BHP

Can any body tell me if a car is 280 bhp what bhp is it at the road wheel Thanks.

260-265 at a guess

280BHP on engine will be something below 200BHP on wheels.
Power losses on drivetrain system on 4 wheel drive cars are pretty large.

That much?

I've asked Martin Tracey, Andy Forrest and a few others about this
and basically it's very complicated to work out but it can be done.
also 2 identical cars can have differen't losses .


Most said ............well gave very very rough estimates at around 40 bhp

So a 280bhp should be somewhere near the 240bhp at the wheels , all did agree that the AWD system
dose loose at lot of bhp

Niall.

[quote author=Niallyboy link=topic=9713.msg115420#msg115420 date=1222088494]
I've asked Martin Tracey, Andy Forrest and a few others about this
and basically it's very complicated to work out but it can be done.
also 2 identical cars can have differen't losses .


Most said ............well gave very very rough estimates at around 40 bhp

So a 280bhp should be somewhere near the 240bhp at the wheels , all did agree that the AWD system
dose loose at lot of bhp

Niall.
[/quote]

280bhp @ flywheel on a 4wd car has no chance of having 240bhp @ the wheels. Basically a good rule of thumb is a 4wd car looses about 20% - 25% of power from flywheel to wheels. And thats basically for all 4wd cars and I have casually checked that in my head every time I hear of a 4wd rolling road figure and its proven true from skyliners to Gti-R's

Paddy

usually around 25% for a 4WD..15% for FWD and 12% for a RWD

so a 280bhp 4WD should make about 210 @ the wheels thios is the figure that counts in fact as all flywheel estimates are just that estimates as power on a dyno is always measured at the wheels ...unless you have an engine dyno its the only sure way of getting a flywheel figure as their are always different variables from one car to the next even with the exact model of car..tyre pressures...wheel diameters etc

Roughly around 40 horses...

If you're on the rollers or dyno, you can get an exact reading

When you see the operator hit the clutch at the redline and the wheels keep spinning, that is the machine calculating how much power is being lost through the drive train

Dyno is the best method as it is far more acurate

40 horses is realistic for 2wd - much underestimated loss for 4wd.
Actually many of you have cars checked on dyno - you can simply check values.
On mine it's like 274PS estimated on engine - but what you actually test is the power on wheels - it was around 195PS as far as I remember.
Tested on MAHA dyno in Enfield.
And actually power on wheels is the one you can be more sure about tested on rollers - engine power is only estimated, but as it's those good "few" horses bigger makes a lot of good for mental health of driver

http://www.isdc.ie/discussion/index.php?action=dlattach;topic=4580.0;attach=2151

Taken from the thread about dyno runs in members section.
Compare wheels power with engine power.
You can also check some other printouts

[quote author=Cill link=topic=9713.msg115425#msg115425 date=1222090036]
Roughly around 40 horses...

If you're on the rollers or dyno, you can get an exact reading

When you see the operator hit the clutch at the redline and the wheels keep spinning, that is the machine calculating how much power is being lost through the drive train

Dyno is the best method as it is far more acurate
[/quote][quote author=RudeBoy link=topic=9713.msg115433#msg115433 date=1222092215]
40 horses is realistic for 2wd - much underestimated loss for 4wd.
Actually many of you have cars checked on dyno - you can simply check values.
On mine it's like 274PS estimated on engine - but what you actually test is the power on wheels - it was around 195PS as far as I remember.
Tested on MAHA dyno in Enfield.
And actually power on wheels is the one you can be more sure about tested on rollers - engine power is only estimated, but as it's those good "few" horses bigger makes a lot of good for mental health of driver
[/quote]

so its more like 28.8% for your car....general rule is 25% for 4WD

[quote author=Cill link=topic=9713.msg115425#msg115425 date=1222090036]


If you're on the rollers or dyno, you can get an exact reading



Dyno is the best method as it is far more acurate
[/quote]



Actuallly not true and a lot of it depends on dyno make and also on dyno operator.......

dyno's are not gospel by a very long shot..............

My dyno sheet for the forester say 386 @ fly and 321 @ the wheels that's 20.2% loss
My dyno sheet for the skyline says 332 @ fly and 292 @ the wheels that's 13.6% loss
Dan

very hard to see a true figure for this. you have to allow for losses through the gearbox, cv joints wheelbearing tyres etc etc. all cars will be different. but as a rule of thump about 22-26% on a road car 4wd(ie not straight cut gears/ slick tyres etc). rolling road if done correctly can give a good estimate but not really exact.

so if the official power of a wrx is given as 280bhp does that mean that wat it actual power is, or do u have to take away 20-25% asu have all been saying

280bhp is powert at the flywheel..around 210 is power at the wheels but it can vary

at least there quicker than most no matter what machines and dynos say
so happy days fellow scooby drivers

here , here

[quote author=davelegacy link=topic=9713.msg115660#msg115660 date=1222122431]
[quote author=Cill link=topic=9713.msg115425#msg115425 date=1222090036]


If you're on the rollers or dyno, you can get an exact reading



Dyno is the best method as it is far more acurate
[/quote]



Actuallly not true and a lot of it depends on dyno make and also on dyno operator.......

dyno's are not gospel by a very long shot..............


[/quote]


Have a gander around youtube Dave, there is a video out there showing an m3 on a dyno with low pressure tyres and then high pressure tyres, makes 30hp in the difference

Dyno is pure physics, the measuring device is connected straight to the hubs instead of having the vairable caused by wheels and tyres... there is no argument here, physics is physics! Tyres have slip and wheels can be unbalanced and cause a variable, with the dyno, these things don;t matter and I can see no reason the operator of the dyno would have any effect, again, physics is physics. The operator on rollers however can have a big effect and the jerking of the car on the rollers is also causing a measurement difference, again, not so on the dyno

Sorry for the rant, I just believe in the dyno, mechanical power connect directly to the measuring devise...

For the second point and I am very open to correction, I believe that companies choose rollers over dyno's for their cost... I have talked to TDP about his dyno before and the cost of it was massive ( and his skyline wouldn't be able to be mapped in rollers as it would just spin the variable tyres, I'm sure everyone has seen people sitting on the boots of cars to keep them down on a rollers run... looks very professional in my opinion )... I can;t see the rollers coming anywhere near that cost. I would also be a believer in "you get what you pay for"

Anywho, with the dyno, you can get an acurate engine power reading and the dyno calculates exactly how much power is being lost through the drive train and has no variables like tyres and wheels

280bhp @ flywheel on a 4wd car has no chance of having 240bhp @ the wheels. Basically a good rule of thumb is a 4wd car looses about 20% - 25% of power from flywheel to wheels. And thats basically for all 4wd cars and I have casually checked that in my head every time I hear of a 4wd rolling road figure and its proven true from skyliners to Gti-R's

Paddy

Click to expand...

Cheers Paddy ...............
"Ya learn something new everyday"

Niall.