Emergency AFC tuning, 2g gsx

[Alphahookups]

My girlfriend bought a 97 gsx that was modded but had stock injectors and the afc set to zero so that it would pass smog. We recently reinstalled the 660's and I was in the process of tuning it when the egt probe broke. I bought a replacement probe from TRE but it hasnt got here yet and the car is running like shit. It is running rich to be on the safe side, but my girlfriend says it bogs hard when she trys to accelerate, and then it finally gets going. I think the basemaps are set to somewhere around -20 across the board for low throttle and -45 across the board at high throttle. I know these probably seem strange, but I am new to DSM's and I had a buddy help. Now that I think about it, it seems like the low throttle should be leaner and the high throttle should be richer.

In either case I need a little help setting some "safe" settings.

The setup is
Greddy FMIC
3" Turbo back
Frank2 turbo
660's

Thanks a lot guys.

Alpha

 

[ROOKIE1]

I understand the frustration here . Every car is different , so at best you will get some guesses . Do you have a logger ? Here is a link ..http://roadraceengineering.com/newafcsetting.htm . There is also writeups on site for this .

 

[Alphahookups]

We just have the egt gauge, but it broke so we have nothing until wednesday.

What do the positive numbers mean, ie +35.

 

[ROOKIE1]

http://dsmtuners.com/forums/showthread.php?t=58403 , read also . I would " guess " . New to tuning also . But you have larger than stock injectors . They already give more fuel , so you would not add more ,ie.. + . I would have to say from what I have read that you need to take out fuel , - . Also read the upgrade path on main page .

 

[CanadianTSi]

-45 for the high settings is WAY LEAN. Set it to -25 to be safe.

Also the lows are pretty tricky and you probably need a logger but you can try -10 until like 2k and then -15 and -20 around 5k.

 

[Alphahookups]

So I leaned it out a bit for the low end and riched up at the top end. I drove it and it feels ok and Im not sure WTF my gf is talking about, but she is going to drive it to work tommorow. I told her to keep taking it easy, but it feels decent to me.

I changed my settings from

1k 2k 3k 4k 5k 6k 7k

Low
-20 -20 -20 -20 -20 -20 -20

High
-40 -45 -45 -45 -45 -45 -45

to

1k 2k 3k 4k 5k 6k 7k

Low
-25 -25 -25 -25 -25 -25 -25

High
-30 -25 -25 -25 -25 -25 -25

 

[Rice Over Wheat]

-45 for the high settings is WAY LEAN. Set it to -25 to be safe.

Also the lows are pretty tricky and you probably need a logger but you can try -10 until like 2k and then -15 and -20 around 5k.

Yeah I was going to say the same thing. Dayyyyum! -45 is good for 780s!!

 

[gsx4g64]

I think that the other members are right. I would however check the spark plugs. They can tell you alot about what the car is doing. If the plugs are black, you rich. If they are gray or look burned, you are lean. You would like to have something in the middle. Keep in mihd that it is not the easiest thing to do (tuning) your car on a afc.

I would suggest getting a good fuel pressure regulator. This will assist with controling fuel. Remember that a afc is a glorified bandaid.

you car drive the car around and tune the car. Have your girlfriend drive the car, while you change the settings. You have to do some WOT pulls to see where the breaks up (stumbles). You may need to buy some extra spark plugs also. Once those get messed up, the car will run bad until you change them.

I hope tat helps you. Let me know how it turns out.

 

[Alphahookups]

Thanks guys. I did some calculations and the way I see it is the 660's are roughly a third larger then the 450's so if I cut 30% of fuel across the board, it should be like stock injectors. I then richened it up a little more since the turbo is flowing more air then stock.

Does that sound correct to you guys?

 

[Rice Over Wheat]

That's about right. Canadian's recommendation of -25% is a bit richer than your baseline of -30.78 and is a good place to start without tuning.

But you should look at it with a logger or wideband to be safe. For example, my car is a bit retarded and I get lots of pulled timing any leaner than -23% or so on 650s. I'm still trying to determine why.

 

[spyderturbo007]

Hang on.......Back up the truck

I would let the car sit until you have a logger and a boost gauge. Tuning blind is the easiest way to melt things. As Tyler stated, if you have to drive the car, go with something really rich like -20% or so. But since you are new to tuning, I would let it sit until you have the appropriate tools, time and knowledge to get it running right.

You could always slap in the 450's until you get your logger.

 

[Alphahookups]

So correct me if I'm wrong(which I probably am ), but wouldnt setting the AFC to ~31% across the board be the same as installing the 450's. I mean running 660's @ 69% is equivalent to running 450's injectors, correct?

Also, isnt it safe to drive as long as she doesn't go heavy into boost? She has been taking it easy, never really going about 5k and even when she does, its at a slower acceleration so the boost isnt built high. The egt probe comes today, so I should try getting that it.

 

[Rice Over Wheat]

I asked almost the same question a couple months ago. Larger injectors spray more volume of fuel when opened for the same amount of time. So your AFC is hiding 31% of airflow that the ecu reads in order to trick the ecu into holding the injectors open the same amount of time it would have if the 450s were still in.

So a lot of these guys here with 650s start rich at say -20% or -25% on 650s, and tune towards -31%, getting leaner as long as they can control knock/timing based on their boost level. But different factors can play in so each car is different for its ideal setting. That's why you want to start richer and work leaner. But without a logger or Link you can't do that safely, which is why others recommend you to keep it at a safe level like -25% HI.

Oh and it's never safe with a woman driving, but that's another matter entirely.

 

[JayRolla]

Oh and it's never safe with a woman driving, but that's another matter entirely.

I was going to say that.

 

[Alphahookups]

Oh and it's never safe with a woman driving, but that's another matter entirely.

Haha.

The sad part is, as it sits, her 2g gsx is faster then my 1g gsx...but the time is coming...oh its coming fast.