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This is the Seal that sits around the Snorkel & is held between the Bucket & the Filter-box.
Replacing my old seal did several things:
a.) when car is moving, any ram air I might have, is not lost here (see the narrow grey coloured crescent of daylight just laying overtop of the Snorkel's entrance O.D. in the photo above, thanks to whomever for this photo);
b.) when car is stationary, no warm engine compartment air is sucked in here;
c.) when driving, the engine is definitely quieter!
What I used was a black closed cell foam seal for a toilet bowl, 3/4' thick. Because its' I.D. was too large, I cut out a section in the same fashion as the "Phone-Cord Fix" such that in place, the seal is maintained because, cut on an angle, the gap is held closed.
A single long tie-wrap, or two in series, lightly fitted around the Seal's' circumference keeps it in place during installation. The new seals profile is not rectangular, I put the relieved side towards the box.
This new seal is thicker than the original, so installation is slightly slower, but it also prevents the snorkel sealing forward flange, from rubbing on the back of the bucket.
a.) The short, convergent "front half" bell-mouth.
De-glazing the surface finish:
I simply de-flashed & contour sanded the front half. As found, the O.D. has two square edges that that are not condusive to good flow. The removal of those two edges is the only change to the shape I will make. I took particular care to ensure that the O.D. edge of the bell-mouth was carefully rounded to form one continuous decreasing-radius curve, right around to it's back-side.
What I am trying to do here is, encourage as much air as possible, to enter the the snorkel from the sides & behind the bell-mouth O.D. The bell-mouth, when installed, protrudes proud of the bucket back wall to best admit clean, dry air. Hopefully, this attention will yield a little more flow from the sides & behind, than would otherwise enter.
See also the link to Mance's notes below. Make it uniformly dull, take the shine off; use a grit that is not to rough so that there are no threads or even fuzz raised off the plastic surface, note (photo above) how the surface of the black plastic material almost turns white when you do this.
Note also my old crumbling Bucket to Filter-box Seal, yours may be similar; &
b.) The long, divergent "rear half" reverse megaphone (or cone).
Perhaps the reason why the stock snorkel is so quiet, is this part of it. It may also help to keep water off the filter, as I imagine the air slows down again here and any moisture can fall out.
Cone wall straightening:
I used the rounded back side of a wide straight hand file to first remove all the waviness out of the cone wall, this took the greatest amount of time of all the work here. You will immediately start to see the low spots as you begin; continue until they are all gone. To best do this, sit down in a comfortable chair & spend some quality time, just you & the whole lower half of the Filter-box. Ensure the trailing edge of the cone is de-flashed when you're through.
Then I used the file to just blend into the narrowest section of the cone where it joins the "front half". Note that this work can enlarge the the I.D. of the duct, if only fractionally.
Last, I used my long I/M tool & some sandpaper, to reach in with the die-grinder & again, give it that reco'd dull finish, such that all the file marks where removed.
An attentive reader may have noticed that I have not mentioned the air filter at all. Of all the (good IMHO) arguments against using anything but the OEM one, I like this one; would you ever consider using an reuse-able oiled-cotton filter for the cabin air? All paper air-filters are not the same, the ones made by Mann fit the tightest, and its' perimeter seal best ensures the filter-box top and bottom halves will be a closed assembly. The reason my car saw the improvement it did was due to the collective sum of all these simple little details.
Last edited by Lago Blue; 05-16-2020 at 03:46 AM.
Reason: clarity & clean-up after "the up-grade"
I just made sure the loose ones where providing about the same clamping pressure as the tighter ones by re-bending the wire just a little. They should all take about the same amount of force to close.
This will improve & maintain the filter & air-box seal; & help prevent warping of the lid (see Mance's notes in the paragraph below).
The top and bottom halves, the clamps and the air filter foam seal all have to work together to seal the assembly shut and avoid pulling in short-circuiting warm unfiltered air. To summarize Mance's testing here, the Mann filter does this best as the "One noteworthy mention is that all air-box upper halves seem to develop a slight warpage along the front-to-rear engine side sealing lip. Probably due to engine heat and only being retained by spring clips at each extreme end. They tend to "bow" upwards in the center on that side approx .010"."
From Mance's filter fit testing:
"MANN: Best fit of the bunch by far! Absolutely zero movement when lying in lower airbox. Excellent sealing when lid is placed on top and even seals the warped area with sealing material to spare. Takes some grunt to get the clips over the top half of the airbox retaining when re-installing this filter. Zero leakage around this seal even with the warpage. Best of the bunch!! This is also the only filter so far with a glue-strip on top and bottom preventing the media moving upwards/downwards. All other have the glue strip on top side only and filters will "lop" over if held horizontally upside down."
Last edited by Lago Blue; 05-13-2020 at 04:19 AM.
Reason: clarity
...It was not without some trepidation that I did this mod, as at the time IIRC, Mance was not making any more. That may have since changed, or not? In order to do this, I had to hammer (a great deal) on one of Mance's lovely & rare creations (Gasp!). That I was successful, I am relieved, but be warned, if you try this, you may not be! It also took a long time to do.
My 2nd-hand V-Stack (Mk 1?) came w/o instructions & may have originally been designed for some other application, the A4 perhaps?
I thought I could improve the fit, the method of mounting & its' function here as follows:
a.) Increase the base (outlet) outside diameter to permit a different way of re-mounting the stack directly into B4 MAF screen recess / counter-bore. This, in turn is going to allow a step-less transition from inside the stack into the main MAF I.D.);
b.) Curve the straight tapered walls such that they have a more parabolic profile; &
c.) Reverse bell-curve the inlet to the V-stack itself.
