A week ago I took my car for a dyno test.
The dyno was a Rotronics capable of mesuring cars 4x4 tilll 1000hp. It is suposed to be the Rolls Royce of the dynos.

We were 7 cars mesuring that day, and only one car was in pair with factory specs. It a BMW X5 35D who mesured 286hp to the crank, which is the factory spec all the others mesured slightly more than factory specs.
My 997.2 S mesured 265hp at the whell and 388,2 at the crank. There was a 997.1 4S that mesured 373Hp at the crank

Here´s the plot with power and torque at the crank. 388,2hp at 6608RPM and 432,2Nm at 4797rpm. Power was mesured in fourth gear.
PDK002.jpg?t=1274146430

Plot with power at the wheel. 265hp at the wheel and 318Nm torque. What you experts have to say about the huge loss in power at the wheel?
PDK004.jpg?t=1274146225

TestePotncia012.jpg?t=1274146595

TestePotncia015.jpg?t=1273531605

 

997.1 that measured 273 at the crank or wheels? I'm pretty sure you meant at the wheels...

25% parasitic loss seems high but I have no idea. I would assume more like 10% but I have no idea.

 

it should be somewhere in the mid 300's

 

All the #'s seem off as you report them. Making no sense. Sorry

 

Sorry, it was 373hp at the crank. Have already correct it on my post. Thanks.

 

That´s what I thought too
On the road, my 997.2 S is way much faster than my friends 997.1 4S that measure 373hp

 

How could you know what it measures at the crank?

 

According to the tech the Rotronics machines makes the conversion to crank hp, and gave me the plot I posted here with power at the crank.

 

Your power at the crank seems ok but power at the wheels seems way off. You are showing more than 25% drive train loss and that is not correct.

 

I can only assume that the dyno uses a user inputed percentage for parasitic loss (due to drive train and friction) and I think it was inaccurate for the Porsche.

I can't imagine that the rolling road dyno can actually calculate the HP at crank (you'd have to use an engine dyno).

 

On the road, my 997.2 S is way much faster than my friends 997.1 4S that measure 373hp [/quote]
The 373 vs 388 sounds about right now that you have corrected it.Don't know if that should be "way much faster" but a 4wd does have more friction and wt to push and with no pdk ....?... The rw figure for your car is just wrong. Enjoy.

 

all that 'at crank' computed power is total baloney anyway. what matters is what was actually measured on wheels.

or even better one can just run a 1/4 mile drag and post results. that is an ultimate test.

 

It probably uses a simple conversion factor for drive train loss (ie:8%) and does the maths. It is, after all, the Rolls Royce of dynos. Come to think of it, maybe thats the problem

 

Do a search on dynos here, or check google, or ask TPC. If I recall wheel HP is about 83% of crank ( or crank is 1.21% of wheel ).

 

My engine is very strong and I´m not worried at all with this results. We made this dyno day to get together and have some fun among friends.

The sad part of the day, was the fact one 996 3.4L from 2000, blown the engine while making the test. Everybody was very sad about this and the owner was devasted. It must have been the IMS. The engine was vibrating alot, oil pressure was below 1 mark and oil light was flashing. We also found oil under the engine just after the blown up. As soon as I got in the car and felt the vibration, I knew the engine was dead. It was exactly the same signs my 996 made when the engine blew. . This engine was already the second, the first blew on the hands of the first owner, and normaly rebuild engines don´t blow...shame on you Porsche