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Where to get 4" flanges
- Thread starter RV7Guy
- Start date
Build9A
Well Known Member
try Aircraft Spruce
http://www.aircraftspruce.com/catalog/mepages/alumangle.php
Looks like they have 4X4X1/4.
http://www.aircraftspruce.com/catalog/mepages/alumangle.php
Looks like they have 4X4X1/4.
gmcjetpilot
Well Known Member
Are you talking round duct flange?
I did not think you where talking about angles. I see that Spruce only goes to 3" on the duct flanges. Hummmmm
You could make your own? In fact buy just bolting on a flange to the baffle where you cut a 4" hole is not super good. The radi on the flange is too tight. A nice 1" radius would be nice. One word: Fiberglass
You could incorporate a "bell mouth" that extends into the plenum (upper engine area) to smooth out the airflow? May be overkill but it can't hurt and will produce less drag.
Have fun, repost if you find the larger dia. Cheers George
I did not think you where talking about angles. I see that Spruce only goes to 3" on the duct flanges. Hummmmm
You could make your own? In fact buy just bolting on a flange to the baffle where you cut a 4" hole is not super good. The radi on the flange is too tight. A nice 1" radius would be nice. One word: Fiberglass
You could incorporate a "bell mouth" that extends into the plenum (upper engine area) to smooth out the airflow? May be overkill but it can't hurt and will produce less drag. Have fun, repost if you find the larger dia. Cheers George
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az_gila
Well Known Member
Wonders of Google.....:^)
Try this out....
http://www.grow-light.com/cgi-bin/store.pl?item=430
or a smaller one....
http://www.grow-light.com/cgi-bin/store.pl?item=429
Apparently the hydroponic indoor gardening folks use 4 inch and 6 inch ducting for their airflow needs.
This might do what you want if you don't like fiberglas...:^)
...gil in Tucson
Try this out....
http://www.grow-light.com/cgi-bin/store.pl?item=430
or a smaller one....
http://www.grow-light.com/cgi-bin/store.pl?item=429
Apparently the hydroponic indoor gardening folks use 4 inch and 6 inch ducting for their airflow needs.
This might do what you want if you don't like fiberglas...:^)
...gil in Tucson
OneTwoSierra
Well Known Member
before you use 4 inch...
I have an RV-9A with 160 hp with remote mounted oil cooler and my buddy has an rv6 with 180 and a remote mounted cooler and we both use 3 inch round flanged fittings and 3 inch scat tube. i see oil temps right at 200-204 in the heat of texas summers. My buddy has already build a cockpit controllable door over his to keep his temps up in the winter. 3 inches has been plenty for us.
I have an RV-9A with 160 hp with remote mounted oil cooler and my buddy has an rv6 with 180 and a remote mounted cooler and we both use 3 inch round flanged fittings and 3 inch scat tube. i see oil temps right at 200-204 in the heat of texas summers. My buddy has already build a cockpit controllable door over his to keep his temps up in the winter. 3 inches has been plenty for us.
RV7Guy
Well Known Member
4" flanges
The 4" tubing was recommended by Pacific oil coolers because of our extreme AZ heat. I'm confident 3" is adequate in most places in the US but here I'd rather have the 4" and not need it than having 3" wishing I had 4.
I'll shoot some photos when it is done.
Darwin N. Barrie
Chandler AZ
The 4" tubing was recommended by Pacific oil coolers because of our extreme AZ heat. I'm confident 3" is adequate in most places in the US but here I'd rather have the 4" and not need it than having 3" wishing I had 4.
I'll shoot some photos when it is done.
Darwin N. Barrie
Chandler AZ
gmcjetpilot
Well Known Member
CFM and LB/MIN
If you forget all the engineering the area of the oil cooler face SW 8432R is about 27 in-sq and the 4" duct is about 25 in-sq. Hummmm A 3" duct area is only about 14 in-sq. With out any rocket science you might guess the closer the area of the duct to the area of the cooler face the better. (of course I ignored the "solid" part of the cooler face, fins and passages.)
A SW 8432R can flow or use well in excess of 40 LB/MIN or 530 CFM of air. At a certain point the heat rejection will not increase as much with a significant increase in air. The SW is very efficent up to 40-50 LB/MIN. The issue is can the duct system provide this amount of air or does it need to?
