What's inside a C6 S6 Intake Manfold? Find out inside!

A6 All/ S6 All
#1

Sorry for the cheesy title.

After removing my manifold yesterday, and discovering it was faulty, I decided to take it apart to see what was up.

So, before we go through how to take apart your intake manifold, let’s make sure we know what each of the components are, and what it is they’re doing.

HOW THE MANIFOLD WORKS

From the service training document, we have a good overview of the design-

There are two flap systems;

  1. Intake Manifold Flaps - used to induce tumbling of the air at low rpm by in order to increase torque.
  2. Change-Over Flaps - Used to switch between a long-path and short-path

Intake Manifold Flaps

http://i57.tinypic.com/2qxxbth.jpg

Change-Over Flaps (click to enlarge)

http://i61.tinypic.com/m81ob7.jpg

Identifying them on the manifold:

http://i59.tinypic.com/azgwv7.jpg

The two sensors are used to determine in what position the flaps are - and if they are not operating correctly, you will get a CEL. It doesn’t seem as though the Change-Over Flaps have the same.

Now, to business-

TAKING THE MANIFOLD APART

If you read my thread here http://audirevolution.net/forum/index.php?topic=3221.0, you will see how to remove your manifold.

Now that it’s off, here’s how you can take it apart.

Be aware, before you start, that to put it back together, you are going to need to do a LOT of rebuilding fine gaskets.

First, remove the two actuators and the sensors. The sensors use Torx T20 screws, and the actuators use Torx T30. To remove the Intake runner ‘tumbler’ flaps actuator, you will also need to remove a circlip at the end of each arm. Use two flat screwdrivers to push on each end of the ‘C’ and it will come off (most likely flying off, so put a rag or something under to catch it)

The manifold is in two main sections, top and bottom.

From the top, there are 5 Torx T30 screws along each long side.

From the bottom, there are 5 Torx T30 screws along each long side, set in from the edge. There are 4 Torx T30 screws on the intake ‘mouth,’ and 2 Torx T30 screws at the ‘front’ of the manfold, one of which is hidden under the Intake runner ‘tumbler’ flaps actuator.

Once you have removed all the screws, you will need to break the sealing gasket which is still holding the top and bottom together. The joining face of the top and bottom half have a ‘ridge’ which means you won’t be able to wedge something all the way through until you have already broken the seal. So don’t try and force anything straight through.

http://i57.tinypic.com/fmlylj.jpg

Start to break the seal by starting at a corner at the front of the manifold, where one of the ‘top’ screws was previously seated. Wedge a blade partway into the gap, and gently tap it with a hammer to open the gap. Work the gap open until you can wedge something slightly larger in (like a (smooth) flat head screwdriver). Leave that wedge in place, and now go to the next ‘top screw hole’ (which direction you go doesn’t matter) and do the same. Three screwdrivers/wedges should be sufficient - when you reach the fourth point, remove the first wedge and place in the new position, etc.

Continue this way, using progressively larger and larger wedges, and eventually the manifold will come apart.

WHAT WAS INSIDE MY FAILED MANFOLD AND WHAT WE CAN LEARN FROM IT

Here’s what you first see:


http://i58.tinypic.com/2rxgtnk.jpg

One the left, the top half, on the right, the bottom half.

Each of the ridges in the centre part of the bottom half have gasket material on them to keep the runners separate, as well as the square shaped borders of each port. These gaskets will pretty much be destroyed when you take it apart, so you’ll have to be prepared to use a liquid gasket to remake these if you want to use the manifold again.

Now, let’s have a peek down the tunnel and see what the flaps look like. Note that you should be able to see this same view by just removing the ‘air distribution housing’ (the thing the two throttle bodies sit on), and putting a camera down there.


http://i60.tinypic.com/141r2te.jpg

Oh. That’s not good. Aside from the bits that already fell out and into my intake runners, looks like there’s more to come.

However, the Intake Manifold Flaps (tumblers), look to have full movement with no jamming or much resistance (one was slightly gummy).

Back to the changeover flaps-


http://i57.tinypic.com/w6s2us.jpg

The issue of manifold destruction is already well noted, in other models, if not on the C6 S6.

In my humble, non-engineer’s opinion, this really seems like a poor design. My car has about 150,000 km, but I can’t be sure how long it’s been like this. I can’t recall a time when it had significantly more power than it did before I took the manifold off, and I picked the car up at 70,000km. That’s about all I can say for longevity. Apparently the new manifold has an improved design, but I’m not willing to crack open my new manifold to find out what that entails. If anyone has this info, please share.

Upon a closer inspection, each of these “link holders” which provide a housing in which the flaps rotate, are ‘formed’ into the manifold. They are not held in place with screws, but rather there are three plastic stubs which go through three holes in the metal - then the ends of the stubs are melted and pressed so they ‘mushroom’ out and are retained. I hope that makes sense. Because these stubs back into the manifold runner, you can understand why they didn’t use screws, which would interrupt the air flow.


http://i62.tinypic.com/110ezuo.jpg

It seems as though this is the first point of failure (again, not an engineer), and all other failures follow from this. The plastic is worn away as the supports are lost because the geometry changes. Then the flaps must get jammed, and the initial link snaps.

So, I hope you can appreciate that unless you’re some sort of CAD wizard with a 3d printer, there’s pretty much no hope to save your manifold if it is in this condition. It is a great shame that Audi don’t offer the parts to replace the changeover flaps (so far as I have seen - I have searched through ETKA as well). As a new manifold is the best part of $2000 - it seems like quite a lot to spend for some plastic parts. The rest of the manifold just goes to waste - but maybe this one can be used for testing/development!

-P

#2

awesome

title was funny as hell. I clicked.

#3

Paul this was really great for you to share. Now that you have taken it apart did you see any other weak spots. Did you ha email any idea that the intake was damaged before you removed it. Did you have any miss fire issues.

#4

Thanks mate - great questions that I should have included the answers to!

I have to say that the whole changeover flap system reminds me of a barrel of monkeys all linked together. One bit of force in the wrong direction and the whole system fails. Granted, mine is worn and well destroyed, but you can still appreciate the looseness of the whole system. It really seems cheaply made for such a complex system. Even if the ‘holders’ hadn’t come loose, the plastic would have soon worn away in other areas. It should be made of metal with proper bearings.

I did suspect there was something wrong with the manifold. Last time I had the car checked over, they noted a rattle coming from the manifold while on the dyno. I took this to mean things were getting a bit loose in there, but had no idea it was this bad.

Another interesting note is that the service centre reckoned there was a leak in the manifold top/bottom seal, because when a fluid was sprayed over certain parts of the joint, the idle would change. I didn’t see any evidence of a failed seal, but then it got pretty well destroyed when taking the manifold apart.

The car has had a CEL on for some time - related to O2 sensor out of range, and many random misfires. Interestingly I also had ‘intake flap stuck open,’ though as mentioned above, there are no sensors related to the changeover flaps, only the tumbler flaps, which seemed to be OK - at least they weren’t jammed or broken. But who knows?

I suppose that both of these issues can be explained by the manifold. Because two of the intake ports were jammed with plastic bits, it’s very possible that they were running rich into that cat, and causing the O2 sensor issues. I will report back once it’s all back together.

-P

#5

Thanks for all these amazing technical writeups. If you dont mind, I will link them all in the S6 Info Dump. Really great stuff.

#6

What is the possiblity of running a “fixed” mani? I would be curious to see if there would be much of a felt difference.

#7

Wow great info. Sorry about your destruction. Are you going to replace with a new one? Has anyone just taken the flaps and tumblers off? Im assuming it wouldnt work well lol

#8

Running a ‘fixed’ runner manifold (like the v10 R8 and Lambo use) or removing the flaps would both be a sacrifice. On the old S6/S8 manifolds, two different sources (JHM and another one I cant remember) found that going from a variable intake to a fixed one lost a lot of power, on either the low are high end of the range.

JHM reported…

We also found during dyno testing that we lost 55 ft lbs of torque at the wheels (over 70 crank tq) when disabling the dual plenum flap design. This ruled out a complete fabricated replacement that was a single plenum design since losing torque kills throttle reponse for day to day driving.

http://www.audizine.com/forum/showthread.php/368739-Just-Released-JHM-Intake-Manifold-for-B6-B7-S4

On the v10, it would be even more. So, you are probably looking at a loss of up to 85 lb/ft tq at the crank on the v10, by locking it into a short runner manifold.

On the C5 cars, I had a love/hate relationship with the manifold. I knew that provided a ‘free’ boost of power, but they were always breaking. And, you had to rely on the aftermarket for replacement parts, since Audi only sold the manifold as a whole.

Fast forward to the C6 S6, and I was happy to finally leave the POS design behind, only to find out that it was deja vu, and even worse! The problems are mostly now internal, and not easily fixed. There were some reports of the actuator motors going, but they can be replaced on their own.

Possible solutions

Try and DIY a fix

This may be possible in some cases, but not in all. We need more data to figure out exactly what is breaking, and the different stages of destruction. There is more info in a long thread on a German forum. Link is provided in the S6 v10 Info dump http://audirevolution.net/forum/index.php?topic=2614.msg90903#msg90903

Add a supercharger and go single plane manifold like the RS6

Definitely not the cheapest solution, and there is nothing available as of today.

Aftermarket fix and upgrade

Someone like JHM comes in and identifies all the weak spots of the manifold, and then has custom parts manufactured to sell an upgraded manifold as a replacement unit. It may have other upgrades, like porting, to increase performance. You would send in your stock manifold or pay a core charge.

Buy a new one from Audi

At about $1700, not my favorite solution, but might be all we have right now. The good news is that with new ones going for $1700, there is some incentive for the aftermarket to develop a cheaper fix.

#9

It’s a big no no to remove the stages of the intake. That will loose big Hp. The single plane intake manifold will be just as bad as just having a single stage intake. It might male sense to send the intake to JHM and see if they or someone will fix it. I know they worked with 034 on the fix for the rs4 intake arms that break.

#10

What they said ^^

I am buying a new manifold, and I’ll report back to this thread to see what I can notice about the improved design once it arrives.

#11

Ok. Maybe someone can run a snake cam down into the “revised” Intake Mani’s, ideally you would crack a new one open, but at $1,700 bucks, I wouldn’t want to be the one…

#12

If this is possible then it shouldn’t be that be of a deal.

#13

I received my new intake manifold today - and one of the plastic sensor mounts is cracked!! It’s not a part I can replace from my old manifold so I might be waiting a while longer before the car runs again.

I have had a poke around it, and the only difference I can see is that the intake/tumbler flaps are now metal instead of plastic. The change-over flaps look the same, except the softer sealing edges on the flaps are blue instead of tan colour. Still looks very plastic inside the tunnel.

#14

That sucks. Was that on a brand new piece from Audi?

#15

Lots of awesome information in this thread. That intake looks like the 3.0 intake tumble flaps. They are a mess. Any chances of getting some pictures of the new intake guts. I know you probably don’t want to take this one apart but any angle you could get would be great for document sake. Great work so far.

#16

I ordered a brand new manifold from Jim Ellis Audi. Packaged in an OEM Audi box with expanding foam - however the sensors on one end had only about 1.5" of foam between them and the end of the box, and since it is 13Kg, a good drop on that side has probably done it.

In any case, DHL has owned up to it and has paid the full amount, and so another new manifold should be here today or tomorrow from Jim Ellis.

I’ve taken one pic so far, and it doesn’t look like they have updated the changeover flaps as they look plastic to me. But the tumbler flaps are now metal.

http://i60.tinypic.com/of955u.jpg

FYI: New Redesigned Intake Manifolds are shipping from JHM (Mine just arrived)
#17

mine failed recently… not catastrophic, but enough to give constant CEL… which prevents me from completing registration lol… we’ll see how long it takes before Audi gets the new ones out to us…

#18

Since someone else revived this old thread, I figured I would post my experience with the manifold on my 07 S6.

A couple of months ago, I had a rattling coming from my intake right after starting it up one morning. The noise disappeared after about 20 seconds and the car idled fine. A couple of weeks later, I pulled the manifold to do a carbon clean and I found an odd shaped piece of plastic sitting on top of the intake valves for cylinder 6. I had no idea what it was. I grabbed the manifold off the bench and shook it to find that it rattled. I turned it on its end and one of the flappers fell out. Picture of the two loose parts below. There is about 100k on the clock.


http://img.photobucket.com/albums/v205/eng92/manifold/IMAG1977.jpg

I stuck a borescope down into the end of the manifold and saw a mix of open and closed flaps.

I ordered a new manifold from the local dealership and they had it in the next day. It is a night and day difference in how the car performs now after replacing the manifold and doing the carbon cleaning.

I separated the old manifold and took the picture below. The missing flap for cylinder 6 is on the upper right.
You can also see that all the flaps are open except for 7 and 8. The link between 8 & 9 had broken leaving the flaps for the three cylinders inoperative.


http://img.photobucket.com/albums/v205/eng92/manifold/IMAG1979.jpg

I will have the manifold off again this weekend to pull all the injectors for cleaning and flow testing. Believe it or not, I am chasing a misfire problem

#19
#20

I live in Canada (about an hour east of Toronto)
The manifold the local warehouse had in stock is an 07L133185M The original was a rev C