Which CIS do I have?

[CAPierce]

Stock 82 SC (but not original motor). It is a 3.0 motor (930/16).

I have read that there is a CIS-Basic and a CIS-Jetronic. I have no box under my pass seat, but I do have the harness and there is an O2 sensor plugged into my cat converter.

This weekend I replaced my fuel accumulator to solve a hot start problem. During that replacement the O2 sensor connector in the engine room was damaged. I fixed it the best I could and put it all back togther. The hot start problem is fixed but I was greeted with a new backfire...never had one before. I assumed I had done a crappy job on the O2 sensor connection. But now as I read through some posts, it seems if I have no box under my pass seat that the O2 sensor doesn't go anywhere...?

1. Could a new accumulator cause backfiring until warmed up?
2. If I have no Lambda box, is the O2 sensor not hooked up?
3. Will I ever pass CA smog this way?
4. How do I tell if I have CIS-Basic?

Thanks
Craig

[Ken311]

sorry for my lack of knowledge in the technical department. i dont believe i can help you with your O2 sensor problem.

please, if any more knowledgeable user finds the thread correct me if i am wrong, but i believe the 2.7's and 3.0's both used K-Jetronic fuel injection and not the basic mechanical.

other than that i am really of no use. only that my 78 SC passed smog ironically with flying colors, and that exhaust has not been touched since its purchase. i could see an O2 sensor problem becoming a hassle with smog though.

good luck, hope this somewhat helps.

[randywebb]

the 2.7's and 3.0's both used K-Jetronic fuel injection

- right, aka CIS. it works via hydraulic signals and is not really mechanical in operation

[javadog]

K-Jetronic is the Bosch name for the system and CIS is acronym that is commonly used to describe it, as it injects fuel continously, rather than intermittently, like electronic fuel injection. It is a mechanical system, as opposed to an electronic system like Bosch Motronic. The injectors in a CIS system flow fuel all the time. In a typical electronic system, the injectors are opened and closed by electrical signals. The basic CIS design relies upon fuel pressure changes to regulate the mixture, as Randy stated.

In broad terms, there are a couple versions of the system. There are basic systems and systems with O2 sensor feedback. In the basic system, Bosch has sized all of the components in such a way for each different engine to give a particular engine the correct fuel mixture (or, close enough) at all times, provided the system is working correctly. The later systems have a computer of sorts that uses various means of altering the fuel pressure to affect changes in the fuel mixture, in response to feedback from the O2 sensor measuring the results of combustion. Within these two groups, there are many small variations. So, really, no two systems are truly identical. They pretty much made changes on a yearly basis, to correct little problems that were uncovered during real world use of the system.

As to your car, it would have originally has a 930/16 type engine, which used the version of CIS with an O2 system. You should have a computer, as the sensor will not accomplish anything without one. It sounds as if whoever installed the engine didn't correctly finish the job. If you want to continue running the cat, I suggest you give the car to a shop that is knowledgeable and let them sort out the details. Without a functioning O2 system, if you run the engine too rich you can destroy the cat. I've seen them actually get so hot they catch fire, which is not a pretty sight.

JR

[JohnKo]

Originally posted by javadog
K-Jetronic is the Bosch name for the system and CIS is acronym that is commonly used to describe it, as it injects fuel continously...

In broad terms, there are a couple versions of the system. There are basic systems and systems with O2 sensor feedback.

JR

That's a really solid and concise post, javadog. The fact that Craig refers to "Basic" makes me wonder if this comes from reading Probst's Bosch FI book, in which he insists on using the slightly unusual terms "K-Basic" ('basic' K-Jetronic) and "K-Lambda" (K-Jetronic w/O2 sensor feedback loop). FWIW, "CIS" is an acronym for Continuous Fuel Injection and, as 'javadog' points out, is just another name for K-Jetronic, not a different system.
John

[CAPierce]

Thanks for all the replies -
Javadog, I don't have a computer, so is it possible that whomever built my motor backdated the entire CIS system? How could I tell? Other than the lack of the computer, are there other tell-tale signs that I might have a "correct" non-O2 sensor CIS system?

Thanks again - I'm starting to be afraid of the $$$...

Craig

[Gunter]

With a 930/16, You should have a Lambda brain under the pass. seat.
If not, someone may have converted the engine to Euro specs?
Or put an earlier '78-'79 CIS on top of an '82 bottom?
What is the O.D. of your intake runners?
Or the Bosch number on the fuel distributor?
Don't worry about the OX sensor. Many people, including myself, run with it disconnected. You just have to adjust the mixture accordingly.
A quick trip to a Porsche mechanic would sort out what you have there.
Without the Lambda brain, the OX sensor is not doing anything anyway.

