1975 Testing Throttle Valve Control Pressure Regulator, and 008 WUR

[strictly]

1975 911S 2.7 ROW

On my 75 (recent purchase), i have an early style WUR (#008) no vac, just an in and out. My CONTROL pressures are out of whack (both cold and warm control). I'm not worried about that, i'm confident (now) of adjusting it for hot and cold, although i do need a new heater for it.

I have two questions

A) Throttle control regulator testing

The manual says, at idle, the warm control pressure is approx, 3 bar, then at part throttle, approx 3.8 bar, then at full throttle 3 bar again. Most of the warm control pressures i see are around 3 bar (i.e for other WURS).

I could not get the throttle control regulator to go from 3 bar to 3.8 and then back to 3 bar at full (or even back to 3 bar) when returned to "idle". (Engine off, FP running). So i can assume my throttle control regulator is probally tits. It would stick at 3.8 and not go back, i tried cleaning it, adjusting it on the screws etc.

Has anyone tested this, and had their pressure gauge swing up from 3 to 3.8 and then back to 3?

B) Correct Warm Control Pressure for a 008 SET UP

My main question is what is the correct warm pressure for a 008 WUR - is it 3 bar or
3.8?

The porsche manual it states if you cannot get the pressure at either idle or full throttle, then the throttle control regulator is faulty. It then said that if you cannot get the 3.8 pressure at partial throttle, then its the WUR not the throttle regulator.

I took the throttle valve apart, and could see that at idle and full the regulator was open for flow (either end of cam) but at partial it was closed, which means it is the WUR which is controlling the pressure at this point, and therefore shuld i set the WUR up warm for 3.8 bar?

I know its confusing. I will post the procedures from the workshop manual, and let everyone else read it to see if im reading it right

[boyt911sc]

Strictly,

I was doing some testing with a '75 throttle switch and WUR-008 on my CIS bench tester last week but I am presently away from home. Actually, I have two (2) sets that I was tinkering. If you could post some pictures (WUR and TS) would be beneficial for discussion. Thanks.

Tony

[strictly]

Hi Tony,

Ok will do. I'm going to post the procedures from the manual in a minute. I'll be intrested in your testing, did you get the pressure to swing when controlling the throttle regulator from approx 3.0 to 3.8 to 3.0 (i.e back to the start?). I understand your away. Enjoy the trip!

My pressure just stuck at 3.8 bar. I could get it back to the 3 bar, by disconnecting the tester and then reconnecting (i.e bleeding) which was very confusing. Presumably the TCR is not working

I'll post the procedure, im absolutely sure you have them, but benefit for discussion. I'll make some comments as to what i think and see if every one reads them the same way.

Luke

[strictly]

Ok here is the procedure for testing the thottle control regulator. I'll make some comments in the next post :

[strictly]

Ok so i need help with the second picture.

it says if you cannot achieve the pressure at idle or full, then replace the throttle control regulator. Okay in my case, i could not achieve it at full throttle, so i presume its tits and i need a new one

BUT

my WUR is also tits (the heater dosent work). I havent tried testing it without the TCR also connected to it, i'll try that just to see what the current warm control pressure is (ive taken heater out - hence warm, no action on the plunger inside the WUR).

My understanding is the flow from the the FD is flowing thorough the TCR and the WUR at the same time, hence the 3 bar, when you turn TCR to partial throttle, it closes the plunger on the TCR (its open at idle and full throttle), and there is no flow at partial. Therefore only the WUR is regulating flow at this stage, which in my case is 3.8 (the TCR must allow the 0.8 bar to flow through when its open).

Remeber im trying to figure out what to set the warm control pressure of the WUR to. In the second picture, it clearly states if you cannot achieve the 3.8 bar pressure (i'll post the pressures too in a minute) then its the WUR at fault. As i can achieve this my WUR is fine (okay its not), but i think i can deduce that if i were to have the WUR only then i should set it to 3.8 bar (which it is, so i can actually just focus on the cold control adjustment) for warm, and when connected in series with the throttle control regulator, it would then get to the 3 bar warm we all know and love. I think that makes sense!

In my example above i'm at 3.8 which is the limit of spec, so of course i'll adjust it closer, im just trying to be certain that is the correct deduction.

[strictly]

[strictly]

[boyt911sc]

Strictly,

Have you considered upgrading or eliminating the TPR (throttle pressure regulator) to improve your CIS performance? Remove or disable the TPR and replace your WUR-008 with a more versatile WUR. Unless you are into "concourse" restoration, eliminating TPR and WUR-008 for a better set up would be a better course of action. I have converted and assisted several members of this forum with good results.

Tony

[strictly]

Hi Tony,

I have been thinking about that. Presumably, i need to change to a VAC WUR and reroute the VAC lines. Do i also need to change the throttle body?

Luke

[boyt911sc]

Originally Posted by strictly

Hi Tony,

I have been thinking about that. Presumably, i need to change to a VAC WUR and reroute the VAC lines. Do i also need to change the throttle body?

Luke

Luke,

You could retain the throttle body. Disable the TPR (throttle pressure regulator) and replace the WUR-008 with -009 or -033 (vacuum assisted) plus decel valve and thermotime switch. These combo is more versatile and easy to manage than your present set up. But do not forget your FD. Check it too.

Tony

[strictly]

Hi Tony,

Thank you that is intesting. I'm juggling this and problems on my 78 (the dripping injector post). Ive decided to focus on the 78 for the moment, and come back to this one. Once i get that one running properly, then come back to this problem. I can always try swapping some of the parts over to see how the 75 runs with (i.e the parts you mentioned above). Thanks for your help =) Ive updated the info on the 045 WUR charts on the other topic.

Luke