The problem is that bench dynos for these motors don't exist. I know of 1 DFI Porsche "engine dyno stand" in the world and it's not even operational. If you think about it, it's easy to understand why when the requirements are a chassis harness, a key, an ECU and everything else required to run the car. The reason I know of 1 that is operational is because it's being run by a Bosch motorsport ECU and harness. Motec is supposedly yards from the finish line with their aftermarket ECU for DFI Porsche engines and until then, I don't think you'll see another engine dyno surface for one of these cars. This is the reason why we rely on information as much as we do from the chassis dynos. I personally prefer the most simple and most repeatable I have seen and that's the Dynojet. If you're doing ECU testing though and looking to benchmark improvement over a session, the load dynos are the way to go because often the ECU will want to "learn" or it will want a load or something to speed up the learning process. These numbers look to be spot on with what you would expect though. Having to convert PS to HP and NM to torque is what will make it feel like you need a decoder ring from the Cracker Jack box.

 

That's good to hear. So, you think that the stated wheel hp is in line with the factory spec of 385hp? Looks to me as though power/tq curves sustain better at high revs than the factory and Sport Auto graphs (which seem to roll off a little earlier).

 

 

 

Preuninger insists the 385hp number is the absolute minimum that the GT4 will make and said something like "that's at 10,000 feet on the side of a mountain". I'm confident performance will not be an issue.

 

I don't think this is accurate.
Altitude HP calculator
http://www.wallaceracing.com/braking-hp.php

 

The point is that 385 is an underrated number.

 

I read somewhere that with the new larger side air intakes, that when the car is at speed they have a ram air effect and increase horsepower.

 

I think it is pretty accurate. It says that the GT4 would have to make 550hp at sea level in order to make 385hp at 10,000 ft (165hp loss - basically 3% per 1,000 ft seems to be the conversion used).

Obviously AP was just trying to make a point by exaggerating to an extreme degree. Unfortunately, the measured acceleration and dyno numbers show that the GT4 might be slightly over-rated at 385hp, not wildly under-rated.

 

This is true and that advantage will not appear on a dyno (nor the factory rating). But it is not a big deal - probably single digits hp at best and need to be going pretty fast for any real benefit.

 

AP's "GT" horsepower in this case is is about 1:1 with normal porsche.com horsepower.

American magazines such as C&D and motortrend typically have faster acceleration #s but we may not see those for a while. If someone had a 991S manual to test right beside a GT4, it would be nice to see.