View Single Post
  #2 (permalink)  
Old 08-02-2001, 10:31 AM
CobraEd's Avatar
CobraEd CobraEd is offline
CC Member
Visit my Photo Gallery

Join Date: May 2000
Location: Northern VA, VA
Cobra Make, Engine: Classic Roadsters
Posts: 2,765
Not Ranked     

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.


Last edited by CobraEd; 08-02-2001 at 11:51 AM..
Reply With Quote