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paul.the.aviator(at)gmail
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 Posted: Tue Sep 08, 2009 12:21 pm Post subject: Congrats to Jeff,Cooling feedback for Bud |
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Hi Bud,
I am deep in the middle of doing cooling modifications on my Europa. I am finding that it has taken me much longer than expected, I think I started in March and I am still at it.
Rather than get into the details of what I have been doing, I'll leave that for when we get together at Rough River.
I do have a couple of questions and a request. In your note you state that the air inlet on the XS is 14 square inches. I come up with the following:
'Dog box' 4 x 7.125 = 28.5 Sq"s
'Round Inlets' 3" (2 off) = 14
"914 NACA Engine air inlet' 1.25 x 4 = 5
If I have done my maths correctly the this is a total of 47.5 square inches. Am I missing something ?
When I compare this to something like a 160hp RV6 then it doesn't seem right to me.
Would you be prepared to bring some photographs to show what you do on your exits?
I have a couple of theories on what is happening on my 914. On the ground I think that the issue is more about thermal gain from the exhaust & turbo, rather than anything to do with the oil/water radiator configurations. I decided this from talking to Erich. He told me that he can taxi around for as long as he wants without over heating when the top cowl is off. As soon he puts the top on, it over heats in 15 minutes. He lives in Nevada.
In the climb I think the 'Dog box' has stalled air in it due to the angle of attack and I get over heating. The internal shape is a miserable. It has all kinds of excuse for an expansion duct. It has all kinds of bends and sharp shapes in it.
In straight and level, I get over cooling because the radiator inlet is too big.
I'll bring photographs of what I have been doing to Rough River, its very radical.
Cheers, Paul
On Wed, Aug 19, 2009 at 6:22 PM, Bud Yerly <budyerly(at)msn.com (budyerly(at)msn.com)> wrote:
[quote] Jeff,
Glad to hear the cooling issues are relieved. Well done and thanks for passing it on.
For consumption by others and for feedback, I'd like to hear other fliers comments also.
From my shop experience:
Evans replaced by 60-40 or 50-50 is a 10 degree drop minimum. (Sorry Mr. Evans)
I Jeff's case, by moving the duct two things probably happened:
For the tri-gear, (those with the wide open area around the nose gear trunion and with the firewall moved back behind the nose gear to the added bulkhead), moving the duct down, doesn't cause as much of a difference. But the bungees/springs/hoses etc. in the back portion of the nose wheel well can restrict flow, and moving the duct down will help as it opens the two triangles on either side of the duct adding significant air exit for the heat. It also moves the hot accelerated air of the radiators lower in the duct. This heated air streaming out can cause a potential suction which may help pull air out of the cowl. (Same affect as using the exhaust venturi.)
I once did this with a cowl flap which lowered a reshaped upper metal duct ramp and and the cowl ramp bottom together and went from 12 minutes to overheat on the ground to 30 minutes to 240 F. It was capable of max continuous climb with the flap open. I now just reshape the fixed ramp dimensions for simplicity.
Finally, I have found that moving the air intakes up to near the seam and putting a plenum over the engine or perhaps adding a duct like Jeff did, forces air over the cylinders. This helps on climb out in super hot conditions, but not much affect in cruise.
Tips for those who prefer a stock install:
Sealing the front and sides of the metal duct tight to the fiberglass cowl opening is really important. A leak in this area can cause a high pressure bubble of air in the cowl under the cylinders and literally trap heat under the engine and reduce the effectiveness of the inlet air intakes. It also reduces the pressure differential across the radiator/oil cooler which is essential to the heat transfer for cooling.
The hole for the nose gear leg adds turbulence and pressure to the back side of the radiator exit. Consider a piece of silicone cowl seal slit to make cowl installation easy and close this hole up.
Open up the inlets fully. Don't leave a lip as it just restricts the flow into the cowl.
Mostly, you can lower temps 20 degrees just doing the following:
Begin by closing off the area between the sides of the oil cooler and duct.
Always lower the oil cooler as far as you can if you have a 912S or 914 (2-2.5 inches is possible but change the elbow out for a straight fitting).
