Cis Equiptment Matching

William Miller · 10-20-2003, 12:05 PM

1983 Euro Cabrolet
I have been trying to sort out the CIS since I bought this car almost 2 years ago.

I'm almost there. I think. But I need help!

The PO had the car since it was imported and federlized.
He wanted to rebuild the engine in 1996 and was told that it would take longer than he wanted to wait. The mechanic offered him a rebuilt engine to be installed in a few short days.

This was the beginning of the problems. He ultimately got frustrated and sold the car to me. I'm more patient and knowledgeable (Now anyway since I spent a lot of time learning.)

The supposed rebuilt engine was a US based 930/16 block (dated 1982) and they reinstalled the euro CIS Parts. I herd it ran ok for a while and then another mechanic began part swapping. Confused (I hope) by the engine number he installed parts for an 83 US car. K-Lambda stuff with no computer. (I found the fuel connection on the fuel distributor with a bolt in it. the port to the lower chambers that was supposed to be connected to the frequency valve.

Last winter I overhauled the CIS with '79US K-basic parts. (I couldn't locate the euro fuel distributor or control pressure regulator at that time) It was running much better, but still not right.

I then lost compression in one cylinder due to a broken ring.
A month or so ago I finished a complete top and bottom rebuild of the engine. (Thanks Wayne for your book!) I enlarged the intake ports on the heads to match the euro intake runners. The pistons and cylinders measured looked fine so I re-used them. Everything else was basically a stock rebuild except I set the can timing to the euro specifications. (I did Waynes recommended upgrades!) I assume the pistons are the US spec 9.3:1 because I have no way of confirming this without getting them cc'd. Since I wasn't going to replace them it doesn't really matter.

Anyway, the car runs pretty good. Since I don't have an exhaust gas analyzer I set the mixture by feel. I recently installed a Air fuel meter which runs off an oxygen sensor screwed into the left SSI heat exchanger.

I found that I was not that far off with the A/F setting and I have been tweaking the setting. With the A/F meter I now have a lot more information that explains the symptoms I have been "feeling" over the last year.

Currently at idle I have the mixture adjusted rich between 12-13:1 as soon as I touch the gas pedal 1100-1200 the A/F rises to above 17:1 which is the limit on the gauge. It will eventually get so lean that it will begin to miss on 1 or 2 cylinders.

This morning it was in the mid 40's deg here in Maryland. The warm up was fine. Before it was at the first notch on the temp scale it was running in the middle of the A/F scale which is good. I could accelerate up to 5-6K and could see the A/F getting richer as I went above 4000. Later as the car warmed up it continued to get leaner and start missing before it would get to 4500 rpm with a light load.

I was testing the vacuum enrichment on the control pressure regulator by putting it in 3rd at about 20-30 mph and pushing the pedal to the floor. I could watch the mixture getting richer on the gauge so this seemed to function.

So it seems like warm up and full load are working pretty well but it runs too lean when warm with a light load.
I was reading the blue Bosh book I think Probst wrote it.
It was explaining about the conical shape of the opening above the plate in the mixture control unit is designed to make the mixture richer with higher air flow. This explains what I was seeing on the A/F gauge.

I think the mixture is rich at idle because it's adjusted rich while it is still in the narrowest part of the cone. It seems that as soon as the plate lifts above this narrow part the mixture gets way too lean. This of course until it gets to the point where the angle of the cone gets steeper.

I think it will run best if I set the mixture so it is at (or near) the 14.7 while in this mid range. If I do so it will be very rich when idling. (I've been there too and it pops out the tail pipe.)
I am looking for help from someone who knows these systems in detail.
I have an unusual situation and I have been trying to find out what the differences are between the 79 fuel distributor and the 83 euro distributor. (Same for the Control pressure regulator.)
I have seen that the newer fuel distributors are supposed to have a updated system pressure regulator. (The one on the fuel distributor.)
I don't want to continue swapping parts unless there is a reason. I knew the 83US equipment that was in the car when I bought it was wrong because it had no enrichment capability without the computer and frequency valve.

The car also has the US version ignition distributor in it. The 83 Euro did not have the retard hose. I unhooked and plugged this hose this morning as a test. The car had a little more throttle response and the A/F mixture leaned out slightly.
I saw no reall effect on tempature. It was cool this morning.

Any help would be appreciated!
Thanks!

Doug Zielke · 10-20-2003, 12:45 PM

You have the Probst book.
Do the CIS pressure tests he describes to give your set-up a baseline.

William Miller · 10-20-2003, 01:12 PM

That was on the when I get arround to it list. I'm going to double check the routing of the vacuum lines first. I have the gauges and just need to get them out. (That's how I figured out that I had the wrong Control pressure regulator. The US lambda system runs at higher control pressure then the 79 and euro set up.

