Difference between CIS and Motronic

[gt_diesel]

I was just browsing the technical help section and noticed a article about CIS cars, then another with Motronic Cars.... I guess with CIS ending in 1982...

What is the difference between the two, and what are the power limitations with each?

[Bill Verburg]

Cis was used on 911s(as well as a lot of other european cars)from late '72 911T to the end of '83 SC production. It's command and control functions are mostly fuel handling related w/ some relatively minor electrcal input for things like O₂

Motronic has been used on all 911 and derivatives since '84. It has a strictly electric command and control structure. W/ a chip for a brain, which resides in the DME unit, usually under the drivers seat.

[Bill Verburg]

I should add that CIS continued to be used on 930 and 965s untill ~'96 993tt

[gt_diesel]

my car is an 86' and when moving the raicng seats forward the other day, I saw all the electronic stuff for the Fuel Injection... I was a little confused becasue I was under the impression that it was a CIS car... I thought it said motronic on it, but talking to someone else, it could have possibly said Jetronic... Any thoughts on this? I am just trying to learn more about everything.

[Bill Verburg]

'86 Carrera was Motronic oem, the DME is under the drivers seat.

[gt_diesel]

How much power can a motronic injection support without problems?

[Bill Verburg]

lots of people claim up to 300, who knows what the truth is.

Big thing is, neither CIS nor Motronic can deal w/ lumpy non smog cams.

[DW SD]

GT Diesel - take a picture of the top of the engine (under the intercooler, ideally) and the brain you found and post. Someone will get you sorted, likely Bill.

Doug

[Bobboloo]

Bill,

From looking at his signature it appears but I may be wrong that he has an 86' 911 that was modified by the additions of a Turbo body and turbos. This would explain the Motronic setup.

GT_Diesel,

Creating more power with turbo motors is more a function of the design of the turbo system, displacement, and the motors ability to not grenade under high boost. The engine management system plays less of a role in gaining more power. The fuel system just needs to be able to supply enough fuel which CIS can do. I guess that's part of the reason factory turbos had CIS well into the 90's. This is where the confusion comes in on your cars system. A factory 86' Turbo had CIS not Motronic so your car is either an 86' Carrera with Turbo body and Turbos or it's an 86' Turbo with Motronic added. My guess is that you have a modified Carrera.

Judging from your signature your beyond 300HP.

I know very little about Turbos but I will tell you that Motronic is a better engine management system for metering fuel, keeping emissions down, and making good use of the fuel without wasting it. There is a guy on this board who makes custom chips for Motronic systems that allow you to squeeze extra horsepower out of the system. His name is Steve Wong and his chips are sold by Pelican as "911chips".

Now for getting more power you should really chat with some turbo guys. Juan Ruiz who posts on this board is a horsepower junkie and pretty much knows the limits. Do a search on his name and you'll see his quest for more power. I believed he got around 600 RWHP. Pelican Craig911 also has a nice late 80's Turbo. Also Goran aka Beep Beep on Pelican knows his turbos.

[Bill Verburg]

From looking at his signature it appears but I may be wrong that he has an 86' 911 that was modified by the additions of a Turbo body and turbos. This would explain the Motronic setup.

That's why I said "'86 Carrera was Motronic oem, the DME is under the drivers seat."

Who knows what was added or subtracted since day1 for that car.

[gt_diesel]

I know the carfax on the car shows that it is a 911 Turbo, and it had the widebody package. I have all the origional paperwork and everything, maybe I should go thru it and see if I can find anything.

[Bill Verburg]

Ok, Carrera, widebody turbo look Carrera and turbo are 3 different animals.

If the car is a 930(turbo) then it was oem CIS aka K Jetronic I, II, or III('86 930 was K Jetronic III), the electric package consists of the O₂ subsystem again under the drivers seat

[gt_diesel]

You are correct, the stuff says Jetronic, I guess when I saw the article about the motronic I got the two confused.

[S2GART]

If your engine has hard fuel lines going to each cylinder, coming from a fuel distributor, it's CIS. Otherwise it's electronic fuel injection.