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08-23-2017, 01:02 PM
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Join Date: Dec 2014
Location: Just Minutes from KBVI!
Posts: 1,039
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Quote:
Originally Posted by rleffler
I have a Rod Bower RAM air mod for my RV-10
http://www.ramairforhomebuilts.com/
I typically don't open it until I get about 5,000 ft. Although, I usually don't close it on the descent. It yields about a 1" MP increase.
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Glad you posted this. I was getting close to sending a message about it! I remember when I came out to look at your airplane and we talked about it, but I was drinking from a firehose and forgot so many things you told me, including who made the ram air for your bird.
Are you still satisfied with it? I remember looking at your build log and not seeing too much in the way of plan modifications to install it. Is that really the case, or did it require a lot of fiddling with the cowl and such?
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08-23-2017, 01:15 PM
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Join Date: Apr 2005
Location: White Salmon, Wa
Posts: 71
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Most of the Harmon Rockets have the Y for Ram or Filtered air. I only use the filter when in dirty environment like taxiing on grass or dirt and also when shutdown. Nothing unusual in oil analysis. Unfiltered for start in case of fire belch in intake!
Russ
HRII
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08-23-2017, 01:31 PM
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Join Date: Jan 2007
Location: Battleground
Posts: 4,348
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Russ McCutcheon's RV4, horizontal induction, no filter. He has flown it that way for many years. I do not know how many hours but a bunch. Perhaps he will chime in.
My '42 Aeronca L3 didn't even have provisions for a filter. It had 1000 hours on it when I got it and I put 600 more in the ten years I owned it. It ate a lot of bugs and never seemed to mind.
So, plenty of examples running without filters but I don't think you will find any real data on engine life comparisons filter vs not.
I agree with DH. There is no reason not too given the small, perhaps insignificant, gain going naked.
__________________
Smart People do Stupid things all the time. I know, I've seen me do'em.
RV6 - Builder/Flying
Bucker Jungmann
Fiat G.46 -(restoration in progress, if I have enough life left in me)
RV1 - Proud Pilot.
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08-23-2017, 02:31 PM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
Originally Posted by rleffler
I have a Rod Bower RAM air mod for my RV-10
I typically don't open it until I get about 5,000 ft. Although, I usually don't close it on the descent. It yields about a 1" MP increase.
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As compared to pulling air from inside the lower cowl, through the plastic flap valves. The rise is large because it's so badly choked with the butterfly closed. It is definitely not an optimized filter system.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
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08-23-2017, 03:06 PM
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Join Date: Aug 2016
Location: Asheville, NC
Posts: 2,104
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I put one of these 4" O.D. K&N filters (with that rubber fitting on the left end cut off) in my ram air intake. It keeps the bugs out of the carb.

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(2020 dues paid)
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08-23-2017, 03:10 PM
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Join Date: Nov 2005
Location: Tellico Plains, TN
Posts: 561
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Thanks for the excellent comments. Sounds like I'm probably worrying too much about the unfiltered air, but I'm pretty sure I'll change the system at some point to include a low loss filter full time. The engine didn't have an oil filter either, and they were routinely going well past 25 hours on the changes, so that probably did more harm than the unfiltered air. I've already added a filter.
As the 4th owner of this plane, there have been some changes through the years, and plenty of things I need to make right. Dan was right on the money about the RAM air though, the second owner did race it at Reno. I kinda figured he was responsible for the RAM air.
Anyway, thanks again, at least the unfiltered air is not an immediate concern.
Cheers,
Rusty
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RV-8, SN-80587, built, flown, sold.
RV-3B, SN-10751, rotary engine, built, flown, sold
RV-8, SN-82470, built, flown, sold.
RV-3B, SN-11351, purchased, , flown, sold
A&P - 2018
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08-23-2017, 03:12 PM
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Join Date: Jan 2005
Location: Ontario, Canada
Posts: 1,544
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I use a Bower airbox on my rocket for winter use only. With the snow potential where I live I do not like the possibility of plugging the filter with snow. With the ram air closed you lose about 2" of manifold pressure. It is sort of like using carb heat as you are now drawing air from the hot lower pressure area of the plenum. Good for snow conditions though. The system does work well in the summer with the ram air open but I do not like unfiltered air. My engine has a fresh rebuild, ECI cylinder problems, but after that big expense I will use filtered air as much as possible.
I built a custom filter that fits in the same spot as the Bower box. It has a much larger filter and MP are very similar to the Bower set up with the ram air open. It is a clean simple filter box with no moving parts.
__________________
Tom Martin RV1 pilot 4.6hours!
CPL & IFR rated
EVO F1 Rocket 1000 hours,
2010 SARL Rocket 100 race, average speed of 238.6 knots/274.6mph
RV4, RV7, RV10, two HRIIs and five F1 Rockets
RV14 Tail dragger
Fairlea Field
St.Thomas, Ontario Canada, CYQS
fairleafield@gmail.com
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08-23-2017, 03:13 PM
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Join Date: Nov 2005
Location: Tellico Plains, TN
Posts: 561
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I had another question about the Rod Bower system. They don't seem to show a lot of details on their web page, but in looking for info online, I could swear I've seen his system with a filter, and then later it looks like the filter was eliminated. Does his current system have a filter or not?
Thanks,
Rusty
__________________
RV-8, SN-80587, built, flown, sold.
RV-3B, SN-10751, rotary engine, built, flown, sold
RV-8, SN-82470, built, flown, sold.
RV-3B, SN-11351, purchased, , flown, sold
A&P - 2018
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08-23-2017, 03:30 PM
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Join Date: Sep 2016
Location: Scottsdale, AZ
Posts: 216
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Hey gusy don't forget Air Flow Preformance makes a alternate air "Y" with nice filter. It's honestly a pice of art work it's so nicely made. Much cheaper than than Rods system and much simpler. I agree ram air is probubly more work than it's worth and filtered air is best but if your like me and have to have ram air check out the Y from Don at Air Flow Preformance.
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08-23-2017, 03:46 PM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
Originally Posted by snopercod
I put one of these 4" O.D. K&N filters (with that rubber fitting on the left end cut off) in my ram air intake.
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John, the cone filters are relatively restrictive, as compared to the flat panel K&Ns. The pleats on the flat filters tend to be 7/8" to 1" deep, while the pleats on cone filters are quite shallow. Imagine cutting the media from the filter body and stretching it out flat. BIG difference.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
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