2.7 CIS WUR and Dizzy vacuum lines routing.

[911S77]

Hello,
I’ve got a problem with connecting the vacuum lines. Yes, I’ve checked the diagrams on CIS site at rennlist, and searched the bbs, but haven’t found a simple answer. I’m really confused. Car is from 1977.

According to the diagrams that I found:
I’ve tried connecting dizzy to the lower fitting on the throttle body, than the line from the side of the WUR to the upper fitting on TB, and the top line from the WUR via the thermo-switch and a T fitting to the deceleration valve, an then to the back of TB.
But that set up didn't work well. The car hesitate to accelerate :/

So, there are a questions to all 2.7 owners with working CIS system:

1. Where should I connect the distributor vacuum line?
2. Where should I connect top and side vacuum line coming from the WUR?
(the top one is routed via the thermo-switch, but I’m not sure what’s next)
3. The deceleration valve should be connected to the back of the throttle body alone, is that ok?

Also I’ve read that at some point the factory switched the top and side connections on WUR.
How about mine (no 0438140033)?

Please help me!
Best Regards
/Jack

[Grady Clay]

Jack,

Here is a diagram for a USA ’77 that one of my mechanics (Chris Peck)
made contemporaneous with these engines. This is NOT a Factory
diagram but we used it many times after it was made so I suspect
it only may be correct. EDIT Note my next post.

I too searched. This is not well documented.



Best,
Grady

[Grady Clay]

Jack,

Here is a Factory engine electric diagram for a USA ’77 regarding
the speed switch (rev limiter). Almost as an aside note the
vacuum connection from the distributor to the Thermo Valve
and then to the throttle body below the butterfly.

The hand drawn diagram shows that hose going to the rubber
boot instead of below the butterfly. I don’t think that is correct.
"
"
© Dr. ing. h.c. F. Porsche A.G.

Can you post images of all the potential connections?

Best,
Grady

[911S77]

There are two connections in the front of throttle body.

According to the second diagram you've posted Distributor should be connected to the lower one (I suppose that's under the tb's butterfly) and the top connection from WUR via the thermo-switch to the same line (with a T fitting). And the line from the side of WUR to the upper one - but that's conflicting with the hand drawed diagram.

Does it make any sense to you?

I suppose I'll try both ways of connecting it.

But maybe someone could check it on their car?

Thanks!
/Jack

[Gunter]

Jack:
That looks alright to me.
Those 2 lines go to the distributor and top of the WUR as described.
If the WUR has a vacuum chamber on the bottom, there is a nipple with a line going to the top of the adjustable Deceleration Valve with a T.
A short piece going into the Dec. Valve and the other side of the line connects to the back of the TB.
There is also the Thermo-time valve between WUR and Dec. Valve vacuum lines.

[kach22i]

This thread is a great source of information, I've bookmarked it.

[Gunter]

A real rats-nest of lines:
#7 is the Decel. Valve. Does anybody remember how the adjustment works?
Is cw more vacuum?
Which way for slower deceleration?

[HenrikL]

Was there ever any conclusion on this thread?

The only factory documentation on the vacuum line routing for 1977 I have found is in the parts manual:



There seems to be two vacuum "paths": The red path goes from throttle body (24), to a T-piece, where one hose (25) goes to the distributor and the other (26) to the termotime valve and then (23) to the top of the WUR.

The blue path goes from the throttle body to the bottom of the WUR, hose no 28.

My problem is that I do not know how the red or the blue path is connected to the throttle body (green circle). It is really difficult (or impossible) to see in the diagram which port on the throttle body is connected to which hose.

[T77911S]

i went thu this same process when i got my car, the routing of the vacuum lines was not a known issue.

the 77 uses vacuum retard for the dist. so find a port that enters the throttle just below the throttle plate. this is where having a vacuum hand pump comes in handy, you can check for vac at idle and verify it is gone just barely off idle, or you could do the same with a timing light, which you need to verify the vacuum retard is not stuck and that the advance is working properly anyway.

the WUR has vacuum all the time, until you go WOT, so this port should be below the timing port. also, check the the TTS. if it is bad, you will not get the enrichment you need. even though it is called WOT enrichment, it also helps in throttle response, kinda like the accelerator pump on carbs, by adding a little extra fuel when you give it more gas.
i tried to run mine without the vacuum, normal diriving was not good. steady speed was OK but when i tried to speed up it did not run well.

so you should have vacuum on both at idle, but above idle, you should only have vacuum on the WUR.


that first 2 drawings show the dizzy and the WUR going to the TTV, i dont think that is right. the WUR and the decel valve are tied in with the TTV, not the dist, the dist has a vacuum retard so it goes to a port that loses vacumm as soon as you come off idle, you dont want that for the WUR.

the third drawing looks more correct in that the DV and WUR are connected to the TTV and not the dist, except what got me for the longest time with this drawing is the vacuum from the TTS is tied to the BOTTOM of the WUR, which is only correct for the 78 and 79, the 77 had vacuum on TOP of the WUR.

speed switch in the 77? i dont know if mine has one. i have one of the mechanical limiters on the rotor along with the one on my MSD.

my car runs great with the connections as i have said. i can drive it down to 1500rpm in 4th or 5th and accelerate smoothly. when the timing or the vacuum lines were not right, i could not do that without the car bucking.

[HenrikL]

Originally Posted by T77911S

i went thu this same process when i got my car, the routing of the vacuum lines was not a known issue.

Is it possible that you could take a look at your car and verify which vacuum path is connected to the UPPER throttle housing port- the distributor/termotime/top-of-WUR or the bottom-of-WUR?

