Well, it was certainly true of the re-engineered Buick 3.5 litre V8 engine which Rover produced in the late 1960's.
This reference
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has it as 161 BHP at 5200 RPM, but my recollection is 160 at 5250.
Torque peaked much earlier - and was just over 200 lb.ft at around 3000 RPM - but power (the product of speed and torque) continued to rise - peaking at about 5250 rpm.
Note: At no time did I say that max torque coincided with max power! Did you think I did?
The BHP figure quoted in those days was gross. I'm not sure what that figure would be in today's money, but a lot less. The last carb engines in the SD1 - with much better heads and exhaust system - produced a quoted
155 BHP. Albeit on a lower CR.
Not after reading it carefully. ;-) It's just that I'd never come across curves giving the same torque figure and BHP figure. But I'd not claim to have seen all.
It only applies at that one speed - and only when using 'proper' units. Because BHP = RPM x lb.ft /5252 the power of *all* engines is numerically the same as the torque at 5252 RPM regardless of where they peak. [It's just that I remembered that the Rover V8 produced 160 lb.ft at 5250 RPM, and that was its peak power speed].
400nM at 2000RPM => 84kW (to the nearest integer) ~= 112HP.
Reverse the transformation, and from 200HP you get 210lb-ft, or 284nM. A little over half. Right?
Now, if you have a gearbox attached to this engine, and you set it to reduce the output shaft to 1000RPM, what is the resultant torque at those two engine speeds?
The point is, Dave, that you are unable to apply these calculations to real world situations when they disagree with your prejudices. I'd hoped to be able to talk you through it.
112BHP / 400nM at 2000 RPM geared down to 1000 RPM gives a little under (because of friction) 800nM at the output.
200 BHP / 284nM at 5000 RPM geared down to 1000 RPM gives a little under
1420nM at the output.
This clearly shows you get more force by choosing peak power in a low gear over peak torque in a higher one.
But, hey, if you want to believe otherwise when you've got the mathematical skills to prove to yourself that your long held prejudice is wrong - I'm not going to argue with you any more.
That's a no-brainer, anyway. Just as you can express engine power in terms of engine speed (times) engine torque (divided by) a suitable constant, you can also express propulsive power as road speed (times) thrust at the contact patch (divided by) a different constant - but they should equate to the same thing apart from transmission losses. So when the engine is developing its peak power, you'll get peak thrust at the wheels.
Having said that, it's not particularly useful unless you've got an infinitely variable transmission because fixed gearing will only allow max power to be applied at the road at a few discrete speeds - not over the whole speed range.
Actually the Jazz hybrid with CVT (with less than 100 BHP including the electric motor) is pretty nippy off the line if you floor it. Regularly sees off 5 series BMWs showing off at the lights :-)
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