It is interesting that the 4" DUCT flange above is discribed as for use with a 265 CFM blower, in a ventilation / vent Fan application. No doubt the 265 CFM is not a limit of the duct but the blower and the pressure is can provide.
The amount of flow thru out the oil cooler "system" is a function of the pressure or force to push the air thru the duct and cooler. The size or cross section of the duct and the restriction of the cooler itself will determine how much air flow you get for a given pressure.
At 175mph you have about +14 in-H2O of total pressure available. How much of this free airstream dynamic pressure (the pressure of the air from the plane's forward velocity) is available depends on the efficency of the design up to the duct or cooler in the back of the baffle. It will be less than 14 in-H2O. There is no 100% pressure recovery.
The SW 8432R has (or needs) a 10 in-H2O pressure drop to achieve a 40 LB/MIN flow (about 530 CFM). 40 LB/MIN is at the upper end of the coolers max or optimal air flow to achieve the coolers max rated cooling. (Oil flow thru the cooler is a factor but we will ignore that.)
The smaller the ducts cross section the more pressure is required to achieve the flow.
If you want to run a SW 8432R at max flow, it will be easier with a bigger duct. Can a 3" work. Well yes obvioiusly it can work. However there is only so much pressure available the way we mount our coolers (in the back of the baffle) and so 3" will flow less than 4" (no rocket science here). What is likely happening is you are limited and will not flow enough air to reach the coolers full potential, but this may be good enough for smaller engines in cooler climates. Good enough is good enough. It is like having a 5-speed transmission and only using may be 3 or 4 of the 5 gears, but some day you may want that extra gear.
The comment of +200F is very good OT in the summer for a O320, but a IO360 (200HP) would burn up with that cooler set up. Engines and OAT make a big difference. Also you really would love to see 190F if possible. Remember what ever you read on your OT gage is 25F hotter in the valve area. Any OT over say 220F-225F (real valve OT not indicated OT) is getting hot. Yes you may be over cooled in the winter but such is the life of aircooled engines. Block the oil cooler. I found I had to disconnect the the duct from the cooler and block the baffle to get OT warm enough in the winter. Also how you fly affects the OT. Some fly at heavy wts., high altitudes or climb for long periods will need more than anothers, who cruises around at 3,000MSL.
Bottom line 3" works and may be the bare min, but 4" will work better and be more efficent. If 3" works 3" works , but I would plan for hot hot temp operations. I also said before more than once buy a Stewart Warner Oil cooler. If you have a O-320 may be the others will be adiquate? Believe me I am a cheap and would buy a less expensive oil cooler if I could, but the others just don't work as well in the real world, 4" duct or not.
(Side Note: Be careful looking at vendor data and how great one cooler is over another. Some require more pressure or more flow or both to achieve the heat rejection a SW can. The venders present the data that shows their cooler rejects more heat, but they are at unrealistic flows and pressures (for a plane installation).
Cheers George
If you forget all the engineering the area of the oil cooler face SW 8432R is about 27 in-sq and the 4" duct is about 25 in-sq. Hummmm A 3" duct area is only about 14 in-sq. With out any rocket science you might guess the closer the area of the duct to the area of the cooler face the better. (of course I ignored the "solid" part of the cooler face, fins and passages.)
A SW 8432R can flow or use well in excess of 40 LB/MIN or 530 CFM of air. At a certain point the heat rejection will not increase as much with a significant increase in air. The SW is very efficent up to 40-50 LB/MIN. The issue is can the duct system provide this amount of air or does it need to?
It is interesting that the 4" DUCT flange above is discribed as for use with a 265 CFM blower, in a ventilation / vent Fan application. No doubt the 265 CFM is not a limit of the duct but the blower and the pressure is can provide.
The amount of flow thru out the oil cooler "system" is a function of the pressure or force to push the air thru the duct and cooler. The size or cross section of the duct and the restriction of the cooler itself will determine how much air flow you get for a given pressure.
At 175mph you have about +14 in-H2O of total pressure available. How much of this free airstream dynamic pressure (the pressure of the air from the plane's forward velocity) is available depends on the efficency of the design up to the duct or cooler in the back of the baffle. It will be less than 14 in-H2O. There is no 100% pressure recovery.
