Fuel Distributers
 

I saw a post on PP where someone was modifying a 81-83 FD to replicate the early Carerra FD which seems to be a jewel.
Charlie, do you know something about this?
My car is still running lean in mid range and load. I checked the pressures last night. I lowered the system pressure a little by taking out some washers. This did lower the control pressure about 1psi.
It had some positive effects but not enough.
I saw a post there about being able to adjust the warm control pressure with a little screw inside the Control pressure regulator as well.
Is this much different than adjusting the mixture screw?

I really need to change the curve of the fuel mixture from rich at idle and then lean at midrange and rich at high rpm's. It needs to be richer in the middle. I'm afraid if I lower the control pressure it will make it richer across the board. This will be way too rich at idle.

Has anyone been here before?

The early Carrera 3.0 FD are a jewel but very $$ to buy new (~$2,800) and very hard to find used.

The best way to richen the mix across the board it to lower the control pressure by modifying the WUR. You can also richen the mix by increasing the system pressure, but lowering the control pressure is more effective as you have more adjustability. By lowering the control pressure, you can dial back the idle CO a bit and still get your richer mix you need elsewhere. BTW: Increasing/decreasing the idle a/f mix does not change the A/F mix throughout the RPM range in a linear fashion....it will continue to lean out as RPM's increase.

Here is a good thread on modifying the WUR to dial in a specific control pressure:

http://forums.pelicanparts.com/showt...;highlight=wur

That was one of the posts I was refereing to.
My mixture control unit actually has 3 different angles in the cone.
One area is for idle which is steep, one is the mid range which is flatter and a third which is steeper. I can see the A/F getting richer as I hit this 3rd steep part of the cone. It happens somewhere above 4000 rpm. It really depends on the air flow.

I think the 80-later mixture control units don't have these steps or different shapes in the cone because the mixture is increased or reduced with the computer and frequency valve.

Mine does not have these so they accomoplished the open loop "Mapping" with the shape of the cone.

It looks like I am going to have to open up and adjust the control pressure regulator.

Has anyone explained what is so special about the early 3.0 FD.
What makes it different? The plunger shape, the slit sizes?

I don't know exactly what the differences are with the Carrera 3.0 FD. I'm guessing its slit sizes are different and fuel mappings are a bit different also. Another thing that people don't take into considerations is that the FD's are matched/mapped to their respective mixture control unit. So, if you swap an FD from a different year, you will also need its matched mixture control unit.

Steve Weiner actually recommended it for my project, but there was no way I'd spend that $$.

If you changed it out you would lose the advantages of a closed loop system. I'm assuming that there are some drivability advantages and others besides emissions.

I recall you mentioning that it was on your list at one time. I was recently thinking that there would be a lot of things to match up. You would really need to almost replace (Backdate) the whole CIS system.
If you are going that far you might as well spend the money on carburators.

I think mine will eventually get sorted out. It runs very good when the A/F meter is telling me that I'm between 13-16:1. The problem is that that is not all the time like it should be.

I figure that somebody knows how to get these parts to match up to their optimimum. If I keep asking I'm bound to find someone who does.
I bet there is just one or 2 parts inside the FD that need to be swopped to get the correct curve. Possibly it's just the plunger.

I bought the 79 FD and control pressure regulator last winter. I was swopping the 83US distributer and WUR. I couldn't find any info at the time about an 83Euro Distributer so it looked like the 79 was the closest because the system works the same way they do however have different part numbers. My little spec book shows that the control pressure on the Euro Control pressure regulator is just 1-2psi (lower I think) on the warm control pressure. I've never seen any info on FD's.

William,

I was talking with Steve Weiner this afternoon and he mentioned the exact same thing. At WOT, CIS will tend to lean out in the mid range, richen up a bit as the RPM's increase and lean out again around 6000 RPM's. Looks like this is the nature of the beast.

