CIS - Differences between WURs
 

I have a 73.5 CIS 911. I've had it for 26 years and over that time, the original WUR was replaced with an 009. I still have the 001 in the garage. My car has been having a cold starting and initial running issue and I'm trying to track it down. In the meantime, I've always wondered if I should get the 001 fixed, or made adjustable.

The curves are not the same, so I've aways thought that perhaps my car is not running as optimal as it should. When I compare the 001 chart to the 009 chart:
001: 1.4-1.7 bar @ 10* to 2.5-2.8 bar @ 35* (range of about 1 bar)
009: 0.5-0.8 bar @ 10* to 2.0-2.4 bar @ 35* (range of about 1.5 bar)

Doesn't this mean that I'm running too rich or too lean at one end or another? FWIW, I just measured mine and I'm getting .5 bar (cold) to 2.9 bar (fully warmed up). So I'm even higher than I should be, meaning I'm richer when cold and leaner when warmed - I think. Does this negatively impact the 73.5?


FWIW, after sitting for 12 hours overnight, my car does not like starting in the morning. It has to spin on the starter for too long, and it runs rough for 3 minutes or so. But, interestingly, 12 hours later when I'm leaving work, after it sat for the same amount of time, but in a warmer garage, it starts fine and runs fine immediately.

The WUR's are matched to the fuel distributor and air sensor assembly. Swapping any one of those three components from what is intended can create poor running conditions. I think you're correct in your assessment above. I think the 009 references manifold vacuum (which I didn't think was the case with the 001) and so you've got some added complication there.

There are a couple of posters here on the board that do a great job with WUR rebuild and testing. I had mine done this winter by Tony (user: boyt911sc ) and things work great!

sounds like its too lean when cold. according to the specs above the 009 runs richer on startup than the 001- if its in spec. you need to put some gauges on there and test the fuel pressure. its probably out of spec creating a high control pressure situation when cold. ive never opened up an early WUR but im sure a mod can be done to adjust it. ok i didnt see you did check pressure, 0.5 bar when cold is going to be too rich. it should be 3x that.

Thanks. I did put a gauge on. I am at .5 bar at cold and 2.9 bar when warmed.

So that should be on the rich side at start, right? If anything, richer than a "stock" 73.5 CIS. Wouldn't richer usually make it easier to start? Or could it be too rich?

thats what im thinking, too rich. usually a hard cold start ends up being too lean.
does your car have an additional throttle valve setup thats tied in to the WUR?

Yes. But to tell you the truth, it doesn't seem to be doing anything. I watched the gauge as I pushed the throttle all the way to WOT and back to idle. Nothing changed. As I understand it, it should go rich at full throttle and no throttle.

If I recall, when I had issues with my WUR years ago, and I went through all this before, it might have had the slightest of impact. I know I bought another TPS, but I can't remember if I swapped them. I need to pull out that other one.

Sorry if I'm out to lunch, but does the 009 use a TPS? I can see that the 001 does but I thought that the 009 would just use vacuum?

My 73.5 has a TPS on it. The TPS does not connect to the WUR. When my WUR went bad, the guidance I received then was that 001s were no longer available, new or rebuilt, and that the standard was to put on an 009. I do not recall anything about disabling the TPS. So, no, I do not believe the stock cars with 009s had TPS on them. But, I to my knowledge, 73.5's that have had their 001 replaced would be running with both.

if you need help with it come out to venice and im sure we can straighten it out

I happened to have a long call with Larry at CIS Flowtech.

He asked, and it turns out, that my TPS is disabled. He also said that the air plate is supposed to be adjusted to match the cone where it straightens out, on the FAR side from the distributor. Mine was adjusted on the close side. He said that there is no way to rebuild the original 001s. With the 009 in my car, though he said I'm missing the part that leans and richens it from the vacuum, and that that would make a big difference in the running.

The problem is that he didn't know how to get a vacuum line. He said to check out how the 75 911s do it. He also suggested possibly pulling vacuum of the distributor vacuum line. But I'd be worried that would interfere with the action of the distributor, and probably not be enough vacuum for the WUR. Anyone have thoughts on that one?

Meanwhile, I did find that one of the rubber joints on the bottom of the air box was pretty loose.

But notwithstanding attending to all these, at this point, my car isn't starting at all. Ugh.

I should add that he also said that with the vacuum added, like about 15" of vacuum, I should instead see 1.4-1.7 bar when cold and 3.4-3.8 bar warm.

On mine the WUR is vacuum T'ed on the lower vacuum outlet, as is the distributor. Neither unit should leak vacuum, so they can share it fine.

