Warmup Regulator Strange Issue Solved

[javadog]

One thing to consider is that Porsche used at least 3 different throttle bodies in the SC era. Whadda ya wanna bet that yours doesn't have the correct nipple for running an 033 WUR, since they took care of acceleration enrichment in a new way?

JR

[boyt911sc]

Originally Posted by T77911S

the parts in your pic from left to right are the AAR, decel valve and AAV.

are you sure your CIS is an 83?
the chart i have for an 81 shows it had a vacuum operated WUR. (like the 033).

Ty,

Where did you find this information? The '81-'83 SC's USA cars use WUR-090 which is non-vacuum assisted. While Euro/RoW '81-'83 SC's have the WUR-089 which is vacuum assisted like those of -033, -045,-069, and -089. Keep us posted.

Tony

[L8apex32]

The discussion on the various WURs and vacuum lines and all the rest is quite interesting. I have an 089 on my Euro. The main point I took away from my project analyzing a similar situation is that the vacuum lines only assist with idle and part throttle emissions by raising control pressure. Like you concluded, with them disconnected, the WUR operates as if WOT conditions exist and they don't do anything at WOT. They are definitely not the problem.

Similarly, the heater in the WUR heats it up to a point (a certain minimum control pressure) and then can do no more. I think you realize that you should do your testing (at this point) with the WUR fully warm. Once you have a good "warm control pressure", the heater and pretty much the entire WUR is good.

If I read correctly, your lean condition at WOT and high rpm is so bad that you get popping. This is a severely lean condition IMO. There would have to be a significant air leak or a significant fuel flow problem to cause this symptom. I think that makes troubleshooting easier since we are looking for a big problem, versus a A/F ratio off by a few percent or less.

What can cause big A/F issues at WOT? Some sort of major air leak could. No air leak affecting only WOT comes to mind though.

That leaves fuel flow. If the control pressure rises for some reason, or if the FD is stuck or if some obstruction is preventing fuel flow... fuel delivery would be too low.

One quick test you can do is the fuel flow test. The Bosch troubleshooting guide describes it. I think you can just disconnect the fuel line going to the WUR, put it in catch container - then run the fuel pump for a number of seconds. Its a simple volume over time measurement. Perhaps you total fuel flow is too low for your pump's spec. Your pump is the right one for your car, right?

There is also the injector flow test. Injectors from '74 to '83 are the same (per the PP catalog) but if you had injector that wouldn't flow enough...

To me, something pretty big is wrong, based on the symptoms.

I realize you are getting very good help from others. I hope these thoughts don't lead you astray.

[Walt Fricke]

Well, I fired up the engine. Started right up. CP at 2.3 at 76C. Rose to 3.0 at 47C and stayed there as temps rose higher.

I put a vacuum on the vacuum nipple on top of the 033 WUR, and voila, at 10KPa (1.5 psi, 3"Hg) it rose to 3.6 bar.

That suggests I don't need the available vacuum system (which, of course, the rest of the fuel system is not set up for) for WOT, doesn't it? Because all it will do is increase CP? That's what I was theorizing the diaphragm down in the middle of the WUR would do.

If I hooked the vacuum up to the smaller pipe sticking out the end of the WUR on the bottom, I wonder if CP would go the other way. But I didn't have handy some tubes and adapters to fit it to my vacuum device, and maybe things don't go the other way if the diaphragm's rest position is as far down as it can go. It feels like that with the top part off - press down on the center seat, and it doesn't budge.

[javadog]

Food for thought... There is less vacuum at WOT than at idle...

JR

[L8apex32]

I notice I said "minimum" control pressure as the WUR warms up, but I meant maximum. The CP starts low (rich) and warms up to a less rich/normal condition, which is a maximum CP.

Agree - you don't need the vacuum system (because all it does is raise CP) when you are looking into issues like this.

[javadog]

Originally Posted by L8apex32

Agree - you don't need the vacuum system (because all it does is raise CP) when you are looking into issues like this.

If you consider that the vacuum causes the CP to go higher, you can also deduce that the CP will go lower when vacuum is reduced.

That might be useful...

JR