Fast 90 Install. Looking for a review.

[97SilverC5]

Guys,
I had my tune nailed down, then I installed a fast 90/90 w/ a 85mm maf. I've been working to get my idle nailed down and its close, but I would like someone elses opinion on it. It dips pretty hard when I come off the gas and is slow to stabilize as compared to my ls6 mani and stock tb.

I got a 97 vette. The motor is a 402 with ported ls1 heads, fast90/90, a 248/254/.612/.612/113lsa, and all other supporting mods.

Attached is my tune, the maf table has been modfied based on the log I am attaching so the A/F is pretty close now. TIA

[97SilverC5]

Anyone?

[Lankness]

I'll look a closer when I get home tomorrow - I had a lot of the same issues with mine (similar setup).

After a quick look...any reason why your IFR doesn't slope up? I am assuming that you have ~42lb/hr injectors from the first entry... Also, your base running airflow looks way too high - might want to run an idle config setup and track that along with your idle air trim.

[97SilverC5]

My IFR is static because I have a 97. It has a vac referenced FPR. Everytime I run the Base Running Airflow .cfg my numbers go up in the 22 range, but when I put those in the tune I get alot of surging.

Thanks

[Lankness]

Bah - it would help to pay attention to your user name and the year rather than just looking at the tables

I can tell you with my 402 with a FAST 90/90, similar cam, etc... the RAF is less than half of what you have. I had a ton of problems with dips and dying when coming back down to idle, surging, etc. before I took the RAF down to where it is now. Just changing that didn't solve everything as it causes you to have to readjust the fueling, but once I dialed everything back in the drive-ability was leaps and bounds better.

Granted, you are saying that your RAF is going UP when you test it? Are you checking with it completely cold up to operating temp, not touching any throttle? How is your IAC acting?

[97SilverC5]

Yeah im running it from dead cold up to operating temp. My IAC doesnt do anything cause I got a ETC car. I've got a log of it, I can post it up when I get home. Would you mind letting me see your tune? I'm kinda curious.

[Lankness]

Yea - I'll send it over when I get home tomorrow and have access to my tuning laptop.

[mike01z]

whats your fuel trims doing, for whatever reason they show blank in the scan.


Also how big of a cam?

[97SilverC5]

Im running it in open loop. The cam description is in my Sig and in the OP. I'm tuning with a wideband...they are within ~5%.

[Lankness]

Sorry about not getting this to you sooner, but here is the tune I'm running right now. Still in OLSD, haven't messed with the MAF too much yet.
Specs: 402 LS2, 244/250@114, .643/.645@110, 85mm MAF, FAST 90/90, Kook's headers, no cats, dual 3" with x-pipe, Racetronix 42lb injectors...

[97SilverC5]

I'l take a look when I get home. Did you drill your TB? Thats gonna invalidate your RAF table as it compares to mine...

[Lankness]

Nope - no drilling, no reason to.

[WS6FirebirdTA00]

How did you know how to adjust the idle airflow without logging that data?

[97SilverC5]

Because I did log the airflow...in another log that I didnt include. I've been playing with it over the last week and the car idles ok now. Still have a dipping issue when I come off the throttle though. Raf is around 19.5 when warm now. I can throw up some fresh logs later tonight or tomorrow. What other values should I look at specifically for the dipping? I know I have a huge cam and if this is as good as it gets then so be it.

[WS6FirebirdTA00]

All idle airflow values are needed for the dipping. The effective area/scalar need adjustment with the 90mm ETC body (when done correctly).

[97SilverC5]

I changed the scalar to the value mentioned here and on LS1Tech. When you say "All Idle Airflow" can you be more specific? What other than RAF should I focus on? I have a feeling i need to work on my throttle cracker, but anytime i do anything more than zero the table out the idle surges like crazy.

[WS6FirebirdTA00]

throttle cracker and follower airflow are the biggest concerns

[97SilverC5]

Thanks for the direction. So should I add to the follower airflow, or slow the decay rate? I'll do some reading. I'm sure the question has already been answered...

[WS6FirebirdTA00]

you should log it, post that up with the tune that was used, and then we can look it over to see

[97SilverC5]

I'll put a tune up tomorrow. Can someone tell me how the follower decay and timing tables apply to a 6 speed? Are the gear tables used at all? I've heard of people saying the follower is tied to the clutch switch, but they dont say which table.