When driving at high rpm/boost the acceleration is not smooth but seems to hesitate over 4000 rpm in gears 2-4 under full throttle. low rpm and fifth gear are fine if you floor it at say 90mph. Any ideas on cause? Shop where I got the car tuned says no faults and I had the turbo replaced under warranty for waste gate problem 9 months ago.

 

You may be getting knocking. Any chance for you to put in 100 octane gas and seeing if it does the same thing?

 

Did you drop to a cooler plug? How many miles on the plugs/coils?

I would guess lite misfire that the DME is not picking up yet.

Mike

 

What tune do you have?
You can log the car and see what's going on.

Also as mentioned plugs and coils are something to look at

 

Evomsit stage 2 612 hp pkg all in. Feels like car shudders at full throttle over 4k rpm. No backfire no loss of traction. Pissed off when a ctsv smoked me the other day.

 

Shutters sounds like a misfire..... Plugs/coils is my vote.

 

Just ordered will install and report results

 

Are the evoms coils significantly better than oem or is there another option. Evoms claims up to 20 hp boost. Any thoughts??

 

im not to familiar with the evo coils, and 20 hp boost ?meh..... i dont know about that ... look at the BBI coils , i have heard great things about them.

 

I was similarly suspect but of I can get it I'll take it. I'll look at bbi thx

 

Just read review that evoms coils added 12 hp to stock 480 hp 997tt and 25 to 1k hp ride

 

Changed out plugs and installed the evoms coil packs. Diagnosis was right on the money. Power loss completely eliminated and you now can't touch the dash from the passengers seat at full or near full throttle in 2-4 gears. Not sure what the evoms coils added but seems like a new at to me. Spectacular advice here. If you have a tuned ride new plugs and coils may be a necessary upgrade. Thanks all.

 

Nice that you got it all fixed. I have a flash and have had to replace coil packs and plugs at tune install and a second time 11k later. Its a normal common thing with tuned cars. What plugs did you go with?

 

Pk20prp8 denso. Next question is whether to get gt3 throttle body and larger bifurcated plenum

 

I'd say before you keep upping the power, do your clutch which will ultimately slip.