996 Turbo Topgear Valved exhausts - Vacuum issue

lethallegend72 · 18 Aug 2018

I eventually got my Topgear exhaust from the group buy installed last week.

The Exhaust switching operation only works occasionally...

So far, I have tested the Topgear electronics and solenoid valve and everything appears to be working correctly.

When I bypass the valve and plug the vacuum line directly into the exhausts there still isn't enough vacuum to operate the valves.

I have plugged my vacuum gauge into the vacuum line used by my installer and the Vacuum reading is very low compared to when the system intermittently works. (I will try to upload photos)

So, there are a couple of possibilities.. probably more..

1) The Vacuum point used by my installer is not correct and there isn't enough vacuum unless under certain conditions.. (e.g. valves activated.)

-- Does anyone else have a turbo and can show me where the Vacuum line is connected to?

2) I have a vacuum leak - (my vacuum tester holds a steady vacuum with no loss when testing at the point used for the exhaust tap)

---My car appears to drive ok, steady idle, no engine warning light.
-- Maybe a smoke test would be more appropriate...

Any other ideas??

Phil 997 · 18 Aug 2018

Call topgear at Bridport speak to Steve hes the head tech there get his advise , they will have seen and resolved most issues and will be able to talk you through the connections etc or may even be able to suggest you take it to one of their filttng shops close to you. If there are any powerflow or long life exhaust centres near you that will be one of their franchises they would be able to advise. :thumb: keep us posted on progress :thumb: :thumb:

lethallegend72 · 21 Aug 2018

I Spoke to Luke at Topgear today and from our discussion is appears that the vacuum location used is the same as they use. Therefore it is possibly an issue with my car???

This is the Vacuum point used (see pic). It is on the right hand side of the engine, near the secondary air pump. The feed is taken from the bottom of the change over valve.

When the exhaust isn't working, this is the value seen on my vacuum gauge. (the exhaust valves move but not quite enough)

When it is working, it is nearly in the green zone on the gauge...

The valves work intermittently, generally when at idle once the engine has been run for a few minutes, not straight away..

very strange...

MisterCorn · 21 Aug 2018

Usually with vacuum operated solenoid there will be a vacuum take-off which goes through a one way valve to a vacuum reservoir. The connection to the reservoir will be t'd off to the solenoid which provides the vacuum. Do you have all of these components?

MC

deMort · 21 Aug 2018

I dont really do mods but a couple of points i was thinking of ..

The vacum supply needs to come from the vacum resevoir .. image below.

The grey Porsche valves are pretty flakey .. ive changed many over the years so is it the vacum supply or the valve not allowing enough vacum to pass through ... they can leak.

lethallegend72 · 21 Aug 2018

I am not sure where the vacuum reservoir is.
It looks like my feed is taken from number 17 in the diagram below.

lethallegend72 · 21 Aug 2018

deMort said:
I dont really do mods but a couple of points i was thinking of ..

The vacum supply needs to come from the vacum resevoir .. image below.

The grey Porsche valves are pretty flakey .. ive changed many over the years so is it the vacum supply or the valve not allowing enough vacum to pass through ... they can leak.

Is this picture for the Turbo?

MisterCorn · 22 Aug 2018

In that diagram it looks like the vacuum comes from the throttle body at the top, 21 is the non-return valve. Any line straight after that should be fine. If taken from 27 it needs to come from the non-switched side which is at the bottom in the diagram. If you take it from the other side of 17 it will only see vacuum when 17 is operating, I'm not sure what 17 is controlling.

MC

lethallegend72 · 22 Aug 2018

Thanks for all of your input so far..

I had a bit of time today to take another look at the vacuum pipes..

I found that the pipe which goes into the T-Piece (33 on diagram) had been pulled off.. It looks like this could easily be knocked when fitting the air filter..
I reconnected it and cable tied it.. the problem was still there..

I dug out a cheap Chinese endoscope my son had bought me for my birthday.. Its first real use and followed the piping to the pipe connection 30 (looks like a cross on the diagram) and saw this!!!

It looks like a split in one of the corners..... I will need to order one of these.. I contacted Porsche Reading and they have to order the part from Germany..

It is a bit strange that it occasionally works and holds a vacuum when I attached my vacuum tool??

I will need to strip some stuff out to get to it..
It is under all of this..

deMort · 22 Aug 2018

17 is the electric valve for the secondary air pump .

The connection from the diagram and your picture seem to be correct but im wondering if that grey valve has failed .. try disconnecting the vacum pipe either side of that valve , blank it and see if the vacum increases on your gauge .

My image was of a non turbo .

lethallegend72 · 22 Aug 2018

deMort said:
17 is the electric valve for the secondary air pump .

The connection from the diagram and your picture seem to be correct but im wondering if that grey valve has failed .. try disconnecting the vacum pipe either side of that valve , blank it and see if the vacum increases on your gauge .

My image was of a non turbo .

I did that as well, no change in Vacuum, just the low value previously shown. I plugged my gauge directly into pipe 18 going into the valve 17 and blanked the other side off.

deMort · 22 Aug 2018

We posted at the same time i think !

You have proved the valve is ok and as the 2 vacum lines connect at 45 which i think is another valve then once thats activated you would loose vacum from the split hose you have found .

Any vacumn leak from 30 onwards would lower the vacumn you need to operate the valve .

Either way fix that and see what happens.

lethallegend72 · 22 Aug 2018

deMort said:
We posted at the same time i think !

You have proved the valve is ok and as the 2 vacum lines connect at 45 which i think is another valve then once thats activated you would loose vacum from the split hose you have found .

Any vacumn leak from 30 onwards would lower the vacumn you need to operate the valve .

Either way fix that and see what happens.

I think that should be my next step. . I will order the part tomorrow from Porsche, its £10.02 + VAT.. (Part number 92857372905)

I will feedback once It's been fitted..

TopGear Exhausts · 28 Aug 2018

Dotting for interest.

lethallegend72 · 30 Aug 2018

Just a quick feedback. I ordered the part from Porsche but it hasnt arrived yet.

I stripped down the car to access the connection and it is not a crack/hole in the part.. It is a raised reinforcement..

I cable tied a number of hoses and clips for good measure and when I put it back together, connected the battery and started it up the VACUUM was working as expected....

Last night when I went to the car, it wasn't working... :frustrated:

Time to start again..

Here is the status..

1) Low vacuum when the engine is running (at home, after a cold start) - see photo of gauge above.
2) The Vacuum connection for the exhaust (& my Gauge) is off the bottom of number 17 on the above diagram (the correct side)
3) With the number 17 valve taken out of the loop, the error is still present.
4) Using a vacuum pump, I can generate the correct pressure in the system and it holds (engine off, ignition on or ignition off)
5) With the engine running, I cannot introduce a vacuum with my pump. the value on the gauge stays the same no matter how much I try to induce a vacuum in the system.

This could suggest that something is opening when the engine is running and releasing the vacuum. (but intermittently changes state when the engine is warm).

There isn't really much on the system apart from the solenoid number 45 and the the check valves - 21..

I still have a few tests to do.. smoke test is still on the cards.. I just need to make a tester..

Would a vacuum leak / problem cause an engine warning light to come on or DTCs/error codes?

Regarding the exhaust system.. I am in the process of relocating the Remote control box from the engine bay to inside the car.. I have found an entry point from the rear shelf into the engine bay and fed the solenoid cable through.
The next job is to locate an ignition feed for the controller box and get that working.. There is a large wiring loom on the parcel shelf, hopefully there will be something there I can use.

996 Turbo Topgear Valved exhausts - Vacuum issue

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