The SW 8432R has (or needs) a 10 in-H2O pressure drop to achieve a 40 LB/MIN flow (about 530 CFM). 40 LB/MIN is at the upper end of the coolers max or optimal air flow to achieve the coolers max rated cooling. (Oil flow thru the cooler is a factor but we will ignore that.)
The smaller the ducts cross section the more pressure is required to achieve the flow.
If you want to run a SW 8432R at max flow, it will be easier with a bigger duct. Can a 3" work. Well yes obvioiusly it can work. However there is only so much pressure available the way we mount our coolers (in the back of the baffle) and so 3" will flow less than 4" (no rocket science here). What is likely happening is you are limited and will not flow enough air to reach the coolers full potential, but this may be good enough for smaller engines in cooler climates. Good enough is good enough. It is like having a 5-speed transmission and only using may be 3 or 4 of the 5 gears, but some day you may want that extra gear.
The comment of +200F is very good OT in the summer for a O320, but a IO360 (200HP) would burn up with that cooler set up. Engines and OAT make a big difference. Also you really would love to see 190F if possible. Remember what ever you read on your OT gage is 25F hotter in the valve area. Any OT over say 220F-225F (real valve OT not indicated OT) is getting hot. Yes you may be over cooled in the winter but such is the life of aircooled engines. Block the oil cooler. I found I had to disconnect the the duct from the cooler and block the baffle to get OT warm enough in the winter. Also how you fly affects the OT. Some fly at heavy wts., high altitudes or climb for long periods will need more than anothers, who cruises around at 3,000MSL.
Bottom line 3" works and may be the bare min, but 4" will work better and be more efficent. If 3" works 3" works , but I would plan for hot hot temp operations. I also said before more than once buy a Stewart Warner Oil cooler. If you have a O-320 may be the others will be adiquate? Believe me I am a cheap and would buy a less expensive oil cooler if I could, but the others just don't work as well in the real world, 4" duct or not.
(Side Note: Be careful looking at vendor data and how great one cooler is over another. Some require more pressure or more flow or both to achieve the heat rejection a SW can. The venders present the data that shows their cooler rejects more heat, but they are at unrealistic flows and pressures (for a plane installation).
Cheers George
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A 3 inch duct will flow over 700 SCFM at 180 mph and SL, 4 inch, over 1300, suggesting that a 3 inch duct, properly routed and kept short will easily feed this heat exchanger with the required mass flow. Even with a 24 inch piece of SCAT hose feeding the cooler, you' likely have in excess of 550-600 SCFM available at the cooler. Perhaps of more concern is the delta P across the cooler, it's pretty easy within an RV cowling to have several inches of H2O back pressure at high speeds. This reduces Delta P and mass flow through the cooler. Exits are just as important as inlets.
It's interesting to note that the RV10 has less exit area per cubic inch of engine displacement than other RVs but has a series of louvers added on the bottom of the exit duct to increase exit area. Does anyone know if these were added due to insufficient cooling on the prototype during testing?
It's interesting to note that the RV10 has less exit area per cubic inch of engine displacement than other RVs but has a series of louvers added on the bottom of the exit duct to increase exit area. Does anyone know if these were added due to insufficient cooling on the prototype during testing?
gmcjetpilot
Well Known Member
Flow and Exit
As far as 3" SCAT flowing 700 CFM in an oil cooler installation in an airplane I think that is optimistic by a factor of two. It has no meaning out of context of an oil cooler installation/system.
Question how did you come up with your numbers: test or analysis?
What Reynolds Number did you use?
What delta pressure did you assume?
What Duct Roughness factor did you use?
What flow characteristics did you assume?
What velocity did you use? (it is not 180MPH)
(The velocity just inside the cowl will be 30% the external flow)
(So at 180mph flow goes right to 50mph at inlet and than less going aft)
(Air velocity at the rear baffle is near zero, like running with a paper bag)
From flight test NASA did for air-cooled engines:
From flight test you have 30%-42% less pressure from the front to the back of the baffle. To add insult the air is hotter. In a perfect world at 175MPH you would see 9.8in-H2O at the rear baffle. This is assuming you have 100% pressure recovery at the front of the cowl (not likely). From SW's specs at 9.8 in-H2O you can flow 498 CFM. Magic, right near its optimum.
