Van's Air Force
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Oil Cooler Plenum
- Thread starter RV7Guy
- Start date
gmcjetpilot
Well Known Member
Don't use Vans Firewall oil cooler mount kit
Depending on oil cooler you should use a 4" dia SCAT**. You might get by with 3.5" dia, depending on the engine. Van's kit is 3" and is too small. You say you have a true SW oil cooler and not a clone? I am all for not using name brands and saving money when it makes sense, but when it comes to oil coolers, SW (Stewart Warner/south wind) is more efficient, fact. You get what you pay for. Making your own parts is easy and no one makes acceptable parts I have seen except LoPresti Speed merchant. I checked with them and they are not really into selling individual parts and want too much for them, but they do make nice properly sized diffusers for the oil cooler. When you say plenum I assume you mean the diffuser that the SCAT will connect to at the inlet (baffle) and exit (oil cooler). Depending on how you mount the cooler on the engine mount or firewall you may also consider some kind of oil cooler exit duct system to route hot air towards the cowl exit. This can promote flow thru the cooler but you may not need to do this. You can make the diffuser from clever sheet metal work or by making them with a foam mold and fiberglass. If you use wieldable aluminum you could weld a diffuser up. Remember you want gental angles (like a funnel), unlike Van's little square shallow sheet metal box. In my opinion anything you can do to keep the oil cooler off the vibrating baffle will help the baffle and oil cooler from structural failure, which is common.
Good Luck
**better than SCAT would be a smooth walled duct.
Depending on oil cooler you should use a 4" dia SCAT**. You might get by with 3.5" dia, depending on the engine. Van's kit is 3" and is too small. You say you have a true SW oil cooler and not a clone? I am all for not using name brands and saving money when it makes sense, but when it comes to oil coolers, SW (Stewart Warner/south wind) is more efficient, fact. You get what you pay for. Making your own parts is easy and no one makes acceptable parts I have seen except LoPresti Speed merchant. I checked with them and they are not really into selling individual parts and want too much for them, but they do make nice properly sized diffusers for the oil cooler. When you say plenum I assume you mean the diffuser that the SCAT will connect to at the inlet (baffle) and exit (oil cooler). Depending on how you mount the cooler on the engine mount or firewall you may also consider some kind of oil cooler exit duct system to route hot air towards the cowl exit. This can promote flow thru the cooler but you may not need to do this. You can make the diffuser from clever sheet metal work or by making them with a foam mold and fiberglass. If you use wieldable aluminum you could weld a diffuser up. Remember you want gental angles (like a funnel), unlike Van's little square shallow sheet metal box. In my opinion anything you can do to keep the oil cooler off the vibrating baffle will help the baffle and oil cooler from structural failure, which is common.
Good Luck
**better than SCAT would be a smooth walled duct.
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pierre smith
Well Known Member
Oil cooler duct
Hi RV7 guy,
We have a firewall mounted oil cooler on our O-360 RV6A and do not have any ducting (yet). I was advised that RVs often have a hard time even getting the temps up where they should be. It was recommended by an A+P to fly it without ducting and if needed, add it later. We haven't flown yet but will soon. A lot depends on where you live/ambient temps, etc.
Pierre Smith
Hi RV7 guy,
We have a firewall mounted oil cooler on our O-360 RV6A and do not have any ducting (yet). I was advised that RVs often have a hard time even getting the temps up where they should be. It was recommended by an A+P to fly it without ducting and if needed, add it later. We haven't flown yet but will soon. A lot depends on where you live/ambient temps, etc.
Pierre Smith
atreff
Well Known Member
Rolled my own......
Darwin,
I too remotely mounted my SW oil cooler on my RV-8. I built a plenum by mounting the cooler and the baffling. Then, I cut squares of styrofoam and placed them onto the oil cooler then shaped them with a die grinder with a sanding disk. Once I had the basic shape in the foam, I fine tuned it by taking the lumps and divits out and making sure that there was a smooth transition of airflow, no sharp bends.
