I have a 93 Z M6 w 3.23 gears (was an auto car). cc306, meziere, 58MM BBk, lloyd heads, mac headers, all bolt ons, 30#svo's. I am having the car dyno-tuned next week. I have a PCMFORLESS tune in the car now which is way off. My question is that can a improper tune cause a car to run a lot slower than it should? The reason I asked this is that even though I have no times yet, I raced a 98 Cobra and a 6-speed LS1 last night and got walked on pretty badly. I was shifting at 6250 and yes I think I am a pretty good driver. How much of a difference can the tune make? It does run way too rich. Just wondering if there might be other problems before I take it to the tuners. Everything is installed correctly and it was triple checked before the motor was put back in the car. How much also would gears help? Thanks in advance guys.

 

a tune can make or break a combination

 

I've been in your situation b4. I had 3.23's in an auto car converted m6. Was running 230/236 cam. It was slow as hell. You will never be able to perform to what you would like without gears. I remember just watching my tach slowly wind up to 6800 and shifting, and being at like 85-90 in 2nd gear. And then going to the track and ending in 3rd. The car would fall way down in r's on every shift, and at the track it would bog dumping it from 4k on bfgs.. Talk about ****ty You'd probably gain a few tenths off gearswap alone, and something insane like 5mph. I gained 2mph from going to 3.42's alone in that car, much less 3.73's or 4.10's

Josh

 

After the tune I am going with a 3.73 gearset. 4.10 is a little too much becuase the car is street driven most of the time and the gearsets I heard are pretty weak. I searched around this site and was surprised at the gains by tuning. I guess I will see what happens next thurs.