I went to the track a while ago when my car was completely stock my times were all over the place but my best time was a 13.9. Now i added a decent cam underdrive pulleys, i uped the fuel pressure and added slicks and i went to the tracks this past weekend and turned the same time i was very consistant but i never actually ran a 13.9 my times were 14.0 why didnt i improve my 1/4 mile time? I tried putting the stock tires back on and ran again and ended up running the same time. I have no clue why my time didnt drop at all i was at least hoping for a 13.7 to a 13.5 does anyone know why my time didnt improve?

 

Depending on the cam, you might need some tuning with your speed density system.

 

Correct, the speed density system uses MAP to sense vacuum in the intake, unlike MAF that senses the amount of air flowing into the engine. With the air density system, the computer has to calculate (or morelike guess) the amount of air flowing through the engine based on parameters the engineers at GM programmed into the chip. So if you increase airflow through your engine (headers, cam, exhaust, intake), the computer doesn't see it through the sensors, it needs to be tuned for larger volume or air moving through the engine.
Upping the fuel pressure was a good step but it might not have been enough, you might still be running lean.

Hopet his helps.
Lou

 

so its my speed density? How do i tune that or fix it? I dont know if this will help any but i forgot to mention what year the car is, its a 91 z28 with 350

 

Could be very well the speed density. That's the disadvantage of the system that when you increase air flow, you have to reprogram the memcal to compensate for the extra air by adding extra fuel.

Are you running hotter than usual? That would be an indication of running lean.

Not sure if there is an easy way to program this new info in the memcal or if you have to alter the VT but if you have a local friend with a burner, he might be able to help you out because he most likely knows what to do.

BTW: fill in the empty location in your bio, you will get more local responses.

 

You might try looking at the DIY-PROM here at TGO... It will have all of the information you could possibly need to tune your car. Visit www.moates.net for GREAT tuning hardware products. Also might want to check out TunerPro as a great tuning program!