Then, I covered it with a three layer layup of 9 oz glass cloth and Epoxy. Once dried, I poured gasoline into the styrofoam, and I was done.
I now have a plenum that conforms nicely to my cooler and bends where I want it to for my engine installation. A very short (3") length of scat hose connects the rear baffling wall to the intake of the oil cooler plenum.
Haven't flown it yet, but I sure like the way it looks and functions. Total time? Approx 3 hours.
Art Treff
RV-8 Finishing
Darwin,
I too remotely mounted my SW oil cooler on my RV-8. I built a plenum by mounting the cooler and the baffling. Then, I cut squares of styrofoam and placed them onto the oil cooler then shaped them with a die grinder with a sanding disk. Once I had the basic shape in the foam, I fine tuned it by taking the lumps and divits out and making sure that there was a smooth transition of airflow, no sharp bends.
Then, I covered it with a three layer layup of 9 oz glass cloth and Epoxy. Once dried, I poured gasoline into the styrofoam, and I was done.
I now have a plenum that conforms nicely to my cooler and bends where I want it to for my engine installation. A very short (3") length of scat hose connects the rear baffling wall to the intake of the oil cooler plenum.
Haven't flown it yet, but I sure like the way it looks and functions. Total time? Approx 3 hours.
Art Treff
RV-8 Finishing
RV7Guy
Well Known Member
Oil cooler plenum
Hi Everyone,
I ordered my SW oil cooler this morning from Pacific Oil coolers. The have the best prices I found $516 for the dual pass version. www.oilcoolers.com It was highly recommended by them to use a minimum of 4 inch scat tubing and 5 if I could get it.
Looks like I will mold my own with foam and cloth. Pretty simple process but I was trying to avoid it if possible.
Thanks everyone. Keep the ideas coming in.
Darwin N. Barrie
Chandler AZ
Hi Everyone,
I ordered my SW oil cooler this morning from Pacific Oil coolers. The have the best prices I found $516 for the dual pass version. www.oilcoolers.com It was highly recommended by them to use a minimum of 4 inch scat tubing and 5 if I could get it.
Looks like I will mold my own with foam and cloth. Pretty simple process but I was trying to avoid it if possible.
Thanks everyone. Keep the ideas coming in.
Darwin N. Barrie
Chandler AZ
gmcjetpilot
Well Known Member
Oil cooler set up
The last part of the equation is the exit air from the cooler. Local airflow and pressure in the cowl can interfere. Consider a small metal shield or duct to guide and shield the cooler's exit air from being impeded.
One note about SCAT. In short lengths they are not too bad, but they are not smooth. They do make a smooth ID SCAT type hose but not sure where to buy ot cost. Using solid silicon hose might be expensive. May be a combo of solid straight metal tube with short silicone hose couples like in a turbo system (or like the induction tubes on your Lycoming).
Cheers George
I guarantee you will run very hot oil temps without air routed to your cooler. Your A&P is thinking of RV-4's which run very cool for some reason. RV-6's are known to run hot. Good Luck.pierre smith said:
Nice explanation of how you made your oil cooler parts. I still think 3" is too small, but it may work OK with the short run and nice diffusers as you describe. I did a flow calc using standard engineering HVAC (heating ventilation & air conditioning) analysis. To feed a SW cooler 4" is an approx good size. Will 3" work? Sure it may work, but work may not mean work as efficently as possible. The key is the SW is a better cooler, so you are starting ahead of the game. However you are not running the cooler to it's full capacity with a 3" duct, by starving it for air (Volume or pressure differential). If 4" is good than 5" would be better? Well yes and no there is only so much air that can be stuffed thru the cooler at a given Delta-P and you are physically limited in space for a tube that size. By keeping the duct length short is key, as Art did. One way to do this is mount the cooler off the engine mount tubes and not the firewall.atreff said:I now have a plenum that conforms nicely to my cooler and bends where I want it to for my engine installation. A very short (3") length of scat hose connects the rear baffling wall to the intake of the oil cooler plenum.
