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A Little Eggenfellner History

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Low power/displacement doesn't typically lend itself to low BSFC

Not really true...an engine is most efficient at its TORQUE peak, not its hp peak.

The large displacement engines are strickly optimised for a very narrow RPM band and are actually very efficient in the 2300-2700 rpm operation because they are at or near the torque peak or point of highest volumetric efficiency.

As to the draq issue...

The issues is that if you have 1000 calories of heat to disipate, it takes less air to do it when the difference between the air and the hot surface is greater...that is, heat transfer increases as a function of delta t. So 60 degree air over a 380 degree cylinder can remove more thermal energy with less air, than can 60 degree air across a 190 degree radiator. The other issue is that heat transfer is never 100% efficient and the more you do the more excess energy must be displaced...so in a water cooled package the heat must transfer from the aluminum engine to the water, then from the water to the aluminum radiator, then from the aluminum radiator to the air.It just takes more air. When a plane is specifically designed around the ducting, improvements can be made, and very successfully, but it is a design from the start approach.

I would encourage you to evaluate installed performance...because the installation as a whole matters.

As to lycoming reliability....everyone can throw out an example of a failure, but the fleet soldiers on with the vast majority trouble free.

What? Maybe I missed something in my Thermodynamics class! George, do you have an explanantion for this? Or John do you want to explain a little more? As far as I can see a liquid cooled engine is far superior than air cooled engine when it comes to cooling. The down side of liquid cooling is the added weight. There is no reason why you can't limit airflow in flight through cowl flaps.
 
Maybe I missed something in my Thermodynamics class

You missed the direct function of Delta T.

The water does not cool, it transports heat to a place where the air can cool.

Ross, fallacy again, compute the catastrophic failures as a function of hours flown....
 
Maybe I missed something in my Thermodynamics class

You missed the direct function of Delta T.
The water does not cool, it transports heat to a place where the air can cool.

Ross, fallacy again, compute the catastrophic failures as a function of hours flown....

There is a lot more than delta t. There is the efficiency of the airflow, the amount of area exposed to the airflow,mass of the objects and thermal characteristics of the objects are among some of the items to consider when it comes to the cooling. Just to say because delta t is bigger therefore my engine is going to cool quicker with less air is a false statement.
 
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Maybe I missed something in my Thermodynamics class

You missed the direct function of Delta T.

The water does not cool, it transports heat to a place where the air can cool.

Ross, fallacy again, compute the catastrophic failures as a function of hours flown....

Negative. As I've explained numerous times, there are many factors involved in heat dissipation. Delta T is only one factor. Nobody has proven either case in using opposed engines, equally cowled on identical airframes. We have only seen proof that water cooled V engine installations have less drag than air cooled radial installations. Search the posts for the examples I gave last year.

Check your math. 0 out of 23 is still 0 no matter how many hours are flown. 72 out of say 1 million or 3 million hours is more than 0.
 
Todd, the cylinders are aluminum, the air is air, the rads are aluminum, so the coefficients are constant. Given that, and given a similar quantity of heat to dissipate, at lower Delta T it takes a higher quantity of air.

Of course if you could design a ducting system which was enough better to make up for all of it, you would have an overall system which was better. However, such a design has been elusive for decades now. In all probability Ross's 10 will be a good test of a dedicated duct design approach.

In the end, you may get to laugh last here....when your plane is weighed and flown, we will easily be able to tell the drag/power/fuel issue.

But, pumping water through an engine, and then into a radiator does not magically change the quatity of air required to dissipate a given quantity of heat, nor does it magically reduced the amount of heat there is to dissipate.


For Subaru, we find 23 in the same period and zero internal catastrophic failures. All these failures were due to supporting systems and poor maintenance- very similar to the majority of certified engine failures. The point here is that there were no core failures.

First, when the supercharger blows the engine up, is that a core failure? When an overheated sub went down with cooked rods, was it core?

Second, if all the ancilliaries are critical to keeping the prop spinning, and it stops doing so, does it really matter? Ross, did you crash any less, because the core was still good. David, did you?

Third, 23 power failures out of a fleet of 500 or less flying versus 75 failures in all GA using recip engines...how is this a sobering statistic about the choice of a certified engine? You should also add yours to the number Ross, because as you know, the NTSB database does not include yours or any of the other Canadian crashes, although my fleet number of 500 does include all of North America, and is probably generous, at that.

I had previously posted general MTBF numbers, which you did not respond to, I will say that the very istant the fleet generates a MTBF in terms of flight hours which is half of the "sobering" failures statistics of the traditional piston recip, I might try it.
 
The Professor is on Sabbatical

What? Maybe I missed something in my Thermodynamics class! George, do you have an explanation for this?
No I don't want to explain anything else; in fact I'll refrain from commenting on this thread ever again, nothing personal. I'm getting death threats. ha ha :D just kidding, but all the best in quest for knowledge, the professor is out.

