:eyecrazy alright guys, i keep hearing about the two main kinds of fuel injection that these bimmers run. I am not totally familiar with fuel injection as i am with carbs, what are the two main kinds and what are the differences? please tell me in noob talk so i understand. also, out of the two which would be best for m20?

E21's actually use only one type and it's Bosch CIS-Constant Injection System, There are some variations between the '78-'79 and '80-'83 models though. The early cars have a multiple piece intake manifold, the injectors are mounted in the manifold and the fuel distributor is in a different location. The later cars have a one piece intake manifold, the injectors are mounted in the head/intake port and this version has a crude ECU and O2 sensor to help reduce exhaust emissions- The O2 sensor/ECU does not hurt performance in any way.

The e30 318i uses Bosch electronic injection-a different animal all together.... though it appears quite like the '80-'83 e21 system as the intakes are VERY similar (they work great for a programable EFI conversion).

ken

Is it possible to fit the fuel rail from an '84 or '85 318i to the m10 in the e21 (80-83)? The intake looks almost exactly the same.

With the efi is there a performance difference or are we talking about roughly the same thing?

I use an e30 318i intake/fuel rail/pressure regulator on my '82 with programable EFI. I use a 2.0L e21 casting head without injector holes like a 1.8L casting head.

http://www.e21motorsports.com/kendanielson/intake.jpg

http://www.e21motorsports.com/kendanielson/efi%20intall.jpg

I have never run the Bosch electronic injection so I can't really say if there are performance gains with that but I suspect so. There are REALLY good gains to be had with progamable EFI.

ken

What inputs does the CIS use to determine pulse width?

Im assuming there is a coolant temp sensor, TPS and some kind of airflow (temp?) measuring device.

How does the fuel distributor work? I didn't see any belts to run it. How much fuel pressure does the system run?

I'm putting on a record now that has a skip in it....as it skips it says...

"You really DO have to get Ben Watsons book "How To Tune and Modify Bosch Fuel Injection"....

It is not so over the top that it's hard to understand. The chapter on K-jetronic FI is only about 29 pages but it will soooo help you understand how your car operates and answers 95% of the questions posed in this forum that are fuel injection related.

Let me put it this way. You wouldn't dare take your toolbox and start working on your car without a Haynes, a Clymer or some type of manual. Well you cetainly don't want to mess with your fuel injection without a good reference on that. So I'll say it again....get the book and read it and reread it...You'll be amazed by what you'll learn.

In this way you won't ask where the belt is to drive the fuel distributor. Simply put. It doesn't have one. It operates on pressure. The fuel distributor works the same way as a 4-chambered heart would. Each chamber has its own pressure regulator and each pressure regulator has its own cylinder it serves.

What inputs does the CIS use to determine pulse width?

Im assuming there is a coolant temp sensor, TPS and some kind of airflow (temp?) measuring device.

How does the fuel distributor work? I didn't see any belts to run it. How much fuel pressure does the system run?

CIS = constant injection system
There's no pulse width, the injectors are purely mechanical valves that spray constantly. The fuel distributor is just a valve body that meters the required fuel based on the position of a mechanical air flow meter, or lift plate. System pressure should be around 70 psi.

CIS Operation (http://www.ncr-pca.org/tech/tech-cis.htm)

Autosolve ("http://www.auto-solve.com)

Sounds alot like mechanical injection used on MB diesels, except with an electric pump. It sounds pretty crude but I bet BMW did a good job. How is the driveability compared to carbs and modern injection? Carbs can be annoying because the car runs different everyday, and they're never "just right."

I should have known there was no pulse width varriations, since I didn't see a fuel rail on my friends car.

Properly operating CIS is better than carbs, cold/hot/warm starts are great, power is decent, fuel economy is pretty good too. I doubt if factory Bosch EFI is much better. Programable EFI is head and shoulders above CIS and factory EFI.

ken

Sounds alot like mechanical injection used on MB diesels, except with an electric pump. It sounds pretty crude but I bet BMW did a good job. How is the driveability compared to carbs and modern injection? Carbs can be annoying because the car runs different everyday, and they're never "just right."

I should have known there was no pulse width varriations, since I didn't see a fuel rail on my friends car.
VW and maybe others used this style of system back in its day. Driveability is very good. The closest to a mechanical injection system ever used for gas was the spica used on early to mid 70's Alfa's(usa). The fuel pump was electric, but the actual injection pump was mechanical. It was way more complex of a unit than cis and so was harder to get right if something went wrong.

Don't forget the 2002 tii and it's Kugelfischer :)

"You really DO have to get Ben Watsons book "How To Tune and Modify Bosch Fuel Injection"....

It is not so over the top that it's hard to understand. The chapter on K-jetronic FI is only about 29 pages but it will soooo help you understand how your car operates and answers 95% of the questions posed in this forum that are fuel injection related.

I agree 100% with this recommendation. I learned more from this book than anywhere else, it's full of great information about, not only K-Jet, but all Bosch fuel injection. Excellent tool!

(waiting for my check, Mr. Watson)

After I read this thread, I got on Amazon and placed my order. Thanks for the "gentle push".

I
"You really DO have to get Ben Watsons book "How To Tune and Modify Bosch Fuel Injection"....

It is not so over the top that it's hard to understand. The chapter on K-jetronic FI is only about 29 pages but it will soooo help you understand how your car operates and answers 95% of the questions posed in this forum that are fuel injection related.


I am confused, does the newer E21's use K-Jetronic FI? And is K-Jetronic the same as KE-Jetronic?

K-jet is the same as CIS. 77-79 used plain K-jet, 80-83 cars used K-jet with lambda control (O2 sensor/frequency valve), and many late 80's euro cars used KE-jet which ditched the warm up regulator and frequency valve of the lambda control system for a computer controlled pressure regulator mounted directly to the side of the fuel distributor.

There were a ton of cars that used K-jet all through the '70's and '80's, including 911 turbos, Lamborgini's (which actually used dual 6 cyl fuel distributors for the V12), Mercedes, the infamous DeLorean (you see the fuel distributor blow out of the car in back to the future 3 when Doc claims "Damn, the injection manifold is blown!"), Audi 5000's, Volvo 240's and 740's, Porsche 924's, almost every VW from the late 70's to late 80's, and I'm sure there are many I'm forgetting.