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Snorkel vs FlyEFII throttle flange adaptor

riseric

Well Known Member
Patron
I am at the snorkel (VA-132-2) installation and wondering if any of you can share hints and thoughts.

My setup:
Aerosport IO-375-M1S
Superior cold sump, horizontal induction

System 32 EFII
Standard Van's cowl


My main concern is (see photos) that the EFII throttle body has a 2-7/8" opening vs a 2-3/8" opening for the snorkel. If I calculate correctly, that's just a tad over 2 square inches of area difference.


Greater area/volume in the throttle body translates to lower airflow speed thus increased pressure, correct?
Would that be a good thing?
Seems to me that's like breathing through a small tube...


I will have to rework the snorkel in any case as I have a B&C starter and it interferes.
Should I just keep the top part and fit/fabricate a custom tube around the starter and to mate with the throttle body?
How about a 3" silicone non-collapsible tube?

I'm far from being a fiberglass expert...








 

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Turbo hose adapter 3.25 to 3

Eric,

I found a silicone throttle body similar to this and a 3in round metal flange that I glassed and riveted to the snorkel. I thought about opening up the snorkel to the full 3.25, but at that time I was living in a different state from my airplane and the focus was on getting it airborne.

I'd also say don't hesitate to reach out to Robert, he's been great to work with.
 

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Aaron, thanks for your reply


I already have an adapter between the throttle body and the snorkel.
This one, from Robert.


My snorkel mates flush with the adapter, like what you did with your flange and silicone hose.
I'm concerned by the snorkel's outlet being 1/2 inch narrower in diameter than the throttle body adapter.
To me, it's like us inhaling through a straw when excersising. (yes, that's a slightly exagerated comparison...:rolleyes:).


The snorkel starts large at the ramp inlet, then narrows progressively to smaller than the throttle body then, bamm, the intake air enters a wider area.



I assume a similar sized diameter as transition between the snorkel and throttle body would be preferable.



Maybe there's no significant effect to the engine's breathing with this setup and I'm over-thinking this ??
 
Aaron, thanks for your reply


I already have an adapter between the throttle body and the snorkel.
This one, from Robert.


My snorkel mates flush with the adapter, like what you did with your flange and silicone hose.
I'm concerned by the snorkel's outlet being 1/2 inch narrower in diameter than the throttle body adapter.
To me, it's like us inhaling through a straw when excersising. (yes, that's a slightly exagerated comparison...:rolleyes:).


The snorkel starts large at the ramp inlet, then narrows progressively to smaller than the throttle body then, bamm, the intake air enters a wider area.



I assume a similar sized diameter as transition between the snorkel and throttle body would be preferable.



Maybe there's no significant effect to the engine's breathing with this setup and I'm over-thinking this ??

Try opening your mouth 15% wider when exercising and see if it makes a difference.

I would argue that the form and shape of the snorkel will have a much greater effect on air flow than does the extra .5”. From what i read turbulent airflow is the real enemy in this situation.
 
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Increasing the snorkel's opening?

Try opening your mouth 15% wider when exercising and see if it makes a difference.

I would argue that the form and shape of the snorkel will have a much greater effect on air flow than does the extra .5”. From what i read turbulent airflow is the real enemy in this situation.


Thanks Larry, your two points are valid !!

Thinking about this on the weekend, I figure that I could use thick epoxy resin to increase the diameter of the snorkel just behind the flange then bore a bigger hole, matching the throttle body's opening.

I'll let that idea simmer a bit before attacking the snorkel, it still leaves me with having to deal around the starter...

Any better ideas from the good folks here??
 

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...Any better ideas from the good folks here??
If you can get Dan to chime in, he's probably got some great ideas. What I'd probably do is use micro to get it close, and then use a layup for the final part. Micro will be easy to remove when you are expanding it to the final size, and a good layup will be stronger.
 
Yes, would be quickest and easiest solution, leave the flange you have mounted on the snorkel, build up the outside fiberglass neck area (flox or glass wraps) and grind out the inside passage to meet the aluminum flange ID.

Have you thought of cutting the snorkel flange off and grafting a short piece of aluminum tube in place instead of using the aluminum flange? Would be a stronger, cleaner solution.

My suggestion for the starter interference:
-map out the snorkel area that has to be removed
-using an appropriately sized can (coffee can or such with big enough radius to allow some clearance from the starter), trim out the the affected snorkel area so the can fits the snorkel cut out neatly
-cut a couple pieces of fiberglass cloth to fit this area with a 1" overlap
-wet out the cloth between 2 sheets of poly
-remove one poly sheet and drape the wetted glass over the coffee can form, -place the snorkel in place over the glass & coffee can form and work the 1" overlap edges to the snorkel
-stabilize the snorkel & can to maintain shape & let it set up
-after glass is cured, clean up the edges, ruff it all up and apply 1 or 2 more layers of fiberglass directly to the patch... done.

Of course there will be other ways to do it too...
 
Thinking about this on the weekend, I figure that I could use thick epoxy resin to increase the diameter of the snorkel just behind the flange then bore a bigger hole, matching the throttle body's opening.

Fast, easy...

Sand back side of the flange, and the surface of the snorkel tube. Wipe in a flox fillet. While wet, add two plies of 9 oz cloth. When cured, bore the inside diameter.

Personally I'd just cut the whole thing off and build a lower end like the new snorkel for the 390-119.
.
 

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I would also do what DanH sketched out. Try to open up the snorkel so that there is no place with a diameter smaller than the throttle body/servo intake.

The aerodynamic issue here is not so much the small hole, as the abrupt expansion with aft-facing step at the flange. This would create such bad flow that your injection system would probably run rich.

You want to have any areas where the diameter is increasing do so very gradually and smoothly.
 
Grateful !!!

Mick, your suggestion is real close to what I was thinking. I saw that you re-worked your snorkel also, great job!! I didn't take the time to congratulate you for getting your 8 to flying status. Maybe you recall my visit to your home in France in 2012 I believe...? I had just started to build and yours was the first RV in construction I saw.


Ralph, thanks for your tip about shaping the snorkel around the starter.Truly, that will help a lot!!!
I did consider chopping the snorkel just below the alt-air entrance and install some sort of tubing. Sourcing/finding the appropriate, non-collapsible, sized accordingly tube might be a challenge. Less so a shorter aluminum tube after the starter.


Dan, your drawings and tip are awesome. Sincerely appreciated !!!
I will follow that path, Doable and fills the bill. I'm not bold enough yet to chop the end off and start from scratch... Maybe later...



Steve, the abrupt change in diameter really bugged me. As you say, the smoother the transition, the better. It will be fixed with Dan's suggestion.
 
snorkel

Mick, your suggestion is real close to what I was thinking. I saw that you re-worked your snorkel also, great job!! I didn't take the time to congratulate you for getting your 8 to flying status. Maybe you recall my visit to your home in France in 2012 I believe...? I had just started to build and yours was the first RV in construction I saw ...
Hi Eric, I do remember your visit. Happy to see you are getting close to flying as well! Whatever you do, don't use my snorkel as a model - it's really an abomination. :eek:
 
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