Fly911

I did a dyno on my 2000 996 C2 yesterday, 243HP@6375rpm on the rear wheels. The factory figures are 300HP@6800 at the crank. The motor is a 2006brand new replacement motor with 15k miles, standard exhaust, standard air box with K&N filter cartridge, cold air intake and the plenum mod. According to the various advertisements, the modifications should give me an additional 25HP, which of course is BS. Assuming I still have 300HP at the crank, is it normal to lose 57HP on the way to the wheels? 57HP lost in the drive train! that's nearly 20% !!!
Could the replacement motor be a 3.4L Cayman S motor (less Variocam Plus)with 295HP@6250rpm? The peak HP occurs at 6375rpm rather than at 6800rpm, that is closer to the Cayman S figures.
There is also a spike in power at 5500rpm where it's up to 235HP, then to dramatically drop to 205HP at 5850, before it climbs up to the max 243HP at 6375. The HP curve seams very strange, I would expect some disturbance around 3500rpm, where the Variocam and Varioram are activated, but at that point the curve is smooth. Could the Variocam and Varioram switching points be wrong?
Please see the attached dyno curve. Are there any one out there who are experts on this, and could tell me if there is something wrong here?

Thanks!

LowStro9

Yea...that's a way weird curve.

AndrewWK

20% is pretty normal for drivetrain loss. You think that's bad, try a awd car next time. A 997 s put down about 298 last time we did runs, so you might be down a few. How new are your o2's, fuel and air filters are fresh?

Andrew

AndrewWK

looking again I see you have a "plenum mod" and K&N... I would try changing back to stock before you try anything else.

1999Porsche911

I would ignore all dyno's, whether they show improvement or not. Do you like the car's performance? Did your car's perfomance drop off on the way home from the dyno shop since it showed less power than you thought you had? Many shops will print a chart out for you showing whatever numbers you want if that will help you sleep better or you are into keyboard racing.


Remember, you drive the car, not the dyno chart.

AudiOn19s

That's about right power wise. 18% drivetrain loss is a pretty common figure.

As far as the mods giving you power. I think it's been well documented that they do very little for peak power, they help out with power under the curve however which you really wouldn't see without stock vs. modified graphs. Peak number isn't going to change much however.

If it helps you any my M3 dyno'd 278 stock and it has approx. 40 more hp than a 3.4 car does stock so your numbers aren't out of the ordinary.

Andy

Bob Rouleau

Chassis dynos are only good for comparing before and after. I have little faith in the absolute readings of power. Mustang Dynos tend to produce lower results than Dynojet for example.

Best,

Tippy

Yes, the numbers are low, but why are you not running full synthetic oil? Valvoline Durablend is blended synthetic and mineral.

pat056

I'm no dyno expert. I get my 964 dyno'd every year as it's a requirement for my race group. I have a RSA 3.8L cup motor. The last dyno showed 266 RWHP and 252 ft lbs. torque(where's your torque number)? With no muffler and cooler, dryer conditions, I've gotten closer to 280 HP. Torque's always around 252.
My maximum HP is also around the 6,300-6,400 rpm range. Mine levels off, but does not dip around. That looks strange to me.
I like to use relative numbers on a dyno, i.e. same conditions, tweak something then rerun and check results. IMHO dyno's are like statistics, that can be massaged to show what you want to see.
Did he not give you any torque or lamda (air/fuel ratio) readings?
If the scale is the same, I'd estimate your torque at about 205 assuming the 2 numbers cross at 5200.
I race with folks in others car w/HP numbers in the 300++ range and beat them. HP ain't everything. Brakes and suspension go a long way.
May want to do a search on that K&N set up. Many folks have had MAF failures running K&N's on 996's. I like K&N's, but evidently they don't do so well w/the 996 MAF.

ArneeA

Was that dyno hand-sketched?

Benjamin Choi

What's the avg drive train loss on a rwd, rear engine car like the carrera? How does it compared to the carrera 4s? Anyone have this data?

Fly911

The dyno is not hand sketched, but the RPM's and other info is hand written.
Even if the top HP figure might be within the normal range, it occurs at a much lower RPM than normal, 6375rpm in stead of 6800rpm. Also the peak and dip don't make sense to me, at least not at that RPM.
I use the Valvoline Durablend and not Mobil 1 because the Mobil 1 is more agressive to some of the sealing materials in the motor, plus the Valvoline has a stronger oil film than the Mobil 1. Based on race engine tests, the engine wear is less with Valvoline Durablend than with Mobil 1. The viscous losses in the engine is slightly higher with the Valvoline, maybe 2-4Hp. The high temperature advantages with the Mobil 1 compared to the Valvoline Durablend, occur at temperatures way above "melt down" temperatures in the engine, and are of no use, even in racing. RMS leaks or failures, and other seal related failures do normally not occur with the Valvoline oils (according to Porsche race motor specialist, Sam Shalala, Pro Technik, Houston).
I will check fuel filter and pressure regulator, and inspect (+clean) the MAF sensor. But still, these things do not explain power drop off nearly 500rpm before the correct 6800rpm peak power.

Any other suggestions ot there?

1999Porsche911

In the 996 NA engine, it is normal to have a power drop at around 5500 rpm as that is when the ressonance valve is thrown open. However, any engine that dropped as much as your chart did would not need a dyno to show it. It would be like pulling your foot off the gas pedal and then slamming it down again. Something was wrong with the run. There is also no way a properly running 3.4 will drop off as much as chart shows above 6500 rpm.

If the chart is a true reflection of your engine's performance, you would feel it when you drove it.

pat056

I think you need to run another dyno. The results between 5500-6000 make no sense to me. When looking at mine, the curves are very similat except in that area. I don't think you'll get any more HP w/a new dyno, but I would be very surprised if the peak/valley reproduce themselves. looks like the driver's foot slipped off the pedal. Did he run 2 runs? Every time I've had a dyno done, it includes 2 runs.

BruceP

Data, no, so flame away. But one of the things Porsche lovers have long bragged about is that the combination of rear engine and transaxle reduces drivetrain loss over systems that have transmissions and driveshafts. Bench racers used to say Porsches lose 15%, where 'normal' cars can lose up to 25% if the car has an old school automatic transmission.

It therefore stands to reason, I figure, that the addition of a longitudinal driveshaft and another differential would cause a pantload more power loss to the wheels.