I just found this leak. The area between the oil cooler and radiator is nearly a 1/2 inch and you'd be surprised how much potential cooling air goes under the radiator, up and over the oil cooler then out through the space above the oil cooler. This high pressure air degrades the radiator effectiveness as the air passes up the back of the radiator and out. Assembling the oil cooler as close to the radiator as possible, or by adding sheet metal/sealing material to reduce this exit air gap is a help. (Don't let any seal rub the cooler though.)
Finally, the seal under the oil cooler must be tight between the oil cooler and the fiberglass ramp and continue up the sides of the oil cooler.
From NACA documentation, I found it interesting that 70% of the air hitting against a radiator will build pressure and force itself out around the radiator in either free air or in a loose duct rather than go through the core. So keep it tight.
Also somewhere I found the statement that in a tightly cowled inline engine, for efficient cooling drag ratios, the ratio of air outlet to inlet should be as close to 1-1 when in cruise as possible, and 4 to one with the cowl flaps open, in climb. I can't find that reference right now. However, in the Europa, with the cowl inlet air hole area of 14 or so square inches, we need a minimum of 56 inches of exit air, just for the cowl air. But in a mono wheel, ours is two triangles either side of the duct and fiberglass ramp of about 15 to 20 inches, and if you are lucky, 13 square inches between the firewall and upper metal duct for a total of 33 inches of cowl exit air max. As you can see, this makes the air exit of the cowl nearly 1 or 2 to 1. This is OK for cruise, but a disaster for cooling in high power climbs at low speed, especially if turbo equipped. This 4-1 ratio works in my experience. To cool well in summer I try to get 100 square inches of exit air (Tri-gear) out of the cowl (Mono with fixed duct 60 square inches, cowl flap added 90). That is just for the cowl air, and does not include the duct exit for the radiator. That is a lot of glass and metal work, and seems to be worth it.
I would like the time to reshape my duct in my demonstrator to see the affect of each of the above. My demonstrator just passed airworthiness, and will fly soon, (N12AY, Classic, tri-gear, 914, fixed pitch for data reasons (LSA experimenting) then Airmaster). I am obligated to do a stock installation with just sealing the duct as above and taking data. It's not rocket science, it just takes time.
Feedback?
Again, Good Job Jeff!
See you at Rough River.
Bud Yerly
Custom Flight Creations
Europa Dealer
[b]
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budyerly(at)msn.com
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| Posted: Tue Sep 08, 2009 2:55 pm Post subject: Congrats to Jeff,Cooling feedback for Bud |
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<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]--> Paul,
I'll snap some photo's of what we've done and drag down some numbers.
For cooling air I am talking about the actual air intakes not the oil/glycol cooler openings. That is a different set of calcs but similar. The Rotax is very much air cooled. You hit the nail on the head that the turbo/muffler is one heck of a heat generator. Therefore when full turbo is selected the scant 14 inches of air to the front of the cylinders is not directed where needed and because of exit design unable to exit freely by draft and/or by force.
The 914 NACA inlet is for induction only, except for what leaks high pressure air into the lower cowl from the hole made for the filter. The NACA disturbs me because it leaks high pressure air into the engine compartment directly below the engine, blocking what air comes in from the front.
Remember the hole we all made around the front of the cowl. Without that closed off any pressure coming in the front leaks away.
The radiator we have is actually large enough to do the job, as is the oil cooler. Our problem is the duct shape and exit. At low speed the back of our coolers doesn't form enough of a draw to compensate for the low air speed coming in. We could probably use a cowl flap.
It is a tangled web we weave. And an expensive one.
Enough for now. My turbo oil seal went and now it sucks the oil out of the engine. Good news is the intake and carbs are really well lubricated now.
Talk to you soon.
Bud
[quote] ---
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air.guerner(at)orange.fr
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| Posted: Wed Sep 09, 2009 2:38 am Post subject: Congrats to Jeff,Cooling feedback for Bud |
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Hi all,
I have been following the cooling discussion with great interest as I have done my own modifications to the cowling over the years with good but not 100% satisfactory results.
As for most Rotax equipped Europas, the main issue is overheating on the ground at high ambient temperatures. Worst case is when you land, stop for 5 minutes, start the engine for another flight and have to hold for a long time due to traffic before being cleared for take off, especially if there is no wind or you cannot face into it.
