2.4 vs. 2.7 CIS

[ahdoman]

I just acquired a 76' 2.7 (911s) CIS engine and I noticed the injectors are on the intake runners as opposed to the 2.4 where they are direct into the head. What is the reason or advantage of either configuration? Are the injectors the same?Also, at what PSI do the injectors open?

[Flieger]

2.4 was Bosch Mechanical Fuel Injection- sequential port injection, better throttle response, better.

2.7CIS is smog-fighting fuel misting into the intake. Better fuel economy, though.

[ahdoman]

My understanding is that both the 2.4 & 2.7 CIS is Bosch (2.4 is 73.5 911T & 2.7 is a 76 911S). Is that not correct?

[tom1394racing]

Porsche introduced the CIS fuel injection system in the second half of the '73 model year on the 911T. These are refered to as 1973.5 911T's. This first variation of the CIS system used unique CIS injectors that mated with the injection bung on the head just like the MFI systems.

The CIS systems on the 2.7 and 3.0 motors ('74-'83) used different type of injectors that mounted on with the intake runners.

[ahdoman]

Thanks for the input Tom. I also noticed a lot more emissions(?) devices on the 2.7S as opposed to the 2.4T. How much of that is "deleteable" if it's going in an earleir car?

[tom1394racing]

Here' the best source for information on the 911 CIS system including the year-to-year variations:

http://members.rennlist.com/jimwms/CIS/CIShome.html