Okay, my car is throwing a CEL. Jason and I datalogged it at idle, the code says I'm rich.

I'm running the Vortech SFMU, 310cc innjectors, 25psi idle fp -- 60psi WOT fp @ 5psi. My LTFT was +23 or so....ouch. STFT was also a tad high. So obviously I am rich...what is the best way to tune this....

I tried leaning my SAFC at idle....and dropped it totally to -50% -- my LTFT only went down a few points to 19 or so...Currently I just put all the SAFC setting to %0 and am just driving with the CEL until I figure out exactly how I should go about tuning this. I cleared the CEL with the datalogger, but it came on as soon as I drove home and I didn't even boost...

For tuning, I'm guessing I should go for a drive with the datalogger and go through the rpm ranges making lean adjustments with the SAFC until proper fuel trims are in effect. Is that right, or is there another way...I hope to get this straightened out this weekend, and I will have a passenger (Jason) to help with the datalogging...but is this the way to go as far as tuning the fuel system to rid of this 'rich' state...

If your trims are in the positive numbers, then that means your are too lean, but maybe you mean its -23% ?? Lower your full idle fuel pressure to around 20 psi, as that should bring down your STFT. LTFT will most likely stay around -25% or around there, but thats ok. YOu really want to concentrate on keeping your STFT no more than about -15%. Ideally, you want you STFT to be around -5% to +5%, but with larger than stock injectors, it makes it hard. When you lower your idle pressure, be sure you have enough fuel under WOT boost. At 8 psi on my car, my fuel was arond 65 psi, so you should have plenty of room to work with.

Hmm...I don't have a whole lot of experience with datalogging, but I must be -23% not 23%, because the CEL is certainly throwing a rich code.

So lower fuel pressure in order to get proper STFT, ok.

Could I put the SAFC to good use at all in this situation? Also, just for the record, 60psi WOT fp @ 5psi is correct, right?

>>>>Lower your full idle fuel pressure to around 20 psi, as that should bring down your STFT. LTFT will most likely stay around -25% or around there, but thats ok.>>>>

Does this mean I'm getting the CEL only because of my STFT, regardless of my LTFT?

>Hmm...I don't have a whole lot of experience with
>datalogging, but I must be -23% not 23%, because the CEL is
>certainly throwing a rich code.


Yes, that is usually it.
>
>So lower fuel pressure in order to get proper STFT, ok.

Yes, lowering your fuel will feed the engine slighlty less gas to lean it out a bit.
>
>Could I put the SAFC to good use at all in this situation?
>Also, just for the record, 60psi WOT fp @ 5psi is correct,
>right?

You prob could use the SAFC to help out, but I dont use one, and i get good STFT with about 20-22 psi fuel at idle. 60 psi of fuel at 5 psi boost will be rich. 50-55 psi will prob be more accurate for your fuel pressure at 5 psi boost. I'd say 55 is a good medium.
>
>>>>>Lower your full idle fuel pressure to around 20 psi, as
>that should bring down your STFT. LTFT will most likely stay
>around -25% or around there, but thats ok.>>>>
>
>Does this mean I'm getting the CEL only because of my STFT,
>regardless of my LTFT?

The ONLY time you will get a too rich CEL, is when BOTH your STFT and LTFT are maxed out at -25%. If your long term fuel trim is at -25%(it prob will be, mine usually was or close to that), and then if your STFT stays at -25% for a certain length of time, it trips the CEL too rich code. Thats why you need to lower your STFT as close to 0 as you can, to give the ECU its fuel adjustability range back to stock.

Thanks for the quick response, you're the man.

p.s. Id give you positive feedback...but I already have previously..heh

I already told you to lower your fuel pressure to 20. :wary :P

I know, I just wanted the facts as far as why the car throws the CEL in the first place - I now know that it's because it sees -25 from both STFT and LTFT. Also, we leaned with the SAFC to -50%....and that just didn't seem right.. Hopefully this weekend maybe we can get it tuned right...without your datalogger I can't tell what my STFT even is at lower fuel pressures.

Also, I did set it at 20psi yesterday, but the car has trouble starting, and dies on me sometime's if I am slowly accelerating. SO I raised it to 30psi and I figure I'll just deal with it sometime soon, won't hurt to run rich for a few days.

>I know, I just wanted the facts as far as why the car throws
>the CEL in the first place - I now know that it's because it
>sees -25 from both STFT and LTFT. Also, we leaned with the
>SAFC to -50%....and that just didn't seem right.. Hopefully
>this weekend maybe we can get it tuned right...without your
>datalogger I can't tell what my STFT even is at lower fuel
>pressures.
>
>Also, I did set it at 20psi yesterday, but the car has trouble
>starting, and dies on me sometime's if I am slowly
>accelerating. SO I raised it to 30psi and I figure I'll just
>deal with it sometime soon, won't hurt to run rich for a few
>days.


Really? Man i know when i was replaced some disks in my SFMU and on first start up my pressure was like 10 psi. The car started, but ran like crap, but it ran. How, well i dont know hehe. The car *should run ok with 20 psi, so not too sure there. I know some brands of injectors dont like low fuel pressures. I run the Accel's FYI. Also, some more info on fuel trims:
Just because you have negative percentage fuel trims, doenst mean that you are actually running rich(more fuel actually getting into the engine). For example, lets say your STFT is at -20%. Basically this says that the ECU is trimming your injector duty cycly by 20% to keep the engine using the stock amount of fuel(stock fuel map). So even if its in the negatives, your engine still uses the stock programmed fuel map and fuel. Only when you peg the STFT to -25%, then that means that the ECU has no more abilitly or "headroom" left to trim fuel back, which then means you are indeed injecting more fuel into the motor. The idea to try and keep your STFT as close to 0 as you can, is to give the ECU its ability to quickly, and instantly adjust for fuel at any given moment in time. If for some reason the ECU has to go from leaning out a lot (like -25%), then has a sudden demand for more fuel (like going to +15%), then it may not be able to do that quickly enough, as it takes more time to go from -25% to a positve fuel trim #. Also, by getting your STFT to 0 or close, in the long run( LTFT), your LTFT will start to decend from -25%. The more you can get the STFT to go above 0(positive numbers like +5), that will help to bring down the LTFT. But LTFT isnt as important as STFT, because instant fuel adjustability is controlled by STFT, which is very important for a turboed 420A.

It starts and runs at 20psi...just when I don't give a lot of gas, and am coming off the clutch will the rpms start to drop. Regardless, I turned it up to about 28psi and now for some reason my CEL has dissappeared.

I'm gonna datalog it soon and get it just right. Pretty much aiming to bring my STFT as close to 0 as possible, and go for a test drive tuning with the datalogger in real time along side the SAFC.