An effective validation test for any cooling improvement should be: ambient temperature 30-35°C (90°F, to be adjusted depending on where you fly), no wind. After a short flight, taxi to the parking area, and run the engine at high idle (2000-2200 RPM). Note the CHT every minute. I would consider this test to be 100% satisfactory if I get the CHT STABILIZED not higher than 110°C (230°F). Up to now I have not managed to pass this test successfully at ambient temperatures above 23°C (67°F).
Could those who have done their own cooling modifications try this test and let us know the results?
Best regards
Remi Guerner
F-PGKL, Monowheel, 912S, 696 hours
[quote][b]
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air.guerner(at)orange.fr
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| Posted: Wed Sep 09, 2009 11:36 pm Post subject: Congrats to Jeff,Cooling feedback for Bud |
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Hi all,
I am resending this message to clarify the temperature units:
I have been following the cooling discussion with great interest as I
have done my own modifications to the cowling over the years with good
but not 100% satisfactory results.
As for most Rotax equipped Europas, the main issue is overheating on the
ground at high ambient temperatures. Worst case is when you land, stop
for 5 minutes, start the engine for another flight and have to hold for
a long time due to traffic before being cleared for take off, especially
if there is no wind or you cannot face into it.
An effective validation test for any cooling improvement should be:
ambient temperature 30-35 degrees Celsius (90 Fahrenheit, to be adjusted depending on where
you fly), no wind. After a short flight, taxi to the parking area, and
run the engine at high idle (2000-2200 RPM). Note the CHT every minute.
I would consider this test to be 100% satisfactory if I get the CHT
STABILIZED not higher than 110 deg C (230 F). Up to now I have not
managed to pass this test successfully at ambient temperatures above
23 deg C (67 F).
Could those who have done their own cooling modifications try this test
and let us know the results?
Best regards
Remi Guerner
F-PGKL, Monowheel, 912S, 696 hours
[quote][b]
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ami(at)mcfadyean.freeserv
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| Posted: Thu Sep 10, 2009 1:16 pm Post subject: Congrats to Jeff,Cooling feedback for Bud |
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The only comparable data that I have was as follows:
20 minute ground at between 2500 and 4000rpm, CHT stabilised at 94C, OAT 12C.
If adjusted for a 30C OAT, then CHT would be 116C.
At 2500rpm, oil temp was cooling down through 109C, or 127C adjusted to 30C.
There was a moderate wind from behind and <1 hour on the engine, so still tight.
Cooling modified thus:
Duncan McF.
[quote] ---
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jeff(at)rmmm.net
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| Posted: Fri Sep 11, 2009 7:16 am Post subject: Congrats to Jeff,Cooling feedback for Bud |
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Remi,
If or when we get another hot day I will give this a whirl and record
the numbers for all. Maybe at Rough River if it's nice.
Best,
Jeff R.
A258 - N128LJ / Gold Rush
On Sep 10, 2009, at 2:31 AM, Remi Guerner wrote:
| Quote: | Hi all,
I am resending this message to clarify the temperature units:
I have been following the cooling discussion with great interest as I
have done my own modifications to the cowling over the years with good
but not 100% satisfactory results.
As for most Rotax equipped Europas, the main issue is overheating on
the
ground at high ambient temperatures. Worst case is when you land, stop
for 5 minutes, start the engine for another flight and have to hold for
a long time due to traffic before being cleared for take off,
especially
if there is no wind or you cannot face into it.
An effective validation test for any cooling improvement should be:
ambient temperature 30-35 degrees Celsius (90 Fahrenheit, to be
adjusted depending on where
you fly), no wind. After a short flight, taxi to the parking area, and
run the engine at high idle (2000-2200 RPM). Note the CHT every minute.
I would consider this test to be 100% satisfactory if I get the CHT
STABILIZED not higher than 110 deg C (230 F). Up to now I have not
managed to pass this test successfully at ambient temperatures above
23 deg C (67 F).
Could those who have done their own cooling modifications try this test
and let us know the results?
Best regards
Remi Guerner
F-PGKL, Monowheel, 912S, 696 hours
|
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