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Input/help please on DesignTek Valvetronic fitting for 996 C4 Cab


New member
4 Mar 2024
Hello all,
I've just taken delivery of the DesignTek vavletronic exhausts, for my 2002 996 C4 Cab. The helpful sales people said it is easy to fit, with useful guides, but sadly I can't work out from the guides sent how to fit to my specific model. A quick call into Design911 and they don't really know either, instead suggesting it is a specialist only job.

That said I have the silencer boxes fitted, new clamps etc. The electrical side seems clear enough, mount the new solenoid in the engine bay somewhere, mount the control box in the cabin somewhere, using a clean earth a finding a live ignition for power source.

It's just the location of the vacuum pipes & solenoid that I'm stuck on. I'm told to hook into the existing vacuum lines, using the t's supplied, but for the life of me I can't work out which are the right lines to hook into, and where I should hook into them.

I've read the various previous related posts but still can't figure it out.

Anyone able to help?
Many thanks!

there's really nothing complicated about the Design-Tek system - all you need is a switched 12V to the air valve solenoid. The system is supplied with a good length of silicone vacuum pipe that resists heat form the exhaust and engine bay.

I wanted to use the OEM Porsche exhaust switch so fitted a 'ratchet relay' so that sucsessive pushes of the porche switch causes the valves to open or close. An additional wire back to the switch from the relay brings the LED 'active' light on when the button is pressed and the valve is open. My car is a convertible and I mounted the relay next to the engine ECU. The solenoid is mounted in the engine compartment, I took a vacuum feed from close to the inlet manifold and the system has always worked fine.

The only 'problem' that I have experienced is that if the car has not been used a a few days then the exhaust is at 'full volume' for a few seconds after start whilst the vaccum system builds enough negative pressure to operative the valves.

I didn't use the remote control system that was supplied with the system - I really didn't want the control the valve with a key-fob and to be honest I don't see why they supply this as part of the kit.

The Design-Tek system is a really good quality unit at a low cost. I would recommend it to anyone.
Thanks. I've watched this video, as aside from the annoying audio (not sure it adds anything) what it doesn't show is the vacuum pipe connections within the engine bay, nor does it show the electrical connections. I saw another which shows a car with regular exhaust and then the DesignTek one fitted, but not HOW it was fitted - that's what I'm struggling with! Many thanks
go back to Design911 on this

does any of this help, even if it's for a 997

then this thread
Thanks again. It helps to show how complex this is, and that i'm not the first to have challenges with getting the right tech support from Design911. I've bought many general parts from them before, but having second thoughts on future purchases now.

Thank you for the extra guides, but still nothing actually looks quite how I'm expecting it to look. I'l attached a few pictures now to see if that helps to define my problem and also point towards a solution.

The instructions start by saying remove the air box (easy enough) but don't say why. I assume it's to allow access to somewhere. Picture below - Pic 1 - is with airbox removed. Does this show anything I need to be aware of but missing through my lack of knowledge?

Next the instructions suggest mounting the solenoid supplied in the kit onto a mount used for the reservoir on left of the engine bay, only the bracket supplied won't fit in the space - shown in pic 2 below.
- So, I will ask Design911 whether the solenoid has to be mounted here, or can be elsewhere. I'll report back

The last of the instructions says 'connect the solenoid valve to the intake manifold' and the solution diagram (pic 4) shows 'Solenoid on inlet manifold' at the top. I assume this is shown in my pic 1 but I don't know what I am looking for, which part is the solenoid on inlet manifold? And, assuming it's there, how do I tap off from it? Pic3 shows things closer, and where I think a vac line is, but not sure.

The kit supplied does have a couple of brass t's, I just don't know which line the 't' connects to in the top of the diagram.


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maybe be worth taking it to Porsche Torque in Uxbridge, best specialist in the country
When I did mine I used a vacuum line from the plenum. Cut it and put the T piece in. Taking the air box out gives you room to do this. You can mount the valve anywhere. I put mine down near the air pump (I think that's what it is...). Left hand side of the engine bay at the rear of the car.
When I did mine I used a vacuum line from the plenum. Cut it and put the T piece in. Taking the air box out gives you room to do this. You can mount the valve anywhere. I put mine down near the air pump (I think that's what it is...). Left hand side of the engine bay at the rear of the car.
Many thanks!

Clearly I'm a thickie here as I've no idea what or where the plenum, perhaps this DIY project is a bit out of my league. I'll do some.extra research, and I don't suppose you have a picture of where you out the t junction in?
the plenium
Brilliant, thanks. When I'm back behind the car tomorrow I'll see whether I can translate this to what I can see and therefore where to tap into
maybe this pdf helps


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Please see a couple of pics of where I plumbed mine in. tempImageGsbLI0.jpgtempImagevo6YrR.jpg
That's perfect, thanks corneg. Out of interest, how did you route the electrical connection from the control box (in the cabin) to the solenoid in the (in the engine bay). The instructions suggest cutting a small hole in a rubber between the cabin & engine bay, but as mine is a cab I can't locate the hole referred to - maybe doesn't exist in the cab models. The power cable is quite thick, especially with the push fit connector attached, so the hole would need to be quite wide, did you remove the connector in order to fit it through? Or find another routing method?
Hello - mine is a coupe, I found a hole with a factory grommet already in under the carpet that covers the rear shelf behind the seats. Cut a hole in that and routed the cable through. I didn't need to cut the connector off. I am not sure with yours being a cab. You have a similar space from memory but its filled with hood gubbins. You will need to put the hood into service mode, remove the two retaining cables on each side in order to be able to remove the carpet/cover. Then you might be able to find a route the feed the cable into the engine bay.

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