F1 power and torque.

[davecooper]

Hi, new to this forum. I have a couple of question s to start me off.
1) The old Cosworth DFV engine developed 400 to 500 BHP at say 9000 RPM and the current engines are developing 900+ at 18000 RPM. Does this double revs, double power rule generally hold roughly true in engine design?
2) I saw another topic in this forum saying that the reason for more torque from a V8 over a V10/V12 was the longer stroke and hence, I assume, more leverage at the crankshaft. My question is, how much does an increased piston surface area affect torque. ie take a V8 and V12 with the same capacity and stroke, the V8 would need a bigger bore and hence piston area. Would this V8 develop more low rev torque than the V12?

[Enzo]

1) No. Double revs is not equal to double power of course. To uderstand this you have to see the factors affecting engine power.

brake power = (BMEP)*L*A*N', where

L = stroke
A = piston area
N' = number of mechanical cycles of operation per second for all pistons.

So, if there was not the (BMEP) factor then the power would be exactly proportional to revs and engine volume. And (BMEP) is a function of volumetric and thermal eficiency:

(BMEP) = (nv)*(nb)*(pa)*CV/AFR, where

(nv) = volumetric efficiency
(nb) = thermal efficiency
(ρa) = air density
CV = fuel calorific value
AFR = gravimetric air/fuel ratio

(In the last equation you cannot find anything about mechanical efficiency just because the term BMEP is enclosing the friction losses, BMEP = brake mean effective pressure)

2) It's a good wuestion here but i don't think that we can compare the two engines (V8/V12) in terms of torque in a specific rpm value as the rpm bands of these egines are different. V8 is limited to 15000-16000 rpm due to secondary torsional vibrations while the V12 can reach 19000-20000 rpm. So low revs for the V12 is something like 10-12000 rpm and for the V8 is 8-10000 rpm. And if you designed a V8 engine with the same stroke as a V12 then you would partially lose the advantages of a V8 engine which are small length, size and weight.

[Alic01]

I personally worrk in hydraulics and know very little about the technical aspects of engine design and calculation.

One thing though which is worth bearing in mind is that Power = Torque (Nm) * Speed (Rpm) / 9550

Therefore if torque remainst the same then double the revs will double the power. If the figures quoted for the old cosworth engine and of course the new engines are correct then it is possibel that output torque has remained almost constant yet speed has increased significantly.

This would allow the use of larger ratios and ultimately providing minor increses in raw top spead with increased throttle response and torque in the higher gears

There are people in this forum who are very skilled who can tell you exactly how these increased are arrived at and how they affect the many aspects of the car, unfortunately my expertise does not lye in these areas, hope this helps!