As a further example, we quickly discovered that these engines are hard-wired to run at anywhere from 11.8:1 to 12.5:1 air/fuel ratio at wide-open throttle (WOT). This is much richer than the more accepted 12.8:1 to 13:1 range for a performance engine for peak power. GM does this to protect both the exhaust valves and the catalytic converter from heat damage. We attempted to reduce the fuel pressure at the regulator to lean out the engine, which at first worked quite well. However, after a few minutes of part-throttle operation and some further adjustments, the computer (using the feedback from the oxygen sensors) realized that the fuel delivery was now leaner and very quickly increased the injector pulse width to compensate. This also affected the WOT calibration and the engine went back to a 12.4:1 air/fuel ratio. What this means is that the only way to consistently change the engine to run leaner at WOT is to modify its programming with dedicated software tools such as EFI Live or the LS1 software editing system that TTS is currently perfecting.
Despite the rich air/fuel ratio, this LS1 is still a very impressive engine. Peak torque appears at a relatively low 4,300 rpm, giving this engine a broad power band up to its peak horsepower at 5,700 rpm. With the stock hydraulic roller cam's wide lobe separation angle, idle is dead smooth and throttle response is instantaneous. All of this contributes to an incredibly responsive engine that would be a blast to drive on the street.
These are just some of the things that we learned with the engine on the dyno for the first time. As we get deeper into this engine and do more modifications, there will be tons more information that we can deliver on how to modify and tweak these new Gen III engines. Next month we'll get into the exhaust side, and we can tell you now that the results are more than a little amazing. Suffice to say that the factory Corvette exhaust manifolds are plenty impressive. Stay tuned as we dive into the deep end of the Gen III small-block performance pool. C'mon in, the water's fine!
By The NumbersOur testing revealed the GMPP LS1 crate engine makes far more than GM's 345 hp catalog claim. As the numbers below indicate, this is a 400hp engine right out of the box!