Mike Koerner Posted June 16, 2014 Report Share Posted June 16, 2014 Ed, I hope your oil line plumbing changes are successful… but I'm doubtful. John mentioned a correlation in time between flattening the prop pitch and instances of higher oil temperatures. Higher RPMs will certainly increase temperatures. As you say, the engine is producing more power. Heat generation from combustion would be at least proportional to power. Oil temperatures would be even hotter as a result of increased frictional losses with the higher surface speeds of the pistons, bearings, bushings and gears. But why didn't you notice the higher temps when you first re-pitched the prop? Was it winter? And why doesn't backing off the throttle to the previous maximum rpm, albeit with less climb performance and cruise speed with the flatter pitch, reduce the heating? How many of you with a thermal problem first noted it after flattening the prop pitch? You need to try opening the pitch back up to see what happens. Off course, this is not a solution; it’s just an attempt to better understand the problem. We need the flatter pitches, as advised by Rotax, to keep from lugging the engine and, more importantly, to get full power out of the engine so we can maximize our enjoyment of our aircraft (especially when climbing out of a field at 7,000’ surrounded by 11, 12 & 13,000’ peaks). I really doubt that the solution will come from flushing or replacing the oil cooler. Although I agree that there are probably various oil deposits (gunk) and resins on the inner surfaces of the cooler, my guess is that the heat transfer across these surfaces, from the oil to the metal, is not limiting the overall rate of heat transfer. Instead, I suspect it’s the air side of the cooler, heat transfer from metal to air, which is limiting. Heat transfer from liquids, as a result of their higher density, is enormously more effective that heat transfer to gases. Blowing shop air through the air fins backward would insure that there is no debris (bugs) blocking the passages of either the cooler or radiator… but I doubt that this is going to solve the problem either. A bigger oil cooler (or a second one in series) would certainly be an effective solution; as would moving the existing cooler off to the side of the radiator so it has its own ram air stream (though this would require a significant alteration). Within the confines of our existing LSA designs, I think a solution might be found in the photo you provided of the bottom rear edge of the cowling. The cowling extends a couple inches below the fuselage. All the air that comes in the through the coolers and through the cylinder vents has to come out this passage. In between it follows a torturous path in and around our engine components. To get more air flow through the coolers, we need more delta P (pressure drop) across them. We can't increase the pressure upstream of the radiator, which is already at stagnation pressure, but we may be able to reduce the pressure downstream of it, the back pressure it sees. The step between the cowling and the fuselage creates suction as the streamlines passing under the cowl can’t make the sudden turn. We need more suction which we should be able to achieve with a bigger gap. Prying the bottom of the cowl down further by repositioning or extending the brackets that holds the bottom 2 cowl fasteners, might accomplish this. Mike Koerner Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted June 16, 2014 Report Share Posted June 16, 2014 http://www.hotflusher.com/automotive/Jay-Leno-Hot-Flush.cfm Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted June 16, 2014 Report Share Posted June 16, 2014 I'm sending my coolers to Hot Flush in Iowa. They will overhaul it for a few hundred dollars. My cooler is over 8 years old and particles that are trapped in it can only be released at operating temperatures. There was a period where sludge in the bottom of my oil tank was keeping my oil black. Hot Flush as an aerospace company in Upland CA that would do this work but that's too far for me to drive. When my CT was new cooling capacity was fine, hopefully this will get it back. I'm not going to change the oil lines again, I agree with the thinking that if the oil flow was restricted the oil tank would empty and I would then have excess engine oil that would be obvious. Link to comment Share on other sites More sharing options...
S3flyer Posted June 16, 2014 Report Share Posted June 16, 2014 Ed -- why not just buy a new one for $250? http://www.cps-parts.com/catalog/rtxpages/912914oilradiator.php Link to comment Share on other sites More sharing options...