The main purpose of all of the above is not just that, perhaps if only theoretically, these changes might each allow a little more flow. Emphasis on <i>might</i>, as I only hope so. Perhaps someone with the required equipment could measure any change? I'd love to know. I really did it to try to get <i>smoother</i> flow, which especially at low speeds, is what I want the sensor to "see"; and because this; was fun to do.
1st photo: The Before Shot down-thread.
An as delivered VAP V-stack installed (borrowed this shot from someone here, thanks BTW). IIRC Mance made a couple of versions, but this is exactly the same as how both my 2nd hand and my brand new one looked to start with.
Note:
- how there is a step between the stack outlet & the MAF I.D.;
- the tapered walls are conical, not curved & all the change from parallel walls to tapered walls occurs in one place; &
- the inlet ring is flat/horizontal.
2nd photo: Partially Mod'd. V-stack Installed Trial Fit.
Almost but not quite step-less transition to MAF I.D. at this stage; curved walls; & reverse curved belled inlet. This was just a trial fit & much more hand work was required to take it from looking a bit like a 50's minature hammered ice bucket, back to something more presentable.
The outlet length of the stack is long enough; & the I.D. of the air-box lid outlet is big enough, that the stack now passes clear through the lid & nests perfectly into the MAF screens counter-bore. Eliminated from the air stream are the steps / transitions for the V-stack outlet; the cork gasket; the screen circ-lip groove; & main MAF I.D. (I realized when I saw photo 1 that I had never mounted my V-stack as well as this one was; I put the wraps of tape on the very bottom of the stack & fitted it into the lid, but not through it! In STFA, I had found this thread: Posted by Hokie_90 on 2003-06-27 13:53:14 re: electrical tape: "I wrapped it around 5 times, ½" up from the bottom of the base". Ah-hah!
3nd photo: Where the stack now mounts:
If you where late to the MAF party like me, in STFA you may recall the phrase "leave the MAF screen lip in place". I have no idea why this was, but now I'm using that spot to mount the V-stack.
The stack base O.D. is now larger (approx. 3 & 1/16") & a tight interference fit into the OEM counter-bore cut for the discarded MAF screen & butts up against the step itself. The stack clicks into place (a very satisfying sound!) with a little twist & even with a tiny smear of anti-seize is held in very firmly (supporting the stack with just one finger under the lip, it hung & held the weight of the air-box lid, MAF, flex hose, my trouble light & the plenum w/vent hoses while I tried to take a picture!). No more 5 wraps of electrical tape!
4th photo: How to Curve the Walls.
Do this before the rim. Clean the pipe first. Note the wood under the pipe. Started with a 2 & 3/8 O.D. pipe & moved up to a 2 & 7/8" when able. File & polish your hammer-face. Check the fit frequently (you will need a few breaks!). The stack outer surface gets pretty ugly during this part but should remain pretty on the inside if you do this right, which is: only strike the stack where it is touching the pipe. It all cleans up v. nicely afterwards with a little hand sanding. Adjust the fit & make the base circumference round & the edge flat & square (sand & file) when you're done.
5th photo: "Rrroll Back the Rrrim" (don't ask, it's a Canuck thing).
Yes, I did get the idea to do this part from looking at the rim of my own Mk 1 V-stack, made from a large "Timmy's" paper coffee cup (it worked!). That I was able to de-screen w/only a modified paper coffe cup reminds me that I should mention I have the diminutive OEM MAF & perhaps it is less sensitive than the larger ones to de-screening?
What I wanted to do here was encourage the air from the sides & behind the entrance lip of the stack to get sucked in.
It was surprising how hard I could hit the thing (& had to!) with a carefully polished ball-peen face hammer (and how long it took!). After reading of Mance's process here...
...I'm surprised it didn't split! Obviously I wouldn't recommend my process unless you could afford to ruin yours.
Do this sitting down. Note the wood underneath. Start by sanding the square edges on the outer lip round to help prevent any stress cracks from starting on the edge & then start hammering carefully round & round the rim.
6th photo: (shown above) Getting There.
This shows the fit into the counter-bore; the curved walls before sanding; the reverse curved bell-mouth; & the almost smooth transition to the main MAF I.D.
7th photo: Purposely Installed w/Filter-box Flat Out of Position.
Very near the level of fit & finish I wanted now.
I temporarily mounted the stack like this to show that I could here employ a stack that did not have the "flat" edge cut off its' perimeter. However, would I have been successful in rolling back the rim if there had been no flat? Perhaps not.
Lucky for me, my only regret is that during one of the trial fits, I broke a rib inside the lid w/my mallet tapping the still to tight fitting stack into place.
vs_1_stock_v-stack.jpg
<center><img src="http://pictureposter.audiworld.com/124134/vs_1_stock_v-stack.jpg"></center><p>...although this is not my stack or photo, mine looked like this to begin with.
What air leaving the filter now sees (a big smooth generous exit rather than the original sharp and square-edged hole).
Place holder -sorry, I've misplaced the one I wanted somewhere (this one will have to do).
Now that you've seen my time-consuming but still rather mild filter-box mods, for some further ideas, have a look at the link below to see Mance's workshop on the subject.
08-16-2010, 09:07 AM
5. Bucket to Filter-box Seal:
