Scooterotica

Am I right in thinking the BHP figures quoted by Innocenti are measured at the crank and not at the back wheel?
Cheers Nick

you are correct dear sir.

...........and they should be taken with a massive pinch of salt as well!!

Remember these figures were "produced" in the 1960's when there was no requirement for any truth in advertising at all. Same goes for their quoted top speeds.

Chris

For the figure at the rear wheel deduct 15% .

Chris CSPE wrote:For the figure at the rear wheel deduct 15% .

most iron standard barrels reach their optimum performance after a good running in period and then decline slowly in output. a good iron barreled bike should hit late 60's to 70 mph as innocenti intended on a long enough stretch. all of this is academic if you are a 16 stone fatty with a bulky coat on, my son is 9 1/2 stone and would add a brake horse or two in weight saving over me, tyre pressure adds a bit and a completely unblocked well maintained exhaust.if you can find a tv200 barrel then you might add a little bit more performance as well.

On our dyno, a bog standard GP200 hits a dizzy 9bhp, with no porting or tuning work you can gain 2-3bhp by changing pipe and carb......

Thats what I thought, thanks for the replies.

And lets remember BHP can be split off into two components, speed and torque.
There is a common middle ground on BHP input between the two, outside of this middle ground one will suffer.

Layshaft Power Kw = Torque Nm x Layshaftt Speed/ 9550

Find Layshaft Speed
Assume 13" (330mm) tyre @110km/h

then (110 x 10³) x (1/PIx0.330)

Transposing our formula then Torque = 9550 x Kw/ Shaft Speed

So if we are saying 9 Bhp @ 1770rev/min at the back wheel then 9Bhp= 6.71Kw

Therefore Torque = 9550 x 6.71/ 1770
Torque = 36.20Nm (obviously torque increases as speed decreases)

Then Wheel Ø plays its part in the overall performance of the scoot, this is part of the overall tractive effort equation

There are other calculators available put together by other members to view also.