knock only at high speeds...


Nov 4, 2003
I have little or no knock (0-2) degrees when running the 1/8 or 1/4 mile. However, if I'm driving say around 40-60 mph and I hammer it, I get about 6 degress of knock. It's not false because I can hear it.

Any ideas as to why?
lets get some info on your car? boost, octane. miles on motor, etc

it will be more helpful. my guess would be motor mounts, DP hitting something, or to much boost and not enuff octane :)
91k miles
New PT52
stock intercooler
Blue Tops (now I know these are small but they are by no means at their limit. I'm only running 13:30's. I'll upgrade them when I'm in the mid to high 12's.
PTE 93 chip
93 octane
15 lbs of boost

Thanks for your help.
I bought the car with the blue tops and stock turbo that was going out. The upgrade will be 50# injectors but I know my blue tops are good to mid to high 12's. I'm not maxing them out yet.
I know your saying you only run 13.30's but what is your mph? This would tell you what kind of power you are making thus relating to your injector size. I have the same turbo and it spools pretty quick. Most of the time I will be at full boost in street trim before I am WOT. My guess is that your lean. Your 52 flows alot more cfm at 15 then a stock turbo at 15. Just my $.02.

what converter are you using with the PT52 turbo? Do you like it? Would you choose a different one if you had to do it over again?
I have a 3500 stall AC nonlockup. I run alittle higher stall because of the cam but besides that I have been happy with it. It was a huge difference from stock. I used to run 12.7 @109 at 22-23 lbs with 110 oct. Now I can run the same mph with 17-18 lbs. The turbo seems to really come alive at 22+lbs but I don't have any track times to compare.