WUR, IMPORTANT INFO!

Okay now that i have your attention. i have as most of you know been doing research on the CIS for the purpose of FI. the WUR (warm up regulator) is a very critical piece of the puzzel, yet many do not know how it works or interacts with the system. first it does control the fuel pressure via a push valve on the fuel distribution block to allow cold starts. once warmed the unit will also control the control pressure via the same push valve until fully warm.

additional controls to the WUR are vacumm/boost and altidute. there is an internal diaphram the works against a set spring pressure to over ride the temp switch. now this is the critical part, a WUR from any other car, i.e. porsche, mercedes will not work in place of your ferrari one. why? the unit is calibrated to our engines based on load and fuel requiremnts. the spring and temp pressure is different for each one. i'll save the specifics but as the bimetalic spring heats up it increases the control pressure, the pressure starts at a specific bar and stops at one too. the porsche or other unit will start and stop at different values.

I have also run across shops and articals explaining how to 'adjust' the unit by 'knocking the plug'. this is a very bad idea. the plug is holding the bimetalic spring at a specific distance from the diaphram, the plug is not to be moved, doing so distrupts the range of the heating element causing problems with the control pressure. if you need to adjust the control pressure it is done via shims on the push valve at the fuel distributor body NOT by 'knocking' the pin holding the heating element.

our WUR is expensive and hard to find, rebuilding one should be done by someone who knows exactly how they work and what the application is, not just a general rebuild. the maps are in the old bosch books, and i do wonder how many shops accutually read them vs tuning by smell/ear.

i hope this helps those in the future when working on there cars or going to a shop. if anyone doubts me by all means pick up the bosch book and read up on the WUR, it's a fascinating and simplistic device.

 

full load enrichment with altitude compensation. the port on top is for the vacumm connection. should be connected after the throttle body to 'see' the vacumm changes and correct the A/F ratio by adjusting the push valve.

 

the vacumm is coming from the plenum, so from that standpoint it would be based on what the engine is doing. idle would have a high vaccum, WOT would have little to none.
to test the WUR you'll need special gauges and meters. to leangthy to describe here. the vacumm from the engine will effect the diaphram under the main spring. if you have low vaccum you may need to replace your lines. but i would check vacumm readings at the EGR port on the throttle body to make sure the engine is tuned correctly.

 

another thing is bosch will defer to the mfg for testing specs as each one is different. this would be in regards to the entire injection system. the bosch manuals are great for understanding how each component works and how to test them, but the specs are in our WSM for each model.