WOT tunning

[CRAWLIN]

OK I hooked up my wideband to my car and did a test pass in almost 100 degree weather... I had an AFR of 13.8. I adjusted it to be at 12.9 and it read 12.9 when I checked it right after. Now later that night it showed an AFR of 12.3. So obviously the car made an adjustment for the cooler weather.

So my question is, what AFR do you shoot for when setting the AFR. If the car adjusts as needed temperature wise, how do you know where to start. What if you were dynoing your car on a 90 degree day or a 50 degree day... would you set your AFR the same? I see that N/A cars like 12.9 or so AFR... Well what about on a 90 degree day when it wants to be leaner...

Sorry if I keep repeating my self...

How would I go about setting my AFR...to make it ok for all outside temps...?

[MeentSS02]

If you are running an SD tune, read this thread:

http://www.hptuners.com/forum/showthread.php?t=6345

Especially when it starts talking about changing the complex cylinder charge bias (only applicable for 2001-2002 PCMs though). This is a common problem in SD that the MAF has an easier time compensating for. The PCM is only as good as its calibration and algorithms...and when you are estimating the airflow coming into an engine and into each cylinder (VERY complex math)...well, it can only do so much.

[Tim05GTO]

OK I hooked up my wideband to my car and did a test pass in almost 100 degree weather... I had an AFR of 13.8. I adjusted it to be at 12.9 and it read 12.9 when I checked it right after. Now later that night it showed an AFR of 12.3. So obviously the car made an adjustment for the cooler weather.

So my question is, what AFR do you shoot for when setting the AFR. If the car adjusts as needed temperature wise, how do you know where to start. What if you were dynoing your car on a 90 degree day or a 50 degree day... would you set your AFR the same? I see that N/A cars like 12.9 or so AFR... Well what about on a 90 degree day when it wants to be leaner...

Sorry if I keep repeating my self...

How would I go about setting my AFR...to make it ok for all outside temps...?

Is COTs on or off?

[CRAWLIN]

its a 2001 and COT is off and I'm running a MAF sensor

[S2H]

yeah...try changing your cylinder bais to 1.0 across the board
...
then you need to retune your VE and MAF tables...
you should see a lot less problems and way more accurate from temp to temp...
I also use spark to help out slightly with AFR issues at high temperature(like heatsoak condiions)

take out a few degress as temp goes up and you can help correct for teh computers bad math calc built in...

adn it works in everything 2001+ ....Its not just 2001/2002

[WS6Fury]

yeah...try changing your cylinder bais to 1.0 across the board
...
then you need to retune your VE and MAF tables...
you should see a lot less problems and way more accurate from temp to temp...
I also use spark to help out slightly with AFR issues at high temperature(like heatsoak condiions)

take out a few degress as temp goes up and you can help correct for teh computers bad math calc built in...

adn it works in everything 2001+ ....Its not just 2001/2002

Where would one compensate via spark as the temp goes up in the editor program? I seem to have this issue I think at higher idle temps (traffic) and hit the gas and I hit knock retard...

[S2H]

yes..I like to reduce teh spark some as temps go up..I do it gebnerically..not just in upper load cells..but in all cells for higher temperatures...seems to help where the airmass calculation and changing the bias starts to let off a little up top from about 130*ish on up

[CRAWLIN]

I dont know if I am missing something here, but I guess my question is, do you set your AFR the same no matter what the temp is outside? On a dyno, do you shoot for a 12.9 AFR weither its 100 degrees outside as well as a 50 degree day?


Maybe I didnt explain it right... I checked my AFR on a close to 100 degree day and it was 13.8, so I adjusted it to be at 12.9 with tuners. When I checked it again it was at 12.9 as I commanded with the 100 degree weather. Now... later on that night I checked it again with cooler weather and the AFR was now at 12.3-12.4. So the car must have adjusted it self for the cooler weather. Colder air = richer - Hotter air = leaner. The car made the adjustment fuel wise for the difference in air temp.

So if the car is going to adjust for the difference in air temp, how do you know what to shoot for that day depending on the weather. Obviously when I commanded 12.9 on the 100 degree day, it took it and didnt adjust any leaner, but when it got cooler out, it richened itself up. What if it were to get hotter than 100 degrees out, would it have leaned itself up? I would assume so. But if 12.9 AFR was too rich for the air temp that day and a leaner AFR would have produced more power, How do shops dyno their cars in different temps and seem to always shoot for the same AFR...?

Sorry so long...

