# wur pressure adjustment



## IrieVDub (Oct 7, 2004)

a dude i know who specializes in fords and old vw's told me you could adjust fuel pressure on the wur by tapping this plug (picture) in or out. another bud of mine with an 82 cab with 87 hydro with cis gathered a few of the wur's from a local junkyard (all vw wur's) ran each unadjusted, then adjusted each of them slightly differently. some unmolested wur's seemed to run slightly richer, with a bit more power. with the plug pushed in, the car seemed to have more power, and to blacken the tailpipe. with the plug pushed out, the car seemed a bit more hesitant, but seemed to run cleaner. his initial intention in starting this experiment came from trying to stablilze the idle. 








i knocked the pin in slightly (1/16" or so)on my rabbit (84gti w cis) and it seemed more powerful, and also seemed to blacken the tailpipe a bit. any similar experiences, or anyone know exactly what this adjustment does? i havent seen it in books or heard of it here on the vortex.


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## Questor (Sep 5, 2003)

*Re: wur pressure adjustment (IrieVDub)*

Yeah, don't do that unless you're running a modified engine (at least headers and P&P couldn't hurt) and you have access to fuel air ratio and exhaust gauges.
Increasing the pressure in a CIS (constant injection system) just dumps in more gas, you've got to be able to breathe it to burn it all








The black is beacuse you are running rich - your engine can't burn all that extra gas effectively.


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## IrieVDub (Oct 7, 2004)

*Re: wur pressure adjustment (Questor)*

my initial intention in adjusting mine was to deal with a cold start problem, as suggested by my bud (it was just a suggestion, kind of an experiment) and it completely cleared up (or masked)the problem. just curious weather any of you peeps had done the same thing. i often hear of replacing them with similar units, but never adjusting them.


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## ABA Scirocco (May 30, 2001)

*Re: wur pressure adjustment (IrieVDub)*

Here's an article on "knocking the plug", Adjusting your warm up regulator. It worth mentioning however that the way most U.S. spec VW CIS systems are set-up, this would only have an effect when the engine is cold, because once the engine warms up, the ECU with input from the O2 sensor take over control of the mixture and over ride the changes you've made.


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## 85vdub (Apr 9, 2003)

but when your running Euro CIS its a good way to get some more fuel to your motor...


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## ABA Scirocco (May 30, 2001)

*Re: (85vdub)*


_Quote, originally posted by *85vdub* »_but when your running Euro CIS its a good way to get some more fuel to your motor...









Agreed, And in Canada and many other places outside the U.S., CIS-basic , similar to the Euro CIS, without the ecu and O2 sensor are very common and this method should work well on those engine as well.


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## WackyWabbitRacer (Apr 24, 2001)

*Re: wur pressure adjustment (IrieVDub)*


_Quote, originally posted by *IrieVDub* »_anyone know exactly what this adjustment does? 

The amount of Control Pressure determines how far the Control Plunger travels in the fuel distributor.
The Control Pressure is a hydraulic counterforce on the top of the Control Plunger.
A lower Control Pressure allows the Control Plunger to raise higher; whereas a higher Control Pressure limits the amount of plunger travel.
Higher the Control Plunger travels, richer the fuel mixture.
On my race Wabbit, I fabricated a manually adjustable Control Pressure Regulator and set the amount of Control Pressure with a CIS Pressure Tester. ....WWR.


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## 85vdub (Apr 9, 2003)

how did you exactly do this and where did you find a guage to hook up? I've been wondering how i can balance out my fueling a bit more... at cruising speed my A/F guage is pegged lean. which kind of bugs me... but when i go WOT it pegs all the way on the rich side... I'd like to get that down just a big and bring the cruising ratio up some. not real sure where to start.


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## WackyWabbitRacer (Apr 24, 2001)

*Re: (85vdub)*


_Quote, originally posted by *85vdub* »_how did you exactly do this and where did you find a guage to hook up? 

I disassembled a CPR and then removed the friction-fit plug that the bimetallic spring attaches to. I then used a lathe to make a new plug with a center metric tapped hole. The new plug was driven into the original hole in the CPR housing.
The heater element around the bimetallic strip was removed. Next I placed a long metric bolt into the hole of the bimetallic strip and secured the bolt with a nylock metric nut. The nut was tightened enough to allow the bolt to turn within the hole.
The bolt was then screwed into the threaded hole of the new plug.
By turning the bolt up or down, the amount of Control Pressure will change and subsequently change the fuel mixture.
I used a CIS Pressure Tester which is used to measure CIS System Pressure and Control Pressure. The tester is a gauge, a two-way valve, hoses, and metric adapters. The tester attaches to the CIS fuel distributor for trouble shooting and diagnostics to adjust the System Pressure (via shims) and Control Pressure. ....WWR.


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## 85vdub (Apr 9, 2003)

To correct my problem what do i need... less control pressure and more system pressure? less system pressure and more control pressure? I hate to mess with the CPR just yet. I'm sure if i had a guage i could figure out which way i needed to go to get things more in check. To me it seems like i need a bit less control pressure thus allowing the air meter to come up just a bit more while cruising at a steady speed to give it a bit more fuel. But on the other hand i could probably do the same thing with shims and the system pressure. I really need to find a guage.


















