CIS Injectors: Calling all guru's

[911 tweaks]

Hi All,
OK, know that I hopefully have the attention of the 'guru's' of the CIS world, here are my questions, revealing my shortcomings of knowledge about CIS in general.

Here is the story... I have been collecting CIS systemS so I could cobble together at least 1 complete 80-83 system for a 80' longblock I have for the resto project I am trying so desperatly to complete and get the "F" out of here so I can get a car for myself... anyway to cut to the chase...

I found a Bosch shop in my area that was willing to flow test 35 CIS injectors I have accumulated over the MANY yrs (7+) doing this resto... anyway here is where I am at and need help interpreting the findings today:
Inj # 1 2 3 4 5 6
1. Brand new oe injectors 88 98 124 97 116 85
2. 1980 CIS from NY 127 98 114 90 102 94
3. 1978 or 79 CIS from CO NFG nfg 127 128 nfg nfg
4. 5 injectors from these that from my using compressed air and berrymans inj cleaner either sprayed like a garden hose and/or dripped w/ no air pressure.
5. buy used from pelican 130 nfg 127 128 nfg nfg
6. inj's from blown engine 110 110 nfg 115 123 82* this was new oe inj to round out 6 injectors.

The procedure we did was as follows:
1. Over the past yrs, I soaked all of these inj's in Berrymans for a while, 1-2 months, then I lasoued the pintel end (idea comes from Marc Rowe in TX... a great guy and very helpful !!) with a strand of ~28 ga wire and reversed flushed the inj's with my air compresor @ 75psi resulting in 1/2 of the inj's spraying ***** back up the inlet side of the inj into a ready rag.

2. as these inj's were come across, I would do this cleaning, than put them in a respective bag labeled where they cam from, and I would spray "Gibbs" penetrant oil all over them to prevent any rust or further rust from what they had.

3. So, then off to Bosch shop... they have a specific machine to test these inj's... we cycled each inj through the 30 sec cycle 2x to see the spray pattern and as some of the inj's needed a love tap to start their spraying.

The Bosch CIS manual says that these inj's are to open at ~ 52psi = 3.5 bar, however, some needed more pressure and a love tap with the side of a wrench to start the spraying.

Due to the above, we ran the test for all of the inj's at 62psi for 30 seconds. The figures above are for the amount of fluid that the inj's sprayed into the cc vial on the test stand. *** THE 62 PSI WAS THE PRESSURE THAT WORKED BEST TO EXAMINE THE SPRAY PATTERN and TO SEE IF ANY DRIPS WOULD HAPPEN AS THE PRESSURE CYCLED UP TO THE 62PSI OR AFTER THE CYCLE ENDED.

My questions are as follows and you all can ask any q's to further/best understand what I am trying to present here:
A. Since the spec says the inj is to open at 3.5 bar = ~52psi, WHAT AMOUNT OF FLUID SHOULD A IN SPEC INJ SPRAY IN 30 SEC ???

B. If "A" can be answered, what are the findings I recorded which were done at 62psi for 30 sec ???

C. If anyone can also spec the cc volume, psi at for what amount of time, that will help us all best understand what I found out today.

My preliminary findings... how can brand new inj's, like 4 wks old to me, spray btwn a low of 88 cc to a high of 124 cc ??? If we have answers to above q's as to what the spec is, maybe I have new inj's that are out of spec ??

My reason for going to all of this bother is two fold: I am too chaep to throw anything away unless it is "FUBAR" and I am trying to salvage out of these used and new inj's, hopefully, 2 or 3 sets of 6 inj's that flow the same so as to eliminate a rich and/or lean running cylinder(s) when the engine is put back into service.

A side note is that Which hunter is no longer doing CIS inj work as too tedious, as I now inderstand, (3 hrs to do these 35 inj's) and not worth it to him or affordable to customers;thus, I present what I did above.

Please input and question away... sorry for the long post.
Pics atached.
Thanks,
Bob

[911 tweaks]

here are the injectors after being tested & bagged

[lucittm]

Bob,
Just a hunch here...

Were the injectors tested one at a time or in a bank of six? What was your source of pressure? How many feet above sea level are you? What was the barometric pressure on the day of the test?

Pressure testing one at a time is a qualitative test. It is designed to test the opening pressure of the injector. This determines the condition of the spring against the valve seat, and to a lesser extent the condition of the valve surfaces (the spray pattern).

You can safely trash any injector that would not open at 52 psi as idicated on the gauge.

What you are trying to do is a quantitative test. Or a comparison of flow rates across all the injectors. I think you would need to pressure test six injectors at a time from a calibrated and regulated system that could supply 62psi continuously for 30 sec. Something like the Bosch fuel distributor!

Alternatively, you could use the injectors that flowed 127-130 cc and be pretty close.

Good Luck,
Mark

[911 tweaks]

thanks Mark for your post and questions. Here are the answers:
1. inj's tested 1 at a time
2. source of pressure was the machine pumping the appropriate test fluid
3. the shop has an elevation of 597' or 182m
4. barometric pressure... sunny day, dry, 75 degrees
5. IF I trash any inj that will not open @ 52psi, then I would need to pitch ALL... even the new ones !! Yikes !!!!!!!!!!!!!!!

