I am sure this has been discussed before, but i was looking at the owners manual for something else and i saw this engine power curve and it shows max power/torque is achieved at roughly 2000, and it stays flat till about 4200. so how is that possible when i have never seen full boost at 2000 rpm. I never saw it before and i am not seeing it now even with the new exhaust. (with the exhaust the boost comes little early though, but no max at 20000) Is there some thing wrong with my car or is the power curve misleading

 

I have noticed this before.Absolutely,boost starts later than Porsche's power curve shows!In this regard,my 996 turbo was superior.I was surprised at this when I bought my 997,expecting it to boost earlier.In my opinion Porsche's curve is incorrect and misleading.Maybe it was done with a low backpressure exhaust on a dyno,and not with the "as installed exhaust".And then maybe they adjusted the curve lower,to compensate,but didn't take into account the different low rpm boost characteristics....We hear debates about certain tuner's power curves perhaps being incorrect and overstated,but one would hope Porsche's own curves would be right....

 

Perhaps I should add that a dyno exhaust system might have almost zero back pressure and might not have the usual cats or even any cats.Your sports system might have 2.5 psi to 3.5 psi (standard is over 6psi) depending on which system it is.Which system is it,by the way?

 

ok so its not me then i have EP stage 1, it has 2.65 psi bp

 

That's about as low a back pressure one can get with a cat system.I was thinking about getting that system myself,by the way.What do you think of it-power,noise,throttle response,increased boost at low rpms?I don't want a noisy system.My car has been re mapped-it does help with power above 2500 rpm,but hasn't really changed boost characteristics at say,2000rpm.I don't think there is much more one can do about that...

 

actually Ep makes a stage 2, it has 1.75 psi bp but it is loud , it has cats. as far as the stage 1 which is what i have. the fit and finish is perfect, the sound is just right, nice and deep, no droning throttle response is more responsive, getting the boost earlier now, did not feel the power as much from but dyno, may be ecu is learning, i dont have software though. i would recommend it. oh and it has 100 cel cats

 

Porsche's VTGs have less lag and produce boost faster than any other previous production 911 turbo. What you are describing is not lag...you are experiencing lack of boost threshold. Under 2000 RPM, you are running under boost threshold. It will not produce power. This is a property of the turbo itself, dependent on the size of the turbo and the compressor wheel used. If you are at 4000 RPM and hit WOT, datalog your boost curve on your 996TT. I guarantee you the lag will be significantly greater than on the 997TT stock OEM VTG turbos.
Their curve is a marketing graphic. It is not intended to be accurate. You will never find a dyno curve that looks like the one they display. It is for marketing purposes. Furthermore, Porsche does not use chassis dynos. They use Maha engine dynos. Every Mezger engine is dynoed before installation to ensure production of at least 105% of quoted HP and torque.

 

Yes,you're right-throttle response at 4000rpm is quick-very little lag.But didn't Porsche claim a wider powerband and for torque to be delivered at lower rpm,with the 997,compared with the 996?

 

Porsche's brochure says

"...Porsche used a variable-geometry turbocharger for the first time with this engine. This technology permits extremely fast boost pressure build up with good response characteristics, high torque values, even at low engine speeds and over a wide RPM range, as well as high maximum power combined with low fuel consumption..."

In a comparison to the 996TT, "...fuller torque curve, particularly in the low RPM range."

I do not believe you will see these changes on a chassis dyno...especially at very low RPM.

 

Porsche didn't say that you could actually notice the 'improvement'.

 

Bob

totally understand your comment. makes sense , but isn's that false marketing.

 

It would be...if they ever claimed that that pictogram was a true dyno.

 

claimed horsepower has been an issue for every car owner ever since there was a combustion engine.
I have a 996tt and recently had it dyno'd and was suprised to learn that even all dynos are not made the same.
But i learned alot about how my turbochargers work by looking at the power curves.

 

That is weird that they have the TQ and HP on different scales, it really throws off the look of the chart compared to normal dyno charts. Your HP looks artificially high in the graph because of how they scaled it.

 

I agree. The scale is weird.
but I was surprised how quickly the torque drops off.
I was also suprised to see the HP didnt drop off with the torque.
And this is a 996 not a 997 so it has k16's not k-24's