Being a mathematical equation, the reverse is also true. If we produced 400 hp at 6,000 rpm, this would equate to 350 lb-ft. Dropping the 400 hp number down to 5,000 rpm would yield 420 lb-ft, while dropping it further to 4,000 rpm would produce 525 lb-ft. Combining a given horsepower with lower engine speeds will yield greater torque numbers. The same 400 hp produced at just 3,000 rpm would unearth 700 lb-ft of torque and an astounding (and probably rod bending and piston smashing) 1,050 lb-ft down at 2,000 rpm. This is, of course, modified turbo diesel territory, but it is important to show the relationship between horsepower and torque as maximizing the horsepower or torque outputs may require rethinking where the motor makes power. This shifting of the torque curve can be accomplished with the installation of a wilder cam, a different intake design, or even a set of ported heads. Our pair of turbo test motors demonstrated this fact perfectly, as the L98 TPI motor was clearly designed with low-speed torque production in mind. In stock trim, the TPI motor produced peak power at just 4,400 rpm and peak torque at just 3,200 rpm. Not surprisingly, having the motor produce peak power at such a low engine speed resulted in huge torque numbers. The L98 TPI small-block in the Corvette produced 100 lb-ft of torque more than it produced horsepower. Such was the benefit (or curse) of the TPI system. By contrast, the 383 from Pro Comp shifted the torque curve higher in the rev range, resulting in more peak power (the increase in displacement further increased torque production).
Boost from either a turbo or supercharger is a wonderful thing. It acts as a multiplier of the power output of the original normally aspirated combination. The reason this is possible is that your normally aspirated combination is running under pressure already. It is the atmospheric pressure (14.7 psi at sea level and a given temperature) that literally forces the air into your motor to fill the low-pressure area created by the downward moving piston. A turbo or blower simply adds to this pressure differential. Using the power/boost formula, it is possible to predict the power output of any given combination with reasonable accuracy. If we take a 350 hp normally aspirated motor and add 14.7 psi of boost (basically doubling the current atmospheric pressure) we should (in theory) be able to double the power output to 700 hp. Adding 7.35 psi (half atmosphere) we should see an increase of 50 percent to 525 hp, while 10 psi will increase the power output of our 350 hp motor by 68 percent to 588 hp. Basically, the power output of the boosted motor can be calculated by multiplying the NA power output by the percentage of atmospheric change (14.7 psi equals 1 bar).
Sharp-eyed readers should now be seeing the potential gains offered by this formula and the reason for this article. If we have a 350hp normally aspirated motor and add 7.35 psi, we wind up with 525 hp. If we increase the power output of the normally aspirated combination from 350 hp up to 400 hp (with a cam change and ported heads for instance) and then add the same 7.35 psi, we wind up with 600 hp. Improving the power output of the normally aspirated combination by 50 hp resulted in a gain of 75 hp once we added .5 bar (7.35 psi) of boost. The gains increase even more as we further increase the boost. That same 50hp gain (going from 350 hp to 400 hp NA) jumps to an even 100 hp if we add 1 bar (14.7 psi). Adding 14.7 psi to the 350hp NA motor will result in 700 hp while adding the same amount of boost to the 400hp motor will produce 800 hp. You see, the power gains on the NA combination are actually multiplied by the boost pressure, so it is easy to see why starting with a powerful normally aspirated combination is so important.
 The TPI induction system was...  The TPI induction system was a major contributing factor to the shape of the torque curve. The long runners promoted low-speed torque, but restricted power production past 5,000 rpm. |  The only internal modification...  The only internal modification to the L98 was a mild XR270HR cam from Comp Cams. The XR270HR cam offered a 0.495/0.502-inch lift split, a 218/224 duration split and a 110-degree lobe separation angle. |  To demonstrate the effectiveness...  To demonstrate the effectiveness of the turbo system, we first ran the L98 combination normally aspirated. The nearly stock L98 produced 331 hp and 394 lb-ft of torque with a set of long-tube Hooker headers and an electric water pump. |
 Equipped with the HP Performance...  Equipped with the HP Performance turbo kit, the L98 thumped out an even 481 hp and 579 lb-ft of torque at a peak boost pressure of 7.0 psi. |  Test motor number two came...  Test motor number two came from Pro Comp Electronics. The 383 stroker featured forged internals, a 10.0:1 compression, and a hot hydraulic roller cam. Additional Pro Comp components employed on the test motor included a billet distributor, plug wires, and electric water pump. |  The hydraulic roller cam used...  The hydraulic roller cam used in the 383 offered a 0.545/ 0.565-inch lift split and a healthy 248/254 duration split. |