Yah, the TPS didn't attach to vacuum but it fed back to the WUR control pressure in a manner analogous to the vacuum on later models.

you can change the throttle body to get the vacuum port. even better put a TB from a 3.0 on because it is bigger. i put a 3.0 TB on my 77.

JMO
the curves dont really matter. if you notice, porsche started doing more to lower the cold pressure to make cold starts better and to eliminate the backfiring when cold. look at the vacuum controlled WUR's. they will drop to .8 bar with the thermo time valve (TTV).
(the chart shows above 1bar at its coldest but that is with vacuum. without vac the pressure drops about .8bar)
i would rather have a low cold pressure any day.

Correct information........
 

Jay,

Larry has given you the correct information (partial). If you have a good working WUR-009 that's the way to go and get rid of the TPS. I am presently away from home and in Sydney, Australia right now. I could test your WUR-009 for free if you could wait till I get back home. The first thing you need to do is test and calibrate your WUR-009. PM me if you need some assistance.

Tony

Thanks for all the thoughts and suggestions. I have some comments back:

(1) This goes back to my physics classes, and I don't remember. The hose size for the distributor vacuum is smaller than the one for the WUR. If I was to T it, and have to step up the size for the WUR, that creates greater volume, and from a smaller port. Does vacuum still stay even across, like pressure? Or is the vacuum some how robbed or limited because of the smaller size of the port or because it is now serving two devices?

(2) I always thought that adding a larger throttle body was not necessarily a good thing for these CIS cars. I've read many times over the years that it's a big no-no to swap parts - and that this WUR swap is only out of necessity. If this is ok too, anyone got a '75 TB for sale?

(3) If someone takes an 009 and makes it adjustable, and adjusts to top end and bottom end to match the 001 curve, is there any difference between them? And if not, why not just run with a TPS and not the vacuum?

Thanks!

Jay,

I have a 74' 911S, that originally came with the 001. As others have said is not rebuildable, but it has some degree of adjustability, both for warm and cold pressures.
Due to old age, mine started getting out of spec and outside the limits of adjustability.

As I like to try "new" things and I'm handy with electronics, I decided to replace it with a digital controlled WUR. Not everyone's cup of tea, but it can be programmed for any range of pressures.

http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/820323-digital-wur-plus-frankencis-13.html#post8388089

Since then, cold and warm starts (and restarts) are a non issue.

I've heard about something like that. Is it able to become variable based on idle/WOT or on vacuum too?

Yes, it can support that. You'll need an additional sensor, either for vacuum or Throttle position, of course.
I just left my TPR plugged in as normal, although when I measured, it wasn't doing much.
However, the TPR main effect is to lean the car in the midrange (for emissions and mileage, I suppose), so it's not a big "deal"...

1. you are over thinking it. it does not matter. its still going to pull vacuum to operate both.

2. the bigger TB may give you more in the upper RPM's or at WOT. it wont matter for normal driving. my 77 2.7 ran fine with it. i could not really compare before and after because i had some other issues that limited my power before i swapped.
i know in some rule books for SCCA it talks about larger TB's putting cars in a different class or they are not allowed if that tells you anything.
all the TB is doing is controlling the amount of air coming in. it is not like a carburetor that is using vacuum to pull fuel from a bowl. also at WOT it is a restrication compared to a larger opening.

3. this is my take on the WUR warm up curve.
dont worry about it. set it for the WCP and just check the CCP for the WUR.
if you start trying to either limit how much change there is from cold to warm or expand how much change there is, it may mess up things for the WUR. IE, if the pressure goes from 1.5bar to 3.6bar and you try to make it go from .8bar to 3.6 bar, the WUR may not be capable of doing that. so just set WCP for the CIS and the CCP for the WUR spec. (actually for the difference between the 2). if CCP to WCP is 2.5bar, maintain that. that is what i would shoot for if i had to use a non original WUR.

i dont remember how the TPS works for the older cars. the vacuum may be more simple, plus with the TTV you could drop the CCP even more. that could be good if you live up north.

not trying to talk you into anything, just giving you ideas for what you can do or how to do it,.

Thanks for this further information.

I don't know if you saw the other thread I started looking for how the 009 WUR vacuum is hooked up. Some guys posted some great pictures of the T that goes into the bottom of the Decel Valve, sending the hose over to the WUR.

Larry at CIS Flowtech seemed to think that I'd see marked improvement by adding it. So now that I know what the part is, I tried to find it in the PET, but couldn't find it. So I've emailed my local Porsche dealer parts guy to see if he can get it for me. I'm game to give it a shot.

