White Evo V
Renault say that the clio 172 produces 172bhp at the crank, does anybody know what it is at the wheels??? Standard.
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bhp at the wheels
- Thread starter Ben_Stevo172
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White Evo V
:lolup: Any estimate?
In another thread Edde justified the figure he has been quoting, about 143 bhp at the wheels, by calculating from the Clio's drag factor and the top speed the 172 gets in road tests to the amount of horsepower it'd take to do that. And I calculated in the other direction from the horsepower Renault claims at the flywheel minus the generally accepted power loss (15%) through a front-wheel-drive drive train and got the same figure.
That's what a dyno should show at the wheels, about 143 bhp maximum.
The trouble is different dynos show different figures. They give repeatable figures, ie take the same car back to the same dyno and run it in the same conditions and it'll show about the same figure. And if you change that car to produce 10 bhp more the same dyno will give you a reading of about 10 bhp more. But different dynos aren't consistent with each other.
Oh, and by the way, a Clio Sport 172 doesn't produce 172 bhp, it produces 172 ps. That's 168.2 bhp.
That's what a dyno should show at the wheels, about 143 bhp maximum.
The trouble is different dynos show different figures. They give repeatable figures, ie take the same car back to the same dyno and run it in the same conditions and it'll show about the same figure. And if you change that car to produce 10 bhp more the same dyno will give you a reading of about 10 bhp more. But different dynos aren't consistent with each other.
Oh, and by the way, a Clio Sport 172 doesn't produce 172 bhp, it produces 172 ps. That's 168.2 bhp.
Officially from the factory they came with 166bhp...joy.
As for RR jibberish, its quite simple. 1bhp is 1bhp, mathmatically there is no way around it. And its not very hard to measure either, its not rocket science, you just use a load sensor and a torque arm of a known length........fairly impossible to get wrong. Different dynos will use different methods to measure torque, but essentially its all the same result. Note its harder to compare inertia dynos to constant load/eddy current dynos as they are different........but i dont know many inertia ones in the UK, its a yank thing really.
Then the complication comes with engine bhp conversion, which again isnt that hard. Sure, if your starting from scratch a guestimate isnt the most accurate. But if an engine is run on an engine dyno (which uses the same torque measure x rpm mathmatical basics) then its output is known, run it up on the RR and then you can calculate the losses backwards, with pretty good accuracy to use on later runs for similar vehicles.
The problem occurs when you have to trust your operator keeps his dyno in good condition and calibrated. That he is competant and not a moron just running a dyno.......and that he is honest.
You can always find inaccuracies........but in this game you have to use something as a reference, you cant sell performance modifications without knowing how much performance they gain. And since were not dealing with units in the thousands, percentage point differences make very little difference to the total values. People can get far too hung up on things and numbers..........but you do have to use them.
As for RR jibberish, its quite simple. 1bhp is 1bhp, mathmatically there is no way around it. And its not very hard to measure either, its not rocket science, you just use a load sensor and a torque arm of a known length........fairly impossible to get wrong. Different dynos will use different methods to measure torque, but essentially its all the same result. Note its harder to compare inertia dynos to constant load/eddy current dynos as they are different........but i dont know many inertia ones in the UK, its a yank thing really.
Then the complication comes with engine bhp conversion, which again isnt that hard. Sure, if your starting from scratch a guestimate isnt the most accurate. But if an engine is run on an engine dyno (which uses the same torque measure x rpm mathmatical basics) then its output is known, run it up on the RR and then you can calculate the losses backwards, with pretty good accuracy to use on later runs for similar vehicles.
The problem occurs when you have to trust your operator keeps his dyno in good condition and calibrated. That he is competant and not a moron just running a dyno.......and that he is honest.
You can always find inaccuracies........but in this game you have to use something as a reference, you cant sell performance modifications without knowing how much performance they gain. And since were not dealing with units in the thousands, percentage point differences make very little difference to the total values. People can get far too hung up on things and numbers..........but you do have to use them.
