Torque vs Horsepower primer
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Northstar Engines and System Technical Discussion Discussion, Torque vs Horsepower primer in Cadillac Engine Technical Discussion; I think a few are still confused why horsepower is what makes your car fast vs torque... So here's a ...
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    eldorado1 is offline Cadillac Owners Connoisseur
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    Torque vs Horsepower primer

    I think a few are still confused why horsepower is what makes your car fast vs torque... So here's a GREAT article about it.

    http://www.yawpower.com/tqvshp.html

    What determines a fast car is gearing and horsepower (and weight).... that's it.

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    Elmer Fudd is offline Cadillac Owners Fanatic
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    Re: Torque vs Horsepower primer

    Excellent article......thanks

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    Re: Torque vs Horsepower primer

    I'm not confused...

    HP and gearing may indicate the maximum speed a vehicle can ultimately reach and sustain, but torque determines how fast it will reach it.

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    Re: Torque vs Horsepower primer

    Exactly. Horsepower doesn't determine how fast a car is. Peak torque, peak torque RPM, and width of the power curve determine how fast a car is along with the gearing.

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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Torque vs Horsepower primer

    Quote Originally Posted by danbuc View Post
    I'm not confused...

    HP and gearing may indicate the maximum speed a vehicle can ultimately reach and sustain, but torque determines how fast it will reach it.
    Really? Because in that article, it showed a 550 ft-lb cummins diesel being beat by a 290 ft-lb formula 1 engine....

    I think you're still confusing torque *at the wheels* with torque at the flywheel.

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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Torque vs Horsepower primer

    Quote Originally Posted by 90Brougham350 View Post
    -Peak torque
    -peak torque RPM
    -and width of the power curve determine how fast a car is
    -along with the gearing.
    No
    No
    YES
    YES!

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    Re: Torque vs Horsepower primer

    Quote Originally Posted by eldorado1 View Post
    Really? Because in that article, it showed a 550 ft-lb cummins diesel being beat by a 290 ft-lb formula 1 engine....

    I think you're still confusing torque *at the wheels* with torque at the flywheel.

    It's a little hard to compare a Diesel who's power band may span 2000k rpm, and a high winding small displacement V10 who's power band can easily reach into the 15k rpm range. You put that High-winding V10 into a Dodge Ram, and line it up to another Dodge Ram equipped with the Cummin's diesel, and tell me which one is faster. Something tells me that diesels got he V10 beat.


    As for the F1 Honda being faster than the deisel it's quite easy to explain why. With it's 18k+ rpm power band, the V10 in the Honda has the HP to carry that torque up through the rpm range. Sure it's probably no the flatest torque curve around but it makes due.....plus it's idles around 10k (so it's really only got an 8k rpm power band per say). Now that Cummins diesel has make it's peak hp around 2krpm, and it's peak torque is mostly like around 1500. It's doesn't have the ability to carry that torque up through the RPM range like the Honda motor does, that's why it relies on short shifts, and a taller final drive. Also, the Cummins Diesel is not a thorough-bread race engine. It is a big torque, low RPM beast of a motor, designed for the soul purpose of making huge power, and low rpm/speed. So yeah, it's gonna be an ass load slower than the crappy Honda V10. Your not gonna pull any tree stumps out with that V10 I can assure you that.

    That article only begs the question....do people really think about what they are saying before they say it? I say, that article is a good example of a maybe he did, maybe he didn't...who knows type of situation.

    I'll end with this. Torque, is the engine ability to turn the driveshaft, which turn the axle, which then in turn spins the wheel....so, Torque is the engine ability to turn the wheels.

    HP, is the engine's ability to carry that torque up the RPM range, making it usable at higher speeds.

    The acceleration your feel in your ass when you nail the throttle....that's torque. The more of it you have, the harder the engine's going to turn the wheel. The more hp you have, the faster the engines going to turn the wheels. Without torque, the engine has to work much harder to reach a give speed. Without HP, it takes a longer time to reach that speed, but will be done with much less effort.

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    Re: Torque vs Horsepower primer

    The Guru once posted a very lengthy and detailed (as usual) explanation. He pretty much said what Danbuc is saying. I remember him saying "People buy HP, but drive torque".

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    Re: Torque vs Horsepower primer

    What people don't realize it that's it's all relative. In some applications (like heavy utilitarian vehicles designed for towing and pushing) lot's of hp is not necessary. All they need is lot's of low end torque to proved the brute force needed to do heavy work. In other applications (like that of the F1 car) lots of torque isn't necessary, since it's not really pulling/pushing much weight, and isn't required to do much work. All it has to is spin the tires really fast.

