Don Carter

327 HP at the rear wheels is incredible! If I'm doing my math right, that's 327/.85 = 385 HP at the crank, almost a 100 over stock. Seems too good to be true, but if it is, I'm excited. (my 87 FPR is on the way)

I dynoed at 264 RWHP (310 at the crank) over the summer. This is 22HP over stock and all I have is clone chips and RMB. This makes me wonder about Ken's dyno sheets showing a stock 86.5 producing around 249, maybe it wasn't running great? If the AA chips don't effect max HP, then the RMB actually adds about 15HP, all other things being equal between the two cars, which they probably aren't.

dprantl

Looks like you have 290-300rwhp. Drivetrain loss for a 5-speed is usually around 10 - 15%. This seems to be the norm with well-running 32-valve 5.0 liter engines with X-pipe (S3's with some tuning help). The dip is normal with stock intake. It was something that Porsche tried to change with the S4 intake. The S4 still has a dip there, just not as big and the torque peak is after the dip instead of before.

Dan
'91 928GT S/C 475hp/460lb.ft

Mike Frye

Don,

I made the same mistake. It was actually an estimated 327 at the crank. He said about 307 at the wheels. If 15% drivetrain loss is the rule for 5 speeds, that's about 361 at the crank, right?

Darklands

I have here another datachart for a 928 gt. The software says enginepower 340 HP,wheelpower 319.5 HP.
Drivetrainloss 20.2 HP

The question is :how efficient is the 5 gear in a Porsche 928 gearbox?

327 HP -15 % = 278 HP /wheels.
327 " -12 % = 287 HP "

Edit:

I did a call with the dynooperator and he says between 12-15 %.

Mike Frye

Yeah, I think it's weird that they didn't give you the actual rwhp, but instead told you it was an estimated 327 crank hp. Usually they give you what it actually showed at the wheels (and the correction factor) and then you can estimate what it would be at the engine.

So what we need is to know what it actually showed at the wheels in order to get a better idea of how it compares with others who have done the same.

dprantl

You can't go back 7% then forward 15% . I bet the operator added ~12% to the wheel HP numbers then printed that graph and called it crank. It was also probably corrected for temperature/pressure.

Dan
'91 928GT S/C 475hp/460lb.ft

Darklands

The dynocomputer use the draq torque after pressing the clutch at the end of the pull.
This draq torque is used for calculating the drivetrain loss.

dprantl

That is not very accurate, because actual drivetrain losses are very different during coasting down and at full-throttle acceleration. But I guess a %-based number is also not very accurate either. Doesn't really matter, you are close to 300rwhp and that's good.

Dan
'91 928GT S/C 475hp/460lb.ft

puyi

Hi,

Is there any project of chips developpement for a GT? If you have added functionnality as the OEM chips did not have, it could be interesting to improve it on a GT no?

Puyi

Mike Frye

He originally said they subtracted a flat 20hp and that the number he was given was about 327 at the crank, or about 307 at the wheels. I was taking the 307 that he thinks they showed at the wheels and figuring that was actually 85% of the crank hp.

I've read a lot about dyno numbers and two things are pretty consistent:

1. Using a percentage rather than a flat number for HP loss is generally the way it's done. Whether you agree on the percentage of drivetrain loss is another question.
2. Nothing is consistent

BC

This is a really great reason to find a 86.5. Make it black.

PorKen

The stock torque peak for (5-speed) S4s is before the dip at 317@3000, the torque peak for GTs is after, 317@4100.

PorKen

It's tough to compare Karsten's dyno run to a SAE DynoJet. It's obvious it's better than stock! (I'd say roughly 12% over stock.) The curves look very nice, and it was done in 5th gear, a 1:1 ratio, which normally doesn't happen here because of the high tire speeds with the 2.20 ratio!

Roughly 300 ft/lbs at the wheels at 2580 rpm! That's why it drives so nicely. When dynoing a S3, if you start the run after 2500 rpm, you're missing the first torque peak! Need to start at 1500 or so.

Note that Karsten's S3 is the lower compression, 9.3:1 ROW 32V. Stock, they are rated -4 hp/-7 tq than the 10.1:1 USA 32V. I can't wait to see Mike's or some other USA 5-speed on a DynoJet!

I think the latest LH2²r version, which is a little leaner overall will make higher numbers. With the fueling sorted, I'm wondering if retarding the cams 3-5° would push the hp higher?

Funny that the factory power graphs edit out the harmonic 'hole' in torque at 3200 rpm.

For a rough chip/no chip comparo, here's a MS SLC dyno of a '86.5 5-speed with their X-pipe w/pumkin vs. an Ott pipe w/pumkin vs. stock (from this thread).

PorKen

AFAIK, there is not a lot of room for improvement on the more sophisticated LH2.3/EZK programming. Louie has shown you can gain some hp and better driveability with some SharkTuning of both.

Someone should at least make chips for S4/GT/GTS to work with 24# injectors. (Don't look at me! )

Darklands

My cams aren´t exactly positioned.Maybe room for improvement?In 5th gear or overdrive you have roughly - 2% drivetrainloss compared to 4th gear.