505CI Twin-Turbo Pontiac Engine - Twin-Turbo Tail Twister

A chassis dyno provides a double bonus, as it can simulate real world run and drive conditions and it also can take into account the addition of air filters and a full exhaust system. The tuner can pay close attention to the transition periods, such as gear-shifts, full-throttle-to-closed, and cruising-to-full throttle operations when working on a chassis dyno.

Besides tweaking cold-start calibration and accelerator-enrichment functions, the tuner can closely monitor how this engine will respond on the street once it's turned loose on an unsuspecting public. The changes to the fuel maps are usually subtle, but that's what makes for a flawless driving experience. It's more than worth the price of admission.

Now let's see how much power we make.

Dyno PullsFor the 91-octane pump-gas tests, the wastegates were basically open for each entire pull. Once on racing fuel, we adjusted the wastegates to provide about 4 more psi and saw peak power jump about 150 hp and torque climb 200 lb-ft. We intended to keep going, but Fiala noticed the fuel pressure falling just a bit at the end of our last pull, indicating the dyno fuel pump wasn't keeping up and we were running out of fuel. Unfortunately, we were out of time to swap pumps and so had to settle for the numbers here. Jeff feels very strongly that if we could have run the boost up into the mid-20s, we realistically could have seen another few hundred hp, but we could not document it.