macrafic

macrafic

Well Known Member
Does everybody with the FI Horiz induction setup generally install the Filtered Air Box for alternate air?

Anybody NOT do this?
 
macrafic said:
Does everybody with the FI Horiz induction setup generally install the Filtered Air Box for alternate air?

Anybody NOT do this?
Click to expand...

Direct ram air in flight is the way to go.

The filter is used only for take off and is alternate air. I have a Bracket filter at the usual left intake but some guys are going with an internal K&N cone. You should have some kind of filter for take off as the prop can stir up grass clipping and other stuff that the engine might not like.
 
Van's Way

macrafic said:
Does everybody with the FI Horiz induction setup generally install the Filtered Air Box for alternate air?

Anybody NOT do this?
Click to expand...
Cannot speak for everybody, but I chose to install the alternate air per Van's FWF subkit and drawings.

11b19ol.jpg
 
David-aviator said:
Direct ram air in flight is the way to go. The filter is used only for take off and is alternate air. I have a Bracket filter at the usual left intake but some guys are going with an internal K&N cone. You should have some kind of filter for take off as the prop can stir up grass clipping and other stuff that the engine might not like.
Click to expand...

Dynamic pressure recovery ("ram air") aside, perhaps bypassing a perfectly good filter to get performance is merely something everybody keeps doing because everybody does it.

Recall DanC's system, a filter in the left cooling intake combined with an unfiltered ram directly through the front? When he switched the AFP Y-valve back and forth he saw little or no difference in MP.

ChrisZ did a large area filtered system for his Lancair with excellent results.

Recently built a filtered ram airbox with lots of media area. http://www.vansairforce.com/community/showthread.php?t=44856&page=2
The measured contribution to intake pressure loss is 1.9" H2O, or 0.14" Hg @1400 PPH. Sure, 0.14" is a loss, but probably not much more than loss caused by the butterfly in the the popular switched systems. For scale, it is about 130 feet in altitude, or less than 1 hp. The filter part number I used is K&N 33-2124, but there are many of similar size.

No point in going naked just because of old wive's tales. I'd suggest the real requirements are a filter with enough media area, a cold air source, and obedience to the usual rules of airflow. The trick is packaging.
 
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terry.mortimore said:
Hi Rich, I purchased the James filtered air box. I have not installed it yet, but it is well made.
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Don't have actual measurements for the two James filters (E-0995 or RC2600), but I suspect they are more restrictive than an "area of a truncated cone" calculation would lead you to think.

The first intake I built was similar to a James assembly and used a K&N RU-3120 with the butt end cut out (cone filter 2x4, 6 long). Don was kind enough to run it on the flow bench at AFP. The airbox contribution to pressure drop was 4" H2O, or 0.294" Hg. Not horrible, but not good enough.





Don suggested media area was the key, not surface area of the shape. I thought he was right and went back to the drawing board, concentrating on flat filters with deep media pleats. The RU-3120 has pleats about 3/8" deep. Most of the flat filters, including the too-small-at-first-glance stock Vans filter for the left cooling intake, have pleats around 7/8" deep.

I'm aware of a bench run with that Van's filter and a slightly modified duct. The filter and duct contribution to pressure loss was only about 2.5" H2O. Surprise!

Side note: previously I mentioned "obedience to the usual rules of airflow". The above pictured design also upset fuel metering, driving it rich nearly 13%. I think the cause was turbulent flow into the throttle body mouth....no intake bellmouth. That was also corrected with the new airbox.
 
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Hi Dan, thanks for the reply.

I'm currently assembling my engine, so I'm at least a month away from starting the cowl mounting job.

Do you have a drawing or photo showing your final configuration of the intake area?

I'm wondering if I can create a bell mouth to help smooth out the flow into the throttle body with the James parts I have?

Thanks for the education, terry.
 
terry.mortimore said:
Do you have a drawing or photo showing your final configuration of the intake area? I'm wondering if I can create a bell mouth to help smooth out the flow into the throttle body with the James parts I have?
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Terry, my airbox is scratchbuilt and won't fit the available space in a James cowl. It should not be hard to make a bell for the James intake if it doesn't have one....it's fiberglass.
 
DanH said:
Terry, my airbox is scratchbuilt and won't fit the available space in a James cowl. It should not be hard to make a bell for the James intake if it doesn't have one....it's fiberglass.
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We saw the data from the flow bench of your 2 filter boxes at AFP at the FI 101 class in November - very impressive. Part of the course was actually doing such a test hands on. I wish I remembered all the detail of what we did - it was interesting.

My by-pass filter is not optimal as it is too small (Bracket BA6108) and flows through scat. I was determined to get this thing flying again ASAP after being grounded for 7 months with the engine change and did not take the time to do it as you suggest. It took forever to modify and finish the cowl to accommodate the Y duct in front of the FM200 as is. I would not be flying yet if I had taken on the air box. Yes, one can be bought that is very nice but they are rather expensive.
 
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