Discussion
s3am said:
Just spoke to Allan at WRC..
ATW fig was 351.3 bhp.
Bringing this thread back from the dead...
I was on the dyno at Thorney motorsport yesterday and measured a 346bhp at the wheels, which isn't so bad eh? This was estimated as a 400bhp+ flywheel figure.
Out of interest my brother's CSL measured 310 at the wheels which is apparently very good for an M-Powered car, as the standard figs can be a little optisitic.
400 is about right for an RS, although i have seen some from 410-420bhp
G.
DanH said:
If you were dyno'd at WRC, don't they have figures for the GT3 drivetrain already?
It wasn't at WRC but Thorney motorspork in MK, but yes they did; 412bhp, this was worked out on a 19% drivetrain loss figure. I was just wondering if that figure was low, high or accurate for drivetain loss, as they didn't use a coastdown figure.
Its also a great modern setup they have there. Top guys.
>> Edited by s3am on Wednesday 24th May 21:19
s3am said:
If you were dyno'd at WRC, don't they have figures for the GT3 drivetrain already?
It wasn't at WRC but Thorney motorspork in MK, but yes they did; 412bhp, this was worked out on a 19% drivetrain loss figure. I was just wondering if that figure was low, high or accurate for drivetain loss, as they didn't use a coastdown figure.
They are the same dynos, using the same loss program
vixpy1 said:
If you were dyno'd at WRC, don't they have figures for the GT3 drivetrain already?
It wasn't at WRC but Thorney motorspork in MK, but yes they did; 412bhp, this was worked out on a 19% drivetrain loss figure. I was just wondering if that figure was low, high or accurate for drivetain loss, as they didn't use a coastdown figure.
They are the same dynos, using the same loss program
I didn't think dyno dynamics measured loss, but instead had a table of values from the dyno's manufacturer?
DanH said:
If you were dyno'd at WRC, don't they have figures for the GT3 drivetrain already?
It wasn't at WRC but Thorney motorspork in MK, but yes they did; 412bhp, this was worked out on a 19% drivetrain loss figure. I was just wondering if that figure was low, high or accurate for drivetain loss, as they didn't use a coastdown figure.
They are the same dynos, using the same loss program
I didn't think dyno dynamics measured loss, but instead had a table of values from the dyno's manufacturer?
Yep... I call it the loss program
19% !!!! Thats why you get 412hp. Its pretty easy to massage owner's egos with this sort of approach. With 19%, the rear wheel figure is 334~ish. Using a slightly more believable 15%, 392 hp is the result. These corrected dyno figures, unles on hte same dyno, in very well controlled conditions, are not really much use.
vixpy1 said:
If you were dyno'd at WRC, don't they have figures for the GT3 drivetrain already?
It wasn't at WRC but Thorney motorspork in MK, but yes they did; 412bhp, this was worked out on a 19% drivetrain loss figure. I was just wondering if that figure was low, high or accurate for drivetain loss, as they didn't use a coastdown figure.
They are the same dynos, using the same loss program
I didn't think dyno dynamics measured loss, but instead had a table of values from the dyno's manufacturer?
Yep... I call it the loss program
Vixpy, do they dyno dynamics shoot out graphs show the loss figure that is used?
I wish people would stop pissing around trying to estimate power at the flywheel. Its power at the wheels that counts anyway!
The Dyno Dynamics programme for Porsche on extrapolated flywheel horsepower is very accurate. John Thorne should be able to print you a graph with this on, crossing over at 5252rpm etc. An approximation of losses for Porsche rear engine/rear drive is 15%. [front engine/rear drive is c18%]
So in effect 346 dived by .85 = 407 BHP All in all not shoddy for a GT3.
On the bottom of the graph would be all of the atmospheric conditions. AT / IT / BP / RH etc all of this will also allow repeatability of performance.
Allan
So in effect 346 dived by .85 = 407 BHP All in all not shoddy for a GT3.
On the bottom of the graph would be all of the atmospheric conditions. AT / IT / BP / RH etc all of this will also allow repeatability of performance.
Allan
weltmeister said:
The Dyno Dynamics programme for Porsche on extrapolated flywheel horsepower is very accurate. John Thorne should be able to print you a graph with this on, crossing over at 5252rpm etc. An approximation of losses for Porsche rear engine/rear drive is 15%. [front engine/rear drive is c18%]
So in effect 346 dived by .85 = 407 BHP All in all not shoddy for a GT3.
He did this for us, does this lower loss in a rear engined, rear driven car account partly account for the idea that Porsche have 'stronger horses' as standard than say Aston, BMW?
s3am said:
The Dyno Dynamics programme for Porsche on extrapolated flywheel horsepower is very accurate. John Thorne should be able to print you a graph with this on, crossing over at 5252rpm etc. An approximation of losses for Porsche rear engine/rear drive is 15%. [front engine/rear drive is c18%]
So in effect 346 dived by .85 = 407 BHP All in all not shoddy for a GT3.
He did this for us, does this lower loss in a rear engined, rear driven car account partly account for the idea that Porsche have 'stronger horses' as standard than say Aston, BMW?
Or alternatively the figure for the loss is a bit high and it's inflating at the crank estimates. It is power at the wheels that counts in the end anyway, so this estimated stuff isn't too useful imho.
You will rarely find a modern Porsche that under delivers in the Horsepower stakes. IIRC the factory quote +-5% but it is usually + something.
Allan
BTW Power at the wheels is everything but most people like to compare with manufacturers stated horsepower so extrapolated flywheel is a necessity.
Allan
BTW Power at the wheels is everything but most people like to compare with manufacturers stated horsepower so extrapolated flywheel is a necessity.
s3am said:
The Dyno Dynamics programme for Porsche on extrapolated flywheel horsepower is very accurate. John Thorne should be able to print you a graph with this on, crossing over at 5252rpm etc. An approximation of losses for Porsche rear engine/rear drive is 15%. [front engine/rear drive is c18%]
So in effect 346 dived by .85 = 407 BHP All in all not shoddy for a GT3.
He did this for us, does this lower loss in a rear engined, rear driven car account partly account for the idea that Porsche have 'stronger horses' as standard than say Aston, BMW?
What I mean is that for any given engine more of the power (which I imagine is bench tested) is transmitted to the road.
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