Question on Torque>><<<????????????
Race Director
Joined: Oct 2004
Posts: 10,089
Likes: 14
Torque is the product of force acting over a distance. In the English system it is expressed in units of foot pounds. In physics, this is called work. Power is the rate of doing work, ie foot pounds per second. In the English system, one horsepower is 550 foot pounds per second. Torque has no time component, power does. Acceleration also has a time component, feet per second per second. So acceleration is a function of available power.
Example, a 550 pound wagon is pulled one foot up a ramp. This requires 550 foot pounds of work. 549 foot pounds won't do it. Wrap the pull rope around a 1 foot radius cylinder, and 550 foot pounds of torque will exist. Doesn't matter if it takes an hour, a day, a month, etc. But now lets hook that wagon to a horse and whip him. He'll pull the wagon up that ramp in one second, exerting 1 horsepower to do so. So power is the relevant number to know if you want to figure out how fast something can be done. Torque is the number you need to know to determine if you can do the work required.
Example, a 550 pound wagon is pulled one foot up a ramp. This requires 550 foot pounds of work. 549 foot pounds won't do it. Wrap the pull rope around a 1 foot radius cylinder, and 550 foot pounds of torque will exist. Doesn't matter if it takes an hour, a day, a month, etc. But now lets hook that wagon to a horse and whip him. He'll pull the wagon up that ramp in one second, exerting 1 horsepower to do so. So power is the relevant number to know if you want to figure out how fast something can be done. Torque is the number you need to know to determine if you can do the work required.
Team Owner
Joined: Sep 2003
Posts: 43,084
Likes: 33
From: Raleigh / Rolesville NC
Safety Car
Joined: Dec 2006
Posts: 4,642
Likes: 9
From: Dalllas/Ft Worth Area TX
Power losses through the driveline result in numbers lower than the 400/400. 400bhp/400ft lbs of torque generated at the crank won't end up being the same amount after the energy expended by turning all the gearing and such in the transmission, the differential and then finally the wheels.
I hate this "rule" but it is said that driveline losses for manuals amount to 15% and for automatics 20%. Thus a bone stock manual C6 should dyno with 340 RWHP or thereabouts.
I hate this "rule" but it is said that driveline losses for manuals amount to 15% and for automatics 20%. Thus a bone stock manual C6 should dyno with 340 RWHP or thereabouts.
The factory likes to "spice up" the numbers, don't believe the brochures, a selling tool.
Racer
Joined: May 2006
Posts: 255
Likes: 1
From: San Diego County CA
More on HP vs torque.
That said, an engine that makes lots of HP down at low RPMs gives a very satisfying kick in the back when you punch it in ordinary traffic situations.
So the vett can accelerate nicely in 6th gear at 60mph (it makes a lot of HP down low). In contrast, a Mitsubishi Evo might be able to hang with a vett in a 1/4 mile, but you punch it in 5th at 60 mph and you will wait a long time to accelerate (it doesn't make much HP down low) . You have to keep the engine on the boil to get any work done.
Hope this is useful. Lloyd
Drifting
Joined: Sep 2006
Posts: 1,355
Likes: 70
From: Kansas
I forget what his numbers were, but I'll take my old GTO for example. It put down 344 hp to the rear wheels. I assumed a 15% drivetrain loss, ballpark. Take 344 / .85 and you get ~405hp at the crank.
With a 16.5% drivetrain loss, you would take your RWHP number and divide it by .835.
I think.
With a 16.5% drivetrain loss, you would take your RWHP number and divide it by .835.
I think.
Moderator
Joined: Dec 2002
Posts: 40,898
Likes: 4,351
From: Lakewood Ranch, FL
I forget what his numbers were, but I'll take my old GTO for example. It put down 344 hp to the rear wheels. I assumed a 15% drivetrain loss, ballpark. Take 344 / .85 and you get ~405hp at the crank.
With a 16.5% drivetrain loss, you would take your RWHP number and divide it by .835.
I think.
With a 16.5% drivetrain loss, you would take your RWHP number and divide it by .835.
I think.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Drifting
Joined: Sep 2006
Posts: 1,355
Likes: 70
From: Kansas
I get the math. The ~15% is an assumed constant. Since you said that you had a drive line loss of 16.5% that indicated to me that you had a known Crank HP and a known RW HP and thus determined the actual DL loss for your car. What I wanted to know was how you got the actual crank HP to make this calculation - a engine dyno, for example? Thanks, JD
Instructor
Joined: Mar 2006
Posts: 247
Likes: 0
From: Clarksville Maryland
As for the calculator and hp being everything, practical experience says otherwise. My CLK55 AMG had less hp, but more low end torque than my C6, and subsequently it got consistently better 60 ft times, and 1/4 mile times.
