1990 GS-T just picked up, S-AFC messed up

[jwlonehart]

Alright, well first off i'm doing this for my buddy.

He just picked up a 1990 GS-T stock turbo, 110k miles, came with a manual boost controller, Apexi S-AFC and a turbo timer, and an aftermarket 3" exhaust AND 650cc. The rest of the car is stock. Whoever owned it before did have a bigger turbo on there, the bolts are brand new. (probably beat the piss out of it)

I just did an oil change on it, plugs, cleaned the maf sensor, and the car runs absolutely horrible.

I'm not too familiar with the AFC though which is why I am on here. I have a feeling the car running poorly is a result of the AFC because we have gotten it to run decently before, but we can never get it to run smoothly through all the RPM ranges.

He does not have a widband o2 or a logger or anything, and doesn't have the money to buy one. I would like to know if there is a way to get this car running correctly, and if there is a way just to get it to run reliably. Don't really care if it's super fast, just want it tuned so it will run ok, and so that it won't bog out at 3-4000rpms.

Here is the Apexi he has: SpeedStash.com - APEXI S-AFC Controller

All the lo-hi throttle points are set between 20-28%, but other than that i'm not too sure how to use the controller.

I have read up on how the S-AFC works and several other posts but am having a hard time understand what I should be doing without a wideband or anything just so the car will run correctly.

If I just zero everything out the car runs very very poorly, and can't even go over 2500rpm.

I'm not sure if there is too much fuel going in, or what not.

Please I would appreciate any help, THANK YOU!


Also, the S-AFC has to be set to 2 cyl. mode to read the RPM's correctly, should it be like that?

 

[kottyking]

Of course the car runs poorly withwhen you have the afc zeroed out, it has 650 injectors the stocks are 450's. Also, I can t really help you unless I see some logs. Also what did you gap the plugs to?

 

[jwlonehart]

Plugs are gapped to .030, they are NGK BPR6ES plugs.

I was reading they should have been gapped to .025 but I did not know that before hand, but I don't see that being the problem only being off by a little.

Also, i'd like to know how I am supposed to get a log.

I'm a good mechanic thats why i'm trying to figure this out and help my friend out. Under the hood is a confusing mess with these cars honestly, so i'd love to get any info I can. I'd really love to get this thing running correctly.

 

[kottyking]

Well in all honesty you would be surprised what a properly gaped plug set means to any car let alone a dsm. ALso here is a guide for "blind tuning" an AFC. Apexi Super AFC For The Eclipse/EVO

 

[jwlonehart]

The guide you gave me seems to make no sense. I was told with 650cc injectors the fuel should be in the -20/-26% range, but in this guys guide he is saying to raise the fuel to +39%. I don't get it, can someone just help me find a base for this so I can just get it running?

 

[JusMX141]

Actually, using the formula (450/650) - 1, I'm coming up with -31% to be your global correction.

You'll need to adjust that slightly, adding fuel up top and taking it away from down low to come up with the perfect tune.