how accurate are rollers when measured in whp and bhp?

[cantbassed]

as title above really, how dose whp compare to bhp. i know bhp is power at the fly and kinder doesnt count for the power you put on to the road, but whp would tyre presures, size wheels affect whp?? just some better info would be great!

 

[dave-izzle]

depends really. to get a good WHP you can get dyno's the bolt onto the hubs that give accurate whp figures

 

[cantbassed]

i had a power run of which was printed in whp, of which i wasnt to happy with. i was told by someone that whp can differ if you have diff wheel presures and size wheels? is this so?

ah sorry for being in the wrong place!

 

[herbie]

Yeah ive heard pressure makes a difference. Pumping them up harder would result in less "drag" on the rollers.

 

[Dan3SGTE]

hi mate,

Was this your EG? how much did it make, list of mods on the B18? Is it a UK version B18 or JDM B18C?

PM me if you prefer bud.........

 

[Rory]

A rolling road measures the Wheel horse power of your car.

It then calculates your flywheel horsepower from a random figure etc etc.

Trust the wheel horsepower over the fly horse power.

 

[Dan3SGTE]

i wouldnt trust any if it were me! lol

bloody dynos are nonsense.... i say take it to a dyno for a bit of fun for a rough estimate... On the road it will very anyway and on a day to day...... Take it with a pinch of salt.

 

[aaron425]

^^^^thats the truth....

ive had my car on two different rolling roads in the same month
the first reading was 168@the fly and the second was 155.8@the fly??

it makes sense to always use the same dyno whenever you have work done it may not be 100% correct to start with but atleast you can compare with your previous print outs and see any gains or losses.

 

[glanzaV195]

the only way to get a more true figure is remove your engine and take it to a direct to crank dyno,
wheel hp can be affected by wheel alignment/tracking, tyre pressure, strap tightness, the list can go on, the set up/calibration of the dyno plays a massive part also.
quite often power lost through the transmission is miss calculated as well, so fly wheel hp calculated on a rr means nothing tbh, just pub talk.

 

[Starlet_Sam]

the only way to get a more true figure is remove your engine and take it to a direct to crank dyno,
wheel hp can be affected by wheel alignment/tracking, tyre pressure, strap tightness, the list can go on, the set up/calibration of the dyno plays a massive part also.
quite often power lost through the transmission is miss calculated as well, so fly wheel hp calculated on a rr means nothing tbh, just pub talk.

But who gives a shit about BHP at the fly?! It would be great if the flyweel drive the car but it doesn't, the power has a gearbox, a diff and the wheels to go through. I don't even like the hub dynos because losing the effect of the tyres is losing the realism! The only power figure that matters is the one at the wheels.

 

[glanzaV195]

But who gives a shit about BHP at the fly?! It would be great if the flyweel drive the car but it doesn't, the power has a gearbox, a diff and the wheels to go through. I don't even like the hub dynos because losing the effect of the tyres is losing the realism! The only power figure that matters is the one at the wheels.

but it IS a bullshit figure and can be so far off, only a number on a piece of paper.... nothing, meaningless. what matters is how it really goes on the road.

 

[ChrisGT]

but it IS a bullshit figure and can be so far off, only a number on a piece of paper.... nothing, meaningless. what matters is how it really goes on the road.

So the best way to gauge a cars performance in your opinion is what? Just curious

 

[Starlet_Sam]

but it IS a bullshit figure and can be so far off, only a number on a piece of paper.... nothing, meaningless. what matters is how it really goes on the road.

Yes, but you can't quantify that now can you.

 

[ChrisGT]

Yes, but you can't quantify that now can you.

QTR mile?

 

[Starlet_Sam]

QTR mile?

The driver is the biggest variable there, would be a worse way than a power figure. In the most part the wheel BHP will be more accurate because although there are still variables, they are reduced.

 

[ChrisGT]

The driver is the biggest variable there, would be a worse way than a power figure. In the most part the wheel BHP will be more accurate because although there are still variables, they are reduced.

Oh yeah I know, I'm not disagreeing. But if you did want to test how well a car "goes on the road" using a method that actually uses, well, a road the quarter mile would be best. But yeah, shit driver = shit time, which doesn't represent the cars performance.

 

[Starlet_Sam]

We just need to get a robot driver or all auto motors.

 

[ChrisGT]

We just need to get a robot driver or all auto motors.

I'm a robot!

 

[Boab]

A rolling road measures the Wheel horse power of your car.

It then calculates your flywheel horsepower from a random figure etc etc.

Trust the wheel horsepower over the fly horse power.

he's spot on here - it calculates the wheel horsepower when the car is actually driving on the rollers. then it applies load to the wheels as they are slowing down to work out drag from the transmission, to get the flywheel hp.