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971of1000

Well-known member
Joined
Oct 29, 2008
Messages
100
Location
joplin, mo
Under boost the car feels like it is gaining and losing power. It has boost leaks out of the tb shaft and biss screw. I have been thinking a afpr would help alot considering i am running a 255 pump and 550 injectors. I didnt know if anyone has any suggestions. It is 16g, exhaust, head studs and gasket, fmic and a few other odds and ins.
 

971of1000

Well-known member
Joined
Oct 29, 2008
Messages
100
Location
joplin, mo
Also has meth injection and gm maf and is being tuned by tuner pro
 

Do you have noisy lifters? It can be causing the knock sensor to pull timing.
 

971of1000

Well-known member
Joined
Oct 29, 2008
Messages
100
Location
joplin, mo
stock clutch and new lifters. it is possible that the clutch is going out.
 

broxma

Well-known member
Joined
Nov 16, 2009
Messages
911
Location
San Antonio Tx
Do you mean it feels like the power at a constant acceleration rollercoasters?
What is your Boost gauge doing during this period? Is it steady or fluctuating?
Does it do this only under boost or can you replicate it steady state reving the engine?
Have you performed a boost leak test to at least the pressure your turbo normally produces at the hot side of the intercooler, say 1-3 psi higher than read at the manifold?

I do not think in this case any TB or Biss leak is large enough to cause this. Usually I have found this to be a problem where a clamp has a partial seal to a certain pressure which bursts and then reseals once pressure drops below burst level. Knock has typically presented itself with a single drop in power rather than a fluctuation in my experience. I have never seen quick knock correction cause power fluctuation except in minor knock circumstances and most of those were noticeable only on a log, not the seat of the pants. Another possible condition which I could see cause a fluctuation, if that is in fact what you are experiencing, is a leaking or improperly sized injector, which would add unwanted fuel increasing RPM's. this might be almost unnoticeable during idle due to the lack of fuel used in idle situations. A boost leak at the injector would have to be fairly large to cause noticeable fluctuations. The clutch is possible but you would probably smell it to some degree.

/brox
 

971of1000

Well-known member
Joined
Oct 29, 2008
Messages
100
Location
joplin, mo
I leaned it out a hair last night and switched from all meth to 50/50. Pulls really hard now. No fluctuations in boost pressure, just put the new motor together and had to tune it a little different. Thanks for the help and suggestions.
 
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