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robin(at)PaintTheWeb.com
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 Posted: Fri Aug 31, 2012 8:04 am Post subject: Differential Pressure Test - Results Question |
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Jason,
Just a comment on leaky baffles vs. a sealed plenum and my real world experience.
On my RV-8A we have a James Cowl plus a homemade metal plenum. We worked very hard at sealing the plenum as well as we could prior to first flight. Because it's the 4 cylinder vs. the 6 cylinder the inlet rings and outlet area were appropriate or should I say functional for the application. All temps (Oil, Cyl, EGT) were excellent and speed was notably faster than Van's posted numbers probably because I am running a BA and a new 200 Hp IO-360. So fast I could not break in the engine FWF down low.
I then decided to replace the plenum with a baffle system. To test the set up prior to finalizing everything we flew the plane w/o any RTV sealing. There were gaps where my inlet ramps transitioned to the baffle and narrow but long gaps where the lower baffle edge metal transitions to the engine case fore and aft. The only seal that was actually correct was out top rubber seal to the inside of the upper cowl.
To my surprise I have the exact same speed numbers and there were no noticeable differences in any temps. I continued to fly in this configuration for another 20 hours with basically perfect numbers. I have a hard time getting over the joy of looking at my EMS and seeing numbers that don’t scare me like on the -10.
The plane will be out of paint in the next 2 weeks (surrrre!) and it will be the first time I fly it with a completely sealed baffle system.
Not sure what to say as I was expecting to see some issues with an unsealed baffle system but that was not the case. Maybe I will see some improvement once we are sealed up but I am just as likely to attribute any difference to a freshly painted & polished plane that has been re-rigged since all the control surfaces have been removed & replaced than I am to attributing any change to the sealed baffles.
Just one (4 cylinder) data point.
Robin
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rv10flyer
Joined: 25 Aug 2009
Posts: 364
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| Posted: Fri Aug 31, 2012 8:08 am Post subject: Re: Differential Pressure Test - Results Question |
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After reading all of this, I sure am glad I went with stock. On a 90-100F day I can exceed 400F cht's if I climb out at less than 100 kias to 5000'. Oil temps peak around 205F. I usually climb at 115-120 kias to keep it all cooler. Good luck with your testing as you will probably help several.
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Wayne G. |
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jkreidler
Joined: 13 Feb 2008
Posts: 151
Location: Sheboygan Falls WI
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| Posted: Fri Aug 31, 2012 8:11 am Post subject: Re: Differential Pressure Test - Results Question |
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Yup, thanks Robin - and keep in mind the NASA report was looking at a factory install job. We all know that the factory install jobs do not pay as much attention to the little details like sealing the baffling to the engine.
I would say all speed gains from your paint can be attributed to the paint and not sealing the baffles. $10k paint job, $3 tube of RTV - the paint without question will make it faster! Enjoy, I am glad at least one of your birds isn't suffering from the heat issue.
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Jason Kreidler
4 Partner Build - Sheboygan Falls, WI
Tony Kolar, Kyle Hokel, Wayne Elser, Jason Kreidler
N44YH - Flying - #40617 |
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jkreidler
Joined: 13 Feb 2008
Posts: 151
Location: Sheboygan Falls WI
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| Posted: Fri Aug 31, 2012 8:23 am Post subject: Re: Differential Pressure Test - Results Question |
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Wayne, that seems boring! Why just build it stock and know it will work when you can add all of these gizmo's to make it 'better'. I have got to say that I was a bit disappointed when we first started flying; we had added enough $1000 upgrades that promised 3 and 10 knots that I was sure we would have the first RV-10 doing better than 300 knots! Shoot, all of that and we can just keep up with you 'standard' guys. But that chrome spinner and round inlets really make it look good, crap - maybe they meant they meant the James Cowl would make it LOOK 10 knots faster!
There is a ton to be said for building it standard, I can never fault anyone for going that way. But, since I lack the basic ingredients of a life and am cursed with the mind and personality of an engineer I sometimes actually enjoy solving these sorts of problems.
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Jason Kreidler
4 Partner Build - Sheboygan Falls, WI
Tony Kolar, Kyle Hokel, Wayne Elser, Jason Kreidler
N44YH - Flying - #40617 |
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robin(at)PaintTheWeb.com
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| Posted: Fri Aug 31, 2012 8:32 am Post subject: Differential Pressure Test - Results Question |
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The James cowl is EASILY 10 knots faster on the ramp.
I got to get back to work...