Originally Posted by T77911S

the 77 uses vacuum retard for the dist. so find a port that enters the throttle just below the throttle plate. this is where having a vacuum hand pump comes in handy, you can check for vac at idle and verify it is gone just barely off idle, or you could do the same with a timing light, which you need to verify the vacuum retard is not stuck and that the advance is working properly anyway.

I have no vacuum at idle at the distributor and that's why I started to suspect that mine is connected wrong. On my car the UPPER port is connected to the distributor.

Originally Posted by T77911S

the WUR has vacuum all the time, until you go WOT, so this port should be below the timing port. also, check the the TTS. if it is bad, you will not get the enrichment you need. even though it is called WOT enrichment, it also helps in throttle response, kinda like the accelerator pump on carbs, by adding a little extra fuel when you give it more gas.
i tried to run mine without the vacuum, normal diriving was not good. steady speed was OK but when i tried to speed up it did not run well.

so you should have vacuum on both at idle, but above idle, you should only have vacuum on the WUR.


that first 2 drawings show the dizzy and the WUR going to the TTS, i dont think that is right. the WUR and the decel valve are tied in with the TTS, not the dist, the dist has a vacuum retard so it goes to a port that loses vacumm as soon as you come off idle, you dont want that for the WUR.

the third drawing looks more correct in that the DV and WUR are connected to the TTS and not the dist, except what got me for the longest time with this drawing is the vacuum from the TTS is tied to the BOTTOM of the WUR, which is only correct for the 78 and 79, the 77 had vacuum on TOP of the WUR.

speed switch in the 77? i dont know if mine has one. i have one of the mechanical limiters on the rotor along with the one on my MSD.

my car runs great with the connections as i have said. i can drive it down to 1500rpm in 4th or 5th and accelerate smoothly. when the timing or the vacuum lines were not right, i could not do that without the car bucking.

I think that when the throttle is closed, then there is a lot of vacuum on the port below the throttle and not much at the port above the throttle.

When the throttle is open, then there is the same vacuum at both the upper and the lower vacuum ports.

[T77911S]

i meant to dig out my old 2.7 TB yesterday. i put a 3.0 TB on my 2.7.

if i remember correctly, i was using the 2 ports on the back, the one just a tad below the plate is to the dist, the WUR should use a port below that, basically manifold vacuum.

hereis a pic i have, C is to the WUR, i think the one just below A is to the dist.

[HenrikL]

Thanks! The picture looks more like the 1978 setup with a T-piece for the decel valve.

I'm using the ports on the other side of the throttle body and I will try swapping the connections and see if I get better results.

[RoninLB]

on my stock 1977 when I ran with CIS and 8.5:1 compression

I disconnected the dizzy vacuum retard line and plugged it. Then I set total timing at 35 BTDC and let initial timing fall where it may. It ran better.

My deceleration valve was hanging up so I disconnected the hose and plugged it. The faster idle drop at lower rpms was no big deal to drive with.

My car never had a rev limiter that I know of except for the dizzy rotor.


once in a great while I was happy I had a pop-up release valve installed correctly on the CIS intake

[T77911S]

my decel valve was hanging too. mine got removed when i put the 3.0 TB on. my DV had a lot of oil in it, from blow by, my rings are shot. so i thought that was causing it to hang.

i forgot to look at my car again. i got busy putting control arms on my BMW last night. WOW, what a differnance!

[T77911S]

here is the back of a 2.7 Tb. my WUR goes to the bottom one.



here is the bottom front of the TB. this should be for the dist retard. as you can see, as soon as you move the throttle plate, the plate passes by the hole, removing vacuum from the retard.



here is the front top, you can see the little notch cut out of the plate, this helps to make the retard come out even quicker. the other hole higher up could be connected to the vent on the WUR.



here is the bottom rear of the TB. the large hole on the left is for the decel, the one next to it is for the idle adjustment and the small on is manifold vac for the WUR.



here is the top, you can see the notch better here. the large hole on the left is for the idle screw, the right is the decel that bypasses throttle plate

[HenrikL]

Thanks for the info! Just two questions before I start work on my car.

Originally Posted by T77911S

here is the back of a 2.7 Tb. my WUR goes to the bottom one.

Do I understannd correct that the BOTTOM throttle body connection goes to the TOP connection on the WUR? Is the thermal valve on this path?

Originally Posted by T77911S

here is the front top, you can see the little notch cut out of the plate, this helps to make the retard come out even quicker. the other hole higher up could be connected to the vent on the WUR.

The vent on the WUR - is that the BOTTOM WUR connector?

[Cipotifoso]

In all the searches I've done, I haven't found anything definitive as to the routing of the vacuum hoses on a late '75; specifically to the WUR. Other years have the WUR tee'd into the hose coming off the top of the decel valve. Mine is tee'd into the hose on the bottom. Is this correct for this year? Anyone have a '75 with the same layout?

[NeedSpace]

I am trying to reconstruct my 1976 2.7 CIS. Based on my research, I think your T valve is supposed to be on top of the vacuum limiter, not the bottom.

Here is my link. I haven't tried it yet but this appears to be a more common.

1976 911S – from garage find to on the road

[fanaudical]

Old thread: Cipotifoso - My early '75 WUR vac routing is done just as your picture shows.

[artwangler]

Theoretically, the "TEE" can come of the top or the bottom of the decel valve. Because each is connected to a port below the butterfly valve. EI: each receives "manifold vacuum"
If you "TEE" off of the bottom of the decel valve, your vacuum will drop slightly sooner. Therefore, your fuel/air mixture will only be made lean for a shorter time. Since you have just taken your foot off the throttle, no need for a rich mix. If you "TEE" off the top of the decel valve, it will take a split second longer for the vacuum to drop. (I think....)