How do we "properly" calibrate the IAC effective area when making a change to a 90mm TB?
How do we "properly" calibrate the IAC effective area when making a change to a 90mm TB?
Maybe copy or interpolate the data from a stock tune that has a 90mm? I would think the flow rate shouldn't change too much because IAC effective area has to do with the flow of the idle air circuit at various IAC motor steps not the size of the throttle body. As long as the idle air passage is the same size it should be real close to the 78mm TB data.
2001 Camaro SS
Built 370 LQ9, Ported 243s, D-1SC 14 psi. 691 rwhp, 643 rwtq
Best time: 11.6@124 on nitto drags with a 2.1 60'
"if you're gonna build a time machine into a car, why not do it with some style." Dr. Emmett Brown
I believe all the LS2, LS3 and LS7 engines in Corvettes (2005 thru 2013) have 90mm throttle bodies. Be aware that in 2009 there was a change to the TBs that seemed to affect WOT voltage signals, however. These new ones are identified by having gold or brass colored TB plates instead of silver colored ones.
CorvetteFlorida.com
2002 Corvette Z06
427 RHS block built by LME
STS rear mounted twin turbos
It nearly died on the operating table, but I'm bringing her back.
Are there any stock vehicles that came with a cable operated 90mm TB? I couldn't find one. They all seem to be ETC (Electronic Throttle Controled) so they don't have an IAC module or passage to use as reference. I just upgraded to a 90 FAST and left IAC Effective alone. Had to tone down the Desired Air and throttle follower to get rid of some hanging idle when hot, but other than that I really didn't have to do much.
2001 Camaro SS
Built 370 LQ9, Ported 243s, D-1SC 14 psi. 691 rwhp, 643 rwtq
Best time: 11.6@124 on nitto drags with a 2.1 60'
"if you're gonna build a time machine into a car, why not do it with some style." Dr. Emmett Brown
For my 92mm NW TB - I did some reading and found I had to map Desired Airflow B4307 vs. ECT and also Desired IAC Airflow (IACDES_B) vs. ECT. If the two tables don't match during warmup you need to offset the entire IAC Effective Area table B4403 up or down, re-flash & map until they do match. It took about 3 tries but I finally got it right - ended up offsetting the table B4403 down about 5 cells. My stock tune had zeros in the top 7 cells (0 thru 12 sq.mm) and now I have zeros in the top 12 cells (0 thru 22 sq.mm). I was amazed how much better the car idled and driveabilty is a little better too. I guess the PCM works better when actual airflow = calculated airflow LOL.
IAC effective area does not change on a cable throttle body. You use the same idle air control valve on the 90mm TB that you used on the 78mm TB. It opens the same amount for the IAC counts and allows the same amount of air in no matter the size of the throttle body. What does change is that you can get more air around the throttle body blade because it's larger. It should be all about RAFIG when you are cable-driven.
Actually, after thinking about it, this makes sense. What I have thought was correct may well be incorrect. That calibration must be taking into account some air coming either around the TB blade or the factory hole in the oem TB, so a larger TB with more air coming in around the TB blade would have more idle air entering the intake, so 0 steps on the IAC would be more square mm.
How about MAF-less tunes? Any alternatives to RAFIG/RAFPN?
Last edited by Aint Skeered; May 2nd, 2018 at 11:18 AM.
2000 NBM trans am.
427 Dart ship block,Lme ported Ls7 heads 12.5 compression
246/262 .730/.712 112+4 low lash solid roller
Rmvb 4l80 with transbrake, 8" FTI converter
12 bolt Moser rear end with 4.10 gears