error in airflow, and 5% off in fuel, that's 1.05/0.95=1.102 or 10% error in the final AFR!

10% will make a target 13.0 go to 14.3AFR!

errors like that happen all the time. that's why you want your air and fuel filters clean, maf without gunk on it, fuel pump that can hold steady and fuel injectors that spray what they were intended to. errors pile up quickly.

i have some logs from a very well done track car, and the target AFR is all over 12.x range. i did some stats on all the WOT cells and while the average is right around 12.4 as intended, the standard deviation of AFR is 0.57. that means most AFR is stuck between 13.07 and 11.83 that's quite a spread from a car with flow matched injectors. so i wouldn't sweat it. we are working with explosions afterall, this isn't a precise science.

ZL1Killa

iTrader: (17)

its called cat protect. there should be an area in your tuning software to enable or disable it or set higher temps. my car on the dyno went rich like that once it got a steady load(Above 2nd gear) and we were wondering why, well it was the cat protect

Tripintaz

its already fixed LOL


it was CAT overtemp casuing the issue...i forgot to delete it out of the new tune.......I fixed it last night

ZL1Killa

iTrader: (17)

yeh its one of those stupid cat things....

dynocar

As a general rule, I do not care if my 1st, 2nd gear go a little lean because the engine is not under as much mechanical load as the higher sustained, loaded gears and it will usually perform better. 1st and 2nd can also use more ign advance, many of us old school carb/distr drag racers used to advance like hell, then have a mechanism to pull some of it out in 4th gear to prevent detonation for better trap times. Someday I would like to experiment with setting up different fuel/ign maps to optimise each gear.

SSpdDmon

iTrader: (10)

Backwards??? I thought it leans out in the higher gears because of the greater load???

oange ss

iTrader: (50)

less of a load on the engine to keep the car moving than to move it initally

dynocar

Some combos go leaner, some go richer. Note, I stated "if it goes leaner".

dynocar

Yes, the higher the gear used the more the mechanical load on the engine. One way we know if an engine is mechanically loaded more or less is the engine's ability to accelerate. Its rate of acceleration is greater in 1st then in 4th meaning less load in 1st. In 1st gear the piston can be pushed down easier then in 4th because of the transmission's torque multiplication to the axle, or restated as torque division as seen by the engine. Granted, there may be some applications where the engine is briefly loaded very heavily at launch in serious drag cars but usually it is more loaded and sustained longer in the highest gear and a given sustained load is much more dangerous to an engine then a brief one. Again, there can be exceptions to the rule such as severely shock loading an engine.