Lawnboy

iTrader: (54)

I have a 01 SS with a Procharger D1-sc supercharger system.

The car has a bad stumble and drop in RPM as i try to get her to roll out ,

I have to wake up the throttle by peddleing the gas as i come off the clutch and slip into 1st, i have to realy rev her up to prevet stalling.

after shes in 1st she drives fine , pulls hard to red line (6,000) made 540 RWHP and 500TQ.

I think its the mass air flow sensor,
has any one had this problem with a SLP F-body 85mm mass air sensor?
please let me know.

EPP

iTrader: (22)

Yes indeed, I think everyone has. If you are using the ATI ProCharger supplied tune, you need to immediately get that SLP mass air flow off of there, as it is more than likely causing the engine to run lean. If you had the car dyno tuned, the tuner should of told you to get that mass airflow off of there. Bob

rufretic

iTrader: (37)

Can it be tuned to work correctly? I wanted to try to keep the larger 90mm intake and tb along with the 85mm maf to let as much are in as possible. I figured it would help make good power at a lower psi. It seems if you bottle neck the system with the stock maf, it doesnt make sence to have the rest of the 90mm set-up. Bob, I'll pm you in the next day or two about making my purchase before the price hike.

ZL1Killa

iTrader: (17)

any mass air flow meter can be tuned correctly. if you have it on your car just get a tune or a tuner to make a table for you. all mass air meters work the same way.

Lawnboy

iTrader: (54)

I am trying a new stock one today

Lawnboy

iTrader: (54)

This is what someone over on the ( LS1Tech) PCM Diagnostics & Tuning , Forum-board replyed to me about what is going on with my Procharged LS1 SS with the mass air flow sensor .

=
I had the same deal with my STS. Here's the real deal. Your VE tables are probably WAY off....as in calculated for much less airflow than the SC is actually pushing. Fuel is added in relation to the calculated airflow per cell in the VE table. Bigger VE cell number = computer telling the injectors that more air is present and thus add more fuel. If the value in the VE table for a particuliar cell is too small, then the injector in turn adds too little fuel to the cylinder. The O2's pick this up (as a lean condition) and tell the computer to add fuel over the "Long Term" to compensate for this...thus LTFT's are +25%. This is maxed out. The result is a car that is running "rich" and is way down on power. It's only "rich" because the computer is telling the injectors to dump in 25% more fuel at all times, part throttle/WOT, etc whether it needs it or not. This is also why your fuel economy sucks.

To fix you need to tune the VE table. Put the car in SD mode. Reset fuel trims. Drive for a good bit till the fuel trims settle (probably near 25%) and then start logging data. Drive the car about at part throttle (I would not suggest going WOT in your current state) and get a good 25 counts or so per cell in the LTFT and STFT histograms. Then add the two and take this adjustment as a paste full % into the VE table.

Then repeat. You'll see on the 2nd go around that the LTFT's will be WAY less. Mine went from 25% to around 10%. Keep this up (but make adjustment as paste special - 1/2%) till the LTFT's are -4 to 0. Then you can start going WOT and tuning from there.

If you have a SC do you have a 2-bar MAP sensor? You'll need one + 2-bar on the tuning program to tune properly for boost. The stock MAP sensor only registers to 1.05. With 7PSI the MAP is really at 1.50. This will make FI tuning all but a guess in "1-bar" mode.

Also, has the car been tuned (ie mail order, etc)? My problem (and how I learned all this $hit) was I got a mail order tune from a company when I added the turbo. The car was fine for a week and then was feeling like it was still NA and running like crap. Fuel economy sucked *** too and I could sniff gas from time to time at idle. When I checked my $500 mail order tune (with the copy of HP Tuners I ordered)....I rudely learned that the VE table was STOCK except for idle! Might have a similiar thing going on with your car.

Anyhow, bit long, but this should help. There are a bunch of stickies and posts on tuning. It's not hard....no tricks. Just takes time and consistency.

Good luck.
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Lawnboy

iTrader: (54)

I just tryed the stock Mass air flow sensor, , its better but not right
My LTFT are very high 20+

98turbls1

iTrader: (17)

Your tables are probably way off now... Are you tuning it??

Lawnboy

iTrader: (54)

No
my tuner said to through a new set of O2's in, and bring it down next week , he is
going to go over the whole thing.

I ran a few gals of 110-114 octang , 20-80% mix over the past 3 months while playing with the car , and it looks like my O2's are switching a little slow,

But i have a Razor methanol injection system , i now want the car tuned for pump gas (only) , at about 11.8 - 12.0 AF and add methanol to get the AF down to around 11.0-11.2

this should be a safe tune and keep the knock away.

I made 540WRHP as it sits now with 9-10 PSI of D1-sc boost , i am happy with the power , since its only a stock LS1 with FLP long tube headers and a accufab 75mm throttle body ,
but the off idel and under 2,500rpm acelatration sucks and my gas milage is about half now , i might be only getting 10 miles to the gal,

I know at a cruise anywhere from 2000-3,000 RPM at 40-70 MPH the car is using to much fuel and with LTFT's at 20-25%
something is telling the ECM to dump fuel.
This sucks but i will figure it out ,
And thank all of you for helping me out