Haven't flown it yet, but I sure like the way it looks and functions. Total time? Approx 3 hours.
The last part of the equation is the exit air from the cooler. Local airflow and pressure in the cowl can interfere. Consider a small metal shield or duct to guide and shield the cooler's exit air from being impeded.
One note about SCAT. In short lengths they are not too bad, but they are not smooth. They do make a smooth ID SCAT type hose but not sure where to buy ot cost. Using solid silicon hose might be expensive. May be a combo of solid straight metal tube with short silicone hose couples like in a turbo system (or like the induction tubes on your Lycoming).
I sent my used cooler off to POC for overhaul and repair and the work was very good, highly recommend them. As I said 4" good, 5" may be getting to overkill and not practical in the limited the cowl area. You can overcome a poor design by overkilling one aspect of the system, but it will cause more cooling drag. Getting low oil temps is good but not at the cost of 5 MPH. IF you want cool just bolt the cooler to the belly of the plane hanging out in the breeze. The key is volumn (4" dia) and delta pressure (good inlet and exit flow) and minimizing loss (smooth short ducts and good diffusers). The pickup on the baffle for example should have a smooth (no sharp corner) bell mouth shape. Details of the system will improve cooling with out adding lots of drag.RV7Guy said:
Cheers George
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Scat tubing diameter
I had a thought about the scat tubing, which went something like this:
Larger diameter is better, because reducing the air speed through the tube for a given mass flow rate will reduce the pressure loss in the tubing. So the larger the cross-sectional area of the tubing prior to the hard shell "plenum", the better. Given this, has anyone used 2 or more parallel runs of scat tubing, rather than just one wide tube? It seems that two 3.5 inch tubes will have the same cross sectional area as a single 5 inch tube, although they will have 41% more surface area. This might be an easy way to increase the cross-sectional area of the tubing run.
The air velocity through the tube is roughly inversely proportional to the cross-section area, and the drag on a given section of tube is roughly proportional to the square of the velocity. That would suggest that drag through the scat tubing goes down with the 4th power of diameter. I don't think it falls off quite that quickly because the surface area goes up, but it should be significant nonetheless.
I had a thought about the scat tubing, which went something like this:
Larger diameter is better, because reducing the air speed through the tube for a given mass flow rate will reduce the pressure loss in the tubing. So the larger the cross-sectional area of the tubing prior to the hard shell "plenum", the better. Given this, has anyone used 2 or more parallel runs of scat tubing, rather than just one wide tube? It seems that two 3.5 inch tubes will have the same cross sectional area as a single 5 inch tube, although they will have 41% more surface area. This might be an easy way to increase the cross-sectional area of the tubing run.
The air velocity through the tube is roughly inversely proportional to the cross-section area, and the drag on a given section of tube is roughly proportional to the square of the velocity. That would suggest that drag through the scat tubing goes down with the 4th power of diameter. I don't think it falls off quite that quickly because the surface area goes up, but it should be significant nonetheless.
gmcjetpilot
Well Known Member
May be a bigger cooler before more duct area?
Alex wrote: I had a thought about the scat tubing, which went something like this: Larger diameter is better, because reducing the air speed through the tube for a given mass flow rate will reduce the pressure loss in the tubing.
True, good idea. I think there is only so much the cooler can flow and increasing the diameter is not going to increase the delta-P with any significance, because it is determined by the system. By system I mean how much air pressure is going in the tube in the first place, which is based on the aircraft cowl, upper plenum, exit pressure and forward speed.
Alex wrote: "So the larger the cross-sectional area of the tubing prior to the hard shell "plenum", the better. Given this, has anyone used 2 or more parallel runs of scat tubing, rather than just one wide tube? It seems that two 3.5 inch tubes will have the same cross sectional area as a single 5 inch tube, although they will have 41% more surface area. This might be an easy way to increase the cross-sectional area of the tubing run."
