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21 Posts
Discussion Starter #1
I have a US market, 2009 MY, 3.0 TDI with the diesel-scandal fix on it. There's been some chat lately about intercoolers so I thought I'd have a look at mine to see what the possibilities might be. I was poking around under the hood trying to track where all of the intercooler piping runs when I found what seemed like a path that didn't go through either intercooler.

I have to say I was in a bit of dis-belief. I've never heard of this before. I can't fathom a reason why some air gets intercooled and some doesn't.

So I spent a bit of time internetting around to see what's what.

I expected the paths to be a typical VAG twin-intercooler setup with the charged air splitting in half, with one path to the left SMIC, one path to the right SMIC. They join back up on the cold sides of the intercoolers and then head up to the intake.

Something like this parts fiche:


What I found instead, both in real life, and at was this parts fiche:
INTERCOOLER.. Volkswagen Touareg

The flow paths aren't shown here but based in part on the first diagram I pasted (which does show the paths), I put the following together:
Orange - charged air that travels through the right-hand (passenger) SMIC
Blue - charged air that travels through the left-hand (driver) SMIC
Yellow - charged air that travels through NO INTERCOOLER

First things first, does the air really split three ways instead of two? This would be part 22 on the fiche which is
Volkswagen Touareg Turbocharger Intercooler Pipe. HOSES, PIPES, Air - 7L6145945H - Genuine Volkswagen Part

The perspective isn't great but that looks like three outputs to me. Plus, if you search that part number you'll find a bunch on eBay

So I'm not crazy and I did see the the charged air split three ways.

Secondly, the air from the intercoolers and the bypass combine in a funky plastic piece. My visibility in the engine bay wasn't great so I left open the possibility the bypassed air didn't actually collect back to the cooled air. Or maybe there was a valve or something. The funky collector is #33 on the fiche, part number 7L6145770AD
2009 Volkswagen Touareg 3.0L TDI V6 DIESEL A/T Pipe. Turbocharger. Intercooler. Outlet Tube. Air. Pressure. 3.0 LITER. 3 - 7L6145770AD - Genuine Volkswagen Part

A search on the interwebs for an actual photo of that part and you'll find something like this:

As far as I can tell there are no valves or other funny business. Just a molded 2 into 1 collector. Furthermore, there are no valves or anything besides a plain tube running from the 3-way split straight into this collector.

So what am I missing here? Does some of the charged air really bypass the intercoolers? What purpose could that possibly serve? Is this part of the diesel scandal fix? Is this the same in other markets?

Very confused.

Long post so thanks for getting this far.

21 Posts
Discussion Starter #2
I found the answer: Turns out there IS a valve in the funky plastic 2-into-1 collector.

It just wasn't showing on the fiche and of course your typical auto-dismantler takes everything down to the component parts so it wasn't in any eBay listings. And it's buried in the engine bay so I couldn't see it.

I'm attaching Self Study Program 941803, Audi 3.0-liter V6 TDI which shows clearly the plumbing and explains the operation of the valve.

Essentially, the valve exists so during cold start they can bypass the intercoolers which sends hot charge air into the engine which increase EGTs which activates the emissions controls equipment as fast as possible.

Here's a picture of the engine and I've labelled the bypass tube:

Here's what they say about the valve:

"The bypass flap element consists of the flap housing
and two flaps that are mounted at 90° angles on a
common shaft.

They permit continuous mixing of cooled air from the two
charge-air coolers and heated air from the turbocharger.
In the final positions of the flap, either only the heated air
from the turbocharger or the cooled down air from the
charge-air coolers is delivered into the intake manifold.
The advantage of variable charge-air mixing is that the
intake air temperature can be regulated to the desired
specified value depending on the characteristic map
through a variable mixture ratio.
This permits constant thermodynamic boundary
conditions for low-emission and low-consumption

The Charge-air Pressure Sensor G31 with integrated
Intake Air Temperature (IAT) Sensor G42 senses the
charge-air temperature. It is installed just upstream of the
throttle valve in the pressure hose."

Here they show the valve:




1,313 Posts
Super information! Love the engineering in a volkswagen!
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