CIS? Please educate me.
 

OK I am not too proud to ask. What is CIS? "Carburated Injection System" vs. MFI? How would I know the car has it '74 (2.7's seem to have both?) and what are the pro's and cons.


Thanks

Continuous Injection System.

The injectors are constantly injecting fuel. They don't monitor fuel by opening and closing, like a Motronic injector does.

Makes them somewhat inefficient.

All injected 911s prior to 73 had mechanical fuel injection.

1973 was also all mechanical injection, except the T, which was mechanical for the first half of the year, then switched to CIS for the second half of the year.

All US 911s has CIS by 1974.

CIS ran from 74-83, then it went to Motronic in 1884.

CIS Pros: Doesn't need a lot of fiddling with, easy to pass smog, smooth power and good power, decent mileage. An older system, but not a bad system. Used on millions of cars throughout the world. Cons: Are limited to using a mild cam. Is not really a "performance" injection system. A lot of the injection parts are exposed to fuel, so it is sensitive to bad fuel.

Mechanical: Pros: Good power, great sound! Looks cool, too. And is interesting from a historical perspective. Cons: Can be hard to get it tuned right. Which is why so many have been converted to carbs. Can be hard to find someone who knows how to work on them, depending on where you live.

[This message has been edited by Jim T (edited 10-03-2001).]

If you really want to expand your knowledge,
go to Barnes and Noble and pick up Probst's book called "Bosch Fuel Injection and Engine Management" Gives great theory/explaination of how CIS and Pulsed injection work...as well as general diagnosis/repair info.

Nick.

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_ _ __ _ _
Nick Shumaker
1982 911SC Coupe
nickshu@yahoo.com
PCA -- Rocky Mtn. Region

I agree, Probst is a great book for D-Jet, L-Jet, Motronic and CIS. Really excellent for anyone interested in learning the theory and mechanics of those systems. Kind of a "must read," I think, for a serious enthusiast.

(I don't recall that it covers Bosch Mechanical Injection, though. That's a whole other book!).

Thanks!