Miata Mailing List: March 1997, Message #162
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   From: (none)

Subject: re: HP or torque

   Date: (none)



At 01:54 PM 3/6/97 -0500, you wrote:

>(re-sent message  - got an extra C/R in that formula...sorry)

>

>HP = (Torque x RPM)/5250

>

>Here's a web link with more to say on this topic: 

> 

>http://pop3.dcc.edu/vettenet/torquehp.html

>

>Harry

>



>> in a previous message I said:

>> I am no expert :-) , but I do not think the above statement is correct.

>>If horsepower was a calculation derived from torque then all cars with 

>>xxx amount or torque would have the same amount of horsepower - and they 

>>do not.

> >



  I think I understand it better now.  What I left out of the above

statement was "at a given rpm" - d'oh !  The torque'y 2 valve large

displacement GM motor makes the same horsepower as a Honda Vtec but it

makes it at a lower RPM.  The torque of the GM motor is also higher.  The

net result is that if the two were in cars that weighed the same and were

geared the same the GM motor would be quicker 0-30, 0-60, etc (until it

broke - sorry I couldn't resist).



  Applying Harry's formula to some numbers I got from the Honda web page

seems to "prove" his formula:



  For everyone's favorite -> Honda DelSol:



Model                        S            Si          Vtec                 

Horsepower @ rpm (SAE net)   106 @ 6200   127 @ 6600  160 @ 7600

Torque (lb.-ft. @ rpm)       103 @ 4600   107 @ 5500  111 @ 7000



  So even though the Vtec version of the motor has a LOT more horsepower it

comes at the extreme top-end and it only has 4 more ft/lbs of torque than

the Si motor, and it too is 1500 revs higher.  SO unless you drove the Vtec

car all the time in the 6500-8000 rpm range the Si might be quicker (as I

read in a car mag review).



  Dennis

  '96M