Increasing system pressure or decreasing control pressure will richen the mix throughout the whole range. There is really nothing you can do by modifying fuel pressures to compensate for a lean mix at a specific RPM w/o affecting the whole curve. The a/f curve (a/f mix at a specific RPM) is determined by both the fuel distrib and its corresponding mixture control unit.

Tuning tips:

13.2 is the magic ratio for max power output.
Anything above 14.0 is too lean. Anything below 12.8 is too rich.
This is all at WOT.

I spent most of the day yesterday working on this.
I adjusted the warm control pressure to 46 psi based on the recommendation of 1980SC on the PP board.
Woth the vacuum hose off it drops to 40psi
System pressure is 75psi.
I spent a lot of time looking for vacuum leaks that have the potential to introduce un-metered air. I couldn't find anything sugnificant.
I ran the car at idle fot 2-3 hours and sprayed carb cleaner everywhere.
I also hooked up the vacuum gauge while doing this to see if there were any indications of vacuum change as I pushed, pulled and prodded every conection. (At least all the ones I could get to.) I also tightened all the hose clamps for good measure.)

The vacuum gauge stayed pretty constant 17-18 in vacuum. This was effected a little by leaning and richening the mixture. (Not much.)

I left the vacuum gauge connected with a long hose so I could watch the gauge as I drove. (The readings were as expected, and it's an education watching how the throttle effects the vacuum.)

Prior to doing this I had the control pressure way low for experiment purposes. (Something like 42-43psi) It's better at the current setting because the mixture screw is in a more normal range for adjustment.

I'll drive the car for a few days, but I don't think it's going to cut it.
The next option is to send the FD out to get it rebuilt to the 930/10
specifications like it should be. I have been trying to avoid that cost.
I recently found someone who can do this and I think it's about $250-350.

I also have a realitivly new FD that was on the car which was the 930/16
like you have on your car. This is what was on the car when I bought it.
I might put this back on and test it to see what A/F readings I get.
I also would be able to drive the car with this one while I send the other one out. (I hope it doesn't take forever.

Guy's I think I solved the mystery!
After all the time I spent this weekend the car ran like crap on the way home last night. There was a period of time where the mixture went lean and stayed lean 17:1 plus. Normally If I shut it down and restart it this symptom would go away. Finally about halfway home and about the 3-4 times of shutting it down it fixed itself again. This is the kind of intermittant symptom that has been driving me crazy for 2 years.
As things usually happen the symptom has to get bad enough to identify the cause. Like a small noise that you can't identify untill it get's loud enough.

Anyway the lightbulb went off!
After all that checking and tightening and testing with carb cleaner what could let air in and seal itself back up when you shut the car off?.............................................. .................................................. .............


THE POP OFF VALVE!
This came to mind late last night.
This morning I had enough time to take a look.
I found the hinge pin for the pop off valve sticking out of the right side of the hinge about 1/2 inch. There are 2 arms on the hinge with the spring in the middle. The pin was out far enough that one of the arms was not being held in place. So, the valve flap was not centered over the hole and the o-ring.

I went over this several times this weekend. While the car was idling I tried to pull the flap open to see if it was sealed. It was! At idle the vacuum was 17-18 psi. I couldn't budge the flap without possible dammage. (I never noticed the pin sticking out.)

Here's what I think may have happened. The seal is stuck tight at idle. At WOT there is little or no vacuum, not much more on light cruising. So the only thing that holds the seal is the little spring on the flapper. If the mixture got too lean it probably popped the valve open. This is because there is little vacuum at that time. I think on an intermittant basis the flapper did not close in the correct alignment and caused the leak. When I shut it down There was enough time with no vacuum that the flapper could re-align itself! Ergo intermittant vacuum leak and lean condition!
The lean condition may continue to create more backfires up the intake making it pop open again. Like a programming loop. It wouldn't stop until I shut it down.

