We had our local PCA Dyno Day this past Saturday. Whomever guessed closest to their hp at the wheel, not the the engine, gets a free wheel alignment. I guessed 370, which is close to 75% of the supposed 430hp it's supposed to have. My car was second to go up on the Mustang Dyno, and from the start there were issues. The PDK, not seeing the front tires moving would not shift past first gear no matter what we did. They reset the dyno to AWD which would then move the front rollers. Then they were able to get the car to upshift. Even still, the power the dyno was showing was far below what it should be. They ran it three times even adding more fans for greater air movement and cooling.
I have attached a video and a copy of the Dyno report. It did sound good.
Their guess as to why it was not reporting properly is due to the PDK computer, from the front rollers not able to keep up and sucking some of the HP, and/or not enough air movement. Needless to say I was a bit disappointed. Now, if the dyno is accurate, then there is a real problem somewhere. I will have to find another dyno and see what results they get.

 

Hmm, this is way lower ...around 335 ish Hp?? Definitely due to front wheels...

 

Most modern cars have to be put into "dyno mode" via the computer system with some sort of OBD II machine, or else the results will just not be accurate.

With my old M3 this was done with a GT1 machine, not sure what the Pcar will need.

 

Do your math again. 0.75 x 430 = 322 and 335 shows as your max hp. Each dyno and each brand of dyno will display different drivetrain losses. Go to a Dynojet if you want a bigger number.

Getting a Mercedes into dyno mode is easy through the multi-function steering wheel. On my 987 it just takes turning off the PSM to avoid the front and rear speed differential problems.

 

Yeah, I may have been hoping for too much, but a stock Cayman R was showing 282. 282/.75 = 376hp? It is closer to 85%. By that account mine is showing numbers for a base S of 394hp.

The traction control was off, even still the car refused to upshift by wheel buttons or stick. Either way, I will be looking for another dyno to see if they get different numbers.

 

Counting on 25% drivetrain losses seems very pessimistic. I think the 'usual' number is closer to 15%.

I have wanted to dyno my 991 but have been told you need to trick the car's computer or use a dyno where the front rollers are perfectly in sync (same responses you have seen on this thread and basically what you experienced when you had to go to AWD mode). Even then, the shops I talked to were not convinced they would get an accurate reading. Because of this, I had been quoted $300 I've given up for now.
The only practical (track) experience I have is that my standard 991S has a better acceleration than a 997.2S and even than a 997.1 GT3 that has more hp's.

Do not worry, all the promised horses are there and Porsche has the reputation of understating its numbers.

 

I think Serge is right when he says that Porsche wouldn't misrepresent the number. So unless you want to have data where you can made mods to the car and compare you might just want to take it to the track and ensure the times meet spec.

ChuckJ

 

That's the exact same thing STALKER said earlier...are you related?

You guys are talking me down. Thanks Serge, ChuckJ! I know the difference is there so I should not be too worried. It's just this car has so spoiled me and like having a child, I am expecting the best for my baby.

 

German law prevents Porsche from advertising specifications that are not true. Every car off the line must meet every performance specification and engine specification or be better. Essentially their performance/output specifications are the absolute minimum. Way back, in the 70's when engines were built by one person (and were around 170hp) there could be as much as a 10 15hp bump over spec if you were lucky.

 

I have no fear of the car not performing as it should, but as cars get older they do require tune ups and so forth. My concern was for whatever reason the engine not spitting out the power it was designed for. I don't have the newest car here by far. It's been ridden quite a bit. I could only compare it to how it performed on the track in October vs February. And there was a noticeable difference. I know tuneups are required after quite a bit more mileage than what I have put on.

Just want the best for my baby. :-)

 

I share your concern with mine. I'm keeping a record of mileage from a specific point and back to make comparisons as mileage indicates a healthy engine. There's a 1/4 mile track up the road and at 10,000 miles I'm going to go test it there for a power (using a 1/4 mile run), record and do that perhaps every 10,000 miles. If I see anything amiss in either of the tests, it will warrant a trip to the doctor.

ChuckJ

 

How many miles so far??

 

26k + so far. Since Feb of 2012

 

Gee Chup, do you own a home or do you live in it?

ChuckJ

 

he he he: same mileage since Feb 2012 here : 17k in my first 991, 3k in my short lived GT3 and 6k in the new 991 = 26k total. These cars are meant to be driven!
It kills me when I see used cars at the dealership that are 5 years old with only 5,000 miles on the odometer. Drive your car until it dies or you get tired of it, whatever comes first