WUR Calibration Set up
08-30-2010, 10:29 PM
#1
Rennlist Member
Thread Starter
WUR Calibration Set up
I have a couple of spare WUR on hand, with new O rings and cleaned passages, and I want to build a rig to calibrate them, mostly out of interest in the challenge - mine is currently working fine.
I have an adjustable pressure regulator, that will handle from 30-90 psi. I have a used Bosch 580464??? pump off a BMW E28, which should be able to deliver the pressure needed - 75psi is the aim.
The technical manual shows what it calls a 'decoupling restrictor bore' where the control pressure supply is tapped off the system pressure in the distributor body. My plan was to get the pressure to 75psi, and run a T piece off the pressure side of the regulator to the test WUR, but I dont know enough hydraulics to assess whether, for my intention , I need a restrictor in the T outlet, or if I do, what size it should be. I have fittings around 1/4" ID to use. If necessary, I can make a restrictor , and I can drill down to 1mm.
Does anybody know from opening up a distributor what size the WUR feed hole in the steel shim is please? There is a pic of it in Rich Andrade's article on rebuilding the distributor, but its difficult to judge the size.
thanks
jp 83 Euro S AT 52k
I have an adjustable pressure regulator, that will handle from 30-90 psi. I have a used Bosch 580464??? pump off a BMW E28, which should be able to deliver the pressure needed - 75psi is the aim.
The technical manual shows what it calls a 'decoupling restrictor bore' where the control pressure supply is tapped off the system pressure in the distributor body. My plan was to get the pressure to 75psi, and run a T piece off the pressure side of the regulator to the test WUR, but I dont know enough hydraulics to assess whether, for my intention , I need a restrictor in the T outlet, or if I do, what size it should be. I have fittings around 1/4" ID to use. If necessary, I can make a restrictor , and I can drill down to 1mm.
Does anybody know from opening up a distributor what size the WUR feed hole in the steel shim is please? There is a pic of it in Rich Andrade's article on rebuilding the distributor, but its difficult to judge the size.
thanks
jp 83 Euro S AT 52k
09-25-2010, 03:54 AM
#2
Rennlist Member
Thread Starter
I have started on this now. After a couple of issues, I have a -005 wur (spare from ebay.de, bmw 323?) set up with new O ring, 45psi with no bimetallic (ie, hot control), and 20psi with bimetallic at 65F...close to spec - ~25psi cold control at that temp is how I read the book. Initially this unit with no bottom half fitted, showed 60psi, so I changed the O ring from 14x1.5 to a 15x1.5, and it came down to 20psi. fitted the bottom half, control went up to 60psi again. Tapped the regulator body out, control went down below desired, tapped reg body back a bit, got the 45psi I was looking for.
On the -086 unit, I got hot control to 45psi easily, but when I fitted bimetallic strip parts, I cant get control under 30psi - post is ~6mm down from flush. It shows 30psi from 3mm in , so something is wrong. next I will remove all and see what minimum pressure is (no bottom half), and see if its same O ring issue as other unit. This makes me wonder if O-ring size is something odd, between 1.5 and 2.0mm section. I think I have tried a 2mm section once before and it was too thick.
Anybody have any specs on O-ring size please?
jp 83 Euro S AT 52k
On the -086 unit, I got hot control to 45psi easily, but when I fitted bimetallic strip parts, I cant get control under 30psi - post is ~6mm down from flush. It shows 30psi from 3mm in , so something is wrong. next I will remove all and see what minimum pressure is (no bottom half), and see if its same O ring issue as other unit. This makes me wonder if O-ring size is something odd, between 1.5 and 2.0mm section. I think I have tried a 2mm section once before and it was too thick.
Anybody have any specs on O-ring size please?
jp 83 Euro S AT 52k
09-25-2010, 03:33 PM
#3
Rennlist Member
The fuel distributor restricts to flow of fuel to the WUR via a tiny hole in the stainless plate/gasket. Without this in place you will not get correct pressures, because the WUR is not actually a regulator...more is just a variable restriction and a big part of its function is actually done by the screen material in it that is just a fixed restriction. If you want to tune these off of your motor you will have to simulate the orifice in the FD. I can think of three ways to do this:
1) try to guess the ID of the orifice and build one. It is pretty small, 0.020 or 0.030 or so. Obviously the best way to do this would be to take apart a FD and use a pin guage to measure, but that may not be practical.
2) disconnect the WUR on your car, jumper the fuel pump, and measure the flow rate into the WUR using a bottle. Then try to reproduce that flow rate.
3) find a spare FD and run the fluid through it. You might / might not need to plug the lines to the cyls.
I think your easiest approach would be to swap these in and test them on the car.
Oops, read your OP more closely. You know most of this. Sorry, I rebuilt my FD last week but did not measure the orifice.
1) try to guess the ID of the orifice and build one. It is pretty small, 0.020 or 0.030 or so. Obviously the best way to do this would be to take apart a FD and use a pin guage to measure, but that may not be practical.
2) disconnect the WUR on your car, jumper the fuel pump, and measure the flow rate into the WUR using a bottle. Then try to reproduce that flow rate.
3) find a spare FD and run the fluid through it. You might / might not need to plug the lines to the cyls.
I think your easiest approach would be to swap these in and test them on the car.