The mass flow thru the (6 cyl-horz Lyc) engine used in the flight test, was 310CFM. The pressure drop across the engine was 6 in-H2O at 310CFM. The oil cooler flows 360CFM at 6 in-H2O.
WHAT DOES IT MEAN? You have just enough air volume and pressure at the back of the baffle at cruise to get the job done (max heat rejection the cooler can offer). To neck air down to a 3" tube (14 in-sq), shove it thru the rough tube and transition back to a rectangular area of 27-inch square (the face of the cooler) is abrupt, even with a good diffuser. A 4" tube has almost the same area and circumference and fits well in the coolers rectangular outline (approx 6" X 4.5"). The length is not as much the factor it is the transitions.
You might conclude a big rectangular hole in the baffle and bolting it direct would work. IT does but two big problems: Vibrations shake the hell out of it and cracks the baffle and/or cooler; The air flow in and near the rear cylinder and top of plenum/cowl make for poor air flow direction. (Remember air is flowing down between the rear cylinders and baffle, not aft.) That is why a duct smooths and directs the flow. Air aimed and aligned with the cooler fins helps. IF you MUST bolt the cooler to the baffle, make a little tunnel or plenum off set aft to give a vol of air in front of the cooler, moving it away from the rear cylinder.
Note when you climb you will have lower airspeed (dynamic pressure) and even less of the total pressure makes it to the rear baffle (poor airflow pattens in climb angles). You have 1/2 the air in a 120MPH climb than in cruise. Thats why step-climbs do wonders for the OT.
The larger 4" duct also act as a reservoir, has slower velocity and is less turbulent. This improves the entrance of air into the cooler. A smooth duct of the same size flows more than a SCAT with less loss. So if you use a 3" duct consider a smooth ID Vs. a SCAT. 3" will work, 4" will work better and get the optimal performance from a SW cooler. I understand room is tight sometimes, but I would go to the largest size I could, even a 3.5 might be a good compromise if space is limited, using a duct with a smooth ID wall.
Cheers George
Two good points, keep duct short (I like hanging the cooler off the engine mount), exit shrouds or ducting round or on the cooler exit towards a known low pressure area under cowl can improve flow.rv6ejguy said:
As far as 3" SCAT flowing 700 CFM in an oil cooler installation in an airplane I think that is optimistic by a factor of two. It has no meaning out of context of an oil cooler installation/system.
Question how did you come up with your numbers: test or analysis?
What Reynolds Number did you use?
What delta pressure did you assume?
What Duct Roughness factor did you use?
What flow characteristics did you assume?
What velocity did you use? (it is not 180MPH)
(The velocity just inside the cowl will be 30% the external flow)
(So at 180mph flow goes right to 50mph at inlet and than less going aft)
(Air velocity at the rear baffle is near zero, like running with a paper bag)
From flight test NASA did for air-cooled engines:
From flight test you have 30%-42% less pressure from the front to the back of the baffle. To add insult the air is hotter. In a perfect world at 175MPH you would see 9.8in-H2O at the rear baffle. This is assuming you have 100% pressure recovery at the front of the cowl (not likely). From SW's specs at 9.8 in-H2O you can flow 498 CFM. Magic, right near its optimum.
The mass flow thru the (6 cyl-horz Lyc) engine used in the flight test, was 310CFM. The pressure drop across the engine was 6 in-H2O at 310CFM. The oil cooler flows 360CFM at 6 in-H2O.
WHAT DOES IT MEAN? You have just enough air volume and pressure at the back of the baffle at cruise to get the job done (max heat rejection the cooler can offer). To neck air down to a 3" tube (14 in-sq), shove it thru the rough tube and transition back to a rectangular area of 27-inch square (the face of the cooler) is abrupt, even with a good diffuser. A 4" tube has almost the same area and circumference and fits well in the coolers rectangular outline (approx 6" X 4.5"). The length is not as much the factor it is the transitions.
