Injector / AFC tuning...

[my98gsx]

I know the Answer to the question im going to ask is A- GET THE CAR TUNED, or B- get a logger and/or a Wideband. BUT... i dont have the money at this very moment to buy any of them so what I have to play with is all I can work with at this moment. I just installed a set of 650CC injectors in my 98 GSX, I have an EVOIII 16G in the car now and i know that 650's are quite large for that size turbo. I went to the track the other night to do a test and tune and i made my first pass with the AFC set at 0... WAY TOO RICH... i made a 2nd pass with the AFC set at -7% and much better, no more smoke but i think it was still running fat. Then my 3rd pass i ran it at -10% and it was even faster... now i only have a Narrow Band Autometer AF gauge that i know you cannot go off of, but stays in the far far side of rich when im getting on the car. Does anyone know where about in the negitive numbers i should be on the AFC? one guy was running my whole setup on 550's and he was at -20%.. but i dont want to risk running lean and doing damage before i get my wideband... If anyone has any ideas on where about i should set my AFC please let me know.

 

[donmagicjuan]

First of all, I wouldn't say 650s are too big for an EvoIII. I'm currently maxing out a set of 560s and will be upgrading to 650s in the near future. For the offsets, it's just a simple math equation:

650 - 0.308*650 = 450 --> taking out ~30% should get you close to the stock AFR of 9.5:1.

 

[20psi_GST]

Yea those wide-band gauges are definately very expensive. But in the long run tuning by feel is not something to do. But with your 650s your gonna have to take out alot with only a 16g. I have a 20g with 625s and mine are -20 most of the way through. But every car is completely different, setup, altitude, etc. Id try around -30 though if everything is running smooth and you dont have any boost leaks.

 

[spyderturbo007]

Uh, oh.......tuning with the butt dyno is not a good idea unless you aren't concerned about melting things.

You really need to get yourself a logger before you blow something up. Get the logger first and worry about the WBO2 later.

 

[chuckg]

I have a 2g mas, 16g at 17psi with 550s and an S-afc, and I'm at +4ish across the board and decently tuned. Going off what you guys were saying this sounds like a pretty rich setup... For whatever it's worth the air/fuel read out on my TT is 11.2-11.5 at full boost...does this sound ok?

 

[donmagicjuan]

Somewhere I remember hearing that a 2G MAS will run lean when used in a 1G. Don't treat it as gospel, but that might be the reason. Someone else who's done the same mod (I'm sure there are many) can chime in if I'm wrong. If you're seeing the correct AFRs, though, I wouldn't sweat it.

EDIT: Out of curiosity I just confirmed this. Check out the first paragraph on this page. http://www.vfaq.com/mods/2GMAF-1G.html

If you install 550s at the same time as the 2G MAF, very little tuning should be necessary on the AFC to have the car running as strong as ever, without the MAF overrun problems.

 

[spyderturbo007]

Yep, the 2g MAS in a 1g "pretty much" compensates for 550cc injectors. Normally they require a little adjustment with a SAFC for optimal functionality.