Author Topic: HORSEPOWER AND TORQUE  (Read 2589 times)

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Offline 69cobrajetrugae2

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HORSEPOWER AND TORQUE
« on: February 18, 2016, 09:34:51 am »
Can anyone explain the 5252 rule?  My CJ seems to run out of pull after about 5200 RPM.  My car seems to perform best between 4200 to 5200 RPM. I found the link and the following quote and would like further clarification if possible.

Below 5252 RPMs any engine’s torque will always be higher than its horsepower, and above 5252 RPMs any engine’s horsepower will always be higher than its torque. At 5252 RPMs the horsepower and torque will be exactly the same.” —

http://www.allpar.com/eek/hp-vs-torque.html

Offline 161854

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Re: HORSEPOWER AND TORQUE
« Reply #1 on: February 18, 2016, 10:59:15 am »
       Torque is what a dyno actually measures and HP is a mathematical derivative of that. RPM is a factor in the calculation and the HP and TQ are the same at 5252 because of the formula.
       Randy
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Offline 69cobrajetrugae2

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Re: HORSEPOWER AND TORQUE
« Reply #2 on: February 18, 2016, 12:05:37 pm »
Okay. Let me see if I get this concept.  Horsepower is a theoretical time based rating of power, or the amount of work done in a period of time  Torque is a real time measurement of power, or the amount of work done immediately.

When the 80 pound crankshaft of my CJ is spun to 3200 RPM I have stored energy or torque when WOT is applied. Since the transmission is in 4th gear there is minimum parasitic losses through the transmission so the engine torque is sent to the ring and pinion to the wheels. Due to the port velocity developed by the engine with the cam lift and duration and piston stroke there is good volumetric efficiency between 3200 RPM and 5200 RPM which keeps the torque from falling off as the engine RPM increases.

The rear end gear ratio and tire diameter will determine the maximum acceleration in relation to road speed.

Offline redscj

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Re: HORSEPOWER AND TORQUE
« Reply #3 on: February 18, 2016, 03:36:37 pm »
     It's as Randy says. They measure torque & from that they calculate the hp. I don't think that for the purpose of calculating the hp. Any other item factors in. The only example that I might be able to give would be from a pro stock driver many years ago. He had 2 motors for match racing. The motor that made the most horse power wasn't the quickest in the 1/4 mile. Both were ran in the same car. I can't explain it but I trust that he was correct. I believe the quote was that dyno's don't win races.
Grant
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Offline 161854

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Re: HORSEPOWER AND TORQUE
« Reply #4 on: February 18, 2016, 05:11:53 pm »
Okay. Let me see if I get this concept.  Horsepower is a theoretical time based rating of power, or the amount of work done in a period of time  Torque is a real time measurement of power, or the amount of work done immediately.

When the 80 pound crankshaft of my CJ is spun to 3200 RPM I have stored energy or torque when WOT is applied. Since the transmission is in 4th gear there is minimum parasitic losses through the transmission so the engine torque is sent to the ring and pinion to the wheels. Due to the port velocity developed by the engine with the cam lift and duration and piston stroke there is good volumetric efficiency between 3200 RPM and 5200 RPM which keeps the torque from falling off as the engine RPM increases.

The rear end gear ratio and tire diameter will determine the maximum acceleration in relation to road speed.

        Nothing to do with it. You are talking about kinetic energy when speaking of the flywheel energy.
  In "drag racing" terms , torque is required to make the object move. A PERFECT example is an electric motor which has TREMENDOUS "instant torque"  and NO "torque curve" for neck snapping performance in your golf cart but it goes 15mph. Try to slow it down with the throttle down and you'll burn up the brakes due to the torque. Often as redscj said an engine with more torque will produce a better ET yet not run as much MPH and vice versa. This happens to us drag racers all the time
       A gas engine produces less torque at lower rpm due to inefficiency , more later and then less later yet. IC ( internal combustion) engines have torque numbers that are a reflection of cubic inches , compression ratio/power adders. There are other additional factors like rod to stroke ratio and camshaft, cylinder head alterations that affect the torque produced in a major way. Dyno testing reveals where the power curve is and how changes affect it. This is the main reason for dyno testing.
68 1/2 CJ FB San Jose white/blue "C" stripe Foulger Ford
 66 GT350 Hertz SFM 6S 477 white/ blue side stripes 1  of 18
3 magazine covers- Car Craft July '77,  Modified Mustangs Feb '11 , and June '14 Mustang Monthly
'78 F350 Oleynik racecar hauler

Offline 69cobrajetrugae2

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Re: HORSEPOWER AND TORQUE
« Reply #5 on: February 18, 2016, 06:32:23 pm »
Thanks guys.

I watched a Tesla S jump on it from about 70 going east on the 91 just past the 5 and he shut it down at Harbor blvd.

As you know Randy, late at night that stretch of freeway is nice and straight and bump free with plenty of room.

The acceleration was impressive and there was not a bit of smoke of the tailpipe, oh yea, no tailpipe.

My suburban was no match.  If I was in the CJ I'm not saying he would have bested me, but it would have been close.


Offline geraldt52

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Re: HORSEPOWER AND TORQUE
« Reply #6 on: February 18, 2016, 07:25:11 pm »
Thanks guys.

I watched a Tesla S jump on it from about 70 going east on the 91 just past the 5 and he shut it down at Harbor blvd.

As you know Randy, late at night that stretch of freeway is nice and straight and bump free with plenty of room.

The acceleration was impressive and there was not a bit of smoke of the tailpipe, oh yea, no tailpipe.

My suburban was no match.  If I was in the CJ I'm not saying he would have bested me, but it would have been close.

Oh, I think he would have bested you in the CJ without a lot of trouble...those things will run mid 11s in the 1/4 mile.  Your best hope would be that he was about out of battery power.

Offline 69cobrajetrugae2

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Re: HORSEPOWER AND TORQUE
« Reply #7 on: February 18, 2016, 08:50:00 pm »
Telsa S do between 9 to 13 seconds 60 to 120, my CJ is in the middle of that.

I might have to remove the fold down seat and the 27 battery and run a quarter tank of gas to beat him!

In reference to Reds observation of one engine running faster on the track than another engine that shows more power on the dyno, I found this on the web and have wondered what the effect is of a cam lobe that is not ground perfect in 360 degrees rotation in relation to the other 15 lobes.

That's why an old engine builder I talked to a couple of weeks ago spends a day or so checking EVERY lobe on every cam. He will even adjust the valves different for each lobe to maintain the same valve timing for each cylinder. He's been building engines for oval track for 50 years and has had some famous drivers do good with them.
 Jim N.
« Last Edit: February 19, 2016, 08:54:13 am by 69cobrajetrugae2 »