i have a greddy kit on my 99 Si and it uses to spool up to stock boost(6psi) at alittle over 4k but i notice now that after i got new piston and rods put in that its taking even longer to spool up.. ..now at about 5k-5.5k i'm hitting 6psi.....why is my car lagging so much..can someone please help...i'm tired of getting burn off the line and having to try to catch up....

 

what compression are the new pistons

 

If you put lower compression pistons in, then yes, you will get lots more lag. Time to crank up the boost to compensate

 

welcome....

Did you lower the compression on you engine? If not, would suspect a small leak somewhere..

 

well i have JE 10:1 piston put it....its not that much of a difference then my stock compression....i've seen other Si with the same setup using JE 9:1 piston spool up quicker and make more power then me on the low end....


[Modified by SiR 621, 9:05 PM 3/5/2003]

 

leak?...check for leaks in the couplings...make sure everthings tight...I'd get a water spray bottle with a tad of dish soap and spray the couplings..make sure that they don't bubble up...

 

well i do have a little crack one the coupling that holds the intake pipe to the turbo..but is very small...so you think that can be it....i thought that since the crack is on the intake side that the turbo would just suck in air through there too..

 

try repacing it and see...any leak can be significant....the more your turbo spools the more power that the leak can potentially rob....check everything...make sure its perfect.

 

ok thanks for the advice...

 

A leak on the intake side wont make your car spool any slower......

 

He's probably spooling the same time he did before, but the manifold is not seeing the same amount of boost because of a leak.

 

i think you misunderstood. he was saying that the ripped coupling is pre-turbo. it's the one that holds the filter onto the compressor so it doesn't see any boost.

sir 621, did you replace the exhaust manifold gasket when you put the motor back together? if so, also check your vacuum lines for leaks.

 

i don't think the gasket for the exhaust manifold was changed but if there was a leak on the exhaust manifold i would notice the different sound that would be coming from it. i have had a bolt broke of the exhaust manifold before i it made a loud noticeable nosie...but who knows..i'll just check everything all over again.


[Modified by SiR 621, 9:15 AM 3/6/2003]

 

i am willing to bet you have loose clamps within your intercooler piping

 

Check all of your vacuum lines, it has to be a leak.

 

In an extreme case...you might have a leaky head gasket look for oil in the coolant.

 

Did you seat the rings in properly after the new pistons? If you just got new pistons put in and took the car out and beat the hell out of it with a turbo on it, then you're rings didn't seat so you're not getting the same compression numbers that a well seated (broken in engine) ring would see. So, low BS compression will equal crappy spool.

Just a thought...