Anyway, I didn't drive it today. With the forecasted rain, the old seals on the top leak like a sive. I don't mind driving it, but if it sit's in the rain all day it begins to smell.

Has anyone had any experience with these valves? I pulled the o-ring to take a look at it and it seems OK, But I'm sure they ger dried out over time. Is there something your's supposed to lubricate them with to help them swell up so they seal better?

I think I can figure out some way to keep the hinge pin in place. Actually it's not moch bigger than a wire so maybe I'll find some wire that is the same size and bend the ends like a cotter pin.

I didn't have much time to look, but it didn't look like anything was broken or missing. What's supposed to keep the pin in.
Can someone look at thiers and let me know!
Thanks!

Get out of town!!

Arn't these things supposed to help prevent problems :wink:

I think the pin is just a press fit into/through the small arms of the cap. One of the arms could have split at the seams or cracked causing a loose fit and the pin slipping out.

As cheap as POV's are (and you can confirm that its the cause of your lean running condition) I'd just replace it rather than rigging a fix.

Good thought on replacing it except it's glued in, supposedly with epoxy.
It probably can be done but not as easy as installing the first one.
I'll have more time to look at it tonight. I'm going to search PP board to see if anyone has had the problem before. I wonder if you can just get the o-ring for it or do you have to buy the whole thing?

I can't wait to get home and drive the car and see if that solved the problem. It wouldn't be the first time I was wrong.

My frustration is that when I took on this car there were so many things wrong with it. It's not like it was running good and something broke. If something is not working I have to question the parts compatibility issues first. Then trouble shoot all the posibilities. There were definately several symptoms going on at the same time which effected each other. Because they were intermitant added another dimension. I would have never straightened this out without the knowledge that the A/F gauge gave me.

On that issue: I was reading your post about the meter with the wide band sensor. A few weeks ago I was reading some other posts on that subject. I was trying to clarify what people were commenting on that the narrow band sensor I have is not accurate. I began to doubt that statement because it is too general.

I found an emissions chart which shows the 4 exhaust gasses in relation to the A/F ratios. On that graph the O2 line is bassically flat below 13:1 I think at about 1/2%. If there is any variation below 13:1 it isn't much. Beyong 13:1 the % of O2 begins to climb in an arc and looks linear at about a 45deg angle beyond 17:1 (That's where the chart stops.) I think the Oxigen sensors were designed to work in that range because there are significant variations in O2 arround 14.7:1. I don't recall the control range of the K-lambda system, but the initial mixture control setting is 0.4-0.8% CO which is just a little richer than Lambda. (This is with the lambda control disabled, Right) To the lean side of lambda the CO line is flat at about 3-4%.

My meter's range is from 12:1-17:1. From looking at these tables I think it would have to be exponentially more precise to read below 13:1 because the O2 values don't change much there. It's probably ok from 13:1 up. 13:1 is max power as you stated.

The O2 gas was picked for a control input because it is a good indication of fuel mixture in the range that they want to measure it for emissions equipt cars.

I think the general statement made could be refined to say that if you are tuning at ratios below 13:1 then you will need a wide band sensor.
For lambda control cars the mixture should never get much below that.

FYI: The 78-79 k-basic mixture setting is 1.5-3.5% CO. 3.5% CO happens to be equivalent to the magic 13:1 max power ratio. On these cars the cone in the mixture unit is stepped. It's rich at idle, (This is the 1.5-3.5% setting) It get's leaner during crusing and light aceleration and at high engine speeds or high air flow it get's richer.
The 83 Euro like mine is tuned a little leaner at idle.
I've seen my A/F meter follow this general plan. Rich at idle (12-13:1 leaning out and then richening up at about 4000rpm.)

Since I have possibly fixed my air leak the ratio shouldn't exceed the aprox 16:1 ratio designed into the cone for light loads.

Do we really need a wide band sensor? I'm mainly intrested in the logging function! Where are we on the group buy anyway?