Robin
Do Not Archive
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jesse(at)saintaviation.co
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| Posted: Fri Aug 31, 2012 8:56 am Post subject: Differential Pressure Test - Results Question |
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That's a great real world experience report. I inspected a -10 in Texas that is for sale and it had the standard cowl, but had a plenum installed. That just made it a huge pain in the neck to get the top cowl off and made it hard to inspect the top of the engine. I didn't fly it long enough to check on temperatures, but I really don't see the benefit of the plenum in that setup. I told the potential buyer that if it was me, I would remove the plenum and put on baffle seals per the plans. The baffles were the standard ones, and then the plenum was installed instead of baffle seals.
One thing that has seemed to help is the louvers on the side of the cowl for getting some of the oil cooler air out. I also really like the looks of that. The problem is that in a normal climb, the standard NACA vents get warmer air because of the louvers, but in cruise it works fine.
I worked on one plane that seemed to have high oil temp, CHT's and EGT's, all with a stock setup. When I checked with the engine builder, he said to pull the top cowl after a flight and start the engine again and use a laser thermometer on the oil filter and compare it to the reading on the EIS. He said it would be very close to the same temperature. He said that if it was substantially cooler, then the EIS was reading too high. It was, so there must be something in that EIS with the voltage regulators that are reading temps higher than actual. I don't expect that this is a normal situation, but is definitely worth checking if you just absolutely can't seem to get your numbers down.
do not archive
Jesse Saint
Saint Aviation, Inc.
jesse(at)saintaviation.com
C: 352-427-0285
F: 815-377-3694
On Aug 31, 2012, at 12:03 PM, Robin Marks <robin(at)PaintTheWeb.com> wrote:
| Quote: |
Jason,
Just a comment on leaky baffles vs. a sealed plenum and my real world experience.
On my RV-8A we have a James Cowl plus a homemade metal plenum. We worked very hard at sealing the plenum as well as we could prior to first flight. Because it's the 4 cylinder vs. the 6 cylinder the inlet rings and outlet area were appropriate or should I say functional for the application. All temps (Oil, Cyl, EGT) were excellent and speed was notably faster than Van's posted numbers probably because I am running a BA and a new 200 Hp IO-360. So fast I could not break in the engine FWF down low.
I then decided to replace the plenum with a baffle system. To test the set up prior to finalizing everything we flew the plane w/o any RTV sealing. There were gaps where my inlet ramps transitioned to the baffle and narrow but long gaps where the lower baffle edge metal transitions to the engine case fore and aft. The only seal that was actually correct was out top rubber seal to the inside of the upper cowl.
To my surprise I have the exact same speed numbers and there were no noticeable differences in any temps. I continued to fly in this configuration for another 20 hours with basically perfect numbers. I have a hard time getting over the joy of looking at my EMS and seeing numbers that don’t scare me like on the -10.
The plane will be out of paint in the next 2 weeks (surrrre!) and it will be the first time I fly it with a completely sealed baffle system.
Not sure what to say as I was expecting to see some issues with an unsealed baffle system but that was not the case. Maybe I will see some improvement once we are sealed up but I am just as likely to attribute any difference to a freshly painted & polished plane that has been re-rigged since all the control surfaces have been removed & replaced than I am to attributing any change to the sealed baffles.
Just one (4 cylinder) data point.
Robin
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jkreidler
Joined: 13 Feb 2008
Posts: 151
Location: Sheboygan Falls WI
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| Posted: Fri Aug 31, 2012 10:14 am Post subject: Re: Differential Pressure Test - Results Question |
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Our plenum is held on with (9) 1/4 turn fasteners. It takes us about 30 seconds to remove.
Jason
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Jason Kreidler
4 Partner Build - Sheboygan Falls, WI
Tony Kolar, Kyle Hokel, Wayne Elser, Jason Kreidler
N44YH - Flying - #40617 |
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arplnplt(at)gmail.com
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| Posted: Sat Sep 01, 2012 5:22 am Post subject: Differential Pressure Test - Results Question |
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Give me a call about doing the test Jason.
Dave Leikam
do not archive
On Aug 31, 2012, at 9:54 AM, jkreidler wrote:
| Quote: |
Not that I know of, if someone wants to do a run let me know and we can talk about the equipment.
Jason
--------
Jason Kreidler
4 Partner Build - Sheboygan Falls, WI
Tony Kolar, Kyle Hokel, Wayne Elser, Jason Kreidler
N44YH - Flying - #40617
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=382204#382204
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