CIS Injection and Camshafts

E21 320i, 323

CIS was developed by Bosch to replace mechanical fuel injection. While mechanical fuel injection is very efficient in supplying the engine with fuel, it takes horsepower to drive the pump. In some cases there is up to a 15 HP parasitic power loss. CIS does not have this downside, and is rugged and easy to maintain. It does, however, have some inherent drawbacks which must be taken into consideration. Air flow to the engine is restricted by the sensor plate. Excessive lift and duration camshafts and the inertia of the incoming air itself can cause poor throttle response due to the air sensor plate being bounced around. In addition, a phenomena called "charge robbing" can occur. This is caused by excessive exhaust overlap (i.e. the time span that both the exhaust and intake valves are open right before the intake cycle). This allows the exhaust gasses to flow backwards into the combustion chamber diluting the intake charge. For these reasons, camshaft selection should be carefully considered. Aggressive camshafts suitable for earlier model engines may not work well, if at all. Automatic transmissions and air conditioning also influence the type of camshaft used, due to the changing loads they place on the engine.

Korman will gladly assist you in selecting a performance camshaft which suits your specific needs.

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