CIS tech notes I found

[Samir Shah <gofast1@home.com>]

A CIS tech note I found at www.korman.com. Korman is one of the top BMW
tuners in the US. Thought some of you might be interested. Samir.

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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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