testing/changing air/fuel mixture???

[ravenp]

Hey guys.. I am looking for some advanced tuning advice/help as I think i've eliminated most of the general things.

I took my car to the dyno yesterday and my results were fair. Max power=163hp and Max torque=196. For a CAI and muffler, that's pretty good right?

What concerns me is the curve. It's not very flat, which indicates my air/fuel mixture isn't bang on does it not?

Here's the dyno. http://members.rogers.com/kwf/craig_dyno.jpg

How do I test it? How do I adjust it? I know I could take it to the shop and pray they get it right, but i'd rather put my faith in you guys...the ones that work on MY car [img]smile.gif[/img]

Lately I have noticed some difficulty starting the car, a little sluggish, with occasional surges in the idle.

Thanks...

[ravenp]

anybody??? please? [img]smile.gif[/img]

[John_D.]

<blockquote>quote:</font><hr>Originally posted by ravenp:
What concerns me is the curve. It's not very flat, which indicates my air/fuel mixture isn't bang on does it not?

How do I test it? How do I adjust it?

Lately I have noticed some difficulty starting the car, a little sluggish, with occasional surges in the idle.<hr></blockquote>

The torque curve is driven by a lot of things. Intake, exhaust, cam, timing, compression ratio, etc., etc... It's pretty normal for it to start dropping off on the high end, and it always crosses the hp curve at 5500 rpms. I don't know if the curve you have is typical or not though.

If you want to monitor the a/f ratio, you need either a gauge to tie to an o2 sensor, or use something like autotap or obdii to tie into the port under the dash. I use an autotap.

To adjust the a/f ratio, at wot only, you can use a MAFT or MAFT+ to tweak the air flow being reported to the pcm, which will cause the pcm to flow more or less fuel, depending on which way you tweak the air flow reading. I use the MAFT to set mine to run 2% lean when running na, and 14% rich when spraying.

The pcm will manage the a/f ratio at part-throttle, no matter what tweaks you make. (unless you change injectors or something else to such a degree that the pcm can no longer compensate).

The sluggishness and other symptoms at less than wot point to some other problem. Check the obvious things - vacuum lines, plug wires, sensor wiring. Could be anything.

Some ideas (and likelihood that this is the problem):
plugged fuel filter (low),
plugged air filter (low),
bad plugs (med),
bad wires (low),
tps sensor(low),
maf sensor (med),
weak coils (med),
egr sticking open (high)

Unless you have an SES light, there are probably no codes to pull. If there are any, this would point you in the right direction.

[DEE97GTP]

You need to get an autotap. You cannot guess on these computer equipped cars and certainly cannot do any useful tuning without it.

DEE

[ravenp]

Well, I appreciate the responses. I realize that most of this is above my head right now. Until I get Autotap, I was hoping to at least have some things I could point at if I take it in for diagnostics.

I don't want to be completely ignorant so they can spend days on it instead of hours if I can narrow it down.

Thanks again.