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The FAST is a piece of **** in terms of build quality.
But the LSX92 is even crappier compared to a 102. And the 102 is weak compared to the LSXRT. Which is different than the regular 102 that Darth walked with the MSD. The LSXRT has bigger, straighter runners than the MSD. And like twice the plenum. I'd run it if I could fit it. But if I'm hacking up my car, I'm running a CID 4500 EFI intake.
But the point is, the OP has a FAST. To get it to work, you need to run LS2 rails and LS2 injectors or LS3 injectors with billet top hats and 14mm O-Rings. Then it'll be fine. The fat LS1 style injectors don't work well.
I'd like to see that TPIS add more to my ported FASt 102. Car is an 03C5Z with the stock cam and heads. I'm willing to bet most of the idle problems are from the TB itself.
Well I had my fast lsxrt ported by tony Mano , I think he did a good job .. used the 102mm fast tb noticed it has the classic small iac passage so I bought a 92mm NW . It's a much better tb with a bigger iac port .. with all that this lsxrt is crap , 2 great tuners actually from this site have not been able to tune it .. it's a just a headache.. i guess it's a good intake if all your thinking is wot power but as far as idle it sucks .. so guess what I'm doing? I just bought a stock truck intake with a stock tb to avoid this headache.. I'll cut my losses on the most expensive crappy intake I've have ever bought.. mind you I had a cheap China intake before this one.
I've daily driven my LSXrT intake for a few years now. I'm not sure what all the fuss is about? The FAST 102mm TB is a piece of garbage. I had to attack the IAC passage with a die-grinder to get enough idle airflow. And the tune for IAC, RAF, cracker, throttle follower and what-not are all way off stock. SD tune was a snap. MAF tune is a pain for some reason. Easy to get into surge in off-idle low speed transitions.
Pretty much spot on. Your idle prop, int, and derive tables are almost a complete do over. Especially SD.
But in my case, the MSD walked the LSXR. It could have something to do with the cam. I still think there comes a point when the cam IVC gets late enough that the shorter runners are better match for the cam and vice versa.
You guys are specifically saying DBC. How about DRW? We just starting tuning my LSXRT with a Nick Williams 102 DBW TB. Definitely some idle issues starting from the base tune.
You guys are specifically saying DBC. How about DRW? We just starting tuning my LSXRT with a Nick Williams 102 DBW TB. Definitely some idle issues starting from the base tune.
You really have to look at the whole combo. Like on mine, leaving the maf in stabilized it. But taking it out made a difference in throttle response. The cam can ether fight with or work with the intake. I believe there is a point in cam size where the shorter runners work better with the cam. I can't prove that, but I could feel it and see it in my torque curve.
The stock f body tune tables are basically mirrors for overspeed and underspeed. Later vehicles, they aren't. I've seen in the later ones a trend from the factory to have more underspeed corrective air than overspeed corrective air. I found on mine this would help the car just settle gently to idle and really helped keep it from dipping. So when I encounter persistent idle instability, I go to the proportional idle tables and go 1.5x the underspeed and 0.5x the overspeed. When doing this method I've also usually found that I need a lot of follower air but zero cracker air. I don't disable the cracker. I just put zeros in the table. I don't make that last change unless the idle hangs really bad and then disabling cracker leads to surging.
Anyway, bottom line is that sometimes you gotta get a bit creative. And I gain a lot of good info from newer factory tunes. Those basically are the lessons GM learned from their mistakes. Conventional wisdom is to leave idle tables stock, and I agree in principle. But consider GM learned what's in the stock 4th gen ECU isn't optimal before considering that a. hard rule
We've started with a stock LQ4 tune (truck pcm) and its giving us fits. Engine starts immediately but doesn't want to idle long. Doesnt want to take throttle inputs. We're hitting target idle rpm (some surging) and everything looks pretty close but it seems to always start pulling timing (i think when it flips from the start-up map to the idle map) and the lambda starts from 0.8/0.9-ish and ends up pegged at 1.2. My tuner is a race guy so he is a very competent tuner but more fluent in the bosch controllers and I am new at this myself. With so many different parameters in these controls it feels like we are chasing our tails.
(Its a 403 ci, decent cam (236/238 112 - .627/.603), that big intake, nick williams 102 dbw tb and a set of 42 lb injectors.)
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