I was at the track a few times this spring and have not been able to get anywhere near my best E.T. 14.37 @ 95 MPH 2.07 60 ft. that I ran last October. Yes... I do understand that it will run slower in warmer temps. Right now the best that I can get out of it is a 14.71 @ 93 MPH 2.25 60ft. -thats .34 sec slower - I don't buy that warmer temps caused this. One time at the track I had the air-intake off to do some work and forgot to hook the MAF connector backup and ran a 14.65- 2.17 60ft (no traction problems with the tall 2.77s) afterwards I hooked the MAF backup and ran a 14.70???. How is that? I thought it would have ran worse. Isn't it in limp-home mode if the MAF is off?

Can someone shed some light on this please.

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89 IROC-Z 5.7L
130,000 MILES
2.77 GEARS
K&Ns FILTERS
ALL FREE MODS
FLOWMASTER MUFFLER
PERFORMANCE RESOURCE CHIP
Best 1/4 E.T. 14.37 @ 95 MPH
Best 1/8 E.T. 9.22 @ 76 MPH
Best 60ft. 2.07

 

that wouldnt be your MAF causing this. start looking at other things first that can be cleaned or replaced. change your air filters (if you dont have k&n's, if you do, clean em), change the fuel filter, spark plugs, wires, distrib. cap, rotor, coil, & ignition module. all this can be done for 65-85 dollars. if you do all this at once, id bet you will beat your best time, even running in the summer. just do your running at night/evening when the temps are a little cooler. your MAF has no problem with it, otherwise youd have drivability problems along with it, not just .34 seconds slower in the quarter mile.

 

and about the MAF question, no the computer isnt in "Limp Home" mode when the MAF is disconnected. the computer is in Open Loop. if you have it floored, your in open loop. if the MAF disconnected, and you floor it, the car will go to the same power enrichment mode that it does when its running in closed loop. so no matter what, the MAF isnt being used when the car is floored. it would have no effect on 1/4 mile time. unless your driving with half throttle down the track

 

I thought of this as well. I checked, cleaned or replaced all of the things mentioned above to no avail. I have made some mods since then that I replaced with the original parts to see if thats what it was... NOPE! --I have check O2 voltage, TPS volts and made sure all wire connectors are good. No SES light and no stored codes.

What else would cause a .34 sec.(30 HP)loss?
From 14.37 @ 95 MPH to 14.71 @ 93 MPH???

Anymore ideas?


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89 IROC-Z 5.7L
130,000 MILES
2.77 GEARS
K&Ns FILTERS
ALL FREE MODS
FLOWMASTER MUFFLER
PERFORMANCE RESOURCE CHIP
Best 1/4 E.T. 14.37 @ 95 MPH
Best 1/8 E.T. 9.22 @ 76 MPH
Best 60ft. 2.07

[This message has been edited by whiteroc (edited June 16, 2001).]

 

well I always thaught that the MAF was still used in WOT, but not the O2...so it could somewhat conpensate for weather changes...but then, I'm not saying I'm right...the way I understood it was that the power enrichement would be in function of a certain MAF reading, so when the weather is cold, the MAF "see" it and adjust the table to a given number in function of the enrichement at WOT, so that way you won't run lean in cold weather and too rich in warm weather...again, correct me if I'm wrong by all means ...wich then would make sens that if the MAF reading is off, it would make the car run worse.

 

You only have a 20 hp loss (95-93).

I've seen bigger fluctuations than this at different tracks. Depends on traction, weather, etc.

There is nothing wrong with your car.

 

ET is not a direct reflection of HP. ambient temp affects i think its every 10 degrees you lose a MPH through the traps. perhaps this is your only problem

 

err! sorry guys --thats actually 14.37 @ 95.<u>7</U> MPH and 14.71 @ 93.<u>0</U> MPH /// 2.7 MPH or 27 HP -Thats just too much for me to believe that its air temp. I have ran the car in close to the same temp last year and ran a 14.51 @ 94.8 MPH. (this run was made before some of the mods that got me to the 14.37)Hmmm... I just don't know. It may be too close to call -- But anymore ideas would be nice.

 

I had the same problem, my car went from
14.48 to 15.0. And I put underdrive pulleys
on over christmas so I was hoping for 14.3's
The car ran fine and had a ton of low end torque, but just died up top. So I cut the
cat. convertor and found that it was totally
plugging the exhaust pipe. I have not been back to the track yet, but she feels so much stronger now. Maybe this will help you. Good luck

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14.48@93.72mph

 

Well...That is one thing I know it's not. The car had no cat when I bought it. It feels good on the top end but seems to have lost some power on the bottom. ...I'm still guessing.