[javadog]

Originally posted by CAPierce
Thanks for all the replies -
Other than the lack of the computer, are there other tell-tale signs that I might have a "correct" non-O2 sensor CIS system?
Craig

The easiest way to tell what CIS system you have is to look at the fuel distibutor. Look up "fuel distributor" in the search window at the top left of this page. Have a look at the photos, starting with the correct one for your year, and compare to what you have on your engine.

JR

[CAPierce]

Okay - so my fuel distributor is Bosch 0-438-100-006 described as:

Bosch fuel distributor
FD11X
Porsche 911-2.7
9-73 to 8-75 Euro
9-75 to 6-77 Euro
Porsche 911 2.7S
9-75 to 8-77 US
9-73 to 8-75 Euro.
Volvo 260 76-77

Sitting on top of my 1982 930/16 motor! My intake runners cal out to 42.86-46.04mm depending on where I measure.

Is this bad...or just different? I don't mind different... But if the FD is designed for a 2.7 motor, will it supply enough fuel for the 3.0? Could this be why, after replacing the accumulator I now have backfiring until warmed up?

'preciate the help!
**trying to learn**
Craig

[javadog]

Craig,

It's starting to sound like you ought to take a look at the rest of the injection components to see what sort of mixing and matching the previous owner or shop has done. The fuel distributor and associated warm-up regulator do need to match, in my opinion. You can get more fuel flow out of a CIS system by playing with the fuel pressure but that's not optimum.

You mentioned before that you were running a cat. I think you have two options at this point. Remove the cat and try to tune the collection of parts you now have to run acceptably well. Or, find a complete CIS system from an '81-'83 911 and install whatever parts you are lacking to make it correct. There are a lot of people converting their cars to run EFI or carbs and these things get sold. This second option would be my suggestion. Once you get a CIS system running correctly, they are pretty trouble free.

I am not a fan of either EFI or carbs, for a street driven car, for what it's worth.

JR

[Gunter]

Craig:
0-438-100-006 is indeed a FD for a '77S
If the WUR is 0 438 140 033, someone installed a '77-CIS on top of a 3.0.
Intake runner-sizes are correct for '77.
What number is on the AAR? (That's the regulator sitting on the right side over the #5, it has an electrical plug and vacuum hoses)
A '77-CIS is compatible and can be made to work on a 3.0 #930/16.
A '77-CIS wouldn't have a FV.
With this set-up, the CAT/OX sensor does nothing. The CAT is now just an obstruction, I would replace it with a bypass but................depending on Aircare, you would have to get inspected with the CAT installed.

Installing a later CIS system to match your engine would involve some costs and work because then you would be dealing with Lambda which requires additional electronics.
Stick with what you have for now and make it work meaning: Timing and mixture.
I would check all ignition parts and replace what's needed like Plugs, wires, cap, rotor etc. Then the timing and mixture can be set for very little cost by a shop.

[T77911S]

do as gunter has said above. if it still backfires when cold, it is too lean. check the control pressure when cold with the electrical connetion removed to the WUR and then with it connected. then check the pressure with the WUR hot. if it is not correct, you can try adjusting the WUR. (make sure you have the correct WUR for the system). if the pessures are correct, check the vacuum line to the WUR, also, you can check (or add) the TTV (thermo time valve). the TTV blocks vacuum to the WUR to make it run even more rich when it is cold.

[CAPierce]

Originally posted by Gunter
What number is on the AAR? (That's the regulator sitting on the right side over the #5, it has an electrical plug and vacuum hoses)

The AAR is 0280 140 218 which is correct for 80-83. Was there a change in how it operates from 79 to 80?

With this set-up, the CAT/OX sensor does nothing. The CAT is now just an obstruction, I would replace it with a bypass but................depending on Aircare, you would have to get inspected with the CAT installed.

The 78 and 79 CIS cars used a CAT without OX right? I think I am going to try to set up like that...being in California, the smog guys will look for the CAT every time...

Installing a later CIS system to match your engine would involve some costs and work because then you would be dealing with Lambda which requires additional electronics.

Not interested in a bunch of $$ right now just to be "correct"...just want the car to run nice and pass smog...this is my daily driver...

Stick with what you have for now and make it work meaning: Timing and mixture.
I would check all ignition parts and replace what's needed like Plugs, wires, cap, rotor etc. Then the timing and mixture can be set for very little cost by a shop.

I think that's exactly what I'll do - thank you Gunter for all your help!

[Gunter]

0 280 140 206 would be the right AAR for a '77 but the one you have will work. It can be easily checked for proper function.
The WUR is more important to get this engine to work right.
What number do you have on it?