what causes cars that are cammed to sound choppier at idle?
In: Engineering
The cam can be thought of as the brain of the engine. It decides when valves open and close. By changing this timing, the engine can be made to run well and different speeds. From the factory, idle quality is important, so a cam is chosen that idles well, and makes as much power as possible within that (as well as emissions and fuel economy).
One way to increase power is to make the engine more efficient at higher speeds. Since power is essentially torque multiplied by speed, making the same amount of torque at a higher engine speed means more power. Incidentally, that’s why it’s hard to get a cam that increases torque. It just moves it around. If you have a cam that makes the engine run better at higher speeds, you sacrifice it’s efficiency at lower speeds. That’s why it runs rough at idle. Very aggressive cams usually require the idle speed to be increased, sometimes significantly.
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