[S2H]

yes....
set it to what you want for AFR...there are a slew of other tables in your tune that are made to correct for temperature differences


and when you are done on teh dyno..go do some WOT on the street with a wideband cause it will be lean as hell if you dont tune it in real world conditions

adn I actually shoot for 12.5 at peak torque..and 12.8 at peak HP....and 12.5 again at rev limiter....

its not a flat value..its a curve

[Tim05GTO]

Soundengineer,

I'm curious why you like to go rich again towards redline. I'm not in any way shape or form saying it isn't the right thing to do. I just would like to understand why you do it. The propensity for knock is actually low near the redline areas as the VE has dropped substantially.

Tim

[S2H]

I've actually had good success with keeping more power past peak HP with richening things up slightly

[PurplePiss]

I think he does it incase the motor over revs and the fuel cut kicks in. This way there would be residual fuel when the spark is cut and it won't blow up. Just guessing.

I'm curious. On an LS1, you run 12.5 up to 4000, then ramp to 12.8 near 4800 approx, then back to 12.5 to redline? What does the timing curve look like? Anyone know if the LS2 is similar as far as shape of the fuel and spark? I have yet to get an answer on this. I'm not sure if no one wants to talk, or if no one has done an LS2 on a load dyno. I think it is curious that Tim runs near 12.8-13 AFR with only 20-23* of timing, yet your finding power at a fat 12.5 with I assume 25-28* of timing?

[S2H]

timing curve is basically opposite of fuel...
little less timing at peak TQ little more timing at peak HP

[S2H]

its all basic engine dynamics...looking for optimal cylinder pressure..
the engine obviously is at its peak cylinder pressure at the point of peak torque....in general you want to decrease spark here slightly over what you would have for everywhere else...

[CRAWLIN]

I was thinking, and you said to run the car at 12.9 AFR no matter what outside temp is... I would think it would hinder performance... and why do the carbuerator guys constantly change their "AFR" with weather change?

[S2H]

I was thinking, and you said to run the car at 12.9 AFR no matter what outside temp is... I would think it would hinder performance... and why do the carbuerator guys constantly change their "AFR" with weather change?

carb guys dont change their AFR..they change their jets to maintain teh same AFR when the temps change as they have no PCM top correct for them

[WS6Fury]

Not to complicate, or hopefully not confuse things...

When dealing with SD, would this change in AFR vs weather which hinders consistent performance from one day vs the other, and tuning the VE table, could this not be compensated for with the IAT bias change to 1??

Or is that a completely different issue from this I'm missing.

Can someone better explain?

[Tim05GTO]

I think he does it incase the motor over revs and the fuel cut kicks in. This way there would be residual fuel when the spark is cut and it won't blow up. Just guessing.

I'm curious. On an LS1, you run 12.5 up to 4000, then ramp to 12.8 near 4800 approx, then back to 12.5 to redline? What does the timing curve look like? Anyone know if the LS2 is similar as far as shape of the fuel and spark? I have yet to get an answer on this. I'm not sure if no one wants to talk, or if no one has done an LS2 on a load dyno. I think it is curious that Tim runs near 12.8-13 AFR with only 20-23* of timing, yet your finding power at a fat 12.5 with I assume 25-28* of timing?

Purple, this is one area where things can't be generalized as each combination will have different characteristics. From a pure theoretical point of view I would argue that going rich again at those RPMs is only slowing the burn and that slower burn will actually need to be ignited earlier (ie. more timing). I personally would rather run a little leaner, produce more heat, and run with less timing.

If the Dynojet with load control is free Saturday I will test it out for everyone.

Tim

[PurplePiss]

Purple, this is one area where things can't be generalized as each combination will have different characteristics. From a pure theoretical point of view I would argue that going rich again at those RPMs is only slowing the burn and that slower burn will actually need to be ignited earlier (ie. more timing). I personally would rather run a little leaner, produce more heat, and run with less timing.

If the Dynojet with load control is free Saturday I will test it out for everyone.

Tim

That would be freakin awsome. I would love to see that when your done. I realize that every engine is different and altitude and temp play into it, but I have been just trying to get a general curve for timing and PE for an LS2. I have no idea if an LS2 likes 20-22*(Tim) with 12.9 or 28-29* with 12.0 AFR(Workingman). I just can't believe that stock GTO's could have that drastic of tunes.

I can tell you this, my gto compared to another stock gto I run with, the other guys runs .5 quicker and I can't figure out why. I think either mine is down a little on compression, or is ungodly rich. I guess I need to dyno tune it, but I hate to since I paid all this money for a WB and HPT. I'm rambling again...

[CRAWLIN]

OK so what you are telling me is that you would shoot for a 12.9 AFR no matter what the temperature is out side... 50* or 100*??? Thanks...