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SmokinVette.com Forums : Corvette Forums : Performance & Racing : Naturally Aspirated Engines : Why do torque and hp always cross at 5250 rpm?
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Old 09-18-2009, 09:57 AM   #1
C5inSB
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Cool Why do torque and hp always cross at 5250 rpm?

I think I've only seen 1 dyno chart that that wasn't true. (it was less that 5000).

Is it different for 4 cyl engines?

Just curious on the theory....

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Old 09-18-2009, 04:14 PM   #2
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I think I've only seen 1 dyno chart that that wasn't true. (it was less that 5000).

Is it different for 4 cyl engines?

Just curious on the theory....

you know you could be right, i had to get out the dyno sheet on my 383, and yes hp and torque do cross right at 5300rpm but my hp doesnt peak til 6200rpm. thats odd tho
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Old 09-18-2009, 06:39 PM   #3
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Originally Posted by C5inSB View Post
I think I've only seen 1 dyno chart that that wasn't true. (it was less that 5000).

Is it different for 4 cyl engines?

Just curious on the theory....

my guess is engine design it alot of weight to be throwing around that fast
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Old 09-18-2009, 11:38 PM   #4
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you know you could be right, i had to get out the dyno sheet on my 383, and yes hp and torque do cross right at 5300rpm but my hp doesnt peak til 6200rpm. thats odd tho
Yep - weird huh.

What it really tells me is that you always need to shift before 5000 to keep in the torque band during acceleration.
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Old 09-19-2009, 03:00 AM   #5
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Yep - weird huh.

What it really tells me is that you always need to shift before 5000 to keep in the torque band during acceleration.
actually ,you need to shift above that to get highest average power ,torque gets you started but horsepower gets you thru the trap or so ive been told by racers

Last edited by fishslayer143@yahoo.com; 09-19-2009 at 02:12 PM.
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Old 09-20-2009, 11:37 PM   #6
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actually ,you need to shift above that to get highest average power ,torque gets you started but horsepower gets you thru the trap or so ive been told by racers
Nope - when accelerating you want to be in the Torque band.

HP wins hearts and minds - Torque wins races.
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Old 09-21-2009, 06:44 AM   #7
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Nope - when accelerating you want to be in the Torque band.

HP wins hearts and minds - Torque wins races.
disagree , my motor redlines at 6500 rpm , produces 501 hp @6200rpm ,are you really suggesting the best shift point for best times is 5200rpm? ever ?
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Old 09-21-2009, 09:38 AM   #8
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disagree , my motor redlines at 6500 rpm , produces 501 hp @6200rpm ,are you really suggesting the best shift point for best times is 5200rpm? ever ?
What really accellerates the car? Torque or HP ?

Read this: http://www.elephantracing.com/techtopic/hpvstorque.htm

They suggest both are a factor, but only if you consider "Torque Multiplication"

Read the section of Torque Multiplication. Then consider his example that is a race car - 2nd is 1:1 whereas in a Vette, 4th is 1:1.

I'm sure it varies car to car as well. Mine loses power at 5500rpm and I find the 5200 to 5500 range doesn't do much - I stop accelerating.
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Old 09-21-2009, 10:55 AM   #9
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What really accellerates the car? Torque or HP ?

Read this: http://www.elephantracing.com/techtopic/hpvstorque.htm

They suggest both are a factor, but only if you consider "Torque Multiplication"

Read the section of Torque Multiplication. Then consider his example that is a race car - 2nd is 1:1 whereas in a Vette, 4th is 1:1.

I'm sure it varies car to car as well. Mine loses power at 5500rpm and I find the 5200 to 5500 range doesn't do much - I stop accelerating.
you need to keep reading, at the conclusion of the author ,it says "car will accelerate FASTEST when gear selected puts engine ar PEAK HORSEPOWER not peak torque. it seems horsepower is good for selling cars AND WINNING RACES>" your article proves my point, you need to shift beyond torque peak to achieve best average power for best times. thanks for finding that article. like i said, any racer will tell you torque gets you started, horsepower wins the race. my motor pulls right to 6200rpm, i wont go any higher to see if it falls off

Last edited by fishslayer143@yahoo.com; 09-21-2009 at 10:59 AM.
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Old 09-21-2009, 01:07 PM   #10
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Originally Posted by fishslayer143@yahoo.com View Post
you need to keep reading, at the conclusion of the author ,it says "car will accelerate FASTEST when gear selected puts engine ar PEAK HORSEPOWER not peak torque. it seems horsepower is good for selling cars AND WINNING RACES>" your article proves my point, you need to shift beyond torque peak to achieve best average power for best times. thanks for finding that article. like i said, any racer will tell you torque gets you started, horsepower wins the race. my motor pulls right to 6200rpm, i wont go any higher to see if it falls off
I understand what he says, but he's refering to a 2 speed race car. He's also describing how HP makes Torque.

In my LS1 peak horsepower is about 5300 and it's a pretty sharp peak of about 100 rpm. My torque curve is flat for over 1000 rpm.

I posted another message about my engine getting rough at 5500 rpm - it literally dies off - like cylinders are missing. So maybe my conclusions are misguided by my bad experience Still haven't resolved the problem - but haven't had the time.

Interesting too. The article did explain the 5250 rpm thing (actually 5252!)
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