Another good idea, but is it needed. I know the fire breathing 200HP IO-360's tend to shed more of their heat thru the oil and run high oil temps, especially in RV-8's (which I think Van addressed with a larger cowl outlet). My answer would be not only a larger duct dia but also a bigger oil cooler, really big cooler (see picture). The little coolers we run are OK on the 150-180HP, but when you get to the 200HP you may start thinking about the next size up before a bigger hose. Note the large cooler on this 200HP turbo RV. The cooler vents direct out the side of the cowl thru louvers, efficient but much more drag. (click to enlarge)
Alex wrote:"The air velocity through the tube is roughly inversely proportional to the cross-section area, and the drag on a given section of tube is roughly proportional to the square of the velocity. That would suggest that drag through the scat tubing goes down with the 4thpower of diameter. I don't think it falls off quite that quickly because the surface area goes up, but it should be significant nonetheless."
Oh great, I started everyone thinking like engineers. Again good idea, but my whole philosophy is balanced components, the right size duct based on the pressure, flow and oil cooler limitations and requirements. Going bigger with a hose will not necessary make it better. You got to get the air thru the cooler. There is only so much CFM's the oil cooler will pass for a given Delta-P and only so much BTU?s it can dissipate. The most efficient duct, hose diffuser will not help if the oil cooler is not up to the job (meaning bigger). For most of us (in order of good better best) 8406R, 10599R or 8432R are good enough. However the high compression engines (IO-360-200HP) in hot climates may need a bigger heat exchanger. I think the 10610R or 10611R are the next size up but are about 0.5-1.0 inch wider. The bigger cooler is not a lot more efficient but has the capacity to flow more air and oil, so in the case of a bigger cooler to get the advantage you need the greater air flow because they are designed to use it. I did not calculate the correct size duct for the big coolers, but it is more than the 4" for the smaller 8432R sized cooler.
Also a BIG factor is getting the delta-P up, which is hard to do, because you are dealing with the dynamic q (pressure) from the plane moving thru the air and what you can pick -up off the back of the baffle. The best way to improve source of air for the cooler (without adding drag with an external scoop) is make your two front cowl inlets better (smooth, no leaks and away from the prop hub), seal your upper plenum to be more efficient (less leaks, soft seal which are not as good as the solid top plenum) and improve the lower plenum of restrictions to promote free smooth flow out the cowl exit. The cowl exit air should enter back into the free airstream parallel with it.
That is why those aftermarket round cowls and plenums work. Sealed upper plenums with a tight seal to the round cowl inlets gives the same cooling air with less inlet area, they just have less losses. They get cleaner air away from the dirty air off the prop hub and it does not rely on soft seals and friction to seal against the cowl (one moving the other not). The idea is get the required flow with less inlet area (cooling drag), and it works. If you have cooling problems make sure the baffle seals are as good as you can get. Test by NASA of the GA fleet show cowls have leaks of 50% or more. The GA planes share the same cowl design and baffle as a stock RV uses.
There is only so much total Pressure you have to use. The only way make efficient use of what you have is with components matched in size for the environment and have min losses. Don't forget the oil cooler exit as I mentioned. Local airflow and pressures under the cowl can impede the flow out the cooler. Guide and shield the coolers exit towards the low pressure area in the cowl (exit).
Great discussion, George
Alex wrote: I had a thought about the scat tubing, which went something like this: Larger diameter is better, because reducing the air speed through the tube for a given mass flow rate will reduce the pressure loss in the tubing.
True, good idea. I think there is only so much the cooler can flow and increasing the diameter is not going to increase the delta-P with any significance, because it is determined by the system. By system I mean how much air pressure is going in the tube in the first place, which is based on the aircraft cowl, upper plenum, exit pressure and forward speed.
