shawsan

As I mentioned in a prior post, I've purchased a 993TT with several performance modifications. Next week, I'll dyno it on the latest 'Dyno Dynamics AWD'.

Since this is my first 993TT, and I didn't do the mods myself, I don't have a baseline dyno of a stock 993TT showing rear wheel HP and rear wheel Torque. I've researched this site and some other sources, finding dyno results on 2 stock 993tts. One reports 300 RWHP and 318 RWTQ, the other reports 305 RWHP (but no TQ reported). Is there any other information out there??

BTW, if the above mentioned RWHP/TQ figures are correct, then the implied drivetrain loss is between 20-25% to equate the RW results with manufacturer claims of 400HP and 400ft/lbs of TQ at flywheel. This 20-25% estimate is considerably higher than the 'rule-of-thumb' drivetrain loss for 2WD sports cars of 15%. However, several pros have suggested a 20-22% drivetrain loss on an AWD porsche may be correct.

So, in summary, I'm looking for (i) more stock dyno results on a 993TTs RWHP and RWTQ, and (ii) any conversion rates your dyno operator has used for an AWD Porsche, or that you've heard from an 'authoritative' source. I'll share my results when available.

Thanx. Paul

ScottMellor

My tech told me around 25% for an AWD car.

dbf73

be careful about dynoing your car in AWD. see https://rennlist.com/forums/showthre...light=dyno+awd and search on the subject as well if you value your viscous coupler.

Red rooster

Why not uncouple the front drive . It only takes minutes and is safer for dyno measurements anyway !

Geoff
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KS400200,the oldest 964 on Rennlist,unless you know differently !

Kevin

I wouldn't stick your car on the dyno in 4 wheel drive.. Tell the dyno operator that he can remove your tranny and install a new viscous 4 coupling if his dyno smokes it.. See what he says..

Geoffrey

The Dyno Dynamics AWD dyno will work fine for the 993TT driveline.

Red rooster

The 993tt AWD system uses the speed difference front to rear to determine the relative axle power transmission .
This means that if the rear tire grip cannot put down the correct power the front will take on the challenge !
The torque /power loading allowed on the front is fairly low .
To disconnect the front drive involves undoing the two hex head bolts on the coupler at the torque tube at the front of the transmission , slide the coupler foward and redo the head bolts to lock the FWD off.
This takes 5 minutes and removes any danger of screwing the FWD system.

Always a really low cost 5 minutes when measuring power on a dyno !!!

Geoff
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KS400200,the oldest 964 on Rennlist,unless you know differently !

TB993tt

Doing some spring cleaning and came accross this chassis dyno run from February 1996
It is my tt stock showing 414 flywheel hp and 392hp at the wheels so a 8% or 32hp loss (this was done with the front shaft disconnected.)
I know when I had my car running 510hp it chassis dynoed 460 at the wheels, again a 9% loss.
-the low losses are another reason why these cars are so fast for their rated power compared to other makes.

ACEparts_com

Stock 993TT is somewhere around 300 - 325 at the rear wheels. Anyone who says anything else is clueless

TB993tt

Was a bit harsh that - edited
Seriously - you think a 911 loses 25%+ of its flywheel power through the drive train ?

ACEparts_com

I'm sure someone will be along with another dyno chart that proves this one way or another. I know my car standard was 325 at the rear wheels. My 964 was 200 at the rear wheels (275 flywheel)

BTW, hows the car now it's 4wd again?

TB993tt

Must be the different rollers then -you know my view on rollers anyway
Here is another one from march '97 on the same Bosch FLA machine, 355hp to the wheel with406.5 flywheel, 12.6% loss -have to remember that the losses include whatever adjustment is made for DIN depending on ambient press and temp.


Here is one done on a Dynojet 248C 389.8hp at the wheels and 415.8 flywheel -6% loss !!




Steering feel and turn in destroyed, acceleration and grip awesome, suitability for current UK weather 100%

Jean

Another way to look at this is that if TB's car had a 0.5 seconds slower 60-130mph run on 4WD vs 2WD..

According to my calculations based on actual dyno numbers, CD and weight data, his slower by 0.5 s 60-130mph run represents a loss of circa 8% in HP (across the powerband). The weight difference between his two setups was about 100lbs, that would have represented about 0.1+ seconds.

Net net, the 2WD change on its own (excluding weight factor) represented about 6% friction loss.

The components added back were the torque tube, the front drive shafts and the front differential, meaning these components created that loss. This is assuming identical conditions of course and just a ballpark figure. Tire friction on the rollers is not accounted for so are the gearbox losses.

TB993tt

Confused me abit there Jean Are you able to estimate the friction loss from 2WD to flywheel in the above This is what we are getting hung up on I think ?

ACEparts_com

Not wishing to add to any 4wd vs 2wd controversy but i seem to recall Audi/vw noting that a driven wheel is actually more efficient than an undriven one due to the changed shape of the tyre. This was seen during testing of the first audi 4wd tests apparently.