Newbie tuning questions

[crashed97tsi]

Hi

I have an AGP T-28, 450cc injectors, 190lph fuel pump, and all the other basic mods. I got a dyno done recently and it said I was running rich (9:1 fuel ratio)

The Problem I'm having(right now) is setting the low fuel trims. First off, which of the 2 fuel trims do you tune for. There will be times that the STFT says everything is fine 0%, while the LTFT says it wants 3%. Based on Kpt's site, I thought that this meant to add fuel on the SAFC. Is this correct?

I also can never get consistent results. It's always fluctuating to say -5% at one point to +5 another time at the same rpm. I followed Kpt's tuning guide, I don't have the link available right now. My question is do the results have to be rock-steady or can they fluctuate a bit? Right now I have the SAFC at -1% across the board and it seems to be taking away fuel or adding fuel in no more than 5% increments.


Ok, I also did a log with the SAFC zeroed out just to get a basis for how much my car is untuned. I didn't log o2, but My timing is not a curve at all. It's flat at usually 9 degrees up until about 5500 rpms where it jumps to about 14-16. I'm going to log o2 tonight to see if I'm rich or lean(over .92 is rich, under is lean, right?)

Well I think that's everything. If anyone has any insight I'm more than happy to listen

THanks

 

[kpt4321]

You should not use O2 voltages to see if you are rich or lean, and there CERTAINLY is not a certain "point" that seperates rich from lean. Every car will read differently, and sometimes the different years and generations of DSM's will also get diffeent readings.

Instead, try to garner this information from the fuel trims, and the knock/timing advance readings.

Also, with simplistic base tuning, AF ratio doesn't matter that much. You just want to get it lean enough by getting close to knock, but not having timing pulled.

 

[crashed97tsi]

Ok, the fuel trims I'm having trouble with. It seems to work best zeroed out across the board. I read somewhere else that the 02 sensor voltage was a base for whether your rich or lean. I started my first adjustments by that and the timing started to advance a little more. Instead of 9 or 10 across the board, it goes from 12-13 for awhile until about 5500 where it advances as high as 16 and then it finishes off at 20 at redline. I can feel the timing being advance here because the car seems to get a second pull there.

I know that every car is different and there is no definitive answer to anything, but what is a good timing to shoot for from 3000 - 5500 rpms? Is thirteen decent or should I be shooting for something else?

Thanks for the help, I'm just trying to get a feel for tuning before I get the biger injectors.

Later