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A 3900 swapper complained he was not able to get his engine started with the cam locked in the fully retarded position. I didn't have a problem, however my camshaft had been reground vs. his stock cam.
He reported 215 hp at the dyno with the stock cam fully advanced in the "parked" position and wasn't impressed. My curiousity was with how the engine still cranked out over 200 hp with the cam fully advanced which was far greater than what Desktop Dyno simulation indicated would happen. I expected power to be well under 200 hp. The reduction in torque would explain why the engine didn't feel much more powerful than his 3400.
After reading the Hot Rod article below and looking at their graph from an experiment with a VVT motor, it appears the torque is affected far more than the hp with a fixed LSA VVT cam. Their manual operation of the VVT produced almost as much total power and torque as the PCM did with full control, suggesting that simple on off activation of the VVT cam with appropriate module limitation to the best installed degree angle is very practical, allowing for full or near full advance for low to mid rpm economy and idle, and appropriate retard activation for all out performance.
With my cam fully retarded fuel economy was awful and I'm sure part of that was due to the reground specs which were not as retard friendly as the stock cam specs. In the fully retarded state I could easily chirp the tires between the 1-2 shift. When I advanced the cam to the locked position fuel economy went through the "roof" but I could no longer chirp the tires between the 1-2 shift supporting the theoretical loss of torque from full advance.
I'm planning to have my second cam reground to include additional lift with a more aggressive openning cam lobe and a little increase in duration but leave the stock LSA untouched this time.
He reported 215 hp at the dyno with the stock cam fully advanced in the "parked" position and wasn't impressed. My curiousity was with how the engine still cranked out over 200 hp with the cam fully advanced which was far greater than what Desktop Dyno simulation indicated would happen. I expected power to be well under 200 hp. The reduction in torque would explain why the engine didn't feel much more powerful than his 3400.
After reading the Hot Rod article below and looking at their graph from an experiment with a VVT motor, it appears the torque is affected far more than the hp with a fixed LSA VVT cam. Their manual operation of the VVT produced almost as much total power and torque as the PCM did with full control, suggesting that simple on off activation of the VVT cam with appropriate module limitation to the best installed degree angle is very practical, allowing for full or near full advance for low to mid rpm economy and idle, and appropriate retard activation for all out performance.
With my cam fully retarded fuel economy was awful and I'm sure part of that was due to the reground specs which were not as retard friendly as the stock cam specs. In the fully retarded state I could easily chirp the tires between the 1-2 shift. When I advanced the cam to the locked position fuel economy went through the "roof" but I could no longer chirp the tires between the 1-2 shift supporting the theoretical loss of torque from full advance.
I'm planning to have my second cam reground to include additional lift with a more aggressive openning cam lobe and a little increase in duration but leave the stock LSA untouched this time.
