Stupid question of the day...What does MFI and CIS mean?

[86930]

I have see a lot of references to CIS or MFI cars. What does this stand for?

[pete911]

MFI=Mechanical Fuel Injection
CIS=Continous Injection System (It is electrical)


Pete

[86930]

Ah, I see. I assume that my 86 930 would have CIS then? I take it that MFI is for early cars.

[Tyson Schmidt]

Actually CIS is also mechanical.
It became, in later years, controlled by a piggy-back computer feedback system with an oxygen sensor that altered the control pressure to keep the mixture at stoichiometric. But the core system is still mechanical.

[island911]

Just a little more clarification. . .

MFI; fuel is mechanically regulated, with pressure built with an mechanical pump.

CIS; fuel is mechanically regulated, with pressure built with an electrical pump.
. . .Not to be confused with EFI (Electronic Fuel Injection) . . which also happens to be pressurised w/an electrical pump

[86930]

Thanks for the clarification. What system would I have in the 86 930?

[island911]

Originally posted by 86930
Ah, I see. I assume that my 86 930 would have CIS then? I take it that MFI is for early cars.

Yes & yes. . .. though not all early 911s have MFI. Just the high-end E's & S's

[Todd Simpson]

You've got CIS, as all turbos do until the 993TT was introduced. Regular 911's went to Motronic, or DME in 1984, a more advanced system than CIS that also incorporated ignition timing as part of the system.

[Wayne 962]

Just to clarify again, there is no such thing as a stupid question - everyone at one time had no idea what these terms meant...

Welcome!

-Wayne

[Todd Simpson]

Yes & yes. . .. though not all early 911s have MFI. Just the high-end E's & S's

With a few exceptions. '67-68S's ('68S NA in the US) are still carbed and '72-'73 US T's are MFI