View Full Version : Horse Power & Torque

07-23-2003, 08:36 PM
Why is the torque (315lb) so high in relation to horse power (210) on our 3.8 motors? A new supercharged cobra puts out 390 horse power and 390 foot pounds of torque. Most car engines that I check out are about equal on torque and horse power. I have not seen a thread asking this particular question. Just curious I guess:rolleyes:

07-23-2003, 08:57 PM
That's where the power band on these cars are. They are made to produce torque, if you notice the horsepower peak is at like 4100 rpm and the torque peak is at 2600 rpm. You can shift the powerband up by changing the cam.

The Mustang I am willing to bet has a higher torque peak and hp peak, plus with the added displacment..... well you get the picture.


07-23-2003, 09:51 PM
Its a question of bore vs stroke. wider bore means more torque longer stroke means more hp so if the bore is wider than the stroke, torque>hp. A "square" engine is even on both so you get torque=hp. If the stroke is really long but the bore is relatively small you get torque<hp. Thats wht stroking an engine does more for hp than for torque usually. I hope thats an acurate way to simplify it without algebra. Let me know if you want algebra though:D

07-23-2003, 11:34 PM
wow, I wrote that last part wrong. if the stroke is long but the bore is relatively small you get high hp but low torque.

07-23-2003, 11:35 PM
cam timing has more to do with it than bore and stroke. Yes all things being equal larger bore = more HP, Longer stroke= more torque.


07-23-2003, 11:37 PM
hmmm maybe I need a lesson in torque:D

07-23-2003, 11:45 PM
Why does the Cobra make 390/390? Oh, maybe just a little bit of ------ 4 VALVES/CYLINDER!

Properly set up the SC 3.8 can come close. You will see many SC motors making 350hp/400tq, but they will never run equal numbers due to the overall design of our motor. It just isn't a 7000rpm motor like the Cobra is.

fred 4 pt 3
07-24-2003, 10:39 AM
Okay, yeah a longer duration cam helps the engine breathe at higher rpm, and yeah bigger bore/stroke ratio predisposes a bit toward horses (not on these though, that plays more in a big block).

Check out the Eaton M90 web page.


The power consumption at high rpm is astounding, to put it nicely. So as it goes higher and higher, it takes more and more power away from the crank. Our vehicle spins these things up pretty good, using a 2.5 ratio against crank rpm.

MILL, BLOWER - rpm's
4000, 10000
5000, 12500
6000, 15000

What really matters is that the cam and head efficiency on these is horrid, which causes high boost pressures, further adding to parasitic power loss. In the stock configuration, it is said that at peak hp, the blower is using 75 hp. On the dyno, I've seen over 150 hp used at 5500 with an "S-model" running 110% speed over stock.......


More modern implementations do a better job, as well as the aftermarket efforts of Magnum Powers and Embree Specialty Machine.

07-24-2003, 11:23 AM
That answers my question completely. This foreum is absolutely the greatest for getting information from