Remmi909 wrote:Just out of curiosity how does Dynoing your car mess it up?
Also what is a knock sensor and where is it located and how/why does that blow after the Dyno?
Alos one last question for CDSSOLARA or who ever else might know what are lower compression heads and how do they help benefit your car?
Sorry guys I'm a NOOB with all this Forced induction and engine talk. Thanks in advance!
Dyno runs put a lot of stress on your engine, especially when there is not much of an interval between runs. If your car is in good running order, a dyno run shouldn't hurt your car. A lot of us on this forum have had problems because we're trying to maximize the power from our superchargers on cars that were not designed to run much boost. What usually happens is that we use a smaller pulley, which forces more air into the combustion chamber, but the fuel delivery system is not capable of providing enough fuel to match it. So, either the air/fuel ratio becomes too lean, or the compression gets really high and you get preignition, or knocking. In either case, it creates a situation that is usually recognized by the car's computer as dangerous, and it responds by retarding the ignition timing as a self-preservation action. If you look through some of the threads on the Aftermarket Upgrades section, you'll see a lot of discussion on how to solve the fuel delivery problems. We're still trying to sort it out.
The knock sensors are located under the intake manifold, or under the supercharger if you have one. There is one for each bank of cylinders. They pick up vibrations from the cylinder heads that can be due to knocking, and send a signal to the computer that sets off a Check Engine light. It always seems that once this process occurs, the knock sensors need to be replaced before the car really runs properly again. Many of us with superchargers and smaller pulleys have had this happen, especially on dyno runs when the car is repeatedly taken to redline.
Lowering the compression theoretically allows us to run higher boost. Our cars have a 10.5:1 compression ratio, which is fairly high. When you force more air into the combustion chamber, the compression ratio becomes even higher. Unless you have high octane fuel, you run the risk of predetonation under high compression ratios. For those of us in California, with our 91 octane premium gas, this is a real problem. Lowering the compression ratio allows us to run higher boost a little more safely. Or so the theory goes, anyway. The situation is a lot more complicated, but I tried to simplify it. Hope that helps.