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Made an Adjustable WUR- Step by step, got Pics!

Went to the junkyard today and picked up a WUR of an older VW, I'd say late 80's VW Rabbit if I recall correctly. Either way, I just picked through the VW's till I found a WUR. It was kinda a bear getting it off, luckily I took a lot of tools with me.

When I got it home I took off the attachments and cleaned it up with a wire wheel. Then I prick punched the dowel pin the bi-metal spring is mounted on, and drilled and tapped a hole. I used a 10-32 allen head screw, because I had a bunch lying around, it seemed to be a good size, and I had quality taps to use in that size.

By using an allen head screw, in conjunction with a nut and washer, you can save yourself from opening up the WUR and adding a 1.5 mm dowel pin like in the illustration below. To adjust, I'll just tap the dowel down to richen the mixture, and if I go too far, just hold the allen head screw with a wrench (this will prevent the dowel from turning inside the WUR, and screw down the nut with an open end wrench. I copied this set-up from the user Dean who posted a similar set-up with his WUR.

Total cost of the project was 5 bucks for the WUR. I had no choice but to use a non-stock WUR, because 74's are NLA, and they are different. But my philosophy was that since I'm making it adjustable anyway, it won't matter that its from a VW. The housings all look the same for all the WUR's used on Porsches/Saabs/Mercedes/VW/Audi etc that I've seen. If it doesn't work, it isn't like I spent 300+ bucks for a new one.

Here are some step-by-steps:
Diagram of an adjustable WUR:



Cleaned up and prick punched:



Drilled w/ a #21 drill, for the 10-32 bolt and ~76% thread. In hindsight, the dowel pin is very very easy to tap and you could easily use a smaller drill.



Tapping:



Finished, installed w/ bolt, nut, and washer:



Other accessories mounted, ready to be wired in and have the hoses modified and connected:



At first I was a little scared of this project when I saw the diagram above in another thread, but after doing it Dean's way, I'd say this is a very easy project, only about 15-20 minutes, and will hopefully prove to be worthwhile.
Old 04-28-2005, 04:20 PM
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Very slick, do you have gauges so you can install and see if you can get the pressures right? Be sure and report back.
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Old 04-28-2005, 05:37 PM
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I don't have the guages, I'm hoping to tune it using a wideband Air/Fuel Ratio meter. If it proves too problematic, I'll just buy the guages, but for now I don't want to wait till they come in.
Old 04-29-2005, 03:16 AM
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Looks good on paper.......let us know!!!
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Old 04-29-2005, 03:47 AM
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Hmmm not sure you can be certain about the different pressures with the gas analizer, I am sure you can get close. Yes tell us what happens
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84 lime green back date (LWB 911R with RS rear flares) hot rod - absolute riot to drive!
RSR look hot rod, based on 75' SOLD
73 911t 3.0SC Hot rod Gulf Blue - Sold.
Old 04-29-2005, 03:51 AM
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You can do it with an A/F guage, EW. That will show your ratios thoughout the RPM range. The CO meter only shows you baseline at idle.

I to am curious to see if you can get this to work. These uints are all very old now, we need a DIY option.

Anyone know how/where to get Bosch rebuild kits? I've had no luck. They don't like to sell to individuals.
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Old 04-29-2005, 03:57 AM
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Looks good. If you are able totune it by A/F meter, dont bother if pressures is correct according to old spec. The function af the WUR is to keep the A/F within reasonable limits during warmup, so actually pressures is not that interresting just a way of adjusting before the days of A/F meters. I'm running with a A/F meter in my car right now, and it's interresting to se the A/F ratio warying between 12-17, depending on temp. acceleration and rpm. So do'nt expect to tune tight with CIS and WUR, it's a rather crude system, but it works.
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Old 04-29-2005, 03:59 AM
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I did this a while back. It's great. If the heating element is bad though, it's going to drive you nuts. Test for the correct ohm reading. If one could source the bimetallic heaing element. They could be rebuildable. This is what I think fails and makes the part useless. I took my old one apart after I bought a new one from PP and it is a simple device. The heating element of the old one had a crack in the insulation goo. The ohm reading was open.
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Old 04-29-2005, 06:04 AM
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you don't really need a meter or gauge. if it spits and pops cold, and barely runs, lower the pin until it runs well. too low and it will have a rich surge, then you raise the pin until it just evens out and runs smoothly. keep the electrical plug off when you first start it cold, so you have a bit more time to adjust. try to get the adjustment done within one minute before reinstalling the plug, so have your tools ready. then get it cold again and see how you did.
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Old 04-29-2005, 07:00 AM
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klaucke - My hat is off to you and I'm watching with great interest. I made the mistake of taking mine to a local shop and told them to put in a new WUR. (This was before I knew about JW's shop)

They charged me $390 for the part and $280 for Labor to install and adjust. I was so ticked, I signed up for the Pelican board and have done all my own work since. Thax for the great write-up and pic's...Bob
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Old 04-29-2005, 07:08 AM
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you should see what the new ones go for now. $390 would be a steal.
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Old 04-29-2005, 07:10 AM
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I know they are a ton of money John. All the more reason to do what Klacke did.
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Last edited by LakeCleElum; 04-29-2005 at 03:05 PM..
Old 04-29-2005, 07:14 AM
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Tuning

Ok, I got the WUR installed but broke a fuel line fitting, so I had to wait to get that in from PP. Then I was missing a crush washer.... more down time (I ended getting the crush washer from the same VW at the junkyard). So finally today I was able to hook everything up.