We could of tested a set of six to measure each inj's flow, but, by doing them individually achieved the same result. What we did was cycle each inj 1 or 2 times depending on if we had to tap it to start spray and how the spray pattern looked. Thenwe would stick the end of the inj into one of the graduated cylinders, strat the 30 sec cycle and the cited above cc's of test fluid is what passed through the inj for 30 seconds at 62 psi.

So, based on this info, do you have any idea on how much fluid should pass through the injector per cycle ?? What is the spec range i.e. 80-100 cc's or is your mention of 127-130 'pretty close' to the spec ???

Thanks for any and all light you can help with here guys !! I hope my day was not a waste of time...:-(
Bob

[cmonref]

911Tweaks,

"So, based on this info, do you have any idea on how much fluid should pass through the injector per cycle ?? What is the spec range i.e. 80-100 cc's or is your mention of 127-130 'pretty close' to the spec ???"

First, install injectors that flow "equal" quantities and have acceptable spray patterns together as a set. Then adjust the mixture, which takes care of which set you installed (80-100cc's or 127-130cc's in your statement above.)

Brian

[911 tweaks]

Thx Brian for the idea... or is this some spec you know of ??

Yes, I was thinking the same... cull out 6 inj's that sprayed the same volume (cc's) of test fluid, but the question still remains, HOW HUCH FLUID... i.e. spec should BE FLOWING THROUGH ???

All of the data and technique I presented above to best help those in the know point me in the right direction of, basically, what are good an what are bad inj's & what is the volume spec so I can go by that ???

Thanks guys... any one else able to help solve this ???
Bob

[cmonref]

Bob,

There is a flow test in the factory 911 manual, but IIRC (book is at home, I'm at work -- ssshh!) the specs are for minimum flow in 60 seconds. Or maybe I am recalling the fuel pump delivery test spec?

My suggestion was that it does NOT matter which set you use. The adjustment is in the mixture control. The mixture adjusts the fuel flow rate per air flow. With the lower-flowing injectors, you might be running lean. With the higher-flowing injectors, you might be running rich. The response in both cases: adjust the mixture.

Brian

[911 tweaks]

so... group together a set of 6 inj's that are w/in, lets say, 10cc's of eachother ?? and do the final specific tuning/adj via the fuel dist ??

This makes sense, however, where should the inj's flow rate in cc's I guess, be at for the f/dist to be able to adj properly ??

I will also try to find the spec in the factory book when I get home tonight... ssshhhhh I am at work also !

Thanks... and if anyone can save me the time and dig up this spec, that would be great :-)

Bob

[cmonref]

I would be willing to bet that Porsche designed the fuel distributor to work with new injectors at a certain range of flow rates. They would have then allowed for some degradation in flow rate down to some minimum. They would have QC tested new injectors for flow and then tested injectors in use to see how the flow rate stood up over time.

If this thought pattern is valid, it suggests that the 127-130cc group are the new ones (high and consistent flow rates) and that the 80-100cc group is a happy collection of used injectors, with significant variations in flow rate (and probably in flow pattern also.)

If THIS holds true, then you would be safe installing the 127-130cc group. The 80-100cc group MAY be below the standards that Porsche would have allowed for in their design. And this is the source of your question, of course.

In cataloging the injectors and their flow rates from your first post, you have 6 injectors from 127-130 and 7 from 110-124. I'll bet either group would work fine and be within the adjustability of the fuel distributor. This, of course, assumes acceptable spray patterns across the board.

Why not install the 127-130 group, keep the 110-124 group as spares, and toss the rest?

Brian

[911 tweaks]

That sounds great Brian, however, I am such a stickler for wanting to know specs and any possible deviation... any way, it could be that Porsche has the spec on the low end to increase fuel economy ??? or, something is a miss here ??

In summary on the cc's of the inj's, of the "NEW" inj's, of which their are 7, the cc's are:
82, 85, 88, 97,98, 116 and 124.

I have 22 inj's that flowed btwn 82 and 130 cc's. The viles that we sprayed into max out at 130. Any inj that flowed beyond this I consider nfg (no f'ng good). All of these recorded 22 sprayed well... some a bit better than others... drippers were considered nfg.

So, here is the string of values from the 22 inj's from lowest to highest:
1. 82 7. 98 13. 115 19. 127
2. 85 8. 98 14. 116 20. 128
3. 88 9. 102 15. 123 21. 128
4. 90 10. 110 16. 124 22. 130
5. 94 11. 110 17. 125
6. 97 12. 114 18. 127

So, now what do we do ?? I still would like to know what the flow rate spec is in cc's at what pressure for what amount of time...

Maybe I will have to use any of these groups, but I won't feel comfortable till I know the spec... heck, I am crazy enough to but another 12 inj's and see where they cc at, BUT, only after I can determine the spec or someone can chime in here with it.

