SC fuel injector specs

911 tweaks · 07-16-2008, 07:45 AM

Can anyone help me out with what are the following specs for the SC era (78-83) fuel injectors ?? I need these specs to best make sure a shop that will clean & flow match them knows what they should flow at if working correct.
1. injector # 911-110-225-01
2. minimum fuel press injectors should open at
3. flow rate of injector at what pressure

I believe these injectors once open only spray at 1 rate, dosen't matter what the fuel pressure is as long as it is above the minimum threshold, right? I guess this as they are "CIS = continuess injection system = once they see (open) minimum fuel pressure spec they spray continuesley(sp)", right ??

Thank you !
Bob

jcge · 02:44 PM

Bosch K-Jetronic injectors

Bosch 0 437 502 004

Opening pressure about 3.55 bar (about 52 psi)
Spray cone angle 35°

Most Bosch service centers can check the injectors for you

Regards
John

911 tweaks · 07-16-2008, 02:57 PM

john, thank a lot for the info. I will check to see if there are any service centers in the area that can check them out. I have about 30 injectors, all of the same p/n that I would like to know their state instead of just pitching them for new ones.

Can you answer any of my guesses i.e. once they open at ~52 psi is the flow rate the same at that point up to, say, 100 psi i.e. if the system saw a fuel pump go mad for OR something else that would cause the pressure to spike for a while ??
Also, once these open they spray the whole time the engine is running whether or not that cylinder is getting spark as in "CIS", right ??
Thanks again!
Bob

jcge · 05:57 PM

Bob

The CIS injectors are designed for continuous flow. They open once they see the opening pressure - continuous flow - and close if the pressure drops below that level. They are not pulsed like EFI injectors.

This link provides an overview (pages 16 & 17 describe the injectors, and page 38 covers their testing)

K-Jetronic

MatthewBrum · 07-19-2008, 06:22 AM

The CIS injectors are designed to spray at the regulated fuel pressure of about 75 PSIG. They may open at a lower pressure but that's not what pressure the injector sees during operation. What the fuel distributor does is increase or decrease flow to the injectors while keeping the fuel supplied to the injectors a constant 75 PSIG.

So when the car is running at idle the injectors are supplied a small amount of high pressure fuel and when the car is under full load the injectors get supplied with a large amount of high pressure fuel.

During operation the injectors are open all the time and do not meter the flow going to the engine. The fuel metering happens before the injectors at the fuel distributor.

Constant & "clean" pressure is very critical to CIS operation. The fuel pressure accumulator "cleans" out the pressure spikes or oscillations coming from the fuel pump that are always present and the pressure regulator on the fuel distributor does some "cleaning" but mostly sets the system pressure.

Hope this helps

911 tweaks · 07-21-2008, 02:03 PM

Thanks Matthew for your input.

So, what is the best way to test these out ?? I would think that if they are always seeing your stated ~ 72psi, then they should all fill up cc'd measuring viles equally, right ?? Run the cleaning solvent through at 72 psi for a set amount of time and match the injectors by the amount they flow. How much should they flow at what pressure for what amount of time ?? I reralize that their spray pattern is important also and no drips if pressure below 50 psi ??

Thanks, Bob

MatthewBrum · 07-21-2008, 03:58 PM

I would start by taking the injectors out of the intake manifold and placing each one in a clear empty container. I used clear water bottles. I would then lift the air vane to turn on the fuel pump. I would then fill the bottles up with some fuel and make sure they all have the same amount. I would do this test with the injectors spraying 1/8 load, then 1/2 load, and then full load.

I have cleaned injectors by spraying solvent through them but I don't think it is a good way of measuring flow. Doing the test above gives a clear picture of how well the system is metering fuel to all cylinders of the engine.

I would be more concerned about volume over spray pattern. And you really do not want any injectors that are leaking.

911 tweaks · 07-21-2008, 04:21 PM

great info Matt.
How can I do this "i.e. specs please" to emulate the 1/8 load, 1/2 load and full load ??
I am guessing here... do I need to figure our what psi to squirt the fuel thru the injectors to emulate the 1/8, 1/2 and full load or what do you recommend ??
Thanks again... sounds like you have done this before...?
Bob

911 tweaks · 07-21-2008, 04:23 PM

also... I have 40 injectors out of the car and not a completely assembled ~ functioning cis system so i can't do the lifting or positioning of the air plate and be squirting fuel thru the fuel dizzy.
Bob

MatthewBrum · 07-22-2008, 06:22 AM

I only know how to check flow with the system in the car. I have cleaned my injectors using a rubber hose clamped to the threaded end of the injector. I then fill the hose with solvent and use a rubber tipped air nozzle to seal the other end of the hose. I set the compressor to 75 PSIG and flush the injectors.

Remember the injectors do not meter the fuel. As long as they open and have a decent spray pattern they should be ok. Also make sure they do not leak below cracking pressure which I think is around 45PSIG