12.6@103 1.6 60ft????

[sick GN]

I have a stock setup with a thrasher 108 chip, THDP, K&N, adj. FP reg., XP pump, and adjustable wastegate. I was wondering what could be the reason why my mph is only 103?? I made previous runs in the 13.0 range at like 105 with 1.7-1.8 60fts and this pass is the fastest but also the slowest?? What can I check and look for as the reason for my slow mph??

Thanks

 

[CraigT]

Valve Springs. How many miles on them?

 

[BLACK6PACK]

valve springs, lbs of boost, knock retard, locking the converter, heat

 

[1badTTA]

I will have to agree on the valve springs. I assume you made more than 1 run that had the mismatched mph. If so, what are you shifting at? leaving it in drive? does it fall flat on its face before it shifts? try shifting manually about 300rpm higher, if you can. If you can't you know for sure it is your valve springs. Remember that it really doesn't matter how many miles are on your valve springs, since they have been compressed for the last 15 years anyway.

 

[John Wilde]

I would think it was your valve springs as well.

Super Junk had a stock 150,000 motor, turbo and intercooler.
All it had were K&N, Intank Pump Upgrade, AFPR, 40 lbs and a art carr 16930.

It went 12.5 @ 104.7 with 24* and 22 psi
With a tighter converter and some working valve springs I would have expected 110mph and maybe a 12.0.

About a month later the car developed really bad valve float under boost !!!

 

[Ed Valvo]

Slipping tranny maybe? A while back with a super slipping trans, I went 12.7 @ 100! Slapped in a new or should I say "borrowed trans" I went 12.40 @ 107.

 

[azgn]

your mph will go down as your et gets faster, so some of the difference is that....it would seem something else is going on tho