Torque vs Horsepower
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Racer
Joined: Apr 2003
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From: Katy TX
Torque vs Horsepower
Torque vs Horsepower, which is better for drag racing? When choosing a cam, there are many different choices and some can produce better torque and others better HP. Which one is better torque or HP?
Race Director
Joined: Apr 2000
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Re: Torque vs Horsepower (bhmyers)
Yo gonna open a real can 'o worms on this one :lol:
I'll get the ball rolling, for drag racing horspower wins races at the top end of the track :D
I'll get the ball rolling, for drag racing horspower wins races at the top end of the track :D
Thread Starter
Racer
Joined: Apr 2003
Posts: 349
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From: Katy TX
Re: Torque vs Horsepower (bhmyers)
Im going through this desktop dyno plugging in various cams, and coming up with big differences. I know this software is just a rough estimate, but is it even close? Has anyone used it and then had and actual dyno done to see how close it was? Should I try to get an even torque and HP or one more than the other?
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Drifting
Joined: Oct 2000
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From: Shawano WI
Re: Torque vs Horsepower (bhmyers)
Im going through this desktop dyno plugging in various cams, and coming up with big differences. I know this software is just a rough estimate, but is it even close? Has anyone used it and then had and actual dyno done to see how close it was?
Here is a chart from dd2003 with the specs of a 355 dyno mule we use for testing parts on. The heads are unported Sportsman II with the exception of chamber work and a small amount of bowl work.
DD says the motor should make peak numbers of 563/496. On the dyno it made 572/511, so DD wasn't far off on that combination. The cam in the motor was 264/268 at .050 with 106 LSA. We were going to try a new gring that was very similar except it was 264/272 at .050 with a 106 LSA. According to DD the new combo should have made peak numbers of 632/545. That is up 60 HP and 34 TQ which is hard to believe with a cam change. When we dynoed the new combination it actualy made 578/499 which is only a gain of 6 HP and a loss of 12 TQ.
DD2003 seems to be close on some combos but quite far off on others. If you come across something that makes a huge change it probable is not correct.
[Modified by Pete79L82, 9:14 PM 11/21/2003]
Team Owner
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From: All humans are vermin in the eyes of Guru VA
Cruise-In IV Veteran
Cruise-In V Veteran
Re: Torque vs Horsepower (1969Vette350)
All right, all of the usual things have been said but I have a question. Is there an equivalency between TQ and HP? As in, is 1 HP = some amount of TQ?
http://www.vettenet.org/torquehp.html
[Modified by Guru_4_hire, 9:41 PM 11/21/2003]
Racer
Joined: Sep 2003
Posts: 420
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From: Indianapolis IN
Re: Torque vs Horsepower (bhmyers)
HP is a multiple of torque and RPM. If TQ was the only thing that mattered we would all have Mack or Peterbuilt truck engines in our Vettes. Think about it. They both are important. HP lets you stay in a lower gear longer giving you a numerical advantage. High TQ with Low HP makes you shift at a lower RPM into a stiffer gear.
So the answer is you need BOTH for drag racing or street performance. You need TQ to get you off the line and HP to let you finish the race. Now high RPM cars like Indy cars and NASCAR cars mostly need HP while trucks and bulldozers need mostly TQ to get the weight moving.
[Modified by blunsford, 3:52 AM 11/22/2003]
So the answer is you need BOTH for drag racing or street performance. You need TQ to get you off the line and HP to let you finish the race. Now high RPM cars like Indy cars and NASCAR cars mostly need HP while trucks and bulldozers need mostly TQ to get the weight moving.
[Modified by blunsford, 3:52 AM 11/22/2003]
Melting Slicks
Joined: Apr 2000
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From: San Jose California
Re: Torque vs Horsepower (bhmyers)
If you have a big load to pull, get a C15 Caterpillar engine. 890 cubic inch, 500 horsepower, and 1650 pounds of torque all within a ~2500rpm redline
If you want to go fast, getting a 302 "Dep Special" with 500 horsepower and only 350 pounds of torque a will do a better job within an 8000rpm redline.
For me, I can't get no traction in my first 3 gears so any more torque beyond my 550 ft/pounds is of minimal value. My 550 horsepower moves me to the 7000rpm redline pretty darn quick. A higher torque motor would probably be a more civilized motor, but wouldn't make me as fast. A higher horsepower motor would give me even more top speed than the 1968 Vette of Heinz' LeMans entry in 1971 that went 212mph on the Mulsanne straight. Do I really need more than this? Well, yes I do, but I'm talking about normal people here. Perhaps you are one of them. But anyway, adding only horsepower would make the car even less drivable on the street.
Determining your preference between torque and horsepower is a very personal thing. Don't get caught up in horse power wars. It is an addiction that is impossible to kick. I know what I speak!
Chuck
If you want to go fast, getting a 302 "Dep Special" with 500 horsepower and only 350 pounds of torque a will do a better job within an 8000rpm redline.
For me, I can't get no traction in my first 3 gears so any more torque beyond my 550 ft/pounds is of minimal value. My 550 horsepower moves me to the 7000rpm redline pretty darn quick. A higher torque motor would probably be a more civilized motor, but wouldn't make me as fast. A higher horsepower motor would give me even more top speed than the 1968 Vette of Heinz' LeMans entry in 1971 that went 212mph on the Mulsanne straight. Do I really need more than this? Well, yes I do, but I'm talking about normal people here. Perhaps you are one of them. But anyway, adding only horsepower would make the car even less drivable on the street.
