Main Question or Discussion Point
Ive got a question, which is more powerful and better to have in auto racing, torque or horsepower? Ive gotten mixed answers and wanted to ask some people who know their stuff.
No, the engine that is able to to deliver more torque will be able to kick your butt to the finish line faster.Sure, but in the ideal world (where no energy is lost in the gearbox), if two engines (with different torque) output equal horsepower, than both should accelerate at the exact same rate (even if one does have to shift gears at 2kph) and reach the same top speed (if both cars have the same aerodynamics). Right?
No. Every time you shift gears the torque delivered to the wheels drops, so the acceleration drops. Those two cars will only have the same acceleration for about a tenth of a second.Sure, but in the ideal world (where no energy is lost in the gearbox), if two engines (with different torque) output equal horsepower, than both should accelerate at the exact same rate (even if one does have to shift gears at 2kph) and reach the same top speed (if both cars have the same aerodynamics). Right?
What you're saying seems to be that I'm correct (noting the ideal situation I specified, think massless continuous variable transmission); the only difference is the losses that occur between the engine and the wheels (obviously from real life experience, time lost on the clutch early-on is a major factor).Even in the ideal case, you still have to account for it because it has a huge impact.
Uh, ok...... I guess if your incorrect scenario were correct, you'd be correct. :uhh:What you're saying seems to be that I'm correct (noting the ideal situation I specified, think massless continuous variable transmission); the only difference is the losses that occur between the engine and the wheels (obviously from real life experience, time lost on the clutch early-on is a major factor).
That much is true.This is interesting because it seems to demonstrate horsepower governs maximum speed (circular track), but torque influences acceleration (drag racing).
That's certainly true. It comes up so much in some other forums I frequent that I've thought about writing up a canned response. But I haven't done that yet, so here's another try:This is a frequently-debated topic in automotive performance circles.
Power is proportional to torque at any RPM, so the original question doesn't actually make sense. I think what you mean is, is it better to have a broad power band ("torquey") or a narrow one ("peaky"), assuming the peaky motor puts out more maximum power. If your shifts took zero time, if you had as many gears as you wanted, and if could keep the engine operating at the same high rpm all the time, then a narrow peaky 2-stroke-style power band would be quicker if it puts out more peak power. Factor in limited human abilities, and a broad power band becomes more useful to more people even if peak power is down - so more people would go faster.Ive gotten torque=acceleration and hp=top speed. Well, I want to ask something, if you have alot of torque all over the powerband especially up on the top end does that mean while one car is topped out on the top end you`re still accelerating?
The problem is on many engines the hp rpm peak is above the torque rpm peak....TQ and HP are proportional to each other, so it makes no sense to speak of them as if they're independent...
Just to clarify, all engines have their hp peak after their torque peak (at least if there's only peak for each curve). It's an amusing little math exercise to prove that.The problem is on many engines the hp rpm peak is above the torque rpm peak.
This raises the question, is optimal acceleration at hp peak or torque peak. Also we must define "acceleration". Do we mean momentary acceleration, as from 60-61 mph. Or do we mean sustained average acceleration, as in lowest time from 0-60 mph or 1/4 mile? Also transmission type is a factor: traditional geared transmissions vs CVT.
You might want to visit a few drag tracks and buy a pit pass so you can rub elbows with the racers. One of the most incredible performers in the NE in the early 80's was a Canadian driving a Camaro called Mouse Trick. He ran pro-built small-block Chevy engines and he said that he was dumping the clutch at 10,000 rpm off the line. I don't know if that was true, but I have no reason to doubt him. He had reliability problems because of this "pushing the envelope", and I recall him and his crew at Pembroke, NB one year scouring the camped-out drag crews for clutch parts, so that he could advance to the Sunday eliminations. My buddy was running a 340 Duster (eventually the US champion in his class for a couple of years) and he was dumping the clutch at 6000 rpm - only after a lot of efforts lightening the rods, grinding off piston skirts, etc. 340 Mopar parts are a lot more massive than small-block Chevy parts and he had a lot of work to do to overcome that differential.Even in a drag race, (let's say a 6,000 rpm limit) you are below 3,000 rpm (intial launch) for a short period of time (probably 5% for example). The upper rpm horsepower is crucial here. You can have "gobs" of torque below 3,000 rpm...but if you have trouble breathing up top - no horsepower output...the car with less torque and more horsepower (equivalent vice versa situation) is going to take you. The 95% of the time, he is in his "sweet spot."
No, absolutely not. The top speed will be limited by:So hypothetically, if you had an engine that had unlimited revs or unlimited gears would it have infinite top speed?
But without that friction (and with limitless gearing) every engine could have "infinite speed", trivially (regardless of power etc).What, why doesnt infinite revs=infinite speed? Im talking like theres no wind or air or anything and no universal speed limit like the speed of light.