Performance - Torque vs Horsepower

[LostInMoscow]

What's your opinion on what is most important for a car's performance in regards to torque and horsepower? Obviously, there are a lot of factors that affect performance, including the HP and Trq curves, not just max power and torque. Please chime in! Personally, I really dig lots of low end torque with max HP just exceeding max torque.

Having said that, it is fun to drive a big diesel with like 800 Ft-Lbs of torque sometimes, but they don't exactly scream through the 1/4 mile like a gasoline engine.

[8cd03gro]

HP in the usable rpm range is the most important for total performance, but not necessarily the most enjoyable for driving if you sacrifice too much low end torque and thus low end horsepower.

[ViperTomcat]

Depends on what I want..(talking crank numbers)

I want at least 500-600 torque and around 350-400 HP for a drag racing, 1/4 murdering car.

I want at least 700 HP and 500 torque and gearing to match to break 200 MPH.

For a street car? a mix of both..to me an ideal is the 2011 5.0's.. 412HP and 390 TQ

[LOWDOWN]

"Torque is what launches you...horsepower is what wins the race..."

True on the street, at the strip, and especially when hauling/towing.

[Sax1031]

for a performance car I would be more worried about hp

[DGthe3]

Well, high rpm power is great if you plan on keeping your revs high ... but its nearly useless if you don't. Some people like it because it feels like the car 'comes alive' beyond say 6000 rpms. But its more accurate to say that the engine is simply dead before that point. But with a torquey engine, hit the gas at any speed and you don't have to wait for the car to 'wake up' its raring to go already. A side effect of all this is that if you've got a high reving engine, you can't really use its power all that much. But you can use torque all the time.

Hypothetically, lets say you've got a ~4.5L V8 engine that makes 450 hp @7500 rpm (perhaps from a Ferrari) and compare it against the LS3, which is 426 hp @5900. Now, the high rpm engine might make more absolute power. But if you overlay a pair of dyno charts from each, you'd see that the big torquey LS3 makes more power through out its entire rev range. And it won't be just a little more, its perhaps 20% more. For example, if you were to punch the gas at 3000 rpm. The LS3 would give you around 205 hp in return. Meanwhile, our other little screamer would only yield say 170 hp at that speed. To match the power of the LS3 it would need a few hundred more revs. This sort of thing continues until the LS3 hits its redline. Now, some of it can be corrected with different gearing, then again ... if you can gear one car aggressively, you can gear another aggressively. However ... nvm ... I think I've already gone and made this too technical already.

[Sax1031]

That is why with high rpm hp cars you need gearing.

high rpm hp + gearing = best performance

I do agree that when driving said car on the street it won't be as fun as a car with low end grunt. But it will perform better in a race setting.

[chain777]

If you want to feel fast, you want low end torque. If you want to go fast, you want max horsepower.

[JJ#48Racing]

This old saying pretty much discribes how I feel:

"My true love is torque, but I'm having an affair with horsepower."

[DGthe3]

Originally Posted by Sax1031

That is why with high rpm hp cars you need gearing.
True
high rpm hp + gearing = best performance
partially true

What does more overall power + gearing = ?

You can go and give a screamer short gearing, but there is nothing that says a stump puller can't be given the same mechanical advantage (so long as you're willing to sacrifice 1st gear). Gear a Corvette like a Ferrari and it becomes a no-contest.

Performance wise, gearing does the same thing for all cars nearly equally, regardless of the engine. It might hurt drag times slightly if you have to shift at the near end of the run when you didn't before, and in some cases it might reduce your absolute top speed (not an issue with todays double overdrive 6-speed transmissions though)

[Sax1031]

Originally Posted by DGthe3

What does more overall power + gearing = ?

You can go and give a screamer short gearing, but there is nothing that says a stump puller can't be given the same mechanical advantage (so long as you're willing to sacrifice 1st gear). Gear a Corvette like a Ferrari and it becomes a no-contest.

Performance wise, gearing does the same thing for all cars nearly equally, regardless of the engine. It might hurt drag times slightly if you have to shift at the near end of the run when you didn't before, and in some cases it might reduce your absolute top speed (not an issue with todays double overdrive 6-speed transmissions though)

All I am saying is look at nearly all the professional racing vehicles. They spin the crap out of the motors and gear them to hell. This is the best combination for a performance car.

If it was different F1/indy cars would have vastly different motors.

[DGthe3]

Originally Posted by Sax1031

All I am saying is look at nearly all the professional racing vehicles. They spin the crap out of the motors and gear them to hell. This is the best combination for a performance car.

If it was different F1/indy cars would have vastly different motors.

All professional racing series have strict limitations on engines, most frequently starting with engine displacement and bans on forced induction. Few have ever placed a limit on engine RPM's. Therefore, they wind out their engines because thats the only way left to significantly increase power, not because its best. If anything, this is proof that torque is more important than revs, otherwise the organizers would have capped F1 cars at 4000 rpm and allowed NASCAR to use superchaged big blocks.

[Sax1031]

I can promise you upper rpm hp is far more important than lower end torque in F1/Indy.

If they capped the rpms the racing would be so piss poor nobody would watch.

Even the nascar guys set the engine up for upper rpm hp at the expense of low end torque.

They could allow a million cubic inch engine and they would still be trying to turn it as hard as possible and make the hp up top.

[DGthe3]

Originally Posted by Sax1031

I can promise you upper rpm hp is far more important than lower end torque in F1/Indy.

If they capped the rpms the racing would be so piss poor nobody would watch.

Even the nascar guys set the engine up for upper rpm hp at the expense of low end torque.

They could allow a million cubic inch engine and they would still be trying to turn it as hard as possible and make the hp up top.

I don't find open wheel racing to engaging to start with, so I'd hate to see it get worse.

But yes, you are right that Nascar teams set their cars up so that it produces more power at the top end because thats where the engines operate. They don't dip below 5k except during a caution or on pit road. Soto a Nascar guy, low end power isn't in the 1000-4000 rpm range, its in the 5000-8000 rpm range.

If you have the choice of either getting 20 hp more because of torque, or because of rpms, one or the other (not both!), you'd be stupid to take the revs. Why? Well, if its only at the top end you have to go through your entire opperating range before you get to use it. Meanwhile, the other guy gets more power almost the entire time. As you're waiting for your extra power, the other guy is pulling ahead.