Thanks all,
Bob

[911 tweaks]

oh, by the way, the guys at the shop that did this work for me said that if this was a diesel engine, any deviation of more than 2-3 cc's, and you have serious problems... think this applies to gas ??? The shop thinks that maybe 5-8 cc's would be the max range as these are 'CIS' inj's = continious injection, which may mean that they (Porsche) may want the extra fuel in their to cool down valves and piston crowns as this is/was a racers trick... you would use a lot of gas but it would help the engine survive racing... I am not racing but I thought I would through thie tid bit in.
Bob

[jcge]

Bob

From the K-Jetronic (aka CIS injection) manual

Gasoline Fuel-Injection System K-Jetronic Technical Instruction

"The K-Jetronic system operates by injecting continually, without an external
drive being necessary. Instead of being determined by the injection valve,
fuel mass is regulated by the fuel distributor." (p10)

"The fuel distributor allocates this fuel to the injection
valves of the individual cylinders." (p13)

"The injection valves inject the fuel metered to them into
the intake passages and onto the intake valves." (p16)

"The injection valves have no metering function themselves,
and open of their own accord when the opening pressure of e.g. 3.5
bar is exceeded." (p17)

"the fuel distributor meters the basic injection quantity to the individual engine cylinders." (p19)

Don't confuse the concepts of modern electronic fuel injection, where the injection valve flow coefficient determines the mass of fuel metered to the engine, with the K-Jetronic system. Its a totally different concept. The "flow rates" you are trying to measure are not really relevant, as the fuel distributor will force the requisite mass of fuel through the injector.

All you need from your injectors is good atomisation and minimum opening pressure of 3.5 bar.


Here's the contrast with modern EFI systems....
"Electronic injection systems
Injection systems featuring electronic control rely on solenoid-operated injection valves for intermittent fuel discharge. The actual injected fuel quantity is regulated by controlling the injector's opening time (with the pressure-loss gradient through the valve being taken into account in calculations as a known quantity). Examples: L-Jetronic, LH-Jetronic, and Motronic as an integrated engine-management system." (p10,11)

Regards
John

[MatthewBrum]

The problem with asking for specs of what the injectors flow at a certain pressure is pointless on a CIS system. I don't mean to sound rude but on a CIS system the injectors do not meter the flow to the engine and thus does not matter what they flow at a certain pressure.

As long as they don't restrict the flow (highly unlikly) I wouldn't worry about flow. As long as the injectors open at the specified pressure (cracking pressure) and the spray pattern is good then the injector is OK.

I totally agree with JCGE on what he said.

If you really want a flow number than I would meassure how much the injector flows at 75PSIG multiply the number by six (for six cylinders) and figure out how much horsepower that injector will give you on your internal combustion engine. I'm sure that you will find the injectors being able to supply a ton more power than you plan on making.

[911 tweaks]

great news guys... I think I get it now !!

John, I believe I was thinking as you describe that being a mechanical version of the efi inj's & systems. WRONG on my part.

So, as long as the fuel dist is pumpiong out the correct amount of fuel, the inj will flow it... presuming that the inj opens at 3.5 bar = 52 psi AND the spray pattern is a nice cone shape... NOT a graden hose as some of my rejected inj's sprayed like.

Great news, however, the ever questioning me is still very curious why, enen brand new inj's, would flow different amounts of the test fluid with ALL of the inj's cycled at 62psi for 30 seconds? Can anyone take a guess why these significant deviations occured, especially on the brand new inj's ???

I will use groups of 6 that are the most closely matched as suggested earlier, but, should I go with the higher flow group, middle or least quantity flowing group of inj's ??

OR, does it not matter in the final analysis, because I will be adjusting the fuel dist to the proper air/fuel ratio based on what an exhaust sniffing machine tells me to set at spec.

Thanks again and please confirm I am understanding this correct and which group of inj's to use.

Bob

[MatthewBrum]

Great news, however, the ever questioning me is still very curious why, enen brand new inj's, would flow different amounts of the test fluid with ALL of the inj's cycled at 62psi for 30 seconds? Can anyone take a guess why these significant deviations occured, especially on the brand new inj's ???

It is extremely hard to get nozzles to spray the same amount, especially something like an injector. I was an engineer at an aerospace valve company and I was surpised with the amount of work to get fluid to flow consistently thru a simple drilled hole. the smallest burr can cause the flow to go way off.

[911 tweaks]

hey Matt, thanks for your words.
So, I will ask your opinion, which 'group' of inj's would you use ?? see my earlier posts... the low volume (82-97cc) ... middle volume (98-114cc) or the high volume (I can make 2 ranges of sets here as either 115-127cc OR 125-130cc)t inj's ???

Possibly should I buy more inj's and cull out what needed to hit a specific window of cc volume ??

Bob

[MatthewBrum]

1. Brand new oe injectors 88 98 124 97 116 85

I would install all six brand new injectors for two reasons 1) they are less likely to leak and 2) I would think thy atomize fuel the best.