I've seen on posts that people say these meters arn't that accurate. The do however give relative info on lean and rich. I have seen (on the meter) where the mixture is so lean it begins to miss and when it is so rich it backfires. (Actually it burns gas in the exhaust in both situations doesn't it?)

Before hooking up and watching the meter I wasn't sure that I didn't have an ignition problem.

I think I have ruled that out for the most part.

I might get to the pressure tests tonight, I hope the kids don't have too much homework!

1980SC · 10-21-2003, 08:44 PM

Looks like we have both been through many of the same problems. I have a Euro '80SC, that at some point had USA '80 CIS parts installed. My fuel distributor also had a bolt in the port for the frequency valve, along with the USA '80 style WUR without vacuum enrichment. I replaced those with '78-'79 USA parts. I still have my original engine though with the larger intake ports and runners.

I had dynoed my car, and the fuel/air mixture was real lean. 17:1. Turning the idle mixture screw wouldn't help. My problem was the WUR was not lowering warm control pressure. My control pressure was equal to my system pressure! I was able to rebuild it and get the fuel pressures in spec.

Definitely test your fuel pressures. You may find your warm control pressure is too high.

I spent a few months playing with a voltmeter in the car hooked up to an O2 sensor. I now feel that you really do need one of the expensive wide band O2 sensors to get accurate information on the car's air/fuel ratio.

-Rob
1980sc

William Miller · 10-24-2003, 12:29 PM

I read Probst some more.
What I am seeing on the A/F gauge is consistant with the explanation in the book. The A/F is rich at idle (where the cone is the narrowist) about 12-13:1 It gets lean as soon as the plate lifts into the first angle in the cone. It stays lean until enough air flow raises it to the next angle which is steeper. This happens at about 4000 rpm. The A/F leans out on the gauge and stays arround 13-14:1 all the way up to about 6000 rpm.
(I havent taken it higher since there is stillonly about 1000 miles on the engine.) When you go from light load to heavy load (By stomping on it.) It richens up for a little I guess until the vacuum stabilizes.

So it seems like things are functioning but it is running lean in the light to mid load part of the cone.

It only takes a minute to change the shims in the system pressure valve on the side of the fuel distributer.

I saw a post here where John Walker suggested this.
I took one out first and then a second and then put one back in.
It had some effect but not what I was expecting.
I put the one back in this morning and turned the mixture screw a little richer (Just a hair) On the way to work this morning it was running a little better but still lean (Tops the scale at 17:1) in the mid load situation. I don't have the problem with it missing anymore.

I can continue to turn the mixture screw richer, but at some point it will be way too rich at idle.

Hopefully I will reach a balance before it get that far.
I still haven't had the time to hook the gauges up and hope to do so this weekend.

I'm afraid I will end up needing to find the euro fuel distributer to match the shape of the cone of the euro mixture control unit.

Rob, It looks like you were where I have been. I assume you were eventually able to get it tuned right. Was this with the 79 FD and Regulator?
Do you remember what pressures you were running?

911nut · 911nut's Garage

The control pressure regulator has the biggest influence on mixture through the RPM range. As I see it you have two choices: locate and install an Euro regulator (since there's been so much parts swapping that might not help you) or remove yours and make it adjustable per the tech article here at PP. Once it's adjustable you can tweek the control pressure until you have the mixture that you want.

William Miller · 10-27-2003, 05:09 AM

Thanks for the help.
I had only about 20 minutes to work on the car this weekend.
I got the gauges hooked up but didn't have enough time to do the testing.
I like to hook them up with the engine cold and what the progress as it warms up.

I'll read the adjustable regulator article again but I thought the adjustment was for the warm up process only. I didn't think it applied to the warm control pressure.

The enrichment feature has a lower control pressure with no vacuum attached.
83ROW Specifications: 2.7-3.1 bar (no vacuum) and increased control pressure as vacuum increases. 3.4-3.8 (with 450-550 mbar or 340-420 mmhg)

US79 Specifications: 2.7-3.1 bar and 3.2-3.6 w/vacuum.

The 79 us actually is supposed to have a little lower control pressure when warm.

These are both with the same system pressure 4.5-5.2 (test) 4.7-4.9 adjusting specifications.

I'm still looking for someone who has compaired or knows what the difference is between the US 79 Fuel distributer and the 83 Euro.

I am guessing the plunger is a little different and or the slits are positioned different and/or are longer or wider.

Anybody?