You might conclude a big rectangular hole in the baffle and bolting it direct would work. IT does but two big problems: Vibrations shake the hell out of it and cracks the baffle and/or cooler; The air flow in and near the rear cylinder and top of plenum/cowl make for poor air flow direction. (Remember air is flowing down between the rear cylinders and baffle, not aft.) That is why a duct smooths and directs the flow. Air aimed and aligned with the cooler fins helps. IF you MUST bolt the cooler to the baffle, make a little tunnel or plenum off set aft to give a vol of air in front of the cooler, moving it away from the rear cylinder.
Note when you climb you will have lower airspeed (dynamic pressure) and even less of the total pressure makes it to the rear baffle (poor airflow pattens in climb angles). You have 1/2 the air in a 120MPH climb than in cruise. Thats why step-climbs do wonders for the OT.
The larger 4" duct also act as a reservoir, has slower velocity and is less turbulent. This improves the entrance of air into the cooler. A smooth duct of the same size flows more than a SCAT with less loss. So if you use a 3" duct consider a smooth ID Vs. a SCAT. 3" will work, 4" will work better and get the optimal performance from a SW cooler. I understand room is tight sometimes, but I would go to the largest size I could, even a 3.5 might be a good compromise if space is limited, using a duct with a smooth ID wall.
Cheers George
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Oil cooler
I used a Setrab oil cooler behind the #4 Cylinder and hung it off the baffling. I have never seen higher that 180 degrees in a high power climb when the temps were 95 degrees outside (I have a 180hp RV-6). It a alum cooler and is slim so it has a lot of clearance by the engine mounts. It is also lighter than most and will not have as much problems cracking the baffle. If you live is hot climates, I would not recommend coolers mounted on the firewall as they do not work as well as ones off the baffling. Just make sure your baffling is well seal and seal all cracks around the engine with RTV sealant. Eveyone I've ever seen out the cooler on the firewall has added more weight, long oil lines, and taken up space on the firewall and still had cooling problems to boot.
I used a Setrab oil cooler behind the #4 Cylinder and hung it off the baffling. I have never seen higher that 180 degrees in a high power climb when the temps were 95 degrees outside (I have a 180hp RV-6). It a alum cooler and is slim so it has a lot of clearance by the engine mounts. It is also lighter than most and will not have as much problems cracking the baffle. If you live is hot climates, I would not recommend coolers mounted on the firewall as they do not work as well as ones off the baffling. Just make sure your baffling is well seal and seal all cracks around the engine with RTV sealant. Eveyone I've ever seen out the cooler on the firewall has added more weight, long oil lines, and taken up space on the firewall and still had cooling problems to boot.
Oil cooler
I used a Setrab oil cooler behind the #4 Cylinder and hung it off the baffling. I have never seen higher that 180 degrees in a high power climb when the temps were 95 degrees outside (I have a 180hp RV-6). It a alum cooler and is slim so it has a lot of clearance by the engine mounts. It is also lighter than most and will not have as much problems cracking the baffle. If you live is hot climates, I would not recommend coolers mounted on the firewall as they do not work as well as ones off the baffling. Just make sure your baffling is well sealed and seal all cracks around the engine with RTV sealant. Eveyone I've ever seen mount the cooler on the firewall has added more weight, long oil lines, and taken up space on the firewall and still had cooling problems to boot.
I used a Setrab oil cooler behind the #4 Cylinder and hung it off the baffling. I have never seen higher that 180 degrees in a high power climb when the temps were 95 degrees outside (I have a 180hp RV-6). It a alum cooler and is slim so it has a lot of clearance by the engine mounts. It is also lighter than most and will not have as much problems cracking the baffle. If you live is hot climates, I would not recommend coolers mounted on the firewall as they do not work as well as ones off the baffling. Just make sure your baffling is well sealed and seal all cracks around the engine with RTV sealant. Eveyone I've ever seen mount the cooler on the firewall has added more weight, long oil lines, and taken up space on the firewall and still had cooling problems to boot.
