Hello all,

I was hoping i could get some help on an issue that i started to notice while driving my car for the past week. Under full throttle accelerations to redline i could feel the car slightly but suddenly lose power( not a huge amount, only noticeable to the driver) starting from about 6600 rpm to redline. The revs keep moving but at a sudden slower rate , say about 20% slower. That phenomenon is also accompanied by a reduction in exhaust and intake noise
( come to think of it...it almost exatly feels like im at half throttle from 6600rpm to redline and not WOT). Upon gear change the car pulls like normal until it reaches the rpm range i mentioned. This happens almost everytime i accelerate to redline. First, second, and third gear seem to not show these symptoms but that could be because the revs are flying past quickly and its harder to notice.
I did some search on the issue but couldnt find a definative answer. Solutions ranged from changing plugs, coils, fuel pump, fuel filter, melted catalytic converters, intake leak, or even a dirty MAF.

I would really apreciate any light shed on this annoying issue. The engine pulls like a champ, its only in those rpm ranges that it suddenly( again, very slightly) loses its *****!


P.S: Oil pressure under full throttle is usually at 4 , i called the dealership and they say its normal for 997.2 DFI cars. My car is showing oil pressure at 5 in first and second gear and then drops to 4 for the rest of the gears under full throttle.

 

Sounds like you're hitting the rev limiter...

 

 

No its not the rev limiter .

 

This could just be a normal characteristic of the engine. If you look at the factory power/torque curves for the 997S.2 motor, both tail off very sharply after 6600 rpm. My car feels exactly the same as yours with a noticeable change after 6600 rpm.

Interestingly, this drop-off in torque at the top of the rpm band is exactly what the X-51 powerkit for these engines addresses. With X-51 installed, the power continues to increase above 6600 rpm to the red line

 

Interesting observation. However I do not feel what the OP states; my car pulls strongly above 6500RPM. It makes sense however to shift right above 6500RPM.



Note that the std 3.8DFI engine has a very linear power curve to the peak, whereas the S51 variant is less linear, curving at around 5500RPM. I love the linearity of the std engine. Note also that the std engine torque deficit at 7300RPM (from the peak) is 7%, nothing significant. My car always surprises me above 6kRPM.