HP-Torque Comparison, LT1 and L98 Corvettes

Reprinted by permission of Craig Fry, from http://home.fuse.net/pagrosse/

Here is an example of how horsepower makes a major difference in how fast a car can accelerate, in spite of what torque on your backside tells you.

A very good example would be to compare the current LT1 Corvette with the last of the L98 Vettes, built in 1991. Figures as follows:
 

EnginePeak HP @ RPM  Peak Torque @ RPM
        ------          -------------               -----------------
        L98             250 @ 4000                 340 @ 3200

        LT1             300 @ 5000                 340 @ 3600
 

The cars are geared identically, and car weights are within a few pounds, so it's a good comparison.

First, each car will accelerate or push you back in the seat with the same force - at least at or near peak torque in each
gear. One will tend to feel about as fast as the other to the driver, but the LT1 will actually be significantly faster than the
L98, even though it won't pull any harder. If demonstrated with the formula, we can begin to discover exactly why the LT1
is faster.

                 Horsepower * 5252
             Torque  =       -----------------
                                           RPM
 

If we plug the numbers in, we can see that the L98 is making 328 foot pounds of torque at its power peak (250 hp @
4000), and we can infer that it cannot be making any more than 263 pound feet of torque at 5000 rpm, or it would be making
more than 250 hp at that engine speed.  In actuality, the L98 is probably making no more than around 210 pound feet or so at 5000 rpm, and most drivers would shift it at around 46-4700 rpm, because more torque is available at the drive wheels in the next gear at that point. On the other hand, the LT1 is fairly happy making 315 pound feet at 5000 rpm, and is happy right up to its 5500 rpm redline.

So, in a drag race the cars would launch more or less together. The L98 might have a slight advantage due to its peak torque
occurring a little earlier in the rev range, but that is debatable, since the LT1 has a wider, flatter curve (again pretty much by
definition, looking at the figures). From somewhere in the mid range and up, however, the LT1 would begin to pull away.
Where the L98 has to shift to second (and throw away torque multiplication for speed), the LT1 still has around another 1000
rpm to go in first, and thus begins to widen its lead, more and more as the speeds climb. As long as the revs are high, the LT1,
by definition, has an advantage.

It is better to make torque at high rpm than at low rpm, because you can take advantage of gearing (Vizard 27).
 

Vizard, David. How To Build Horsepower. North Branch: S-A Design Books, 1990.

Nevin, Bradley.  "C-5 Corvette." Car and Driver Magazine. February. (1998): 96-101.

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