PD100 has variable intake manifold...

[Pelican18TQA4]

6 - EGR valve
9 - Anti-shudder valve
13 - Lower section of intake manifold (with shift rod)
17 - Vacuum actuator
19 - Intake Manifold Runner Control Valve (N316)

This is the first I'm hearing of this and this explains what the vacuum actuator is for that can be seen on the passenger's side of the engine. I know the one on the driver's side is for the bypass valve for the EGR cooler.

Anyone seen or heard of this before??

[OdinsRageSS]

very odd! id like to learn more

[Mike_04GolfTDI]

I don't think it has a variable intake manifold comparabe to what you'd find in a Honda VTEC engine or something like that. The only thing variable about the TDI manifold is how much EGR it can cram into our poor engine. It's like the TDI is smoking 5 packs a day. Poor thing...

The item referred to as the "change-over" is the throttle valve that helps create some vacuum to suck in more EGR, and also helps when stopping the engine (closes off the air).

Here's an explanation I quickly found on racingtdi.com:

Link: http://www.racingtdi.com/engine.htm

The EGR system reduces emissions by directing a small quantity of exhaust gases back into the intake manifold to dilute the air/fuel mixture efectively. An EGR cooler reduces the exhaust gas temperature by as much as 50º C. This reduces the amount of oxides of nitrogen (NOx). The funcion of the EGR is managed by the ECU via the EGR vacuum regulator solenoid valve. The remove of the EGR valve also removes the Intake manifold change-over valve. This is a flap valve that closes for aproximately 3 seconds when the engine stops, blocking the air to the engine. This reduces the suddenness of the diesel engine shut-down. The valve re-opens when once the engine has stopped. With the EGR removed there is a much lower air restriction. No more manifold clogging! Soot can no longer accumulate inside intake manifold and the EGR Valve. It's interesting to look at the next 2 pictures. Plus the Allard pipe has a much better looks and it should improve the revving and some marginal power gains at high rpms.

[DPM]

Item 9 looks like the "changeover valve" in this application. There's certainly some kind of dual port/ siamesed setup in item 13...

[Mike_04GolfTDI]

Originally Posted by DPM

Item 9 looks like the "changeover valve" in this application. There's certainly some kind of dual port/ siamesed setup in item 13...

Item 9 is the throttle valve I mentioned previously. It can completely block the intake upon shutdown, and is also used to create some vacuum in the intake when more EGR than would otherwise be possible is required.

By no means is there any sort of variable intake system designed to boost performance such as you'd find in a Lexus IS300...

[Pelican18TQA4]

Item 9 (anti-shudder valve) is what closes off the intake when you shut the engine off and also what creates vacuum in the intake manifold to allow more EGR gasses to flow into the intake. Item 13 has its own vacuum actuator (Item 17 in the first pic), seen in the pic below as Item 1 which explicitly states that it's for the variable intake manifold.




Also, here are some quotes from the Bentley manual regarding the intake:

"Engine code BEW:

• The variable intake manifold is switched depending on engine speed and accelerator pedal position."

"Disassembling and assembling variable intake manifold:

• Note: Tighten the variable intake manifold in the described sequence to avoid distortion.

• Remove variable intake manifold.
• Loosen connecting bolts.
• Disconnect upper and lower parts of intake manifold. Separate both parts with light blows of a rubber-headed hammer if necessary.
• Clean contact surface.
• Replace seal.
• Put upper and lower parts of intake manifold together and tighten all connecting bolts hand-tight.
• Tighten all securing bolts in indicated sequence to 10 Nm.
• Install variable intake manifold."

Now, where's all the TDI experts, we need to figure out more about this variable intake manifold as found on the BEW.

[whitedog]

Thanks for the pictures. I have been trying to find it and I finally have. It looks to me like if there is any intake clogging, it will be in a place that is hard to detect by just pulling off a hose, and if it does get clogged, it appears to be fairly easy to clean. Well, relatively easy since things come apart and you can get into more kooks and nannies. Er... nooks and crannies...

[Sooch]

This reminds me of the IMRCs on the Ford Mustang Cobra 4V's. Usually you just take off the throttle plates or get the delete kit, and change a single 1 to a zero in the ECU. We used to have GTGs to clean them out if you wanted to keep them.

They are usually there to promote higher velocity intake air at low revs, for more torque, or switch in the long intake runner at low revs. Not sure why that's needed on a diesel?

[Pelican18TQA4]

All I know is that for those that have an active EGR valve, it can only make intake clogging MORE of a problem!

[DPM]

In this case, I'll bet it's used to alter the speed/ angle of the inlet air's swirl.
While it's a 16v, the later PSA HDI has dual runners; these are configured to promote swirl...

[Pelican18TQA4]

Resurrecting a thread from the dead!

Browsing new posts today, I came across a pic posted by Birdman353 in a PD EGR thread:



You can clearly see here the variable intake manifold and how different it is from the ALH and prior TDI manifolds. There are clearly two intake passages for each intake port. I'm still very curious about this and how/when exactly it's utilized on the PDs??

[PDJetta]

Thank you for the picture. Very interesting! I've been for a while trying to figure out what the heck the vacuum diaphragm down low, near the turbo actuated, and according to the under hood diagram, it is for the "Variable intake runner changeover valve". This evidently is NOT the throttle plate (which is electrically actuated on the PDs). That picture explains it, but why is it there? Maybe for high EGR flow rates (light load operation) the small openings are open and the large ones are closed to create faster air velocities to prevent intake plugging (via the vacuum diaphragm in the picture). Both ports must be open during high boost/load/no EGR conditions. I'd suspect there is a butterfly valve over each of the large intake ports on the end (in the manifold) that bolts to the head, and these butter fly valves (4 of them) are all on a commpn rod, pivoted by the vacuum diaphragm. Just my guess.

For those of us with non-functioning EGR systems on the PDs, I wonder if the intake manifold changeover valve should just be locked in the position to cause the largest air flow all the time (through the large ports). I think this set-up has to be EGR related only (and to combat intake clogging). Is this on the European PDs?

--Nate

[Pelican18TQA4]

I don't know that is has anything to do with the EGR system though. As you can see from the Bentley quotes I posted above pertaining the the variable manifold:

"The variable intake manifold is switched depending on engine speed and accelerator pedal position."

That leads me to believe it's a performance-enhancing feature, though perhaps not as extreme as Honda's VTEC. In my opinion, the narrower intake passages are probably low-end runners (narrower passage speeds up the air) which enhances low-end torque and the larger intake passages allow more air to flow at higher RPM to enhance top-end hp. Or, I could be totally wrong!!

Point is, VW didn't spend the engineering Euros on something that doesn't serve a purpose.

[NathanMSL]

I had no idea all that junk was down there in the intake. It should be pretty interesting to see what happens when I put the PD150 intake on with none of that fancy flapper stuff.

[andreigbs]

you can "hear" the intake manifold flaps being tested if you do a "output test" with VAG-com. it will go through the tests, shut off the car at a point, then do bank 1 of the intake manifold. You'll hear something flipping open/shut. It's probably good to do the test once in a blue moon, to make sure it's not gummed/crudded up. Works just fine on my PD.