CIS injector flow testing

[jsveb]

I have wanted to do this testing since I read about stup doing it and 911st saying it was one of the most important test to perform on a CIS engine.

I knew my car had been stading for an extended period before I bought it. It drives nice, but I gave it a shot.

Some of you might remember my no-start thread. So this is just me trying to sort out this car.

I all ready had a lot of the necessary stuff removed, due to other small projects so this was pretty straight forward.

I wanted to test for

Fuel Head (FH) flow
Injector opening pressure (the same across the board)
Injector leaks
Flow pattern
Injector flow

I started out by removing the injectors and do a visual inspection, just to see if everything at least looked good. It did.

I then did a 20 sec. test of the FH without the injectors installed. All the lines flowed what I would call exactly the same.


Then I installed the injectors, and started the flow testing.
I took a small cup, so I could mark the individual injectors from each test to record the changes I made during the test.

This is what it looks like in the car. (I know the cups look funny - wife bought them. They worked fine).


I decided to let each test run for 20 seconds:

Test 1: #1 flowed a little less than the others. #2-6 flowed the same.

I realized I probably didn't push down the metering plate all the way, so I dicided on a second go with the same settings.

TEST 2: #1 still flowed a little less, #3 flowed a bit more than the others. Now I have #1 low (not much) #3 high (just a bit).

I have two extra injectors from a friendly Pelican that I would use. For some reason I couldn't make these fit on number 1-3 CYL - weird???
I could however make it fit tight on # 4 (yes I tried several times on the others )

Test 3: I have moved #4 to #1 and fitted a spare injector to #4.
Results: #3 a little high, the rest the same.

I was quite happy with this, since one CYL running a bit rich is better than one running lean. However I thought I might as well try to equal the flow if possible. So I did the following:
#1 injector which had just been removed was put in #3 position, this means the seemingly high flowing #3 is now out of the car.

Test 4: #3 is not as high as earlier. It is still a little higher, but it is close to nothing.

For the first three tests. I poured the samples into a small cup and marked it with permanent marker (which is only permanent if you do not expose it do gas )
The number corresponds the the CYL numbers. The lower dash is test 1, The upper dash is test 2. For the third test I used a common reference line ( no picture).
For the fourth test it was so close that I just ligned them all up:
Test 1:


Test 2:


Test 4:



You can see they are almost the same. Number three is just a bit higher, but I think it is close enough.

I then tested opening: They all opened as soon as the plungerswitch clicked.
I tested leaking by putting ruled "writing paper" under the injectors (easy to spot fuel). None of them leaked.
Spray pattern: They were all OK. I wouldn't say completely uniform, but nicely "sprayed".

That concluded my test. Remember this is just me, a rookie doing what I have seen others do. For further do a search.

Now I just need to find some copper washers, so I can get this thing together again. I simply cannot find anything like that here.

911st, You are right this does give me some sort of comfort knowing this

Please give me your feedback on this.


Thank you

[Thierry25]

Great test ! :-)

I did the same on mine while I installed new stock injectors.



From your explanation and pictures, you should have use an electronic balance to compare some accurate data. 20 sec is a bit short duration and you should have done it a big longer. How much ml did you get ?

;-)

[JBL930]

Good to see people doing this, very important! Did you have a charger hooked up to the car, so that your electrical system was seeing the same power as it would be with the engine running?

[jsveb]

Thierry25, I don't know how much it flowed. I have the marks on the small container I used, so I guess I could find out.
I do realize that the longer I run the pumps the easier it is to tell the difference in flow ratio. I stopped at 20 sec. because with my setup I was affraid I would't be able to get the small containers out from the engine without spilling it.

JBL930, Yes I had a charger hooked up during the entire test. So power should be good. Forgot to mention that - Thanks.

Thank you for you comments.

[jsveb]

Originally Posted by Thierry25

Great test ! :-)

How much ml did you get ?

;-)

I just measured the flow:

They all flow just a bit over 140cc. I would like to say about 142, but that is just me interpolating. #3 is maybe at about 143-144cc. again this is interpolation from my side. However percentagewise they are very close. This is much better than I had ever hoped for.

[911st]

Excellent work!!!

Such a great project for anyone with CIS to consider.

If your AFR's are holding up top your quantity should be ok.

My two cents:

Your test seems to support that we can expect variations in flow rates per cylinder. This is one of several reasons why we do not want to run to close to the edge as to AFR's with CIS. We may think we are running at 12/1 but actually could have one cylinder at 13/1.

I would think if I had a rich injector or two I might put them in the center cylinders. They may see better air filling and with a cylinder on each side may run hotter combustion temps but not sure this is true. (Anyone know which cylinder/s usually go first?)

Do not know if it would help to poor results in to tall thin beakers to better measure quantity variations.

Not sure how easy or accurate it would be to check pop pressure's without a test set up that has a gauge on it and where one can increase pressure in a slow and measured rate. Again variations in pop could make for uneven run on with shut down and I do not know if one could accurately observe this with an in the car test.

Impressive work.

[jsveb]

Originally Posted by 911st

Excellent work!!!

Such a great project for anyone with CIS to consider.

If your AFR's are holding up top your quantity should be ok.

My two cents:

Your test seems to support that we can expect variations in flow rates per cylinder. This is one of several reasons why we do not want to run to close to the edge as to AFR's with CIS. We may think we are running at 12/1 but actually could have one cylinder at 13/1.

I would think if I had a rich injector or two I might put them in the center cylinders. They may see better air filling and with a cylinder on each side may run hotter combustion temps but not sure this is true. (Anyone know which cylinder/s usually go first?)

Do not know if it would help to poor results in to tall thin beakers to better measure quantity variations.

Not sure how easy or accurate it would be to check pop pressure's without a test set up that has a gauge on it and where one can increase pressure in a slow and measured rate. Again variations in pop could make for uneven run on with shut down and I do not know if one could accurately observe this with an in the car test.

Impressive work.

Thanks for your comments. I realize my test is not exactly "pro", pop-pressure being one of the tests, where the way I did it, I can only see if they actually open when is I push the plunger ever so slightly -they did. This and the fact that they are not leaking and further more that the flow ratio seems to be very close, gives me some comfort.

As far as AFRs go, I do not know yet. I have still not finished my LC-1 install.
I just wanted to get his done, because I know if I see decent AFRs I am going to floor it (have been driving like a grandpa since I got the car.
Now I know each "CYL AFR" is not way out in the woods.

Regarding which CYL to give the most flow. When I did the test I remembered reading something about this, but I couldn't remember whether it was high-flow (#2 and 5) or maybe cooling that was the determining factor. I decided that was beyond me at the moment, but will keep it in mind.

I think my goal was reached. I sure have learned a lot

This is all very simple - Common sense

[mark houghton]

OK, so what you (and we) have learned from this is how to do the test. What if...what if you found larger differences between injectors that you weren't able to rectify by swapping injector positions and/or with spare injectors to try to get a good balance? Spray pattern may be good (which means the pintles are in good shape and clean) but flow may be down (which could mean the the internal screen in the injector is partially plugged, or the pintle is not popping open enough, or the flow from the fuel head is too low for that injector). In this example, it worked to mix and match injectors for the best combination.

But back to my what-if.....if flow rates are too far apart, then several options: Have injectors cleaned, spend hundreds of dollars buying brand new injectors, or go to the fuel head and adjust the indivudual injector lines to compensate for injector condition.

No, I've never done it and am just pulling from other's experiences (I can remember JFairman posting info on how to do the adjustments on the fuel head). With injectors and fuel heads being in various states of repair (or disrepair) then it seems logical that this adjustment step be taken advantage of.

[RarlyL8]

Nice work!
Unfortunately Mark, if things are out of spec and cannot be put back in spec with simple cleaning, you need to bite the bullit and consider rebuilding the fuel head, WUR and buying new injectors. This stuff is 20+ years old on most cars and running ratty. Folks get used to it and just complain about CIS when they have never experienced how it should run. I would not adjust the (likely worn) fuel head to compensate for a bad injector. If nothing else, replace the bad injector.

[mark houghton]

Thanks Brian.
Then I guess the only question I would have is why the fuel head (indivudual lines) are adjustable in the first place...unless it's supposed to be a one-time-only to balance a new fuel head.
Just tapping on your experience...

[RarlyL8]

Yes that is what the Bosche approved fuel injection shop mechanics tell me, and also what seems reasonable having had these things apart. These heads are flow adjusted at the factory and not really meant to be fiddled with in the field as the consequenses can be severe should it not be done correctly. It gets dodgy when you start adjusting one aging unit to compensate for another off-spec aging Unit (injector or whatever). Same idea plays out with adjustable WUR's. Real nice to have that ability but if the unit is not rebuilt you're fighting an up-hill battle.

[zcoker]

The fuel head adjustments are do-able but to the likes of putting five marbles in a flat pan and then trying to balance them. Tricky stuff, or so I have heard. I recall that these adjusting screws under the caps dimple the plate permanently - no rebound. I do not know for sure. I did the same test and all was equal, so I did not mess with the flow adjustments. It would be interesting to hear from anyone who has made individual flow adjustments with success. Jim Fairman should know more about this subject.

[911st]

Agreed with all.

Probably first confirm the injectors are balanced or replace. Even new can vary some injector to injector so if pushing the envelope as to AFR's might even send the new ones out for testing.

Even then, this dose not ensure near perfectly balanced AFR's as the exhaust and intake manifold can effect cylinder by cylinder savaging and filling. This is one more argument for equal length headers.

