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Fwd Induction vs updraft induction on a new build


Burlington, NC
I have a forward induction (Stock) parallel valve IO-360 and would like to use it in my Javron Super Cub kit. I can obviously swap out the sump for a vertical induction sump but before I did wanted to see if there were any advantages I was missing. As of now, I plan to stick with fuel injection either way. To me, the possible disadvantages of the fwd sump are:

1) Weight of the actual sumps (maybe?)
2) Exhaust options limited (I have a Vetterman X over for Super Cub but with no muffs)
3) Fitment of adequate heat muffs
4) Air filter/ Intake challenges

I do like the idea of cleaning up the underside of the cowling a bit.

I am an AP with several builds/ restorations under my belt so making custom intakes, lower cowlings, heat muffs, etc is a non-event.

I spoke with an extremely helpful repeat Javron builder that recommended to swap to vertical intake and carb. Just wanted to get a few more data points before I change things.

Appreciate any feedback!
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I am an AP with several builds/ restorations under my belt so making custom intakes, lower cowlings, heat muffs, etc is a non-event.

You could take a close look at the CubCrafters 363i engine. It is a parallel valve Lycoming YIO-360 with no induction tubes in the oil sump. This engine uses a carbon fibre induction manifold fed by a horizontal fuel injection servo. Maybe some ideas there.

CC363i exhaust has very effective cabin heat.
I’m a fan of Superior’s cold air induction, which is forward facing and quite low profile. I have an Airflow Performance 200A injection on mine. My air box is quite large and has to contribute ram air. I can’t think of any down side.


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I weighed the engine driven fuel pump and the boost pump (Airflow Performance) and came up with 5.75 lbs. The Carb and the servo/ flow divider are about the same weight. I know there will be a little more plumbing for fuel injection but I could eliminate carb heat so that may be a wash. Weight is something I want to manage carefully from the start. To me, fuel injection is worth the 6 pound hit.

I wonder if a fwd induction sump on a parallel valve engine really is heavier than a vertical?

Appreciate the intel and pics. Those help a bunch.

Yep- had that on my Pitts and the Murray's are like family to me. We have done several projects together over the years. Good people. Not sure what the lead time is on those right now and the cost is a deterrent until I explore some other options.

FWIW- this is the current sump I have. Not my engine (or pic) but mine is identical. Thanks to the Vans Resource center for the picture.

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My engine came with that sump. I think the height is very similar to the Superior, so fitting it should be simple enough. I’d bet Clint has an exhaust design for it. FWIW I use the dual exhaust with dual mufflers and it sounds great. With both feeding cabin heat boxes I have lots of cabin heat available. I dump both to the front seat but it’d be easy to have a dedicated rear seat heat box.
I actually have the Vetterman exhaust for this set up but without the mufflers. I bet I could send it back and have them added. For sure would be the most direct route.
StewartB- what does your air filter look like? I would go with something really simple that I could bypass easily when in flight
Now there’s a topic! How to fit alternate air was a project. The FI Cubs I know don’t have it so I didn’t have anything to model after. We put a door into the back wall of the airbox and that meant using an air filter with a big enough footprint to cover it. Most guys just put a cone shaped K&N filter on.

My air box sits between dual oil coolers.


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CubCrafters FX-3 has alternate air but no alternate air control. A spring biased door opens when the primary air path is blocked. When that door opens unfiltered air is drawn over the front right exhaust stack.
Acroeric, it took awhile to find these pics. Here’s my alternate air closed and open. And for the critics? When I swapped the engine I did use a metal locking nut! ;)

Honestly? If I was building another FI Cub I’d use a cone filter and skip the alt air. Mine’s a day VFR airplane. A fouled filter is hard to imagine. I’d still make the collector big enough to utilize ram air.


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