Variable Intake Manifold Links

[AusA8]

I did a quick search on the forums but couldn't find anything on this topic so I thought I'd post what I've just done...

A few months back whilst I was cleaning the engine, I noticed that one of the plastic links that controls the variable intake manifold was clean broken. So I started the search for how to fix as Audi Aust said that there is no fix, only a replacement manifold. The SSP clearly states this also - at $4,500 I figured that there was a better ways to spend the $$!

Anyway, cut along story short, I found some parts in the USA from a supplier called Gruven Parts. They make a replacement arm in Al. Given that the internal 'flaps' are plastic, it means that they become the weakest link and not the linkages.

The Audi SSP states that they work by varying the intake length to improve low end torque and top end power. The way it should work is as follows:

With engine off, the arms are under spring tension and therefore the internal flap allows the 'short' intake length. Upon starting and engine at idle, the vacuum pulls the arms down thereby making the length 'long'. It stays like this till 4,480rpm when the solenoid trips and releases the vacuum, thereby allowing the shorter run.

In 'long' length, better torque at lower rpm, in 'short' length after 4,480rpm, better power.

For me, with a broken linkage, I had one cylinder bank running in 'short' length all the time, hence under 4,480rpm I had one bank in 'long' and in 'short', effectively inhibiting low end torque.

After fitting the new links, I did actually notice a better response in low end torque, albeit not a huge gain.

Well made parts and took a few mins to install, here's a pic of before and after.

Before:


After:


Interestingly, whilst rummaging through the SSP, I also found that on WOT when revs swing past 3,000rpm, another flap opens in the air box to take additional air from the engine compartment! So darn complex!! But oh so smart!!

Cheers

[HPsauce]

There's certainly been discussion here about that exact topic, but being a D2 driver I didn't study it in detail or recall exactly where it was posted.

[Adrian E]

There's threads about these arms in the d2 section, but probably not such a common failure on the d3 yet - nice to see some installed pics too

[HPsauce]

Am I right it's only the 40-valve engine in the D2 that use these?
(I'm PF 32-valve and "managing" with "only" 340hp)

[PsYcHe]

Nope.. the PF has them too. Slightly different lenghts though.

Not sure if I've heard of the 32v having a problem with breakages though.

[47p2]

Looks like a nice piece of sturdy engineering

Though if Audi had made such a sturdy part it would have cost them an extra 20p per car

[sarg]

What is SSP & WOT???

Statutory Sick Pay

[Adrian E]

Originally Posted by sarg

What is SSP & WOT???

Statutory Sick Pay

WOT usually refers to Wide Open Throttle

Not sure about ssp though - I'm guessing service guidance related?

[AusA8]

Originally Posted by HPsauce

There's certainly been discussion here about that exact topic, but being a D2 driver I didn't study it in detail or recall exactly where it was posted.

Yep, I found them, but being D2 I figured that I'd post up about the D3. Hope that's ok.

Originally Posted by Adrian E

There's threads about these arms in the d2 section, but probably not such a common failure on the d3 yet - nice to see some installed pics too

Thanks.

Originally Posted by 47p2

Looks like a nice piece of sturdy engineering

Though if Audi had made such a sturdy part it would have cost them an extra 20p per car

Definitely sturdy compared to the plastic ones. I took both of them off and the second one broke on me whilst I was studying it in my hands until a gentle bend being applied to it!! . Glad I bought two.

All things relative, they cost me about $70 AUS. I Imagine the Audi engineers saying to themselves, "well here's a way to make money on parts, we'll make a really weak part that can only be fixed by buying a whole new intake assembly". As you say, it would've cost them next to nix to produce a quality part. Seems in complete contrast to the rest of build really doesn't it.

[47p2]

Originally Posted by AusA8

I Imagine the Audi engineers saying to themselves, "well here's a way to make money on parts, we'll make a really weak part that can only be fixed by buying a whole new intake assembly".

I remember when Mercedes redesigned part of one of their door handles, a small metal part which they had been using for a number of years and they had never sold a single spare. The bean counters decided it was over engineered and the part should be made of plastic, suddenly they were selling spare parts and not only that they saved millions of pounds during the time the handle was in production just because the part was cheaper to produce in plastic. Sad but true