Determining your preference between torque and horsepower is a very personal thing. Don't get caught up in horse power wars. It is an addiction that is impossible to kick. I know what I speak!
Chuck
Race Director
Joined: Jan 2003
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From: State of Confusion
Re: Torque vs Horsepower (71vettman)
5252 im pretty sure
If you look at any HP/TQ figures, at 5252 RPM, they 'cross-over' each other.....
'TORQUE' accelerates a vehicle; 'HORSEPOWER' delivers speed.
If you'd compare a Winston Cup car, set-up for the Martinsville, Va. 'bull-ring', vs. a car set-up for the 2-mile high-banks of Michigan, you'd se the difference.
At Martinsville, the driver lifts COMPLETELY off the throttle, and uses the brakes to navigate the flat, hair-pin turns, then 'mats-the-skinny' down the short straight-aways. They 'may' only hit 130 on the straights, but 'slow' to 75 (only a guess) in the corners. 'TORQUE', along with deep-gearing, allows them to accelerate quickly.
At Michigan, they run almost wide-open around the banked front & rear straights, only 'BARELY' cracking the throttle in the turns. The motors run at a very narrow RPM-band. I think they enter the turns @ 185-190, but slow to 'only' 155 MPH in the center of the turn. With longer straights, and a narrower RPM-band, they rely on 'HORSEPOWER' to run these speeds.
[Modified by Glensgages, 10:19 PM 11/21/2003]
Drifting
Joined: Feb 2002
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From: Berlin
Re: Torque vs Horsepower (bhmyers)
Part of the reason that so many people have a problem with this is that the word torque is used by different people to mean different things.
Some people say an engine has good torque if it runs strong at low rpm, and others talk about the peak torque value of an engine. These are unrelated concepts.
The proper definition of torque is what is measured by a dyno. It is essentially the physical force that the engine exerts. That force changes as a function of rpm, so you get a curve instead of a single number. If you're building a car from scratch (picking the gears), peak torque numbers mean absolutely nothing. The curve is what matters, and hp is one measure of how much potential that curve has if the car is geared optimally. Of course almost no street car is ever gear optimally...
There is no straight answer to your question because gears are just as important as the engine.
Some people say an engine has good torque if it runs strong at low rpm, and others talk about the peak torque value of an engine. These are unrelated concepts.
The proper definition of torque is what is measured by a dyno. It is essentially the physical force that the engine exerts. That force changes as a function of rpm, so you get a curve instead of a single number. If you're building a car from scratch (picking the gears), peak torque numbers mean absolutely nothing. The curve is what matters, and hp is one measure of how much potential that curve has if the car is geared optimally. Of course almost no street car is ever gear optimally...
There is no straight answer to your question because gears are just as important as the engine.
Le Mans Master
Joined: Oct 2002
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From: Silver City NM
St. Jude Donor '05-'07
Re: Torque vs Horsepower (bhmyers)
Torque are the numbers enemic smallblocks advertise when they have no horsepower.
Big blocks don't even bother quoting torque numbers...HORSEPOWER wins races :)
Torque IS great in pickup trucks though :D
Dep
Big blocks don't even bother quoting torque numbers...HORSEPOWER wins races :)
Torque IS great in pickup trucks though :D
Dep
Le Mans Master
Joined: Oct 2002
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From: Las Vegas - Just stop perpetuating myths please.
Re: Torque vs Horsepower (Glensgages)
5252 im pretty sure
Correct-o-mundo! :thumbs:
If you look at any HP/TQ figures, at 5252 RPM, they 'cross-over' each other.....
Correct-o-mundo! :thumbs:
If you look at any HP/TQ figures, at 5252 RPM, they 'cross-over' each other.....
HP = (torque x RPM)/5252
Where torque is the amount of work done – twisting force through the arch of a circle.
And horsepower is power, which is the amount of work done in a unit of time.
Torque and power bands are nice to know but the older I get reality tells me I probably will only get to build few more engines. And economics will determine the power produced by the parts I can afford. $10 per hp is reasonable to about 400. Bigger displacements and custom parts become exponential in price. No warranty here either. But your credit companies will love you. :chevy
Safety Car
Joined: Oct 2000
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From: Allen TX
Re: Torque vs Horsepower (cardo0)
I'll stir the pot a little more and give you a scenario... you tell me which car wins and why (or if you can even determine the winner based on the info I give you).
The fact is that AVERAGE HP across the _useable_ rev-range will win the race. This obviously involves TQ, since (as has been stated before) HP is just a function of TQ anyway. The "useable rev-range" involves things like gearing (trans and rear) and the rpms at which your engine is designed to function most efficiently.
Now for my scenario.
Car 1 weighs 3150lbs and makes 495rwhp on a chassis dyno.
Car 2 weighs 3150lbs and makes 525rwhp on a chassis dyno.
Both cars have the SAME gearing in the trans and rear. Both cars operate in the same rev-range.
From the facts above can you say, for sure, which one will win?
The fact is that AVERAGE HP across the _useable_ rev-range will win the race. This obviously involves TQ, since (as has been stated before) HP is just a function of TQ anyway. The "useable rev-range" involves things like gearing (trans and rear) and the rpms at which your engine is designed to function most efficiently.
Now for my scenario.
Car 1 weighs 3150lbs and makes 495rwhp on a chassis dyno.
Car 2 weighs 3150lbs and makes 525rwhp on a chassis dyno.
Both cars have the SAME gearing in the trans and rear. Both cars operate in the same rev-range.
From the facts above can you say, for sure, which one will win?