Tom Baker Posted June 16, 2014 Report Share Posted June 16, 2014 I'm sending my coolers to Hot Flush in Iowa. They will overhaul it for a few hundred dollars. My cooler is over 8 years old and particles that are trapped in it can only be released at operating temperatures. There was a period where sludge in the bottom of my oil tank was keeping my oil black. Hot Flush as an aerospace company in Upland CA that would do this work but that's too far for me to drive. When my CT was new cooling capacity was fine, hopefully this will get it back. I'm not going to change the oil lines again, I agree with the thinking that if the oil flow was restricted the oil tank would empty and I would then have excess engine oil that would be obvious. You will probably need to send a pair of the hose ends, so they can hook it up to the machine. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted June 16, 2014 Report Share Posted June 16, 2014 Flight Design buys the $330 Rotax part and then welds the radiator to it creating a very expensive assembly. It would now have to be cut apart, then the cps part fastened and everything approved. I bet FD would have little reason to approve it when they replacements. Too many people involved and too many potential points of failure, cps-welder-mechanic-FD-engineering. FD's price on the higher capacity cooler was $2,000. It looks easy to fabricate one, not sure how easy to get approved. If I was experimental this would be easier/cheaper. The overhaul from Hot Flush doesn't seem so bad, Jay Leno said good as new. Ed -- why not just buy a new one for $250? http://www.cps-parts.com/catalog/rtxpages/912914oilradiator.php Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted June 16, 2014 Report Share Posted June 16, 2014 You will probably need to send a pair of the hose ends, so they can hook it up to the machine. I'll ask, they only asked for inlet and outlet sizes. Link to comment Share on other sites More sharing options...
Tom Baker Posted June 16, 2014 Report Share Posted June 16, 2014 Ed -- why not just buy a new one for $250? http://www.cps-parts.com/catalog/rtxpages/912914oilradiator.php It is more than just the cost of the cooler. You would need to factor in cutting, welding, and fabrication work to install it. Knowing what is involved I think cleaning is a better option. Link to comment Share on other sites More sharing options...
Tom Baker Posted June 16, 2014 Report Share Posted June 16, 2014 Ed, I would also order 3 new shock mounts for when you re-install. They are a bit pricey, but if one breaks it might cost you even more. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted June 16, 2014 Report Share Posted June 16, 2014 Ed, did you buy that bigger radiator from fd? Wf No I didn't. Its a lot of money so Tom assumed I wanted to build my own and that idea made Dave think I was experimental and Germany never responded so just a few days ago I told Dave I'm SLSA ... winter was nice, now I need to get this fixed because it has become worse and I don't want to fly like this. Hot flush becomes interesting when you focus on just a few points Your oil cooler is a < 30 micron filter that hasn't been effectively cleaned in 7 years Oil molecules need to come in contact with as much metal as possible < 30 micron and larger particles become trapped long term in openings at that are enlarged only at operating temperatures and are trapped at normal temps and will not flush. Trapped particles and adhered materials reduce surface area available for heat transfer. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted June 16, 2014 Report Share Posted June 16, 2014 Ed, I would also order 3 new shock mounts for when you re-install. They are a bit pricey, but if one breaks it might cost you even more. Thanks Link to comment Share on other sites More sharing options...
WmInce Posted June 16, 2014 Report Share Posted June 16, 2014 . . . "There was a period where sludge in the bottom of my oil tank was keeping my oil black." . . . That sounds like lead deposit. Especially if, 100 LL was regularly used during that period. If lead deposits in the bottom of an oil tank (as I recently observed at Lockwood), then why couldn't it also leave deposits behind in the radiator? What's more, if applicable, I don't believe any current type of flushing would remove lead deposits from the radiator. For that very reason, on my next oil change, it will include a thorough tank inspection and cleaning. Link to comment Share on other sites More sharing options...
sandpiper Posted June 17, 2014 Report Share Posted June 17, 2014 Mike K. - I didn't notice the problem when I re-pitched because it was winter. I flew the entire first summer I had the plane without a problem. Problem started the second summer and I didn't associate flattening the pitch with increased temperatures because the opposite is supposed to be true. I may play with changing it back to the way the factory delivered it just to satisfy my curiosity. That way I will know for sure. Best rate of climb for my bird is 86KIAS at sea level which decreases as you climb. Even when I climb at 90 - 95KIAS I still have the overheat problem unless I also reduce throttle. That's just not the way it should be, especially in the Salem, Oregon area. I will be very interested in what happens with Ed's plane once he has done the hot flush. I really hope to see positive results for him. Why is it that Ed and I seem to be the ones with this problem? Roger has the same vintage plane, lives in the desert, and stays cool. Link to comment Share on other sites More sharing options...
Roger Lee Posted June 17, 2014 Report Share Posted June 17, 2014 Lead can deposit in the oil cooler. It can be flushed out. Other particulate can also slow the oil flow without a pressure difference. It only slows the flow, but doesn't impede it to a point of pressure problems. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted June 17, 2014 Report Share Posted June 17, 2014 Lead can deposit in the oil cooler. It can be flushed out. Other particulate can also slow the oil flow without a pressure difference. It only slows the flow, but doesn't impede it to a point of pressure problems. What was in my cooler looked like lead but I don't use Avgas. The particulate contamination is locked in place until enough heat once again enlarges the small openings, only then are they released using changes in flow direction. If it was a matter of slowing the flow I bet Tom is right and the oil tank would draw down. Instead I think the explanation is the flow remains adequate but the contaminates are in contact with metal reducing the amount of metal available to the oil for heat transfer. Link to comment Share on other sites More sharing options...
mocfly Posted June 17, 2014 Report Share Posted June 17, 2014 You may want to call Dave and ask if its ok to use the bracket assembly shown in the parts and assembly manual as an alternative to welding. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted June 17, 2014 Report Share Posted June 17, 2014 You may want to call Dave and ask if its ok to use the bracket assembly shown in the parts and assembly manual as an alternative to welding. I asked Dave about the bracket assemblies and fasteners and he asked Germany and never got a response. Link to comment Share on other sites More sharing options...
S3flyer Posted June 17, 2014 Report Share Posted June 17, 2014 I asked Dave about the bracket assemblies and fasteners and he asked Germany and never got a response. Ah, Guess I'm lucky on my non-CT installation since it's not welded in. Link to comment Share on other sites More sharing options...
Anticept Posted June 17, 2014 Report Share Posted June 17, 2014 The particulate contamination is locked in place until enough heat once again enlarges the small openings, only then are they released using changes in flow direction. If it was a matter of slowing the flow I bet Tom is right and the oil tank would draw down. Instead I think the explanation is the flow remains adequate but the contaminates are in contact with metal reducing the amount of metal available to the oil for heat transfer. Rotax uses a hot tank design. It draws oil by vacuum from the tank through the cooler; so if there is a clog, you would loose oil pressure to the engine. The level in the oil reservoir will not be affected because the cooler is before engine inlet and after the tank. The other type of oil cooler design, which is not used by Rotax or most reciprocating manufacturers (it's more of a turbine engine thing), is cold tank. The coolers are located after the scavenge outlets and before the oil tanks. Hot tank is the preferred design by recip engines because it keeps the oil in the reservoir hot and thin, making it easy to pull to the engine. You can see the oil cooler design (without a thermostat) in the 912 ULS installation manual, Section 79-00-00, page 4. I have not found an illustration of the cooling system with a thermostat yet, but how that works is now there is a direct link from the tank to the engine through the thermostat, and the thermostat acts as a shunt when the oil gets too hot, routing it through the cooler instead. The thermostat is also a safety design, it never completely shunts all the oil to only the engine or only the cooler, it just varies how much is shunted. By the way, as for the subject of sludge buildup in the cooler: I got to thinking harder on this, and now I'm leaning more towards your belief that your cooler has buildup. While thin buildup would have almost no effect on the thermal convection coefficient on each contact surface, it's the fact that it is multiplied by hundreds, maybe thousands of times, because of all the surfaces within a cooler that makes it quite significant. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted June 17, 2014 Report Share Posted June 17, 2014 Thanks, 13.3) Checking of the lubrication system To control the proper function of the lubrication system the following readings have to be taken on the running engine as part of the test/qualification procedure. ◆ NOTE: The required pressure gauges and connection parts are not included in the BRP-Powertrain engine delivery. 13.3.1) Measuring of the vacuum Measuring of vacuum in the oil suction line (1) (line from oil tank to oil pump via oil cooler) at a max. distance of 100 mm (4 in) from pump inlet (2). At take-off performance the indicated vacuum (3) must not be more than 0,3 bar (4.35 psi) otherwise the oil hose (1) could collapse and thus blocking the oil supply to the engine (Fig. 41). ▲ WARNING: The vacuum (3) must be verified over the total range of engine operation. Specially on cold oil temperature the flow resistance increases, so that not enough oil can flow on suction side. Link to comment Share on other sites More sharing options...
Tom Baker Posted June 17, 2014 Report Share Posted June 17, 2014 My thought on the restricted flow was the line from the crankcase back to the oil tank. If this line is restricted oil will build up in the crankcase and the tank level will be lower. Any other lines with reduced radiuses will cause the oil pump to work harder. Link to comment Share on other sites More sharing options...
Anticept Posted June 17, 2014 Report Share Posted June 17, 2014 The oil is never black, it gets dark amber by the time I change it. Right after the change, the oil is pretty clear on the stick, but visible after warming it up. FYI (for everyone), amber or black oil is never an indication of oil condition. The only time you should be alarmed by oil color is anything except amber, a shade of black, or dark black. My thought on the restricted flow was the line from the crankcase back to the oil tank. If this line is restricted oil will build up in the crankcase and the tank level will be lower. Any other lines with reduced radiuses will cause the oil pump to work harder. I suspect that it would blow the line right off if it couldn't push the oil out. As I understand, Rotax engines are designed so that oil in the case is scavenged by the blowby, rather than having to install scavenge pumps. Therefore, the blowby escapes through the scavenge line and into the oil tank, where the oil is swirled as it is drawn, causing the air to be spun out and ejected through the oil vent. Link to comment Share on other sites More sharing options...
Roger Lee Posted June 17, 2014 Report Share Posted June 17, 2014 Our oil flow can be restricted and not blocked. Our engine circulates 4 gpm of oil. Depending on the restriction it may or may not affect pressure. Reduced flow from either debris or a reduced radius hose can cause temps to climb over time. Oil is pulled via vacuum from the tank the oil tank through the oil cooler and into the pump then pressured out throughout the engine. As it falls down into the bottom of the crankcase the crankcase pressure pushes it back into the tank. This is one reason the vent line on the tank neck can never be blocked. This is the only breather on the engine. Debris over time including 100LL can build up in the cooler and restrict its flow. Is this what is affecting Ed's temps, I don't know, but a flush won't hurt a thing. A regular solvent like CRC carb cleaner will remove it, but needs to be injected under air pressure and should be done in reverse of the normal oil flow direction. Just as an example 2004 Ford diesel trucks, like mine has had issues with oil coolers clogging. The passages in our cooler are small. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted June 18, 2014 Report Share Posted June 18, 2014 One of the oil lines was installed cut too short and it has a deformation/reduced radius/flat spot. It has been replaced with a longer, new hose. the angle of my coolers was 40 degrees to the floor and we are able to move the bottom forward and get close to 50 degrees the oil cooler looks fine but I am sending it off for an overhaul / hot flush we are going to fabricate longer attachments for the bottom of the bottom cowling so the opening where air exits will be enlarged we are doing an oil change and going back to mobil 1 full synthetic. I bet any of these 5 steps has the potential to fix my problem yet it is likely that more than 1 or even more than 2 is needed. Doing them all together will make it impossible to see which was the issue if I get a good result. Jeremy has to drive 5 hours to get here so there is logic to addressing all issues at once. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted June 18, 2014 Author Report Share Posted June 18, 2014 One of the oil lines was installed cut too short and it has a deformation/reduced radius/flat spot. It has been replaced with a longer, new hose. the angle of my coolers was 40 degrees to the floor and we are able to move the bottom forward and get close to 50 degrees the oil cooler looks fine but I am sending it off for an overhaul / hot flush we are going to fabricate longer attachments for the bottom of the bottom cowling so the opening where air exits will be enlarged we are doing an oil change and going back to mobil 1 full synthetic. I bet any of these 5 steps has the potential to fix my problem yet it is likely that more than 1 or even more than 2 is needed. Doing them all together will make it impossible to see which was the issue if I get a good result. Jeremy has to drive 5 hours to get here so there is logic to addressing all issues at once. Good luck Ed, I know you have been struggling with this temperature issue for a while now. I've heard really good things about Jeremy, I'm sure if anybody can get you squared away he can. Link to comment Share on other sites More sharing options...
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