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  #1 (permalink)  
Old 08-02-2001, 08:45 AM
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Default Torque or Horsepower?????

This might seem like a stupid question but I had overheard some people at the track the other day saying that they were looking for ways to raise there torque. One even mentioned that they would be happy to lose some HP in order to gain torque. They weren't driving cobra's but they were in mustangs and doing 1/4 mile runs. I alway's thought you needed horsepower for the 1/4 mile run. Does anyone know what is preferred for the 1/4 mile, horsepower or torque? and why?

Thanks
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Old 08-02-2001, 09:31 AM
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Torque is the actual power of the twisting at the crank. Hp is simply a formula that equates torque in conjunction with RPM to derive power (HP).

Most (but not all) things people do to build a high performance engine simply move the torgue higher in the rpm range to increase HP. This is because 400 pound feet of torque turning at 5,500 rpm does a lot more work (power) than it does at 2,000 rpm.

The things that add torque are:

Increase compression = moderate gain
Advance timing = slight gain
Free flow exhast = moderate gain
NOS = large gain
Supercharge/turbocharge = large gain
increase displacement = proportional gain

Cams, manifolds, carbs, valves, porting, and so on generally move your torque up higher in the rpm range which is very desirable for racing, and does produce more hp. Ironically, doing this can actually reduce your peak torque in some cases.

In a drag race, here is the typical scenario:

Launch at 5,000Rpm, run in first to 6,500rpm, . . shift to second, rpm drops to 4,000, run up to 6,500 again, . . shift to third, rpm drops to 4,000 again, etc, etc.

So you can see in a drag race, your rpm is always high, thus you want your peak torque to be in that range. Think about a low compression mild cammed small port smog motor that produces peak torque at 2,800 rpm. In a drag race scenario like I just outlined, he would always be running 4,000 - 6,500 rpm which is way past where all the torque is. As a result, that car would perform dismally in the race.

ed

Last edited by CobraEd; 08-02-2001 at 10:51 AM..
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Old 08-02-2001, 03:48 PM
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Hey Ralph:

First a brief explanation and then a site for you to check out.

Torque is the measure of how hard we can twist something. It is usually expresed in FT-LBS. For example, there is a well in your back yard. When the bucket in the well is full it weighs 10 pounds. The roller that the rope is attached to is 2 feet in diameter. In order to lift the water to the top you must twist the roller with a torque of 10 FT-LBS (10 pounds X 1 ft radius). Whether is takes you 3 seconds to lift the bucket or 5 minutes, the torque applied was 10 FT-LBS. The time is of no importance since torque does not care about time.

Power measurement, however, do. The power needed to raise the bucket in 3 seconds is far greater than the power needed to do it in 5 minutes. That is why 400 FT_LBS of torque is more valuable at 5500 RPMs than at 2500 RPMs.

The is a great explanation of the whole business at "www.seansa4page.com/resource/torquehp.html".

Check it out.

Bob In Ct
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Old 08-02-2001, 05:43 PM
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from Carroll Smith's PREPARE TO WIN page 110

Carroll Smith writes:
"The validity of some horsepower figures is subject to some doubt and peak horsepower, even if it is acccurate, is largely of academic value. "Horsepower sell engines and torgue wins motor race", the man told me 20 years ago and nothing has proven him wrong yet!"


I believe HP is more equated with top speed where torque is the ability to accellerate out of a corner and this is what wins road races.

Andy
http://www.cobralads.com

Last edited by Andy Dunn; 08-02-2001 at 09:19 PM..
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Old 08-02-2001, 09:31 PM
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Wow, I wasn't planning on reading so much tonight. I love this site because of the information that I receive and all the new things that I learn and I definately learned something today. "It's definately better to make torque at high RPM than at Low RPM." I am actually seeing things differently than I did before I posted this. Thanks alot guys for the help, hope I can return the deed later on

Ralph
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Old 08-03-2001, 05:27 AM
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From a Cobra perspective I look at it like torque is what gets you moving and overcoming inertia...horsepower is what keeps you moving down the line. Of course, HP is a product of TQ. But with a Cobra you can only use so much TQ before you find yourself feathering your pedal to fight slippage. A heavier car like a Mustang must move 1100 lbs more weight from 0-60 so they need more TQ. The Cobra can move very quickly out of the hole with 200+ lbs of TQ where the Mustang may require 300.
(Perhaps a poor comparison). You may produce 400 RWTQ but you cannot use nearly that off the line...feathering the pedal may have you mastering the applied use of 1/2-3/4 through 1st/2nd gear tops. In the Cobras we can use HP much more efficiently than TQ. Once we can get these light weight Cobras to hook, HP is the big advantage from 4000-6000+ rpm . Now if I could only understand what the heck I said .....oh boy .
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