I finally got around to putting gauges on my 76. Using the above method and I swear upon my dogs grave.. exactly 25psi at 55F.

I cant believe it.

try retarding the timing a few degrees. that will make it richer in the upper RPM's

Accept.. mine is a vacuum type CPR.. so I am not sure what it should be with no vacuum.. looks like the manual says 520 - 549 mbar vacuum should be 1.2-1.7 bar roughly...

I dont have a vacuum pump thats accurate so not sure how I can check mine.

JP, you might stick to WUR for the CPR, even took me fue to figure what you meant. its main function is for cold to warm running, unless you have a vacuum controlled one, otherwise, the CP stays the same once warm, but this is not the answer to your Q.
i see about a 1 bar change on my vacuum WUR.
just us the vacuum from the engine if you need to. i got my vac pump advance, very nice to have around.
in case you do not know, or for others, the vacuum is for cold starts to make it even more rich, then the thermo time valve opens (TTV) and the CP is increased about 1 bar. (this is on the 77 and 78 only) the vacuum is also used for wide open throttle (WOT) enrichment, along with quick blips of the throttle, like the accelerator pump on carbs.

if you need to adjust your WUR to get the pressures correct, it is most likely bad and you are putting a bandaide on the problem.

i was a factory trained porsche mechanic when cis was installed on the 1973.5 911. it was a frustrating time with the new cis system. imagine starting from scratch working on this injection system.
the main point here is in 1974 the factory issued a service bulletin for problematic cold start. (many fires in those days) the repair was to incrementally tap the plug on the control regulator while watching the pressure on a gauge so ( as we know now) to lower the cp. tweaking to the low side in real cold climates is necessary. so caller 911 is not far off here in adjusting the regulator. the factory recommended it in 1974.

Mine is a 76 and it has vacuum on top and bottom.. at WOT it pulls the diaphram one way and at idle the other.

Thanks for the info about 1 bar but that doesnt tell me how it should be set at idle. According to the Porsche manual it needs a certain vacuum applied.. however, it does not say on which side. So... this all comes down to my tuning method.. which I think is spot on especially for a car that has malfunctioning componenents..

I've been searching for finctionality of my CPR (some incorrectly call it a wur) vacuum but have yet to find it.. mines a 033 model by the way and I have found at least one post of the exact same CPR (wur) on his 76... and I think this is a california thing... so some 76's might not have it.. mine is definately a california car.. pretty sure it was bought by arnold schwarzenagger.. just kidding.

I guess this debunks the idea that what I am doing is stupid.:cool:

When I raced with CIS I used to file the pins down for control pressure changes.. Id go to the track with 5 pins depending on ambient temp and humidity.. I was sick I tell ya, sick!

nice info kodi, that may be needed on new cars/ WUR, but if that is needed on a 30 or 40 year old WUR, do you think that is still the fix or should the WUR be replaced? also, was the TTV and vacuum enrichment added in 77 to fix the need for this?
the spring does not "move" or bend in the bad WUR that i have, (the heating element is good and gets hot). some have said you will see it bend and some have said you will not. my speculation is that after 30 years of service, the bi-metal springs are going bad, there for the neeed to re-adjust the WUR.

although i still would adjust one without gauges, just to make sure i was not covering up another problem

jp, one port is for vacuum, one just atmosphere.

not on my car. Both go to the throttle body.. just at the botton of the boot there are two connections right next to eachother.

Have you opened up that two-vacuum-port control pressure regulator? I have a theory that the vacuum ports on these devices do nothing other than scavenge the control pressure regulator of fumes and fuel in the event of a failure of the pressure regulator valve (the large round cylinder with the two fuel lines opposite the famous "plug"). Am I wrong in thinking this?

Brian

Yes, you are incorrect.

let me TRY and explain how it works..

Imagine a diaphram that does NOT have a spring on it to locate it in either direction. So if suction is applied on one side the diaphram moved the pin of the CPR one way and if there is suction or more suction the other way it would move the pin the other way.. effectively lowering and raising the control pressure..

Make sense? I could take some photos but until you play with the thing its hard to see.

OK, so the design and function of the control pressure regulator changed over the years?

My frame of reference is the late SC ('82 and '83) control pressure regulator, which has a spring on the bottom of the tiny plunger and a bimetallic strip of heavy gauge material (pics are in that other thread). Anyway, on it, the single vacuum port does nothing, except scavenge the CPR. I just don't see any possibility of diaphragm-like vacuum action.

Brian

I can't speak to the 82-83.. never had one in my hand. Mine had a seperate piece on the bottom instead of just a cover like the ones I have seen with no vacuum connection at all or just a vent.

I didnt know how it worked until I tried it myself.. the diaphram will move in either direction with negative pressure.

I still dont know why they BOTH go to the throttle body right next to eachother.. the diagrams I have seen show a dotted connection between the two ports.. heck if I know what that means.. I'll try and read my US Porsche manual closer but I really think the US version is lacking in information. The US version I have covers many years.. I wish I had a 76' repair manual. If someone wants to send me a PDF Id be more than happy send my email address ;)

Here is what my manual says for 1976/77. But mine has two vacuum lines running to it not one. This one doesnt say which line to put vacuum on... argh!
and mine is the correct CPR per this document.

http://forums.pelicanparts.com/uploa...1228862853.jpg


Note: Its a control pressure regulator.. not a warm up regulator.. well, if you want to trust a Porsche manual anyway..

The lamda controlled cars don't have that lower vacuum line because the lambda system adjusts the mixture.

calling911,

If your WUR has the lower vac port coming off @ the lowest point of the end of the unit, it should connect to the atmosphere or upper TB port. If the takeoff is within a thick plate just up from the bottom, then the connection goes to manifold or lower TB port.

See this pic:

http://forums.pelicanparts.com/uploads3/WUR981085747240.gif

the 033 has a vacuum port on top, the bottom is to atmosphere.
the vac. on the top port pulls the diaphragm up, when the vac. is removed, the spring pushes it back down against a stop. i assume the port on the bottom is there so it does not create a vacuum inside the WUR that would resist the diaphragms upward movement, kinda like putting your finger on a straw that is is water.

the WUR does not really regulate anything, ( maybe thats not a good phrase, but when compared to a true fuel pressure regulator, they are different. if the pressure going in went up, the pressure going out would also go up.) thats another topic.
when the car goes from cold to warm, it raises the CP as the car/WUR warms up. once the car is warm, the CP stays the same and it is pretty much done (unless it has the vac enrichment). that is why it is called a WARM up regulator. if you took the bi-metal spring out and set the CP and it did not change with temp, then i would give you CPR, but its main function is the WARMING up process. more people spend time trying to adjust the relationship between cold CP and warm CP, just ask paulporsche.
please, lets not throw another term out there that will just confuse people. its tough enough keeping aux air regulator separated from aux air valve and thermo time switch from thermo time valve, which all 4 are 4 different parts of CIS.
gotta go, band practice.

use the top port. connect gauges and connect and disconnect the vacuum and check that the CP changes. final CP should be with the vac connected
ok, this time i am going, no more ...stop..thats it...i mean it...go practice...thay are waiting...argh

thats right. mine without vac was 2.8 bar warm, with vac it was 3.7 bar. dont get caught up in the vac pressure, just use the engine vac. now for the hard part, which port on the throttle body to use. i will help later, band practice, we need it! gotta go