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Convert BHP at the wheel into BHP at the fly



  1.2 TCE Clio Dynamique S
How does 166BHP at the wheel convert to the fly power?
Using my Ass-Dyno I make that about 190 or 225 if you want to show off to your less educated mates.

Only ever quote BHP at the wheels...anything else is just monkey-tennis.
 
  1.2 TCE Clio Dynamique S
ok cheers mate, I don't know this type of stuff, hense the question.
In all seriousness I hear figures of 15%-20%-25%-30% from people

It just depends what figure they have to start with.

If you have a proven (dyno read-out) of a flywheel BHP of 200 then you want the figure to be as small as possible

"Yeah, 200 at the flywheel, 180 at the wheels." = 10% loss

But if you only have the wheels BHP figure dyno'd (from a rolling road) then you want the figure to be as large as possible.

"Yeah, 180 at the wheel but that works out as 215 at the flywheel." = 20% 'Gain'

You can see how this works.

I refer to my monkey-tennis comment above.

Wiltsteve
 

Poopensharten

ClioSport Club Member
  Golf R
Suppose all sorts of factors would assitain to what would go down as at the wheel and at the fly?

Such as what the cars being run on, humidity, tyre pressure, air pressure etc so on and so forth?

I know they would only make so many few BHP more or so?
 
  1.2 TCE Clio Dynamique S
Suppose all sorts of factors would assitain to what would go down as at the wheel and at the fly?

Such as what the cars being run on, humidity, tyre pressure, air pressure etc so on and so forth?

I know they would only make so many few BHP more or so?

That will affect the power it can put down, not necessarily the power at the wheels

I don't think it does.

you have 2 figures.

1) Flywheel
+
This is when the built engine is ran on a proper dyno and the is the power the engine produces.

2) Wheels

This is when the engine is fitted to the car and the amount of power the wheels can 'put down' is measured. It loses power as it has to send the power through the drivetrain.

There is a 3rd figure.

3) Ass Dyno figure.

This is my favourite. It is was most people quote on their cars. They know the standard power of the car. They 'know' a big bore 4 (do they still make these?) 'gives' 5bhp so they add that on. Then they have big alloys which also add another 10bhp.

Then chuck on an air filter. Another easy 5bhp there.

Don't forget a body kit that looks like a wide mouth frog. +15bhp.

14 year old girlfriend +3bhp
Pregnant? +10bhp

A sound system that causes the plod to fall out when driving along? +5bhp
Sunstrip with make of car on? +2bhp
Shopping list? +4bhp

Make it not a multiple of 5 so it sounds more true....

Total Ass-Dyno figure for a 1.0 Corsa... 124BHP

Wiltsteve
 
  a thirsty one
i had a figure of 166 @ wheels once and the rr operator printed off two graphs the at wheel and fly wheel. they quoted a fly figure at 188.9

pinch of salt though all cars have diff loses and always arguements about accuracy of fly v wheel figures.
 
  1.2 TCE Clio Dynamique S
i had a figure of 166 @ wheels once and the rr operator printed off two graphs the at wheel and fly wheel. they quoted a fly figure at 188.9

pinch of salt though all cars have diff loses and always arguements about accuracy of fly v wheel figures.
I'd question the RR as unless they have the dyno connected direct to the flywheel, how would they have been able to measure it?

probably used the 30% 'Gain' mentioned above.

Or they connected to their Ass Dyno.

:)

Wiltsteve
 
  cock mobile.
You can calculate a flywheel figure based on the run down speed in gear, or something along those lines.

Of course take this with a pinch of salt, but depending on the dyno involved it can be quite accurate I'm sure.
 
  Nippy white cup
I usually add 10bhp to the wheel result and divide by 0.9 which tends to get a round about reading at the fly.

So 166bhp at the wheels would be 195.5 at the fly which if it is the reading for your motor won't be far off

Chris
 


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