1980 CS Frequency Valve?

[khamul02]

So I'm breaking down my engine and sending some stuff off to have it tested and rebuilt if needed. I have an odd fuel line attached to my Frequency valve. Given the cost ($700ish) of these things, it is a risky to rebuild.

I know Audi, Mercedes, and VW used these things as well so I was curious if anyone knew the BOSH part number?

This is mine:


Here is the standard one that seems to be available for purchase:



From what I read is that this thing is controlled by the O2 sensor. I read a blog that says you can throw a bypass in it to have it 50% open and things should run fine.

The BOSCH FV for VW is BOSCH 0280150302.. so will this one work for me?

What are the differences in these things? IS the VW FV that different that the Porsche?

Just looking for options to avoid putting on one old fuel line back on the car to be the weakest link in a system that will have all new lines.

[boyt911sc]

Originally Posted by khamul02

This is mine:

Tom,

Fuel line #1 is incorrectly connected to the wrong FD port. Were you able to drive the car with this set-up? How is your WUR return line connected? What is the ID # on the fuel distributor? -031 or -077? Picture would be helpful. Thanks.

Tony

[khamul02]

It was driving great minus the clutch issue. It doesn't have a cat on it but the o2 censor was connected. I assume everything was connected properly.













https://drive.google.com/file/d/1XGhVKN31qYQzx60C3bZcu89R7ytGaNy4/view?usp=sharing

[Dan J]

It's also odd that the vent line in the intake boot is plugged. Over the years I've seen many 911's
that were "re-engineered" by some enterprising mechanic. Some of these actually run decent and make you scratch your head some don't run at all.

[khamul02]

I'm working with Tony to get it all figured out. The guy who did most of the work to this car was a local guy, a Saudi I think. That work was done before I got it. In the 15 years that I have owned it, it has never really needed anything other than maintenance, and some CV joints.

The strange thing is that this thing would outrun my 81 coupe and my friends 85 Carrera. It drove great other than one broken head stud and a screwed up clutch that has brought me to this point.

BUT all of that being said.. is this FV stock and where can I get a replacement.. or more importantly with the Audi/VW one work as a replacement ;-)

[boyt911sc]

Originally Posted by khamul02

I'm working with Tony to get it all figured out. The guy who did most of the work to this car was a local guy, a Saudi I think. That work was done before I got it. In the 15 years that I have owned it, it has never really needed anything other than maintenance, and some CV joints.

The strange thing is that this thing would outrun my 81 coupe and my friends 85 Carrera. It drove great other than one broken head stud and a screwed up clutch that has brought me to this point.

BUT all of that being said.. is this FV stock and where can I get a replacement.. or more importantly with the Audi/VW one work as a replacement ;-)

Tom,

If your ‘80 SC was out performing other cars and you are happy, leave it this way. But I doubt your car could out run other SC cars. The FV (frequency valve) shown in the picture is not operational or simply not doing it’s suppose to do. Why? The fuel port where the FV is connected is the wrong one. That is an inlet port for the return line coming from the WUR.

The FV bleeds the lower chamber inside the fuel distributor to increase the fuel delivery to the fuel injectors and enrich the mixture for FD-077. You don’t need a good working FV because it won’t help you or makes a difference.

Find someone who is very familiar with CIS and starts from there. BTW, the WUR-072 that you have in your car is not vacuum assisted. But why are you using vacuum? See your pictures.

Tony

[khamul02]

Tony, I'm clueless.. but I'm in the middle of a complete rebuild and want things to be normal!

And this thing outruns my 81 SC and my friends 85 Carrera.. BUT again.. I just want it to be normal so troubleshooting in the future will be easy.

So what are my options here.. do I get another FV and hook it up properly.. what can I do to bring this thing back to stock?

Is this FV stock?

[BoxsterGT]

Following this with great interest, as I am involved in replacing the CIS Fuel lines and helping to get this back to stock....

Considering how well this runs, where is the "Return from the WUR" if it is not connected to the FD, since that port is filled with the inoperative Freq Valve?

Does a WUR operate properly if not connected where it should be connected?

Just wondering how or why this feels so fast compared to others.

Len

[khamul02]

Len, we have come a long way from the initial post. I hope once I get thing back from you and Tony the stock set up work with whatever other anomalies that might be in this thing.

[boyt911sc]

Originally Posted by khamul02

Len, we have come a long way from the initial post. I hope once I get thing back from you and Tony the stock set up work with whatever other anomalies that might be in this thing.

Tom,

These are the CIS components you sent to me for test and evaluation:



In order of testing:

Cold start Valve....................nice spray pattern when energized. OK.

Fuel injectors (set #1)...........mist-like spray pattern. OK.

Fuel injectors (set #2)...........these with plastic caps. Jet-like spray pattern. Poor.

Auxiliary Air Regulator............electrical test. Valve closed after 3 mins. plus. OK.

Auxiliary Air Valve..................vacuum test. OK.

Decel Valve...........................vacuum test. OK.

WUR-072...........fuel not flowing through the WUR. Building too much control pressure due to blockage inside WUR. This will need some work to get it to work.

FD-077..............the plunger or piston is stuck. Will need some work to free the plunger and be able to test it. Can not do any test at this condition.

Throttle switch........not tested.

I will have them packed and shipped to you. Thanks.

Tony

[boyt911sc]

Tom,

I tried to pull the plunger out from your fuel distributor yesterday and it was stuck. Normally it slides down by itself but prolong stagnation of the fuel inside the FD could produce some formation of varnish that caused this problem. Hopefully, the 120 psi. air pressure from the air compressors could push it out. Otherwise, I need to disassemble the unit and use the hydraulic press to get the plunger out.





Did you inspect the plunger movement before you sent the FD to me? When was the last time the motor ran?

Tony

[creaturecat]

thx for the informative posts, boyt911sc.
always appreciated.

[khamul02]

I'm pretty surprised. It was falling out before I sent it that is why I wrapped it in tape. The engine was running fine minus a broken throw-out bearing in the transmission and one broken headstud I didn't notice until disassembly. I'm baffled but if it needs a rebuild that is the route we will go. It has been roughly 15 years since it was rebuilt.

[boyt911sc]

Tom,

I was successful in pulling the plunger out. There was some abrasion present on the plunger plus varnish deposit on the barrel surface. Cleaning the barrel inner surface with acetone and polishing the plunger made it slide freely now.

I have not measured the individual flow rates of the 6 ports and planning to do it before you come and pick up the parts.



PM me when to expect you. Thanks.

Tony

[khamul02]

Huge Thank you Tony and Len for helping figure out this strangely put together CIS! Hope to get this thing back to stock soon!