gmcjetpilot said:
We do actual inflight measurements for pressures in ducts and cowlings. Other testing is done on our flow bench so results can be accurately quantified. The flow through the duct is calculated at 180 mph/ 264 fps. This is theoretical but what you would see with that sized hole, open ended to the airstream. Not what you would actually see in a duct with a heat exchanger stuck in it of course. There are way too many variables to accurately calculate actual losses and flow without a good CFD program, which is why we instrument the ducts and fly them
We see SCAT hose drop flow rates around 5% per foot over a smooth duct with the same cross sectional area. Remember that a 3 inch OD aluminum flange duct does not have the same cross sectional area as a 3 inch hole. Long runs of SCAT hose are not recommended. SCEET has a much lower flow loss. SCAT shows flow losses near 20% when turned sharply, which exposes the fabric folds to the airflow. Mounting the cooler to the back of the plenum box is most likely far better than running SCAT hose to another box remotely and also ensures no flow separation and 100% wetting of the cooler face. Of course in aircraft cowlings, we often cannot fit HEs (heat exchangers) where and how we'd like to. Us liquid cooled guys have it worse with all the crap in there!
I can guarantee that 310CFM will not cool an aircraft engine at cruise power. Not sure if this was a typo or I am not following you here. The way I read this was that the oil cooler was flowing more mass than the engine cooling? Engine cooling will require in the thousands of CFM.
I was thinking about your post last night and think that the 4 inch will be better bcause the worst cooling scenerio is not cruise at SL where mass flow is higher but the end of the climb at altitude and slow speed. The 3 inch will not feed the cooler with enough air per SWs specs at say 10,000 feet and 80 knots IAS. The 4 inch will certainly be better here. Only thing that helps a bit at altitude is it should be cooler and hp (heat ) is dropping off with an atmo (non turbo) engine. As George points out here, transitions, radaii and possibly guide vanes can make a tremendous difference in airflow rates through ducts and diffusers. The Van's sharp edged oil cooler boxes are almost certainly a mediocre design. No flow bench is required to know that.
George is correct: 4 inch ducting to a remote cooler will ensure that you get all the heat dissipation possible from your cooler in the hot, slow climb, where it is needed most. In cruise, not a lot of difference most likely between 3 and 4 inch on this, relatively small cooler.
RV7Guy
Well Known Member
4" flanges good info
Whoops hit the wrong key. A couple of points.
The SW8432R is a dual pass cooler. I'm not sure of any imperical evidence that this will work any better but sure sounds good.
At this point it looks like I will have about an 18" run of tubing with a bend of approximately 75 degrees. I am going to see if ACS has the SCEET type tubing in 4" for a smooth inside.
I am also going to build a low pressure ramp on the bottom of the cowl. Not sure if it will work but can't hurt either. I did this on a giant scale RC aerobatic plane with a 150cc twin cylinder motor. We don't baffle these because we can usually make a large exit hole. On this particular plane I was getting some minor overheating. I built a ramp on the exit hole opening and dropped the temps 25 degrees as measured with a laser temperature meter.
I'm confused by one of the responses that said the baffle mounted system will work better. I'm not sure why this would be true. With a remote mounted system the air is going to cool a few degrees from the baffled area while in the tube. Additionally, the remote mounting most likely benefits from some free air flow within the cowl. With a baffle mounted cooler you have very hot air going through a very hot cooler with very hot oil.
Just my thoughts. Thanks for the great discussion.
Darwin N. Barrie
P19
Whoops hit the wrong key. A couple of points.
The SW8432R is a dual pass cooler. I'm not sure of any imperical evidence that this will work any better but sure sounds good.
At this point it looks like I will have about an 18" run of tubing with a bend of approximately 75 degrees. I am going to see if ACS has the SCEET type tubing in 4" for a smooth inside.
I am also going to build a low pressure ramp on the bottom of the cowl. Not sure if it will work but can't hurt either. I did this on a giant scale RC aerobatic plane with a 150cc twin cylinder motor. We don't baffle these because we can usually make a large exit hole. On this particular plane I was getting some minor overheating. I built a ramp on the exit hole opening and dropped the temps 25 degrees as measured with a laser temperature meter.
I'm confused by one of the responses that said the baffle mounted system will work better. I'm not sure why this would be true. With a remote mounted system the air is going to cool a few degrees from the baffled area while in the tube. Additionally, the remote mounting most likely benefits from some free air flow within the cowl. With a baffle mounted cooler you have very hot air going through a very hot cooler with very hot oil.
Just my thoughts. Thanks for the great discussion.
