Louie928

In this case, the lower gain per # boost could be the restrictive exhaust.

tv

It also looks like a K-jetronic 80-83 euro which does not have the power or breathing of the LH 84-86 euro. But cool anyway.

GlenL

Yes. Precisely. The area under the curve is not meaningful in itself. That is, a value given in HP*RPM is not useful. (it's not power, or energy or any other real value.) I believe what people are looking at from the area is the average HP over an RPM range.

To really determine if a given pattern is better or worse then you need to evaluate it over time and look specificly at where the RPMs are after a shift.

heinrich

More restrictive intake, exhaust, valves, heads. Surely this makes sense.

m21sniper

Depends on the curb weight, but with truly good traction 400hp should put you in the very high 11's with a gearing change as well.

m21sniper

Not to me it doesn't. If you ran the math it should be much higher..........and i'm sure at about 56-5800rpm, it IS much higher. Remember, they only ran it up to 5k rpm.

James-man

Glen,
I would bet area under an HP curve where HP is one one axis and time is on the other axis would work just fine. Time series is the ticket. The trick is you need to start and stop counting time ticks at the point in time where RPMs hit within the range you wish to study. Shouldn't be hard. If you can you plot time vs RPMs from standard dynojet data, you can easily find the start and stop time points for the RPM range. Using this data for projecting real world application would require assuming a linear relationship as load increases, among other things. Seems reasonable but do not know if it would really hold true.

No cheating though. You have to use an entire upshift RPM band, not just the 200 RPM sweet spot.

In spite of all of this, average is a more understandable number than area under the curve, unless area is expressed in total work done.

Peter F

Very impressive numbers for a CIS car,

looks like new sturdier shocks and springs may be a good investment on this car

Cheers/Peter

Brett928S2

Hi,

Sorry to alter the thread slightly but I think its relevant

On SUNDAY 4th DECEMBER here in UK I am going to a dyno day at Silverstone,its run by Porsche 1 so various Porsches will be there .

Most are short of 2 cylinders of course

But myself and 1 other 928 S4 will be there

The dyno is 1000 hp by the way (so they say) so the supercharged monster should be fine on it

I have 2 questions maybe someone can help with....

1,....My car was a theoretical 310 bhp to start with....now have added Promax Chips ,Rmb and Nology leads...
What do you think the RWHP will or SHOULD BE ?

2.... The guy who runs the dyno says that with a 928 S2 AUTO the calculation for crank to rwp is calculated on around 7% loss ????
That seems a little low to me ??? Id love the figures but id prefer them to be correct ...

Any help appreciated

All the best Brett

928 S2 AUTO V8 4.7 LTR 1986 IRIS METALLIC BLUE WITH PROMAX CHIPS, RMB, KICKDOWN SWITCH.

IcemanG17

Damm that S/C is HUGE.....17psi...in a Euro motor (okay a 8-1 euro motor)....430hp at 5K....I would guess 50 more at 6K? Impressive...I would like to see a dyno chart to see the power/torque curves!

Its good to see the fuel system on an OB can support that kind of power!

sweanders

Interesting to see how a 17 psi of boost on a supercharged 8:1 compression 5 liter 928 engine compares powerwise fairly well to a 2.5 liter 8:1 compression turbocharged 951 engine.

Here is a 341rwhp dynosheet for a 951 with a Vitesse stage 3 turbo and MAF-kit running 17 psi:



And here is one 533 rwhp sheet with 24-25 psi on a car with the same turbo but headwork, 3" exhaust, andial cam (not optimal) and Speedforceracing headers:



Imagine what kind of power a well built 5 liter 8:1 compression twin turbo 928 could put out..

tv

An auto is usually a 20% loss and 15% for a stick.

IcemanG17

Anders
That must be one hell of a ride....look at the curve....nothing than BANG...its gone!!! Damm...but a 928 would have more bottom end + the silly top end

mulik51

Ok. Thanks to all for an answers. Now, I believe when I will get a dyno sheet I will "read" it correctly

P.S. I still kind of don't get why HP to RPM axis are not good for integration and HP to time is better? Like, logically, what I would do for the graph #2 Mr. Hansson attached, I would devide it into exponential function and 3 parabolas. Find the areas under, add them, and then get the area... Graph#1 I would devide into two lines, do the same thing. Then compare the areas...
What I find cool about this is that it actually accounts how much time you spend in a particular hp range... If we compare 12000rpm car and 5000rpm car, and peak hp for the second one will be 1.5 times higher, we still will call the first car more "powerfull" becouse it will spend more time in the correct hp range and will better behave on track. That might be an answer to why weaker 2005 911 is quicker to 60 then more powerfull Corvette. Math, math, math...what a great tool

Thanks,

KLim

GlenL

Because the integral of power with respect to time is energy. Kinetic energy, that is the energy a thing posesses because it's moving, is gained as the car moves faster. So by looking at that integral you see a real value of what is happening.

The problem with RPM versus hp is that it is decpetive. In reality the car spends proportionately more time at lower torque points. This causes the average power applied to be less than might be thought if you just looked at the curve between the shift point RPMs.