danglerb

I've tried hard to pay attention in class, downloaded the engine model year chart from one of the list sponsors sites, but I am still not sure whats a flywheel HP value and whats a rear wheel HP value. To keep it simple manual transmission values are fine for me.

What I am typing below is from the sponsor chart and I assume its flywheel hp etc. Anybody know what the "real" rwhp values are for a stock 928?

year HP Torq tops 060 1/4 wt
77-79 219 245 143 7.5 15.5 3285
77-79 229 250 143 6.8 15.5 3197 Euro
80-82 220 265 143 7.5 15.5 3351
80-82 229 271 143 7.2 15.5 3197
80-83 300 263 155 6.6 15.2 3197 Euro S
83-84 234 263 146 6.8 15.2 3351
84-86 310 295 155 6.2 15.2 3308 Euro S
85-86 288 302 155 6.3 14.2 3351
87-88 316 317 165 6.0 14.5 3505 S4
87-88 316 317 168 5.9 14.2 3484 Euro S4
89 S4 316 317 168 5.9 14.2 3505
89-91 326 317 171 5.8 14.1 3505 GT
92-95 345 369 171 5.7 13.7 3593 GTS

Using a calculator hp = weight / (ET / 5.825)3
So a US 83 is 189 rwhp.
and a 86 is 231
and a 89 is 242.

Thanks for any enlightenment.

John Veninger

Typical manual transmission reduces crank HP by 15%

Mark

And figure a 20% loss for an Auto...

Vilhuer

Your hp numbers are in two different formats. Euros are in DIN and US in SAE.

Also '78-82 4.5L euros have too small number for both ways of measuring hp. Correct number is 240 DIN and 237 SAE.

For '83-84 US factory gives 242 DIN which is 239 SAE. For some reason 234 is repeated in many places. 5 hp more or less is meaningless really but I would bet 239 sounds much better for owners.

One 5sp S4 had 12% measured loss in dyno while automatic S4 has 18% IIRR at same dyno.

John Veninger

How did you measure that? Were the engines on an engine dyno first, then installed in the car and run on a rolling dyno?

Vilhuer

Dyno software had feature which calculated it based on how quickly drivetrain slowed down on neutral. Its obviously not toally accurate but 5sp could be close as only clutch is left out besides engine

John Veninger

Cool stuff

cobalt

I am assuming these numbers are for autos not 5 speeds.

My stock '93 5 speed weighs only 3505 pounds with 1/2 tank (corner weighted numbers) and I have multiple Gtech times of 0-60 in the 5.3 to 5.5 and 1/4's in the mid to low 13's with tire slippage. With a 15% drive train loss factored I have had readings between 289 and 299 max rwhp. How accurate these meters are I don't know but the numbers should be close.

Vilhuer

Official Porsche numbers are almost always conservative compared to reality.

Roger

A few years ago, I had my 87s4 automatic on a dyno. The car was stock and we did 2 pulls:

1. Stock Configuration: 256.9 max power 270.1 max torque
2. Removed Air filter: 264.1 max power 281.9 max torque

The majority of us had s4's (mine was the red one) and had similar sheets. There was one owner that did extensive modifications to his car, but his numbers weren't that much higher (+10) than mine due to tuning issues.

http://us.a2.yahoofs.com/users/yWIBR...aveas=P5120149
http://us.a2.yahoofs.com/users/yWIBR...aveas=DCP00430
http://us.a2.yahoofs.com/users/yWIBR...aveas=DCP00431

Brendan,

You were there in Joliet, what were your numbers on the 89? Do you remember the type of dyno we used?

Roger

mark kibort

Its not accurate at all based on the fact that the coast down is only a fraction of the total losses. coast down is interesting due to the fact that it measures all the rolling friction and very minimal inertial losses. the transmission losses are substantial, and is the reason a ton of heat is generated in the transmission

another fact is that the losses change with speed. we measured 20hp losses from 150mph down to about 90mph and then 10hp from that point lower. ((rpms from 6400 down to 2500rpm) its basically a straight line.

so, that 20hp will be fixed for any car, the trans losses change for each and every gear, 5th being the most efficient. 20hp for 285rwhp is near 7% .
we see 7hp differences just using 3rd vs 4th gear.

generally, 15% for manual is a great place to start. take my car. when i raced the ferarri, at 400hp rated at the flywheel. we were pretty evenly matched at the track, (same weight and slightly quicker) my 320rwhp vs his measured 340rwhp was exactly what we saw on the track as far as acceleration differences. In world challenge, i raced a top prepared T1 C5 vet that was heavier. we were dead even due to the same hp to weight, and his dynoed at 345rwhp while mine was at 325rwhp. weights made this race dead on equal. (see the video). when those cars are stock, they are 335rwhp minimum,(405 engine hp and this has been confirmed on the engine dyno)

again, one of those things that has lots of factors.

mk

Tom. M

Just some ballpark info...from previous PacNW dyno days..
4.5 liter 5spds.160hp range
4.7 liter 5spds. 180 to 190 hp...230 to 240 ft-lbs
85/86 5spds. 250 to 260 hp with torque same (yea Shane..hush...I know yours was 280 )
87 and up S4s AT's 250 to 260 hp...260 ftlbs etc..
87 and up S4's 5spds - 270ish to 280 hp..280ish ft-lbs
GT's are 280 plus usually...and same ft-lbs..torque peak on second hump.rather than first as in S4's
GTS..seen one..5sp..did just a bit over 300 hp..and that was supposed to be good..

There are all sorts of graphs and numbers posted on the pacnw page..(don't have a link)..but I'm sure a search will bring it up..

BTW..a GT with just the x pipe will consistently show 300hp and 300 ft-lbs...and Louie (with some other mods)...did a max of 325hp... normally aspirated..

later,
Tom
89GT
Totally stock with 150000 miles did 282 hp and 280 ft-lbs...(not even an rmb on it)..pretty amazing after that many miles.

Tom. M

OK..here's a link to the past event site with 5 or so dyno events..
http://www.pacnw928.com/events.html#Past

BTW..we have been disappointed by the Euro numbers..most we have done were AT's and didn't show better than 220hp at the wheels.. and the one 5sp..was a hybrid (us car..euro motor and a botched exhaust at the time)...so it's numbers were not quite there yet either .

Later,
Tom
89GT

danglerb

Thanks, thats just the sort of info I needed. So many posts talk about HP and don't say what kind or how it was measured, plus the range of HP numbers isn't that wide, so when I read 325 hp without more context I don't know if its wonderful or average.

For those that don't have a Gtech, its a LOAD of fun, just be careful testing. I haven't tried mine in the 928 yet, waiting on all the PPI bits to be sorted first, but asap afterwards.

John Speake

84-86 Euro S2 auto are just under 15 sec 1/4 mile magazines tested them - 14.9sec....