steve322s

i'm trying to set my wur. my question is this? with bi matallic not installed and the temp outside 60 deg my dimensions and tolerance book states for my wur model 063 that my diagram should be set at 1.6 bar. now i've also read to set it at 3.6 bar with bi matallic out. do i set it at 1.6 with the relay jumpered or the 3.6 then set my cold pressure?

Car has sat all night and will be cold

Thanks, Steve

Mrmerlin

check this out

https://rennlist.com/forums/928-foru...?highlight=wur

Jadz928

What does this mean? (highlited in red)

Why would you run the WUR without the bimetallic strip? Having that removed make it so the WUR never backs off of cold start enrichment.

steve322s

not looking to run with out it just set it. heres what i'm talking about in red.

to my understanding at 60deg or 14c out side temp the diapram will alow 1.6 bar due to ambient temp (press) i read jay kemp where he stated to set warm control with the bi met. out to ensure it isnt effecting the warm pressure. then install the strip and set cold pressure. the way i'm reading this if i set my control at 3.2-3.6 on a 60 deg day then it will be throught the roof on warm up.

Jadz928

I could see how this might work. Basically starting with warm control pressure, then backing into cold control pressure. Well, here are the numbers I've collected:

System pressure spec:
• System pressure 4.5 bar (65 psi) – 5.2 bar (75 psi)

System pressure leak-down spec:
• 2 bar (29 psi)/10 minutes, 1.7 bar (25 psi)/20 min,1.6 bar (23 psi)/30 min.
_______________________________________________________

Control pressure spec (Cold):
• 1.2 bar (17 psi) @ 50°F
• 2.0 bar (30 psi) @ 75°F
• 3.0 bar (44 psi) @ 100°F

Control pressure spec (Warm):
• 2.8 bar (41 psi) to 3.2 bar (46 psi)

Luis_M

Short answer: the warm temp 3.6 bar.

Long answer:The chart you've highlighted shows the effect of the bimetallic strip inside the WUR deflecting downward more at lower temperatures. The strip pushes down on the top of the spring more at colder temps thus reducing the pressure that the small pin on top of the spring puts on the metal diaphragm at the top of the WUR. This results in less resistance to flow between the inlet and outlet on the WUR, so more flow occurs through the WUR circuit, resulting in lower control pressure on the top of the fuel distributor rod, and therefore, more fuel flow to the engine for a given airflow. As the strip warms up after start-up (due to both increasing engine temp and from the heater element wrapped around the strip), the strip deflects less and puts less and less pressure on the spring assembly, such that the control pressure rises over about 7-10 minutes to the warm control pressure listed for your car. At that point, there is really no more pressure on the spring from the strip, so it won't go up any higher. So... if you are trying to calibrate the pin/spring/vacuum assembly without the bimetallic strip, you will need to use the warm control pressure, but also pay attention to the notes regarding the amount of vacuum that needs to be applied to the port at the side near the bottom of the WUR (the top port is to atmospheric pressure, not to vacuum), as there is a second "inner" spring in the assembly that sits on a vacuum sensitive diaphragm at the bottom of the WUR. Both springs and the pin have to be carefully positioned before closing and testing the WUR. Check it with and without vacuum. If the values aren't correct both ways, something is wrong with the vacuum diaphragm assembly or one of the springs isn't set right.

SMTCapeCod

Woot, nice post- ^^^- welcome!

steve322s

luis

i thank you for the reply, however i am aware of all info you listed, i have been reading every post, link and video i could find. You listed the specs same as the manual ( with outside temp being 20 Celsius ) what would you set it at if it is only 10'c outside? this is what im hunting for. and it should not be as listed above.

if im reading the chart rite as engine warms pressure will rise 1.5 bar so if its only 10Celsius outside you need to set cold to ambient temp. that would be 1.4 bar. now if the stip rises about 1.5 bar then my warm at 10Celsius would be 2.9 -3.0 bar not 3.6 bar correct?

Thanks Steve

Luis_M

ok, responding to your first paragraph, the chart shows only the linear part of the temperature-pressure response. just as the upper limit is the 'warm' pressure, there is a lower limit where the bimetallic spring has pressed down so far on the internal spring apparatus that the short vertical pin no longer exerts any upward pressure on the diaphragm in the top of the WUR, so pushing down further (colder) makes no additional difference. This limit pressure is about 1.0 bar, pretty close to the 50F/10C mark at the bottom left of the graph. You can find out exactly what this bottom limit pressure is on your WUR by taking the pin and spring assembly out and measuring the control pressure in that setup with the fuel pump jumpered. If it's much higher than 1.0 bar, then you have a problem in the "top" of the WUR, either the wrong O-ring size or debris in the inlet screens. If it's lower, it's probably an o-ring that's too big (in the groove beneath the flat metallic diaphragm).

But at 10C ambient temp, you are still on the graph, and if your WUR is working right, then with the WUR fully assembled (metallic strip in place, all springs properly and pin aligned), engine cold and off, disconnect the electric plug at the top of the WUR (to disable the internal heater) and apply 500millibar vacuum to the side vacuum port, then jumper the fuel pump relay, and the cold control pressure should read somewhere between 1.2 and 1.6 bar indefinitely. 1.4 is the middle of the range, but 1.2-1.6 is "in spec".

The warm pressure has nothing to do with the ambient temperature. The strip doesn't rise a fixed number of bar. The bar deflects upward as it heats until it no longer puts any pressure on the spring assembly. Then, the system is no longer temperature dependent. Thist will always be about 3 bar without vacuum or 3.6 bar with vacuum.... The "warm temperature". These should also be the measurements you get with the metallic strip out, regardless of ambient temperature. These are +/- 0.2 bar, also.