Well let me tell you, it all turned out great! I let fuel pump run for a little bit to fill up the new WUR and fuel lines, while I checked for leaks. Then, I cranked it over and it started immediately! Before, it took some pedal manipulation and some cranking before it would start. I had to adjust the idle screw just to get it to idle (it was so lean before, causing a high idle, that I had the screw all the way in). After that, I hooked up the AF meter and went for a ride. It was definately better, but still not as rich as I wanted. So I tapped it down with a hammer, WAY to rich, it would barely run and I thought it was flooded. Out came my trusty 3/16 wrench and 1/8 allen, and a quick turn and I was back in business. Its so easy to just tap it down or screw it up. Now, it runs near stoicheometric (14.7) unless I punch it and bring the RPM's way up, and it'll drop to high 12's.

At this point, I think I can do the final tune with just the mixture screw (if it's not seized, I think it might be). All in all, it was a definately worth my time to do this project. Hopefully it will lead to more normal, lower oil temps, also.

I didn't do any checking regarding cold pressures, etc, because I never drive my car unless I let it warm up anyway. Its only a weekend vehicle and not a daily driver, I don't mind letting it warm up. Also, the Wideband meter gets wacky readings around idle, so it would be tough to accurately monitor my cold AF ratio, etc. My old WUR was affecting my mixture all the time, and I just wanted my new WUR to give my the proper AF when its warm and I'm driving.

I should note, my car gets sideways in corners WAY easier than before. Painting black stripes is just a push of the pedal away if you're in a hard corner. DEFINATELY more fun than before. I used to just mash it, let the back end get a little loose and it would come back in on it's own. The first time I went a bit sideways today, I had to let off to keep the back end in check! Otherwise I would have spun.

Here are some pics:

WUR installed in car:



Wideband O2 sensor in tailpipe, cord running into the car:



Note extra battery behind passenger seat, to run the wideband meter from. Also, my two WUR tools are on the seat, just the allen and open end wrench to lean it out. Tap with a hammer to richen. It gets difficult to hold the meter and watch the AF and lamda when you're trying to drive on suburban roads. Especially when you want to see what you're getting at 4k and above. A dyno would prove handy in this respect. I noticed it leans right out when you let off or are just putting around, hence the characteristic CIS backfires.



I got some weird looks when I would pull over on the of the road, take out my hammer, walk to the back of my car and start banging on the engine! Who else tunes their car with a hammer???
Old 05-05-2005, 08:34 AM
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Impressive!
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Old 05-05-2005, 08:45 AM
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Good job......
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Old 05-05-2005, 08:47 AM
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Great writeup and good use of WBO2. What you esentially did was to fine-tune CIS just the way it should be. It would cost you hundreds of $$ if you did this the "traditional CIS-way" -> swapping out components until it starts working.

AFR of 14.7 when coasting and 12.8 at full load is exactly the way it should be!

Remember that test-pipe WBO2 sensor will get innacurate at low power levels as exhaust-gas pulses will inadvertely pull in fresh air into test-pipe, diluting the measurments.

For accurate AFR at idle, you'll need to bung-weld it somewhere after the collector.
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Old 05-05-2005, 08:50 AM
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Crotchety Old Bastard
 
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What is the hammer for? Isn't the srew tapped in and adjustable?
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Old 05-05-2005, 09:07 AM
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The hammer is to tap the pin down, the screw is just there as a 'lever point,' which you use to pull the pin back up. Screwing the nut down (while holding the bolt from turning) effectively pulls the pin up, however, you have to tap it down with a hammer.
Old 05-05-2005, 09:51 AM
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Very nice job. I did this 4 or 5 years back from that same article in Up Fixin'. I went the dowel pin route though. Kind of a ***** actually. I think if you're using just the allen head, you might want to put a drop or two of loctite on it to keep it in the plug so it doesn't turn?

I adjust mine each spring as I find it tends to fluctuate a bit after a years driving. The Porsche factory manual publishes a graph of acceptable pressures for a given temp for each part # WUR.

Well done!

ianc
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Old 05-05-2005, 09:21 PM
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When you adjust the pin (up or down), are you just changing the cold pressure, or the warm pressure also?

Mike
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Old 05-06-2005, 01:15 PM
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