I believe most the balancing is done by a builder with shims under the springs that determine differential pressure about the internal orifices leading to the injectors.

The external adjustably gives the builder the ability to get the balance right without possibly having to take the head apart again and to possibly achieve a finer balance.


Probably good to pay close attention to differences in spark plug colors whenever possible.

Separate EGT monitoring per cylinder might be the ultimate balance test.

[jsveb]

Originally Posted by 911st

Agreed with all.


...Probably good to pay close attention to differences in spark plug colors whenever possible...

Speaking if which. I decided to check my plugs and change them. The old ones had only a little over 1200 miles on them. But I wanted to see how they looked and them fit new ones while I was in there.

The old ones was Autolite. The new I put in was Bosch W3DPO platinum.

I was very happy to see that the old ones looked really good, almost like new. No soot or anything. They all looked the same.

The not so good part is: While I checked and changed the plugs I pressurized the injectors to check for leaks. I got really disappointed when I realized that the number four injector was leaking between the fuel line and the injector. If you remember this was the one with one of my spare injectors put in yesterday.

I decided to put the number three injector (the high flow one) in the number 5 position, and then take the number 5 injector and move to the number four position. This way I put the high flow in the best position as 911st argued. Now I don't know my exact ratio anymore, but I am still confident this setup is safe.
Took some of the YES feelig away though.
I'll get a chance to test it again. Next time with a better knowledge and setup.

Anybody wanna swap four injectors from an 86 930 for four injectors for my 78

[mark houghton]

Originally Posted by jsveb

Anybody wanna swap four injectors from an 86 930 for four injectors for my 78

Different injectors, IIRC. The earlier ones having o'ring seals, the latter don't. Mine don't....they just screw in and seal at the base via the crush washer.

[mark houghton]

I've considered taking my fuel head apart - just because I can - and thoroughly cleaning/inspecting. May find it's fine inside (car runs like it is), but may also find some level of goo that wouldn't hurt being cleaned.
I can take anything apart and put it back together, that's not an issue for me. And it would probably work when I'm finished! Unless there are some "consumable" parts that a person would have to replace vs. re-use.
Someday maybe, after all the other necessary stuff gets done first.

[jsveb]

Originally Posted by mark houghton

Different injectors, IIRC. The earlier ones having o'ring seals, the latter don't. Mine don't....they just screw in and seal at the base via the crush washer.

I think they all use washers. The old ones (for my 78) are 009s. Don't remeber the other part number for the later ones. Maybe they operate on a different pressure??? I bet we'll know soon

[Thierry25]

Originally Posted by jsveb

Thierry25, I don't know how much it flowed. I have the marks on the small container I used, so I guess I could find out.
I do realize that the longer I run the pumps the easier it is to tell the difference in flow ratio. I stopped at 20 sec. because with my setup I was affraid I would't be able to get the small containers out from the engine without spilling it.

JBL930, Yes I had a charger hooked up during the entire test. So power should be good. Forgot to mention that - Thanks.

Thank you for you comments.

Jesper,

I do understand the reason you stop the test after 20 sec. Maybe you can encapsulate the injectors inside plastic bottle as I did.

Prior to do the injector flowing test, you have to make the pumps flowing test and to check the sytem pressure. (according the Porsche procedure)

In the mean time, it would be a good idea to check the WUR fonctionning. In this way, you have to measure the cold & warm control pressure. You have also to verify the enrichment triggering ( CP should decrease about 1.2 bar while you apply 1.3 bar( absolute pressure) on the boost line. ( here also, these verification are made according the Porsche workshop procedure )

To be back on injectors, sincerely, I suggest you to install 6 new injectors. ( As Brian said, these parts start to become old ) .

Then, having the new injector, I would check each flowed volume. If the flowed vol per injector exceed 2% difference. I would adjust concerned flow with the concerned screw on the head. (attention, this screw adjustment is very sensitive... )

Good luck !

[Thierry25]

Originally Posted by zcoker

The fuel head adjustments are do-able but to the likes of putting five marbles in a flat pan and then trying to balance them. Tricky stuff, or so I have heard. I recall that these adjusting screws under the caps dimple the plate permanently - no rebound. I do not know for sure. I did the same test and all was equal, so I did not mess with the flow adjustments. It would be interesting to hear from anyone who has made individual flow adjustments with success. Jim Fairman should know more about this subject.

I did succed to make individual adjustment on the head. When I put the brand new injectors on my car , I've got about 4% max difference. I succed to reduce it to 2% ......not less!

These screws are very very sensitive. We speak something about 5 to 10 ° on the wrench rotation !!!!!

[RarlyL8]

All 930 injectors screw in and use copper washers/gaskets. N/A CIS injectors use O-rings.
I concur with the advice to tread gingerly when adjusting individual fuel head port flow. Very sensitive. A bad injector can exaggerate this sensitivity.