Darwin N. Barrie
P19
I think with most Lyc coolers mounted at the end of the rear baffle or plenum up top, you would be getting cool air but have to possibly watch the directional change down through the cooling fins just prior. Hard to say exactly what the airflow looks like here without a smoke test or multiple pressure probes. For sure, taking cooler air off the baffles somewhere where it has already touched hot cooling fins would be very bad- you absolutely must get ambient air to the cooler face.
The point I was making was that for general efficiency, having the whole core face exposed to the airflow is better than most remote, hose fed plenums. That being said, with careful thought and construction, you can design something that is pretty good. With no throught, you can design something pretty poor.
Basically wet the whole face with ambient air, get the lowest pressure drop through your plumbing with gentle, large diameter bends and exit the cooler into a lower pressure zone for best cooling.
The point I was making was that for general efficiency, having the whole core face exposed to the airflow is better than most remote, hose fed plenums. That being said, with careful thought and construction, you can design something that is pretty good. With no throught, you can design something pretty poor.
Basically wet the whole face with ambient air, get the lowest pressure drop through your plumbing with gentle, large diameter bends and exit the cooler into a lower pressure zone for best cooling.
Cooling Oil
I would agree with the guy on the baffle mounted system. The direct shot of air from the front of the engine is going to have more pressure and less heat. My oil cooler is mounted about 3/4 of the way above the fins on the back cylinder. With the velocity of the air going 180mph, I would guess there is almost no heat transfer from the top of the cylinder fins to raise the temps before it goes through the cooler. Also the air passes straight through the cooler, where as on most remote mounted cooler there is some compromise of air passage through the cooler. You have to factor in line loss, angles and flow designing these systems and that is why you don't see too many coolers mounted on the fire wall. Look at most of the 520 powered Cessnas. The cooler is mounted in front of the cylinders. This is a great spot but doesn't look great. Most coolers mounted remotely have some problems and are jsut too much work with little to no improvment in cooling performance. I'm the third guy to use these Setrab coolers in my area and when we get into debates on cooling I've had guys tell me that my temps are reading wrong. Well I doubt that three seperate airplanes all with different instrument systems are reading wrong with the same numbers. 185 degrees on a hot day, period, all day long. I've never ever had to power back because I was getting to hot and my cylinder temps stay at 300 no matter what I do. I just can't see the logic in adding more weight, making more alterations in the cowling, running longer lines, moving other stuff around to provide room for a remote mounted cooler. But some people just like to tinker.
I would agree with the guy on the baffle mounted system. The direct shot of air from the front of the engine is going to have more pressure and less heat. My oil cooler is mounted about 3/4 of the way above the fins on the back cylinder. With the velocity of the air going 180mph, I would guess there is almost no heat transfer from the top of the cylinder fins to raise the temps before it goes through the cooler. Also the air passes straight through the cooler, where as on most remote mounted cooler there is some compromise of air passage through the cooler. You have to factor in line loss, angles and flow designing these systems and that is why you don't see too many coolers mounted on the fire wall. Look at most of the 520 powered Cessnas. The cooler is mounted in front of the cylinders. This is a great spot but doesn't look great. Most coolers mounted remotely have some problems and are jsut too much work with little to no improvment in cooling performance. I'm the third guy to use these Setrab coolers in my area and when we get into debates on cooling I've had guys tell me that my temps are reading wrong. Well I doubt that three seperate airplanes all with different instrument systems are reading wrong with the same numbers. 185 degrees on a hot day, period, all day long. I've never ever had to power back because I was getting to hot and my cylinder temps stay at 300 no matter what I do. I just can't see the logic in adding more weight, making more alterations in the cowling, running longer lines, moving other stuff around to provide room for a remote mounted cooler. But some people just like to tinker.
gmcjetpilot
Well Known Member
Math error
I guess 310 CFM should be more like 3100 CFM. Conversion error on my part from 2.0-2.5 kg/sec to cubic feet/min. I guess my conversion was off. It looks like 3600-4800 CFM to cooling airflow is need for a 4 cyl engine. Since the test was for a 6-cylinder engine I took 2/3rds for a 4 cyl. I know there are formulas for cooling per HP, but don't recall the source. Georgerv6ejguy said:
