I figured Did you find any APE II chips?
Well, I don't build very high horsepower vehicles and love information...so on that note...
Now for the tech questions (feel free to answer in your new post)
How long do you normally give it between runs? 30m? 1hr?
Then do you hit it with an Infrared thermometer or some other method to check for a control test start temp?(along with ambient)
Or is all this minor in determining accurate test date from dyno runs?
I am guessing a summer night run is the best time for multiple tests.
Thanks for your time.

 

In between sets (runs of 3.....usually they are 3 consistent runs) you usually give it about 15 minutes or so with the fans on and the car off, and about 2-3 minutes in between each run with the car on and fans still blowing. Those fans can cool down the car pretty quick. The longer you test the car, the longer you give it in between runs obviously. We have found this to give us very consistent numbers across the board. Obviously the cooler air is much better to test as the car stays cooler longer and cools down easier, but the kansas summers don't really allow for much below 85 unless you want to be up at 3am, lol. If you want runs within a half a hp or something like that, then you could test with infrared etc, but you really dont need to be that accurate. Runs will usually vary 1-2 hp. As long as you get something like 241-242-241.5, you are about consistent as you need to be. The welts i tested tonight were doing some really funky stuff, and i dont know quite what the deal was. They were way off on each run, while the other chips were consistent.

 

Thanks

 

What's the point of testing with a leaking factory wastegate? Why not install the Tial and do it right the first time.

 

Had a boost leak, wastegate is holding fine.

 

Just went back to the dyno a couple of nights ago. Cold weather (and possibly replacing the shot CV) made a big difference.

 

No offense but why list the crank numbers at all? Does it make sense to use an instrament like a dyno to get the actual wheel power figures and then a "guess" at what the flywheel numbers are? You put the crank horsepower on your dyno sheet as if it is something factual when to the best of my knowledge there is no proof of what the actual drivetrain losses are for a 951. Do you know what your drivetrain losses are? Do you know if they are linear - ie: the same percentage loss at all rpm? The crank power could be more or less than what you assume so why assume anything at all?

Congrats on the wheel power figures by the way. Looks like your car is running very well for a stock turbo. If I can find my dyno with my stock turbo and APE Stage II chips I will post it as well. Your power curve and air:fuel curve looks pretty much identical.

 

Your losing more than 20hp and 20 lb-ft from the crank to the wheel. Your number wheels are about right and match what I saw. when I ran a similar set-up. The crank numbers are off. Whoever set that up is assuming the driveline loss is only 10% when it should be 15-17%.

 

Daniel: How do you come up with the 15-17% number? What testing method was used? Are drivetrain losses linear? How do you know that he should be losing more than 20 hp? If this is just a guess it is no better than bench racing. It's inflating a number based upon no factual data.

 

Its a number from Porsche. It should be mentioned in the specifications or even the owner's manual.

The driveline loss is the difference between the crank hp (bhp) and the hp as measured at the wheels (as ambiguous that is). The clutch, torque tube, gears, and axles all consume power. How much is a combination of a large number factors. Weight, friction, etc all play a part.

Someone should be able to look this up in either the factory manual, haynes, or something.

I'm out of town and can't look it up.

 

OK, so we did the normal runs to get things dialled in, then since we had some time left (minimum 1 hr), we started to play around.

Ran the car up to 65 mph, then popped the clutch. The dyno then records the negative power retarding the drum. Plotted that curve. Re-mapped it from wheel speed to RPM based on 4th gear.

I had to extrapolate it up in RPM. It was an almost PERFECT (R=0.993) fit to a parabolic regression curve. Applied that fit curve to get the corresponding power loss for each RPM for which I had a dyno point, backed out the torque delta, added those to the measured power and torque, and Bob's your uncle - crank numbers, or at least the best estimate I coudl get.

Now, deceleration power was NOT corrected to SAE, since it should be insensitive to air density. I'm also assuming zero loss across the clutch (no slippage).

Other problem: I forgot that we did the acceleration runs in 3rd, but the deceleration in 4th, so there may be a slight difference there.

Here's the deceleration plot. The points are actual data, the line is the curve fit. I'd be really interested to see anyone elses numbers for this.

 

mroberts: That's more like it! Does the fact that the transmission is not in gear during your test affect the results? Wouldn't there be more friction with the gears engaged vs. disengaged?

Daniel: I'll grab my owners manual and take a look. Good to know that these numbers might be published somewhere.

 

The driveline loss is pretty much impossible to calculate, just live with the rwhp number.

 

That was with the tranny in gear (4th), but the clutch in, so the entire drivetrain, except for the flywheel and engine, was engaged and moving.

 

What he said. I wasn't being critical of you dyno at all. Ignore the crank hp as it is all speculation unless you put it on an engine dyno.