WUR experts...what's this?

jeff91C2T · 01-09-2006, 05:14 AM

I've got my WUR apart at the moment and was wondering what this adjustment screw does? Any ideas?

The picture is from the inside of the top section. The grean piece is the heating element on the arm that moves when heated.

jwmarc · jwmarc's Garage

I believe it adjusts the Bi-metal strips tolerances for flexing. In other words you can set it up to modify the pressure effect on the FD head.
Not sure of the exact specification in terms of tolerance that you ould want to set it to since it will be dependent on your climate condition.

Mysterytrain · 01-09-2006, 06:38 AM

What year? Mine doesn't look like that inside. It just has the heating element [green blob in the picture] on the bimetal strip.

Paulporsche · 01-09-2006, 06:45 AM

It may affect the amount of difference between the cold and warm control pressures.

Gunter · Gunter's Garage

Good picture.
Why did youtake it apart?
What year? Different years have different WUR's
Do a search; JW tried some adjustments on that screw.

MotoSook · 01-09-2006, 07:03 AM

Quote:

Originally posted by Paulporsche
It may affect the amount of difference between the cold and warm control pressures.

I think Paul may be correct. A profile view of the assembly would help, but that may require disassembling the WUR further. The screw may change the gap between contacts so that cold pressure (time) is extended. It's probably something you don't want to change. Something like that is usually bench set at the factory and left along. To change it you'll need to make a test rig to power the unit and measure pressure over time.

jeff91C2T · 01-09-2006, 07:20 AM

The part number is 0438140 160 (off a 91 911 Turbo). I took the WUR apart to knock down the pem in the lower section to get more pressure drop while on boost. And now I'm into the "while I'm in there..." syndome.

What's confusing is that these top two "bars" are not connected to the bar that modifies control pressure. The are however on the same shaft that holds all of them. When I checked control pressure it came in at 60 psi and the system spec is 65 psi. I was wondering if the adjustment screw would effect end pressures (ie...cold and warm control pressures) or just the modify rate of change.

cmonref · 04:24 PM

Maybe it is a potentiometer to vary the resistance in the heating element circuit, which would shorten or lengthen the time the WUR takes to get thru the warmup period.

Mysterytrain · 01-09-2006, 12:26 PM

It looks to be a time control for the contacts below it..a switch if you will. Maybe something along the lines of a totally electrical version of the thermotime switch to keep things rich a bit longer at startup by delaying voltage being sent to the element. It could also work the other way and cut off power to the element when the engine is hot enough to rely on the spring to control the pressure. The adjustment that John was refering to was mechanical.

Here is the link to the thread:
internal adjustment screw in WUR

Paulporsche · 01-10-2006, 11:05 AM

Jeff,

Any followup on this? Did you make any adjustments or conduct any tests?

Won · 02-12-2008, 11:02 AM

FYI - (yay for 2-year old threads)

the switch adjusts a contact point for the 2nd bimetallic element. That contact controls the resistance of the green heating element by opening/closing a part of HE winding "circuit". By adjusting the contact point to open/close a certain temperature (hence time elapsed before reaching that temperature, starting cold) one can have two distinct heating "curves" for the WUR - could be used for fine tuning.