    Some vehicle need more low-rpm torque. Other's benefit from high-rpm HP. There's no way to say one's better than the other. Each has it's strong points in certain applications. Sadly, our heavy cars could benefit from more low end torque, which would help out in the acceleration department as it were. Other vehicles, like a 396 Chevelle have all the torque they need, but could benefit from a little more top end power. It's all application specific.

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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Torque vs Horsepower primer

    Quote Originally Posted by danbuc View Post
    It is a big torque, low RPM beast of a motor, designed for the soul purpose of making huge power, and low rpm/speed. So yeah, it's gonna be an ass load slower than the crappy Honda V10. Your not gonna pull any tree stumps out with that V10 I can assure you that.
    Now I can TELL you didn't even read the article.

    How can I tell? Because again, you're neglecting gearing. You can take a motor from a VCR, and with enough gears, you could pull a tree stump out. Or lift a 500 pound safe 1' off the ground.. It would take days (years?) because it doesn't have enough horsepower, but it could do it.

    Power = Force * Distance / Time

    To quote the article:
    To accurately describe the acceleration capability of your vehicle, we must consider time. If we just considered force, and distance, we wouldn’t really be saying much about the car. If I tell you that my car can pull a 3,000-lb. weight 100-ft. up a hill, would you be impressed? Certainly not, because I haven’t really told you much. If I told you that I could do it in 10 seconds, while your car needed 15 seconds to do the same job, you might be impressed.


    Torque's a force.


    BTW, keep it coming, I like these discussions, as long as you keep it civil.

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    Re: Torque vs Horsepower primer

    Now the question is, how to get more torque out of the northstar. My 4.9 is a joy to drive around because of all the low end grunt, my northstar is a joy to drive on the highway because of the top end horsepower, maybe I should just stuff a 4.9 in the trunk

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    chevelle is offline Cadillac Owners Enthusiast
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    Re: Torque vs Horsepower primer

    I good practical comparison of torque and HP is to consider yourself riding a 10 speed bike up a hill. Put it in the lowest gear and you can move the pedals easily but you won't go very fast unless you can pedal at a very fast rate and keep it up forever. On the other hand, you could move to a higher gear. It would get harder to pedal but you would be moving faster. In the first example you would be the high HP, high revving F1 engine. Not much torque but the gearing makes up for it and the engine can rev hard enough to make up the speed lost thru gearing. In the second case you would be the Duramax diesel slogging up the hill with tons of torque.

    The difference is not as easy as just explaining torque and HP and then compare engines on a one-to-one basis. Sure, the F1 engine can pull as much weight up the hill with the correct gearing. But can it live for hundreds and thousands of hours revving at 18,000 RPM to do that? No. The big diesel won't win any races with all that torque necessarily but it can pull hills for hours on end making max torque. Two different applications and two different power requirements. Not very comparible.

    HP is useful for comparing the outputs of dramatically different engines on the same scale, though.

    Just pulling a load up a hill and accelerating a load are also two different things and that also doesn't get addressed in the usual HP vs. Torque discussion.

    The diesel can pull a heavy load with all the torque it makes but it has a very narrow power band. Duramax diesels sign off at about 3500 and class 8 diesels rarely rev over 2400. This requires lots of gear changes to keep the engine in it's torque band. A higher revving gasoline engine can often accelerate quite well even with a heavy load with the right gearing due to it's ability to rev to a very high RPM which makes the power band (and the area under the curve of the torque/HP graph) quite a bit wider.

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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Torque vs Horsepower primer

    Good points.

    Perhaps a more "level" race would be between an LT1 and an L98 powered car. It doesn't illustrate the difference as well, but the LT1 and L98 both make the same amount of peak torque, but different HP. The LT1's a breather...

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    Re: Torque vs Horsepower primer

    Excellent thread. Keep them coming. I love it.

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    Re: Torque vs Horsepower primer

    I read the article, but saying it's only a matter of gearing between the V10 pulling a tree out of the ground, or pushing a car to 200+mph is crap. I guess if I tied a big enough block&tackle to an ant's ass, I could come up with some gear ratio that would allow him to lift the white house....but it doesn't mean anything, because it'll never happen. The gears used in a vehicle, and it's power band (hp and torque curves) are usually designed as a package deal. You don't build an engine and then say, "Let's see what kinda gears we can throw behind this thing". Both have to be carefully selected for their particular application.

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