Torque vs Hp

[chris0276]

You know, that does make sense. So I had it all wrong and so did SR20DE4EVR. Thanks for clearing that up.

[shortysdrop]

Go back to your go-kart days. A large chain sprocket makes for a slower speed but a better hill climber. A small sprocket gives you faster speeds but is lousy when climbing hills.
Same theory goes for engine stroke as mentioned by fugiot.
So what are you trying to do swoop some hills or mash the gas? torque-hp you decide

[sr20de4evr]

Originally Posted by fugiot

I disagree. Torque is the only power that you can feel. Like you said, It's like a hammer hitting a nail with a certain amount of force. Just because you hit the nail more frequently(such as revving high) doesn't mean that the force increases. You're just doing more work in a smaller amount of time. Not more powerful work. The illusion of noticing that the car accelerates more quickly in the higher rpms might contribute to the feeling that you're getting pulled harder but you're actually not.

I see your point, but accelerating faster at higher rpm is not an illusion. Why do we rev to the redline when racing? The qr25 has a flat torque curve straight from 2000rpm to 5000rpm (or thereabouts). If torque really was the only thing that mattered in acceleration, someone shifting at 3500rpm would run the 1/4 in the same amount of time as someone shifting at redline because they would both be making the same amount of torque the whole time (actually the person shifting at 3500 would be making more torque, since at redline the torque drops off dramatically). I think we can both agree that the person shifting at 3500 would loose terribly, but why is that? Gear ratios have nothing to do with it (the person shifting at 3500 would be in a higher gear), obviously it's not a difference in drag since the person shifting at 3500 would actually be going slower and have less drag. The only difference is the amount of horsepower that the cars are making at any given point in time.

When you want to accelerate on the freeway, you downshift, but why? You make the same amount of torque at 3000rpm as you do at 5000rpm, the difference is in that lower gear your rpm is higher and you make more horsepower, which makes you accelerate faster.

[shortysdrop]

I think I see your point, but if you take a car that revs high (say 8k rpm) and only produces 150hp against a car that revs low (say 6k rpm) and produces 250 hp and apply it to your theory wouldn't that mean the car with 150 hp would win? Or is it a matter of power curve and when?

[fry_ed]

I think I see your point, but if you take a car that revs high (say 8k rpm) and only produces 150hp against a car that revs low (say 6k rpm) and produces 250 hp and apply it to your theory wouldn't that mean the car with 150 hp would win? Or is it a matter of power curve and when?

the 250 hp car would win. horsepower is all that matters.

if you have 250 hp at 6k then you must have a lot more torque (at 6k) than the guy who has 150 hp at 8k. so in a sense, it is important that he has torque. but only because it allows him to make 250 hp at 6k.... get it?
what sr20 is saying is that TORQUE at low rpms must be a lot higher to get the same horsepower as the high rpms. in our car (and most cars), the horsepower curve just goes up all the way up to redline. torque is max at 4k but that is not max horsepower because you only need a fraction of that torque at 6k to get more horsepower.
i.e. we might have the same torque at 3k and 5k but clearly more hp at 5k.

[sr20de4evr]

Originally Posted by shortysdrop

I think I see your point, but if you take a car that revs high (say 8k rpm) and only produces 150hp against a car that revs low (say 6k rpm) and produces 250 hp and apply it to your theory wouldn't that mean the car with 150 hp would win? Or is it a matter of power curve and when?

no not at all, I was comparing the same car vs itself, just at different rpm. When you start comparing different cars you get much different results. All I was saying is that in the spec, you have the same torque at 3k and at 5k, but at 5k you have a buttload more hp, which lets you accelerate faster, exactly like what fry_ed said. If you have a car that makes 250hp @ 6k, it will obviously beat out a car with 150hp @ 8k. I wasn't saying that rpm wins battles at all, I'm just saying that if you have 2 cars with the same amount of torque, the one that can carry this torque up to the highest rpm will win, assuming they have similar gearing, weight, etc, because it will have more horsepower at that higher rpm. If you have a car that has dramatically less torque, even if it can rev 2k higher, that's not nearly enough to get enough hp to make up the difference. If you could get that car to hold that amount of torque out to say 12k rpm then it would have more hp than the other car and would win (in a long enough race, in a short race the other car would be able to pull at first since the 12k car would have to reach 30-40mph before the hp got high enough to match the lower revving car).

[fugiot]

Originally Posted by sr20de4evr

I see your point, but accelerating faster at higher rpm is not an illusion. Why do we rev to the redline when racing? The qr25 has a flat torque curve straight from 2000rpm to 5000rpm (or thereabouts). If torque really was the only thing that mattered in acceleration, someone shifting at 3500rpm would run the 1/4 in the same amount of time as someone shifting at redline because they would both be making the same amount of torque the whole time (actually the person shifting at 3500 would be making more torque, since at redline the torque drops off dramatically). I think we can both agree that the person shifting at 3500 would loose terribly, but why is that? Gear ratios have nothing to do with it (the person shifting at 3500 would be in a higher gear), obviously it's not a difference in drag since the person shifting at 3500 would actually be going slower and have less drag. The only difference is the amount of horsepower that the cars are making at any given point in time.

When you want to accelerate on the freeway, you downshift, but why? You make the same amount of torque at 3000rpm as you do at 5000rpm, the difference is in that lower gear your rpm is higher and you make more horsepower, which makes you accelerate faster.

Right, I stated it wrong. You do get pulled harder but you can't feel more power at a higher rpm. You just feel the same amoubt of power more frequently. Which is the"illusion" I mentioned.