I'm not Tony, but I'll try to answer.

Take a look at this picture. I stole it from somewhere else on Pelican and added the notations. This looks like it might be an -090 WUR.

http://forums.pelicanparts.com/uploa...1527603802.jpg

"The Disc" is where most of the magic happens. The basic components are the input/supply line from the fuel distributor (FD), the internal diaphragm of "The Disc" and the output/return line to the FD.

The fuel pressure coming into the disc is the system pressure. This is the fuel pressure generated by the fuel pump. If you do the CIS fuel pressure test for system pressure, when you close the gauge valve, this is the pressure you're reading.

"The Disc" reduces the fuel pressure from system pressure to control pressure. There are two states for control pressure: (1) the cold control pressure (CCP) for when the engine is stone cold and (2) the warm control pressure (WCP) for when the engine is at normal operating temperature.

If you were to disassemble the WUR and look at the disc from the inside you would see there are 4 screws that hold it in place and a tiny little indention in the center. If you were to hook up the disassembled WUR with just the two fuel lines in place (and a fuel pressure gauge) and pushed up on the indention, you would see that by pushing on the indention you would actually be varying the fuel pressure. Inside the disc is an o-ring. Sometimes the o-ring fails with age. In the input fitting there is a metal screen. The screen can be clogged over time. To clean it, soak it in something like carb cleaner and then blow it out with air. Short of the o-ring failing or the filter clogging, I'm not aware of any modification that can be done to the disc itself to affect control pressure.

If you put little or no pressure on the indention of the disc, this would be the cold control pressure. If you applied a little more pressure until you reached a max value, this would be the warm control pressure.

It is important to understand something. When the control pressure is LOW, this makes the mixture more RICH. When the control pressure is HIGH, this makes the mixture more LEAN. Therefore, on a cold engine you want a richer mixture. Once the engine is warmed up, you want it to be leaner (not lean -- I mean "leaner" than rich). Basically, the WUR and the AAR act together to replicate the functionality of a choke - add a little more gas and air until the engine is warm.

So, to calibrate the WUR, you need 3 things:

1) the cold control pressure needs to be correct for a cold engine (based on ambient air temperature)

2) the warm control pressure needs to be correct for a warm engine so that you're not too rich or too lean at normal cruising

3) the rate that the bimetallic strips heats up should not be too fast or too slow. In general, it should take about 3 minutes to go from cold control pressure to warm control pressure. If the element warms up too fast, the mixture will be leaned out prematurely (before the engine is at operating temp).

To set the cold control pressure, the starting position of the bi-metallic strip arm is really critical. In the picture up above, I labelled "The Pin". To adjust the CCP start with the "guts" of the WUR removed. Use a hammer and a drift and carefully drive the pin down until it is flush with the outside surface of the WUR. This will remove the arm pressure from the disc and this should be the maximum warm control pressure.

Now re-assemble the WUR and hook up the fuel lines with a fuel pressure gauge inline. Run the fuel pump and check the pressure. If you take a drift and tap the pin down, the CCP will go down until you reach your desired value for your model WUR and the ambient temp. TINY amounts of movement will affect the pressure. If you knock the pin down too far the pressure will bottom out and you would be really rich on cold start. This is where you need to consult the graph for your WUR model. Check the ambient air temp (if in ºF, convert to ºC) and look up what the CCP value should be. That is your target. If you overshoot you have to disassemble the WUR again and tap the pin back down to the starting point and try again.

Once you have the CCP set, plug in the electrical connector and time how long it takes for the control pressure to reach it's max and record the max value. This is the warm control pressure and it means that the bi-metallic strip is putting pressure on the indention of the disc. The WCP should be within the range specified for the model of the car. Typically, this value should be in the same range as the max CCP value on the chart.

Take a look at this picture too. It's actually a picture of the mod to make the WUR adjustable (but only to raise CCP), but it's helpful to understand how the WUR works.

http://forums.pelicanparts.com/uploa...1470900719.jpg

If you look at the CCP graph in the Bentley, the range of temps is 10ºC (50ºF) to 40ºC (104ºF). Any temp lower than 10ºC/50ºF the WUR treats as the same CCP as 10°C. And any temp greater than 40ºC/104ºF the WUR treats as a fully warmed engine. So the variability in the CCP is only between these temp ranges.

The problem with adjusting the CCP is that you're hoping that by calibrating the CCP at one temp it will be set for the right CCP at other temps. This is why some people complain about seasonal differences on how the WUR operates. Let's say you set the CCP perfectly for a nice spring day. But maybe in the cold of winter you might be too rich or too lean from what the CCP should be. The WUR is an analog device and it has some limitations that come along with that.

Hope this helps!

Well put Tony. I'll take it a step further and suggest the full identity be made known. We all like to promote people & companies who do great work. Those who are not doing so should be recognized for the caliber of their work as well.