Too Rich!!!

[DanBUCF]

Had the car on a dyno yesterday, and came up w/the following numbers.

322 hp / 338 Tq

On my first run, I was running right around 10.0 at WOT.

On the 2nd run, it leaned out a bit to 11.5 or so...but that is still pretty friggin rich, correct?

Here is my guess as to what is happening and PLEASE PLEASE PLEASE tell me your opinion on it.

I am thinking the SLP MAF is obviously larger than the stock MAF, and therefore allowing (a guess) about 15% more air to pass through over stock. However, I believe that my stock throttle body is the culprit in this case and is robbing the engine of that extra air. I think the computer is telling the engine to deliver "X" amount of fuel while for "Y" amount air coming through. However, only Y-15% is the actual air that is making it into the engine. I think X + (Y-15%) = Engine running too rich. Does that make sense to anybody else or am I just pulling all this out of my ass?

I think I'm going to put the stock MAF back on tomorrow and see if I notice any increase in power. Also, what is the best way to chck my A/F ratio with out spending A LOT of money for dyno tuning and all?

Thanks in advance for any help on the matter.
-Dan

[jrp]

all i had to read was SLP MAF. put the stocker back on and reset the PCM and i bet you'll be good as new. your TB is not a problem or restriction. and a wide band is the best bet to check your a/f. you can use atap/efi but there not very accurate.

[DanBUCF]

What exactly do you mean by "wide band"?

[jimmyblue]

SLP MAF should be pulled to roughly-right mass
airflow reporting. However if that little pull
resistor were missing or opened up you would
be at the natural-pig-richness of the Delphi
85mm in LS1 applications.

SLP has two versions of this MAF. I can only
presume that they differ in the cal resistor
value because I've never seen a '98-'00 model,
mine ('02) had negligible LTFT drift after putting
the SLP on (until I molested it anyway) and
the '98-'00 guys seem to get leaned out.

If you bought this MAF used it's possible you got
an early one, whacked your late-model trims,
and have excess (and variable) WOT enrichment.
Or did you specifically order the '01-'02 version
straight from SLP?

Whether this is the deal, you'd need logging to see.
This is where I'd start, with LTFT values by cell and
at WOT.

[DebianDog]

Originally posted by DanBUCF
What exactly do you mean by "wide band"?

A "wideband" is a true air/fuelratio reading. AKA and expensive O2 sensor. I have the LM-1 (http://www.innovatemotorsports.com/)

It or a sniffer at the dyno is a must to tune correctly. I had the 02's dead on at 880 but was running an A/F of 12.8

[DanBUCF]

Originally posted by jimmyblue
SLP MAF should be pulled to roughly-right mass
airflow reporting. However if that little pull
resistor were missing or opened up you would
be at the natural-pig-richness of the Delphi
85mm in LS1 applications.

SLP has two versions of this MAF. I can only
presume that they differ in the cal resistor
value because I've never seen a '98-'00 model,
mine ('02) had negligible LTFT drift after putting
the SLP on (until I molested it anyway) and
the '98-'00 guys seem to get leaned out.

If you bought this MAF used it's possible you got
an early one, whacked your late-model trims,
and have excess (and variable) WOT enrichment.
Or did you specifically order the '01-'02 version
straight from SLP?

Whether this is the deal, you'd need logging to see.
This is where I'd start, with LTFT values by cell and
at WOT.

I bought it new from SLP. I made sure I specifically go the one for 01' - 02' cars.

I'll be dead honest with you guys. I have no idea what you all are talking about with "LTFT" or some of the other tuner Lingo. :(

What is the easiest/cheapest way to correct this problem?

[DebianDog]

Originally posted by DanBUCF
I bought it new from SLP. I made sure I specifically go the one for 01' - 02' cars.

I'll be dead honest with you guys. I have no idea what you all are talking about with "LTFT" or some of the other tuner Lingo. :(

What is the easiest/cheapest way to correct this problem?

Find a friend with a scanner and find out your Long Term Fuel Trim LTFT.

Correction would be put it back to stock or get it tuned right. ;)

[JandJsTA]

Originally posted by DanBUCF
I bought it new from SLP. I made sure I specifically go the one for 01' - 02' cars.

I'll be dead honest with you guys. I have no idea what you all are talking about with "LTFT" or some of the other tuner Lingo. :(

What is the easiest/cheapest way to correct this problem?

Some good reading here to help you understand LTFTs & A/F http://www.vetteguru.com/mods/howto/ you truely need to understand some of it if you wish to tune yourself :)

[DanBUCF]

That was very good reading material. Definitely cleared up a lot of the a/f stuff.

Here is a scanned picture of the dyno graph along with A/F numbers. Let me know if you guys see anything in there.

http://www.pbase.com/image/27002482

-Dan

[DanBUCF]

Put the factory MAF back on yesterday but didn't get a chance to run the car due to the rain. I ran it today and it definitely feels a little stronger all around. I'm not sure if my butt dyno is lying to me or not. All I know is that the tires were breaking loose around 60 mph in 2nd gear and its HOT out today. That never happened before. :cool:

[JandJsTA]

In your graph your peak hp was at @ 5,500 rpm with a A/F on the first run of 11 and second about 12 (big difference between the 2 runs without changes ??) ... still rich with some more HP to be had with some PE vs RPM adjustment (good number to shoot for 12.6-12.7 A/F at peak hp).... I would still stay away from the aftermarket MAF until you hit 500 hp ;) .... just to hard to work with for what they are worth in gains IMHO :)

[DanBUCF]

Yeah, absolutely nothing was done to the car between the 2 runs. I am assuming it was just the computer trying to fix the richness problem, but could only fix it a certain amount. Thats my guess. :dunno:

[JandJsTA]

Originally posted by DanBUCF
Yeah, absolutely nothing was done to the car between the 2 runs. I am assuming it was just the computer trying to fix the richness problem, but could only fix it a certain amount. Thats my guess. :dunno:

The PCM only adjusts for a particular A/F ratio of 14.7:1 (stoich) at closed loop cruise/base mode ... at WOT or PE the PCM will only keep the A/F at whatever it is set at in the PE vs RPM table, not a particular ratio, that is why I thought the 2 different numbers on back to back runs were odd if changes hadn't been made :)

[DanBUCF]

Hmmm...then I have no clue whats up w/my car.:D

I guess my a/f ratio is like potluck then. :dunno: