Positioning of the MAF's - HELP needed

[IchBautAuto]

Here is my make at home solution to check out the functionality of the mod. I think that is a sound concept and once proven, it can be made in a more sophisticated form with workshop machinery.

The "at home" version is:

a spacer ring 72mm ID and 82mm OD and 15-17mm deep to be determined by each individual fit, to be inserted in the air cleaner box from underneath and fill the void between the top of the MAF and the bottom of the air horn. The at home version is made of 70mm ID silicone hose with 5.5mm wall thickness. The final version is likely to be polyurethane.

and, A spacer ring 80mm ID, 91mm OD or greater (no real limit if it fits) and the same depth as the top ring, as one takes up the gap generated by the other. A flange to suit the underside of the airbox, 80mm ID that can be screwed to the airbox where the MAF was originally secured. This spacer ring is glued to the flange so the flange and spacer become a part of the airbox, once attached with the two screws.

The MAF is inserted fully into the manifold using either the original or the Apikol seals, the airbox is placed on top and secured to the inlet manifold normally. The MAF will have no to 1mm of vertical movement and both end of the MAF will have airtight seals and the airbox removal will be simplified for future requirements.

Excuse the rough drawings, I have lost the plot with autocad for the moment and my drawing instruments are in archive.

If you see an obvious elementary error, feel free to call out. I have had to order some silicone hose as the local auto shops only seem to sell the hose in Imperial dimensions and 70mm and 80mm aren't in that lineup. The flange and spacer assembly could be made from alloy, polyurethane, or any number of other materials, all of which are either rather expensive to use as prototypes or hard to come by in the domestic environment. The upper spacer is almost certain to need to be Polyurethane as it needs to be slightly flexible to be inserted into the airbox as the O Ring retaining pieces should be retained. Enjoy

[simonpoulton]

A 3D printer would be great for prototyping these - do you know anyone with one?

[Human Joist]

Do you not just need once spacer under the maf in the horn it’s me f to fill the 17mm gap ? Then screw the maf in to the air box to keep it secure ?

[Human Joist]

Just got mine back together and again there is a gap about the same as yours mate. I have seated the mafs fully as it’s a shallower depth. Then left the spare 17 to go between the mafs and air box as there is more space on the shaft to allow movement without the risk of air getting in

[IchBautAuto]

Do you not just need once spacer under the maf in the horn it’s me f to fill the 17mm gap ? Then screw the maf in to the air box to keep it secure ?

The 45mm section of the MAF body where the O ring seals is actually stepped. That step is 15mm from the flange so if you check carefully you'll see that the O ring actually only gives a minimal seal up to that point. You need to push the MAF fully home into the airbox to see that the actual seal only functions correctly when the MAF is hard up to the airbox. That is why I chose the second spacer sized for the MAF diameter to provide a decent seal as the fitted O Ring won't.

I can't see nay reason to attach the MAF to the airbox with this system. It won't be going anywhere and makes removal of the airbox so much easier, to me anyway.

[IchBautAuto]

A 3D printer would be great for prototyping these - do you know anyone with one?

No, I don't. Way back when I was a fitter and turner at one stage so doing it this way isn't an issue for me. I did consider buying a printer as in theory you could print the final product easily but the elementary issue of being heatproof and thermal printing are in conflict.

The spacer and flange could be made from alloy, a heat resistant plastic, anything suitable. For the moment I'm looking for something that works and then in the refinement phase, choose a suitable material. This would be a piece of cake for someone in the plastics business who can source the most economical version of a product.

Now I'm not in the game, turning down a product from a solid block of polyurethane or buying a few meters of pipe, if it came in close to the right size, for 15mm of it is bloody expensive, at least here. Fit, form and functionality are critical but I wouldn't want to break the bank in the process.

[IchBautAuto]

Just got mine back together and again there is a gap about the same as yours mate. I have seated the mafs fully as it’s a shallower depth. Then left the spare 17 to go between the mafs and air box as there is more space on the shaft to allow movement without the risk of air getting in

Got that, comments about the MAF OD being stepped is in the other response. Once you get that issue, it's as obvious as anything, just something that you would never need to consider normally as you wouldn't even need to remove the MAF from the airbox unless you had a fault. You can actually see the air gap between the O Ring and the MAF until it passes the step in diameter.

[IchBautAuto]

Do you not just need once spacer under the maf in the horn it’s me f to fill the 17mm gap ? Then screw the maf in to the air box to keep it secure ?

On reflection, that would also work provided you were happy to screw the MAF to the airbox, you would have the airway sealed at the top rather than the bottom. Must admit that my solution was coloured by the attraction of the airbox and MAF not being joined at the hip. I'm inclined to remove the airbox whenever I am doing maintenance, ease of access, check all the stuff under for leaks etc, so the brain trail wasn't at all considering a solution that retained the existing OE arrangement.

[Classik]

You should complain, I have the same stalk in three cars. Talk about parts bin design. Anyway, have a temp fix on the drawing board for the MAF. Just one of many options but will get me back on the road while I look at machining options for a fix that meets the standard of the car.

I foresee a group but for these once your done

Oh yes!

[IchBautAuto]

SUCCESS------

This is the proof of concept trial which has actually turned out to be an engineeringly sound product but not necessarily what everyone would seek to fit.
So, all the preamble has been read. The MAF firmly seated in the manifold.

position of the MAF in the airbox is some 15mm short

The parts I made are two spacers from 80mm ID silicone hose and two spacers from 70mm ID hose

The 80mm ID spacers were placed over the MAF to seat on the underside of the airbox. I have omitted the alloy flange in the trial and on reflection I doubt that it is needed, this arrangement improves on the removal and refitting of the airbox over using the flange concept.

The 70mm ID spacers were placed on top of the MAF before fitting the airbox. The ID of the air horn is 72mm so the hose was fractionally too small in ID and is reasonably flexible so I wasn't happy with the outcome there.

Some happy juice and deep thought / lateral thinking led me to the kitchen where a pair of egg rings are in fact the exact size needed to spread the 70mm ID hose and have a 72mm ID alloy ring in the air path.

The outcome,
a. the airbox is able to be removed from scratch in under 5 mins without disturbing the MAF and replacement is really a snap
b. the airbox is rock solid, no movement at all
c. the MAF is positively sealed with an Apikol seal on the lower part and by the O Ring and the face of the silicone hose on the upper part

I have been approached by a member of our local Forum who has offered his 3D printer and the filament to make a heat proof product. All I have to do is draw up the files and pass them over. I'll keep you posted on the outcome.

[Gregstv]

Egg ring ventruis, love it.

[Mɐʇʇ]

Very nice job. Bravo.

And another 2x benefits is that you don't have to disturb the brittle MAF wires to remove the airbox, plus the MAF mesh provides a little protection against dropping the family jewels into the turbos when you pull the airbox off.

[IchBautAuto]

A really interesting outcome courtesy of gregstv. Audi certainly require the MAF to be seated at both ends, so either they have a longer MAF, can find another 15mm to lower the airbox somehow or they just haven't been aware that once the MAF is attached to the airbox, you can't see much with the engine in and that's what is desired rather than what is achieved.

The trial concept is perfectly functional and for the RS6, nicht Teuer. I can't see any problem with using this as a solution by itself. Nevertheless I'm getting my head around the CAD issues for producing a drawing for 3D printing to see how that goes.

In the meantime if anyone can see how AUDI could drop the airbox another 15mm, speak out. I've been over mine and aside from the possibility of missing the bleeding obvious, it is fully down and all fixing points are hard up with no force required at all.

[Mɐʇʇ]

I’m just waiting for ChrisA to organise a group buy of the Egg Rings. I’m in.

[IchBautAuto]

Be careful, don't get the bantam size egg rings, this is an RS6 after all. The Jersey Giant is too big. Maybe a Plymouth Rock.