Revisiting Torque

[Bob Roth]

My apology if these points have been made, I've been busy for a while.

There is no difference between any of the engines at the conditions you list, but there is a big difference in the racing potential of them.

Look at the Honda VTEC 1.6 which is the 160 hp 110 ft pound torque at 8000 RPM. It is limited by valvetrain to 8500, which is kind of academic because everything in its VTEC "racecam", to intakedesign, to 10.5 to 1 compression to 4-2-1 stock exhaust system means there is little to be done unless you wanta cheat big time. Its already 1 hp per liter which is very good for internal combustion engines. If I can't make it rev more, and displacement is fixed, 150 wheel hp at 8000 rpme is all its going to give. And since its torque curve is flat from VTEC cut in, it also means when it shifts loses 25% rpm to 6000, it loses 25% HP to 112 hp.

Meanwhile look at a non VTEC ITS '93 prelude S with a 2.3 liter 160 hp engine that produces 70 hp /liter at 6700 RPM. Given that its heads and valves are the same as the prelude VTEC and given that this was the base prelude, it has no VTEC "race cam" trick intake filters and exhaust and Honda wants to have a significant derate compared to the 190 hp prelude VTEC, its reasonable that there is some increased RPM range and breathing to be found and that the prelude can be revved for good power to 7500 RPM before really bad power falls off. I would assume a 10% increase at the rating point with constant hp at speed above with a drop at redline.

Lets compare the HP across the 75 to 100% for the respective ranges
75% 80% 85% 90% 95% 100%
1.6 6000 6400 6800 7200 7600 8000
hp 120 128 136 144 152 160

2.3 5625 6000 6375 6750 7125 7500
hp 150 158.4 167.2 176 170 150

Delta 30 30.4 31 32 18 -10

The point is that its extremely difficult to increase high Hp per liter engines because there is nothing left to get for torque, or RPM range. On the other hand a non optimized engine "probably" will respond to the headers, air filters and releasing of artificial rev limits allowed in IT. Soo, a long the point is, its easy, get a large displacement, low HP/liter (0.6 to 0.7) engine which is the high torque one. Assuming that its a 2000sx, BMW or Honda Non VTEC with decent chassis, reliability and brakes, things look good. Note this rule falls apart with cars like gremlins, Monza's, and straight 6 ford mustangs, and other crap cars. As long as you avoid the high torque junk, I think you have a good chance wherever you race.

So, if HP is equal, get the lowest stock torque as it has the highest hp potential and area under the resulting curve.