Oops, read your OP more closely. You know most of this. Sorry, I rebuilt my FD last week but did not measure the orifice.
Last edited by karl ruiter; 09-25-2010 at 03:35 PM. Reason: oops
09-26-2010, 07:54 AM
#4
Rennlist Member
Thread Starter
Karl,
I have a set up where a pump feeds to a proper asjustable pressure regulator, set as best I can to 75psi. In the line between the pump and the regulator I have a Tpiece, the stem of which has a plug in it, with a 1mm hole drilleld through it. This is the smallest drill I have, and probably the smallest hole an amateur can drill. The T stem feeds to a cis gauge set , linked to the test WUR. So far I have managed to get a -005 WUR (BMW 323?)to read 45psi with no bimetallic strip fitted, and 20psi (at 65F) with bimetallic, which from my reading is close to specs. Now I have to test that heating the strip will allow the control to rise to the 45psi level. Curiously, with a 14x1.5 O ring in the regulator, I could not get minimum control below 30psi, but swapping in a 15x1.5 Oring, it came down to 20psi. I would not have though the Oring that critical - what will happen as it flattens with age? These things should be able to hold a setting for a long time. My current WUR was obtained used some 9 years ago, and has performed without issue since installation - not going to open it until absolutely necessary. I think I have tried a 14x2.0mm Oring before, but I may be wrong, so will need to test and document.
Re the filters in the WUR inlet - my old one had FIVE (5) layers of brass gauze in there - if they are supposed to contribute to the back pressure, how much should that be, and how low should they go without these? So far all my testing has been with no filters, but maybe I will do a test with a set in place. Browsing ebay recently for WURs, I found somebody selling a 'tool for WUR filter removal' for $3, so I have bought that, waiting for delivery to see what it is.
Thanks for your comments.
jp 83 Euro S AT 52k
I have a set up where a pump feeds to a proper asjustable pressure regulator, set as best I can to 75psi. In the line between the pump and the regulator I have a Tpiece, the stem of which has a plug in it, with a 1mm hole drilleld through it. This is the smallest drill I have, and probably the smallest hole an amateur can drill. The T stem feeds to a cis gauge set , linked to the test WUR. So far I have managed to get a -005 WUR (BMW 323?)to read 45psi with no bimetallic strip fitted, and 20psi (at 65F) with bimetallic, which from my reading is close to specs. Now I have to test that heating the strip will allow the control to rise to the 45psi level. Curiously, with a 14x1.5 O ring in the regulator, I could not get minimum control below 30psi, but swapping in a 15x1.5 Oring, it came down to 20psi. I would not have though the Oring that critical - what will happen as it flattens with age? These things should be able to hold a setting for a long time. My current WUR was obtained used some 9 years ago, and has performed without issue since installation - not going to open it until absolutely necessary. I think I have tried a 14x2.0mm Oring before, but I may be wrong, so will need to test and document.
Re the filters in the WUR inlet - my old one had FIVE (5) layers of brass gauze in there - if they are supposed to contribute to the back pressure, how much should that be, and how low should they go without these? So far all my testing has been with no filters, but maybe I will do a test with a set in place. Browsing ebay recently for WURs, I found somebody selling a 'tool for WUR filter removal' for $3, so I have bought that, waiting for delivery to see what it is.
Thanks for your comments.
jp 83 Euro S AT 52k
09-26-2010, 07:27 PM
#5
Rennlist Member
Looking forward to hearing about the tool. I did a search here when I was going through my WUR and found several posts from people who (like me) had clogged brass gauze. Seemed like they removed the gauze and afterwards could not get their cold pressure high enough. When I read that I opted not to mess with my guaze and got a used unit off ebay that worked fine. Seems like someone could come up with a filter or an orifice that could be placed in the inlet fitting of the WUR. If we had this we could rebuild them, without it we are kinda stuck.
09-26-2010, 07:42 PM
#6
Rennlist Member
Thread Starter
No matter how clear those filters look, they need to be cleaned. Best way I know, once you get them out, is to burn them with a lighter - you would be amazed how much lint and crud gets in there. for The two units I am working On I used compressed air to blow through the two holes to ensure a clear passage. I can envisage the problem with cold pressure you note if somebody adjusted the regulator body position with clogged filters, and then cleaned the filters...
The thing I really would like to get is the proper size of the regulator Oring, as I suspect the section is critical, based on the experience I listed above with minimum pressure value.
The side issue I have with my test rig is using Kero for safety - it SMELLS awful, and the smell is very persistent - her indoors is not impressed with me doing it in the garage - Take it Outside! she says.
With the gauge set tap closed, I am seeing ~70psi, so I think the basics are ok, although the second hand pump may be struggling a bit to deliver it.
jp 83 Euro S AT 52k.
The thing I really would like to get is the proper size of the regulator Oring, as I suspect the section is critical, based on the experience I listed above with minimum pressure value.
The side issue I have with my test rig is using Kero for safety - it SMELLS awful, and the smell is very persistent - her indoors is not impressed with me doing it in the garage - Take it Outside! she says.
With the gauge set tap closed, I am seeing ~70psi, so I think the basics are ok, although the second hand pump may be struggling a bit to deliver it.
jp 83 Euro S AT 52k.