1980SC · 02:36 PM

William,

You can lower your warm control pressure by adjusting a 4mm screw on the inside of the k-basic style, vacuum controlled WUR. Disassemble the WUR, and turn the 4mm allen head screw CCW to lower the warm control pressure, and richen your mixture under load. I use a small pair of vice grips to hold the diaphragm still while I turn the screw, as it can be pretty tight. It may take several tries to get your control pressure where you want it. I'd try one full turn CCW, then put it back together and test fuel pressures again to see what happened.

This is of course a completely different adjustment than the typical "adjustable WUR" post which frequent this board. That is for cold control pressure, and deals with starting and warmup mixture. This adjustment made within the WUR is to change the warmed-up engine's mixture under load.

You don't need to worry about changing to a euro F.D. or having yours enrichened. As long as it's working correctly, you can run your mixture plenty rich by lowering your warm control pressure by means of the WUR. I'm presently running warm control pressures of 46psi with the vacuum line attached, and 40psi with the vacuum line detached. This is on the rich side, but still within the specs, (46-53 and 39-45). You can go richer if needed to get your air/fuel readings the way you want.

-Rob
1980SC

beamonk · 10-29-2003, 03:57 PM

Popping at idle, that is more indictive of a vaccum leak or a lean mixture.

William Miller · 10-31-2003, 05:33 AM

Rob-
This morning I pulled out the WUR in about 10 min. It was a little difficult to open and separate the bottom from the middle section. Luckily I didn't break anything.

Rob (1080SC) suggested turning the adjustment 1 turn ccw. That's what I did and buttoned it back up.
The whole thing took about 30-45 min including hooking the heat back up.

I agree with your procedures but please make a note of caution to look for the loose parts inside.
There were the 2 springs, the spring retainer (It was a cone shaped cap that had a little rod sticking out of it that was held in by grease.

The inside of mine had some dried up grease and some pieces of the green stuff that insulates the heater coin on the arm. I plan to clean this up when I get some more time.

I used Rob's advice because we both have mis matched parts on our euro cars. My warm control pressure was at the high end of the specs but was within specs for the 79 unit. Since I don't know what the control pressure should be for my bastard set up I have to go by trial and error. Actually the specifications for warm control pressure is a range. for the 79 it's 46-53 psi with the vac connected and 39-45 with it disconnected. I wonder if this indicates that it is adjustable or is this the tolerance for manufacturing. The few that I have tested with the fuel gauge were always on the high side of the range.

Anyway on my drive in it warmed up better than ever. After it warmed up it was too rich (It didn't go above 13:1 but this was expected.) so I stopped and leaned out the mixture screw about 1/4 turn. I drove a while to clean out the pipes so to speak and the gauge began to hover around 12 1/2 -13 at idle and showed less movement during most driving conditions. It was still lean at mid rpm's with a light load. This indicated to me that this is the correct approach but I will probably need to lower the pressure some more. (I still have the system pressure low so I'm going to get that back up by putting the washers back in.) I will then tweak the pressure lower to the point that the A/F ratio fluctuates the least through the mid range of the cone. I will then adjust the mixture screw to the max power point of about 13:1.

We'll see how it goes!

William Miller · 12-03-2003, 07:41 AM

bump, update:
Over the last month I have been tracking down and solving a problem with unmetered air leak. That was another thread about Pop Off Valve Failure. I ended up putting a heavier spring on the pop off valve and I am still looking for a replacement o-ring. I took dimensions last night and am looking for a source in the next few days. PP does not sell them.

I think my pop off valve has been in there a long tima and like most o-rings it is probably getting a little hard.

With the air leak problem solved I can consentrate on the fuel distrubuter mismatch issue. I have lowered my warm control pressure as suggested by Rob above. This was very easy to do.

I am still experiencing a too lean condition when warming up (From the time the Control pressure regulator reaches it's normal pressure,after 2-3 minutes until the engine is fully up to tempature.)

It is also lean at about 2500-3000 RPM under light load conditions.
This lean spot is built into the mixture control unit funnel as described in Probst's book for light cruising conditions. He explains the theory but there is really no detail about specific engine applications. I really don't know what A/F ratio to expect but my experience is that with my set up it's too lean.

The only other thing I have left to check is the aceleration enrichment mechanism in the control pressure regulator. I have done the pressure test with and without the vacuum connected and it operates as it's supposed to. One senerio that I can't test is the response time under real world driving conditions. If it doesn't respond quickly enough and drop the control pressure then it makes sense that the A/F will go lean.

I have been thinking about installing a fuel pressure gauge to monitor the control pressure. Actually since it is only for testing I could get a pressure sender that will work with my oil pressure gauge. This would be very temporary and I will still have the idiot light for protection.
This way I could watch the reaction time of the control pressure drop while driving and compaire it to the A/F meter.

Soulk, at one time you mentioned that you were going to reaserch the differences between various fuel distributers. This was on the Carerra FD thread. Did you get anywhere with this?