On a different note and back vaguely on the original subject. I agree Torque is good as ive been in my friends 350bhp/600kg Seight, unsure of torque figure but it has something silly like 180ft at idle and 300 odd peak but diesels are all about torque and I hate diesels so therefore bhp is the winner!
This is kind of what I'm saying though. BHP is frankly meaningless. An engine, diesel or petrol only makes torque, that's all it does. Diesels, particularly diesel turbos make sh1te loads of torque, which some find sexy, others, you and I included don't. I know Maturin loves it. But it arrives in only a small area of the usable rev range which makes it a killer for acceleration if they're in the sweet spot, occasionally I suppose making us look silly.
As a result I guess diesels don't normally display large BHP figures, because a lot of that oomph (peak torque) has gone as they approach the red line, whereas petrol engines seem to deliver that spread of true power, i.e. torque, over a much more usable rev range. Petrol turbos are a half way house I guess, where they make masses of boost enhanced torque at a certain rev range which tends to be higher up the rev range to still deliver the sexy, high BHP figures.
If someone can prove me wrong about BHP, I mean about me saying it doesn't really exist and only torque does, then I will gladly eat humble pie with custard and learn. But I feel confident that BHP is just torque looked at through rose tinted glasses and is a rate of doing work rather than a measure of an engine's capability to rotate a crank.
I have mentioned many times on this forum that a far more realistic rating for an engine would be something like this:
'Using 80% of the rev range (between 0rpm & rev limit), 95%+ of peak torque can be delivered over what percentage of this band?'
Let's say we have an Mi16 with PeterT's stage I road cam & his chip mod.
A PeterT chip on an Mi16 gives a rev limit of 7,500rpm. This means we have the 6,000rpm band of 1,500-7,500rpm to look at (i.e. 80% of the rev range)
Peak torque is perhaps 140lb.ft, so 95%+ is anywhere on the torque curve equal to or higher than 133lb.ft.
If the engine produces 133lb.ft for a band of 750rpm, then that is 12.5% of the 80% band in question.
> This means that engine would have a 133 / 12.5
rating, meaning it generates at least 133lb.ft over 12.5% of the practical rev range.
> This means a peak figure could be shown (or worked out)
> And this means this true power is accessible for 12.5% of the usable rev range, which in comparison to a 133/10 motor would be 'better', and provable so.
This really only compares engines and not cars, as I appreciate that there are so many other contributing factors in grading performance. But this method could be used on an engine dyno or on a rolling road, where I think with the latter it should be done using only ATW figures. In a shoot out however i.e. a rolling road day, providing the calculation back to fly was consistent it would still produce comparitive results.
But realistic ain't sexy, although I think for example a 120 / 40 engine would be mega impressive. It may produce less peak torque (which is where skewed figures come in - like horse power I'm afraid) but the top 5% of true engine power would be on tap for nearly half the rev range from tick over to red line. Now that's SEXY!!
Edited by DrSarty, 08 December 2008 - 10:09 AM.