Alex wrote: "So the larger the cross-sectional area of the tubing prior to the hard shell "plenum", the better. Given this, has anyone used 2 or more parallel runs of scat tubing, rather than just one wide tube? It seems that two 3.5 inch tubes will have the same cross sectional area as a single 5 inch tube, although they will have 41% more surface area. This might be an easy way to increase the cross-sectional area of the tubing run."
Another good idea, but is it needed. I know the fire breathing 200HP IO-360's tend to shed more of their heat thru the oil and run high oil temps, especially in RV-8's (which I think Van addressed with a larger cowl outlet). My answer would be not only a larger duct dia but also a bigger oil cooler, really big cooler (see picture). The little coolers we run are OK on the 150-180HP, but when you get to the 200HP you may start thinking about the next size up before a bigger hose. Note the large cooler on this 200HP turbo RV. The cooler vents direct out the side of the cowl thru louvers, efficient but much more drag. (click to enlarge)
Alex wrote:"The air velocity through the tube is roughly inversely proportional to the cross-section area, and the drag on a given section of tube is roughly proportional to the square of the velocity. That would suggest that drag through the scat tubing goes down with the 4thpower of diameter. I don't think it falls off quite that quickly because the surface area goes up, but it should be significant nonetheless."
Oh great, I started everyone thinking like engineers.
Again good idea, but my whole philosophy is balanced components, the right size duct based on the pressure, flow and oil cooler limitations and requirements. Going bigger with a hose will not necessary make it better. You got to get the air thru the cooler. There is only so much CFM's the oil cooler will pass for a given Delta-P and only so much BTU?s it can dissipate. The most efficient duct, hose diffuser will not help if the oil cooler is not up to the job (meaning bigger). For most of us (in order of good better best) 8406R, 10599R or 8432R are good enough. However the high compression engines (IO-360-200HP) in hot climates may need a bigger heat exchanger. I think the 10610R or 10611R are the next size up but are about 0.5-1.0 inch wider. The bigger cooler is not a lot more efficient but has the capacity to flow more air and oil, so in the case of a bigger cooler to get the advantage you need the greater air flow because they are designed to use it. I did not calculate the correct size duct for the big coolers, but it is more than the 4" for the smaller 8432R sized cooler.Also a BIG factor is getting the delta-P up, which is hard to do, because you are dealing with the dynamic q (pressure) from the plane moving thru the air and what you can pick -up off the back of the baffle. The best way to improve source of air for the cooler (without adding drag with an external scoop) is make your two front cowl inlets better (smooth, no leaks and away from the prop hub), seal your upper plenum to be more efficient (less leaks, soft seal which are not as good as the solid top plenum) and improve the lower plenum of restrictions to promote free smooth flow out the cowl exit. The cowl exit air should enter back into the free airstream parallel with it.
That is why those aftermarket round cowls and plenums work. Sealed upper plenums with a tight seal to the round cowl inlets gives the same cooling air with less inlet area, they just have less losses. They get cleaner air away from the dirty air off the prop hub and it does not rely on soft seals and friction to seal against the cowl (one moving the other not). The idea is get the required flow with less inlet area (cooling drag), and it works. If you have cooling problems make sure the baffle seals are as good as you can get. Test by NASA of the GA fleet show cowls have leaks of 50% or more. The GA planes share the same cowl design and baffle as a stock RV uses.
There is only so much total Pressure you have to use. The only way make efficient use of what you have is with components matched in size for the environment and have min losses. Don't forget the oil cooler exit as I mentioned. Local airflow and pressures under the cowl can impede the flow out the cooler. Guide and shield the coolers exit towards the low pressure area in the cowl (exit).
Great discussion, George
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Andy Duff
Active Member
Dual Duct Oil Cooler Installation
The question of dual ducts came up earlier in this thread. The answer is, yes, it has been done. I have a firewall-mounted cooler on my O-360 powered -4 feed by dual ducts. I originally thought I would install a 3 in duct, but with how close the -4 cowl is to the top of the engine, the baffles are too short to install a 3 in hole without a significant blockage from a cylinder. Instead I used dual 2.25-inch ducts as shown below. Using a couple of small ducts also gives you more placement options. I placed the inlets toward the center of the engine baffle rather that directly behind one of the cylinders.
With where the cooler was mounted, the 90 degree turn into the cooler was abrupt. I was concerned about getting a balanced flow through the face of the cooler, so I molded a couple of turning vanes into the plenum (and offset the left and right vanes, leaving a gap at the interface to try to mix the flow a bit) This is all overkill I'm sure, but I was playing.
Just for fun, I connected the inlet ducts to an air pressure source (the leaf blower) and measured exit pressure across the bottom face of the cooler. It was roughly the same across most of the exit. Yeah, I know, there are lots of difference between the test and reality...but ...
The cooler works well on my -4, but then, as folks say, the -4 usually does not have cooling problems. I will say this though, this past winter I blocked off one of the ducts. As summer approached and the OAT climbed, I noticed that the cooler does need both ducts to get the flow needed to keep the temperatures under control.
Anyway, more food for thought.
The question of dual ducts came up earlier in this thread. The answer is, yes, it has been done. I have a firewall-mounted cooler on my O-360 powered -4 feed by dual ducts. I originally thought I would install a 3 in duct, but with how close the -4 cowl is to the top of the engine, the baffles are too short to install a 3 in hole without a significant blockage from a cylinder. Instead I used dual 2.25-inch ducts as shown below. Using a couple of small ducts also gives you more placement options. I placed the inlets toward the center of the engine baffle rather that directly behind one of the cylinders.
With where the cooler was mounted, the 90 degree turn into the cooler was abrupt. I was concerned about getting a balanced flow through the face of the cooler, so I molded a couple of turning vanes into the plenum (and offset the left and right vanes, leaving a gap at the interface to try to mix the flow a bit) This is all overkill I'm sure, but I was playing.
Just for fun, I connected the inlet ducts to an air pressure source (the leaf blower) and measured exit pressure across the bottom face of the cooler. It was roughly the same across most of the exit. Yeah, I know, there are lots of difference between the test and reality...but ...
The cooler works well on my -4, but then, as folks say, the -4 usually does not have cooling problems. I will say this though, this past winter I blocked off one of the ducts. As summer approached and the OAT climbed, I noticed that the cooler does need both ducts to get the flow needed to keep the temperatures under control.
Anyway, more food for thought.
gmcjetpilot
Well Known Member
Cool
)
If you do the math (2x2.25^2)^0.5=3.18" which means two 2.25" hoses have the same area as one 3.18" diameter hose. Perfect Very clever Andy. I think for ease of installation, if you can get by with one tube, that would be better, but your solution is elegant for your situation.
I also like the idea of not taking air away near the cylinder areas. Another option/idea is make a fiberglass snorkel that goes in the center of the rear baffle like you did. However you would have one oval/rectangular shape opening (at baffle) which than transitions to round, for the hose connection. I may do something like this on my new project, and did not think of it until I saw your design. A 4" hole is big and hard to fit in any baffle.
Thanks for the pictures. Love the wind tunnel (leaf blower) test, hey gives you some idea of the flow. Love unique ideas and solutions, nice work BTW.
Cheers George
PS Why do RV-4'S cool better than a RV-6 for example? Any one have a theory.
Wow that is very cool (no pun intendedAndy Duff said:
) If you do the math (2x2.25^2)^0.5=3.18" which means two 2.25" hoses have the same area as one 3.18" diameter hose. Perfect
Very clever Andy. I think for ease of installation, if you can get by with one tube, that would be better, but your solution is elegant for your situation. I also like the idea of not taking air away near the cylinder areas. Another option/idea is make a fiberglass snorkel that goes in the center of the rear baffle like you did. However you would have one oval/rectangular shape opening (at baffle) which than transitions to round, for the hose connection. I may do something like this on my new project, and did not think of it until I saw your design. A 4" hole is big and hard to fit in any baffle.
Thanks for the pictures. Love the wind tunnel (leaf blower) test, hey gives you some idea of the flow. Love unique ideas and solutions, nice work BTW.
Cheers George
PS Why do RV-4'S cool better than a RV-6 for example? Any one have a theory.
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Steve Sampson
Well Known Member
Has anyone used a smaller cooler
Steve, I hope I am not stealing your thread, but for those of us in frozen northern climates who worry about keeping the engine warm I wonder if anyone has experience of a smaller oil cooler.
There is a bit in RVator some years ago which mentions what I think is a Setrab http://www.bakerprecision.com/setrab.htm unit, but I have not quite dared go for it. Porsche use them I think.
Anyone had a good experience with a smaller cooler than the VANS stuff?
Steve, I hope I am not stealing your thread, but for those of us in frozen northern climates who worry about keeping the engine warm I wonder if anyone has experience of a smaller oil cooler.
There is a bit in RVator some years ago which mentions what I think is a Setrab http://www.bakerprecision.com/setrab.htm unit, but I have not quite dared go for it. Porsche use them I think.
Anyone had a good experience with a smaller cooler than the VANS stuff?
Just a data point; A remote cooler with a 5" duct on an IO-360 angle valve RV8 worked very well. Cooler plenum was glass. The cooler mounted in a plate between the upper and lower right side motor mount tubes and was attached with four rubber lined Adels. Hot air exit was toward the center of the firewall.
RV7Guy
Well Known Member
Didn't work
The remote mounted oil cooler did not work on my 7. I used 3" SCAT and it didn't cool very good. No realestate for 4" or larger. I took a day and mounted on the baffling. I've barely exceeded 200 even on the hottest AZ days.
I can't really think of a good reason to NOT mount it on the baffling.
The remote mounted oil cooler did not work on my 7. I used 3" SCAT and it didn't cool very good. No realestate for 4" or larger. I took a day and mounted on the baffling. I've barely exceeded 200 even on the hottest AZ days.
I can't really think of a good reason to NOT mount it on the baffling.
flyeyes
Well Known Member
Well, the first one that comes to mind is baffle cracks ;-) Dan Checkoway's experience seems typical (although he's documented it better than most).
I spent a lot of time researching this before I flew with my angle-valve. The consensus at the time(early 2005) was that with the big engine you needed a big cooler, and at least a 4" SCAT tube to feed it.
I have flown my airplane with OATs from 20 degrees F to 115 without any issues. Basically it runs right on the vernatherm setting year round (170 degree in the winter and 190 in the summer. Extended climbs at 105 knots will see temps pushing 220 if the OAT is over 100, but I can easily climb at best rate from SL to the mid teens without getting over 220 degrees, even in the summer.
I'm not aware of any angle-valve engines having trouble (too hot or too cold if they have the big 13-row niagara cooler, at least a 4" SCAT tube, and a functioning vernatherm.
I am open to new data though....
I can think of a real good reason for a remote mounting on a -4 -- There's no room on the baffle The area behind cyl. #4 is just big enough for a 3 inch hose flange. The other option is to lay the cooler waaay back, but now you've got the air blasting into the cooler face at a very oblique angle. I'm curious about those that had bad luck with a remote mounting, did you fab a well-transitioned diffuser or just more or less butt the tubing up against the face of the cooler?
The area behind cyl. #4 is just big enough for a 3 inch hose flange. The other option is to lay the cooler waaay back, but now you've got the air blasting into the cooler face at a very oblique angle. I'm curious about those that had bad luck with a remote mounting, did you fab a well-transitioned diffuser or just more or less butt the tubing up against the face of the cooler?
