Article on relationship between torque and bhp

[berg]

http://www.epi-eng.com/piston_engine_technology/power_and_torque.htm

[jhtrophy]

Way over my head torque is great for everyday driving, but I really don't like too much torque when on track, na all day long for me

[berg]

was a bit for me too but simple calculation there of how bhp is calculated and i think gives a few of us on here a more realistic output for bhp and torque ie people getting 400lb/ft at stage 2+ aint gonna happen

[PDT]

Great article, if people are interested in this stuff, look up Tractive Effort:

Tractive Effort is the force(measured in Lbs or KG) at the contact patch that moves the car forward. Imagine a string wrapped around the tire like a yo-yo. Pull the string causing the car to move and the force on the string is like TE.

Torque and TE have the same shaped curve. You don't need a tach signal to get TE either.

Here's the sticky bit. The torque number you see from a chassis dyno is a made up number. Why?

The simple formula for HP is HP= TQ * RPM/5250 or TQ= HP*5250/RPM. The 2 known data points are RPM and HP. The problem is that these 2 numbers come from different places. HP is measured(calculated) at the wheels and the RPM comes from the Engine NOT the wheel rpm. This is why manufactures tell you to use a gear that is close to 1:1 final drive(not trans gear ratio!) with the engine. If you can get the wheels spinning at the same RPM as the engine then the TQ number will be closer. You still have those nasty drive train losses that make that number wrong anyway:) Why because the RPM signal still comes from the engine.

So, torque from a chassis dyno really means:

"If your engine makes WHP then it would have this much torque"

Confused?

It doesn't really matter but that's the truth. The more of either TE or TQ you have the better it is:)