I was looking at a few specs on some cars today, and noticed something (may not be true for some, but seemed like it today)

Piston engines produce more torque than HP, while Rotaries (13bt anyway) produces just a bit less torque than hp.
examples I noticed today
1985 5.0 Litre mustang GT 180 hp and 240 ft-lbs torque
1990 Mazda mx-6 2.2 litre turbo has 145 hp and 190 ft-lbs torque
(side note, the mazda would beat the mustang :-D proof will come this weekend if needed).
While the 13b turbo does 200hp and 196 ft-lbs torque.

Why is it that the rotary is this way?

This is a nagging question i've had all day. Plz forgive any n00bness, I'm still learning a lot about performance on cars in general.

Thanx in advance,
Dustin

 

High-revving engines (rotary or otherwise) tend to make more HP than torque. I am sure everyone will hate this example, but some of the higher-revving V-TEC engines from Honda make even less torque (there, did that save my example) than rotaries of the same HP. Ferraris often make more HP than torque, too (better example, eh?). Rotaries are typically high-revving, so they follow the "more HP than torque" rule of thumb.

-Max

 

I-c. That helps a bit. them my next questoin would be is why do high rev engines produce less torque than hp than the low reving engines?

 

I believe its the nature of the beast. By losing torque it allows for a higher revving engine.

 

The reasoning is in the math. Horse Power = (torque * RPM)/5252.

In the Nov 2002 issue of SCC, Dave Colman writes. "Lets say you manage to make a perfectly linear engine that makes 50lbs-ft of torque from 2000 to 8000 rpm. The power curve would slope straight up, from 19hp at 2000 rpm to 76 hp at 8000 rpm. Why? Because of the formula. Because that's what horsepower means"

The whole article does quite a good job at explaining the difference between horsepower and torque. I recommend picking up the magazine for more indepth explanation. It is the most rescent issue with JDM Fantasy cars on the cover.

Grant