_Modified by 85vdub at 5:10 PM 3-27-2005_


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## superl8 (Dec 31, 2002)

*Re: (85vdub)*

http://www.pelicanparts.com/te...g.htm
Do this mod!!!!
It's easy and it works. There is more power than realized with factory settings.
in enrichens the mixture 
out leans it up.


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## ellocolindo (Jan 15, 2010)

great info man. i am about to get started with a cis turbo 16v set-up from a volvo wur. also i have a cis wur from a 85 cabriolet. now i can try the cabriolet first :wave:


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## Mtjade2010 (Dec 2, 2010)

I am having difficulty to understand all the talks about adjusting WURs to lower control pressure to increase fuel to boost performance. 

You can touch the AFR (air fuel regulator) and feel the increase or decrease of air/fuel mixture by hand. Every time I did that the engine wants to stall and die. It seems if I tweak the WUR to lower the control pressure the air/fuel mixture will increase quite a bit. The engine won't idle the same any more. So I will have to adjust the CO adjustment screw (which is the same as air/fuel mixture adjustment) to stabilize the idle. Isn't this bring back to the same air/fuel mixture before tweaking the WUR? 

Besides, the Lambda sensor and the frequency valve will be the main controller of the air/fuel mixture. No matter how you tweak the WUR the closed feedback loop of the Lambda sensor, ECU and the frequency valve will over rite whatever is changed and keeps the mixture at bay still. I really don't understand why all the effort in tweaking the WUR. Unless your car has no Lambda sensor, ECU and frequency valve stuff. It seems impossible to achieve anything by tweaking the WUR. I maybe wrong. Please comment. Thanks.


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## dkfackler (Feb 8, 2010)

WackyWabbitRacer said:


> The Control Pressure is a hydraulic counterforce on the top of the Control Plunger.
> A lower Control Pressure allows the Control Plunger to raise higher; whereas a higher Control Pressure limits the amount of plunger travel.


Correct. It seems counterintuitive, but HIGHER control pressure(CP) causes a LEANER mixture. 

You want low CP with a cold engine for enriched mixture at idle, and higher CP for leaner running with a hot engine.

If you use a CIS pressure gauge, you can watch the pressure rise as the engine warms up.


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## ellocolindo (Jan 15, 2010)

to the fellow asking " WHY play with the WUR?". i am running no ecu; no frequency valve and no lambda sensor.
CIS BASIC; BABY


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## Mtjade2010 (Dec 2, 2010)

dkfackler said:


> Correct. It seems counterintuitive, but HIGHER control pressure(CP) causes a LEANER mixture.


Yes, higher control pressure reduces fuel and would be leaner if there is no Lambda sensor the frequency valve to self adjust/ self correct the mixture. I guess if it is too high it may be out of the range for the self adjust/correction to work. Then the engine would be running too lean.



dkfackler said:


> You want low CP with a cold engine for enriched mixture at idle, and higher CP for leaner running with a hot engine.
> 
> If you use a CIS pressure gauge, you can watch the pressure rise as the engine warms up.


Thanks for this. The WUR is supposed to lower the CP when cold. The enrichment is necessary for the engine to run when cold. I believe the Lambda system is bypassed when cold. The sensor won't work until it is hot. I still don't understand how tweaking the WUR can overrite the Lambda system when the engine is at the operating temperature. The engine won't run if the mixture is too rich or too lean. If it is slightly off (engine will run) then the Lambda system will self adjust it so the mixture will be brought back to within specs. I don't know if the tweaking of WUR will achieve anything. 

Of course if the car does not have a Lambda system/ECU/frequency valve then it may be a different story. But there is no way the mixture can be too far off. The engie will stall and die. I am having a hard time still to understand how it may actually work to boost performance.


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## dkfackler (Feb 8, 2010)

Mtjade2010 said:


> I believe the Lambda system is bypassed when cold. The sensor won't work until it is hot.


Right. In the early Lambda-CIS cars, the is a coolant temp sensor in a loop of hose connecting the two metal coolant lines. The sensor is near the ignition distributor and is electrically closed(0 ohms resistance) when cold. Somewhere around 70 deg F, it opens(infinite resistance), enabling the Lambda loop to come online. If your Lambda-equipped CIS engine doesn't like to idle cold, short across the terminals. If things improve, replace the switch.


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## dkfackler (Feb 8, 2010)

ellocolindo said:


> ...no frequency valve and no lambda sensor.
> CIS BASIC; BABY


CIS basic is a beautiful thing-- so simple, so easily diagnosed and fixed. I'd like to retrofit my '82 Caddy to basic.


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## ellocolindo (Jan 15, 2010)

not to mention very very easy to boost and lots of room to play with. the new wave of " tunning" guys think that the megasquirt and other " tunning" softwares are the coolest thing.
throw a cis system at them and see how much tunning they can do without a computer or laptop :wave:


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