FWIW, when my car wouldn't start after doing these tests, I went through the system looking for significant vacuum leaks. I looked for vacuum leaks a year or so ago, and sprayed around various joints to see if it would change the rpm, and found nothing. This time, I actually noticed one of the intake rubber joints was wet! Then I found that the hose clamp was totally loose. I tightened it up (which was no easy task).

At the same time, Larry had mentioned to always double check the air sensor plate, and that the top of the sensor plate lines up with the edge where the funnel goes from a cone to straight down. He said that it should line up at the end furthest from the fuel distributor. I actually found that mine was lined up at the side closest to the fuel distributor. So, I readjusted it.

I finally got my car to start again. I now think that I just had too much air in the lines after the pressure test. But, more importantly, I have solved the early morning start issue. It snapped right up today. I don't know if it was the hose, probably, or the air sensor plate. But, it is a marked improvement.

Now I am going to try to add the vacuum line to the 009 WUR as Larry insists will be another big improvement.

Thanks for all the help here.

Jay

So I installed the freshly rebuilt 009 WUR in my 73.5 CIS. If I install it without using the vacuum, the car runs smoothly, as it did before. When I hook up the vacuum, and readjust the mixture, it will not run as smoothly - at any mixture position between obviously too lean and obviously too rich. It idles and drives fine. Just not as smoothly - a bit more gruff or uneven. Not drastically so, but obvious.

I have two suspicions: (1) with the 009 hooked up to vacuum, the normal pressure of the fuel stays much higher than without vacuum, and much higher than a stock 73.5. So I'm wondering if there are other parts of the 73.5 system that do not do well with the higher fuel pressure. (2) without the vacuum, the fuel pressure is completely static. With the vacuum, even when the vacuum is mostly constant, perhaps there are enough pulsing fluctuations in the vacuum that it similarly pulses or fluctuates the fuel pressure. Maybe the 73.5 CIS system is sensitive to those fluctuations, and the newer systems that used the 009 were revised to not be sensitive to the fluctuations. Someone suggested that there might be some sort of vacuum device that would go in the line to smooth out the vacuum pulses. But he is not a Porsche guy, and I don't know if there is such a thing.

Anyone have any thoughts on any of the above? Any other suggestions?

I am comfortable that when I hook up the hoses for the vacuum, they are on especially tight with no leaks.

Oh, and I'm pulling the vacuum from a T I've added to the hose that goes to the top of the decel valve.

CIS components.......
 

Jay,

You have done a lot of troubleshooting work but I never saw anything about your fuel pressure readings. Are you using a TTV (thermovalve)? If not, that's something you have to consider if you want your engine to run good like the other 911 CIS engines. WUR-009 needs a vacuum source. I was away traveling when you started this thread and had some what forgotten about it.

So what's problem/s are you having now with WUR-009? It is calibrated like it should be? BTW, you have to totally disconnect or remove the TPS if you are using the vacuum assisted WUR-009. Keep us posted.

Tony

Yes, the pressures before were all correct. All I did was take my 009 and send it to Larry for rebuilding. I put it back in, without retesting the pressures. It works just fine without the vacuum - just fine. So I feel that is a pretty good gauge that everything else is largely in order. It goes south when I hook up the vacuum.

I am not using a TTV. But as I read it, that has an impact only on start up. Otherwise it is dead weight. So that would not impact this. I am not using the TPS. But I'm thinking that if I don't get the vacuum to work, I might run the TPS with the static 009 when not hooked up to vacuum.

The problem is that it is running a bit rough when the vacuum is hooked up. No matter where I adjust the fuel mixture, it stays rough. I've turned the mixture richer and richer, a 1/8 turn at a time, until I get that drop at idle. And then a bit more. Still doesn't smooth it out.

Follow up question.........
 

Jay,

I found an old PM from you while I was away about the WUR-009 not holding vacuum due to some sort of air leak. Have you resolved this problem after the rebuilt done by FlowTech? Secondly, base from you feedback, I suspect your engine is getting unmetered air (?). Keep us posted.

Tony

Tony has experience with vacuum WUR's so maybe he can help with information. From my understanding, the original WUR and TPS lowered control pressure and had a slight rich mixture at idle and full throttle. Midrange was higher control pressure and slightly lean at cruising. If the vacuum WUR keeps the control pressure higher at idle and midrange, this might give the slight rough running you experience. I don't know if the air flow meter cone angles changed with the '75 for the different WUR's. The change in angle of the air flow meter would affect the mixture being delivered. The later '75 model also had a different fuel distributor, as well as injectors, which could affect things.

If you have a good TPS, I would install that and the 009 without the vacuum connection, set the pressures to '73 control pressure specifications, and see if that helps.