And Ross pulling statistics out of context or explanation? Hummm the time it took me to write this, Lycs & TCM's probably gained another 1000 hours of world wide reliable fleet service time. (Not to mention the 1000's of radials still in service for 65 years, earning a living. Impressive.) This is suppose to be fun and it has stopped to being fun. (nice) PM's & emails gladly accepted if you want to chat. Switching freq to fun. :p

PS: NACA has many papers circa 20's thru 50's on the subject of air and water engine cooling; Also read the often mentioned, "An Experimental Investigation of the Aerodynamics and Cooling of a Horizontally-Opposed Air-Cooled Aircraft Engine Installation", Stan J. Miley, Ernest J., Cross, Jr., John K. Owens, Mississippi State University, Texas A&M University. Everything about the cooling fins on a Lyc/TCM has been optimized, spacing & height to best utilize pressures & flows in a piston aircraft. Have fun learning, that's what it's all about.

Water cooling has the "potential" to extract more heat, more uniformly while simultaneously muffling the mechanical clacking of the engine. Air cooling is sufficient in an Air plane. There are thermal limits air cooled piston engines must observe, e.g., oil & cylinder-head temp mostly. The "work load" to achive this is not difficult, but does require pilot action, sometimes cowl flaps or lowering the nose of more airspeed. Theorically water cooling is "better" from a shock cooling stand point because you have thermal mass (water) and a valve (thermostat). This would be ideal for a Jump plane or glider tow plane. However one must look at the total package, and it comes at the cost of weight & cooling drag. The P-51 was not perfect cooling wise. All this has been tried before. Water cooling, in a modern high quality car is outstanding. I can't remember my last steam geyser spewing around the hood. However any hard core adapter of auto engines will tell you water cooling in a plane can pose special issues like air pockets, steam pockets and cavitation due to the nature of airplane attitudes and g forces. Also a water pump takes HP. Thousands of choices and compromises are made in a design; One path produced the Lyc and TCM engines, which are optimized for the GA plane mission. Water cooling was considered and tested, but at the pinnacle of all piston plane engines, all where air cooled for good reasons, Pros and Cons. It does not make water cooling BAD or not another solution, which I said was better, but engineering designs don't take place in a vacuum. The big challenge with a RV's front tractor engine and small frontal area fuselage, is it doesn't allow much room for engine, prop AND remote heat exchanger (aka radiator). Combining the heat exchanger (fins) and the engine itself makes sense (aka air cooled). This is all supplemented with sodium filled valves and an oil cooler, (aka liquid cooled). There's a big reason for large oil drain lines from the heads to the sump on a Lyc. I hope the anti-Lyc people can see the genius in the desgin, even if they are Alt. engine enthusiast. Those engineers now retired or passed on may have had slide rulers and no "electronics", but they where darn smart. There's nothing haphazard or accidental about every choice made on these engines, just as any engine you would hope. Out of respect to those engineers, I say WELL DONE GENTS AND THANK YOU. First aircraft engine water cooled.
 
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and given a similar quantity of heat to dissipate, at lower Delta T it takes a higher quantity of air...

True, but doesn't the higher delta T also involve far higher (2-3 times) the head temperatures? High head temperatures with all the negatives involved, IS the crux of the argument isn't it, with weight issues an important secondary concern?

I agree completely that water cooling can be less efficient in some applications, but water cooled systems also provides higher cooling capacities and lower head temps as engines become more powerful, where equivalent powered cooling fin size and weight become excessive in air cooled apps.

By the way, the real issue is the drag, or friction, of the air doing the actual cooling... the "quantity" of cooling air is a function of volume, temperature, and pressure. Air cooled engines use fast moving, high pressure air flows that collide with flat surfaces; water cooled systems generally work better with lower pressure, slow moving air flows that are modified by appropriate ducting and diffusers. The actual exposed scoop area (and air quantities?) are often about the same (we mostly use the same cowls). Where smaller, thick radiator cores are used, Id expect about the same drag as air cooled engines; with larger thin radiators, Id expect the system drag to be a bit lower.
 
Todd, the cylinders are aluminum, the air is air, the rads are aluminum, so the coefficients are constant. Given that, and given a similar quantity of heat to dissipate, at lower Delta T it takes a higher quantity of air.
Of course if you could design a ducting system which was enough better to make up for all of it, you would have an overall system which was better. However, such a design has been elusive for decades now. In all probability Ross's 10 will be a good test of a dedicated duct design approach.

In the end, you may get to laugh last here....when your plane is weighed and flown, we will easily be able to tell the drag/power/fuel issue.

But, pumping water through an engine, and then into a radiator does not magically change the quantity of air required to dissipate a given quantity of heat, nor does it magically reduced the amount of heat there is to dissipate.For Subaru, we find 23 in the same period and zero internal catastrophic failures. All these failures were due to supporting systems and poor maintenance- very similar to the majority of certified engine failures. The point here is that there were no core failures.

First, when the supercharger blows the engine up, is that a core failure? When an overheated sub went down with cooked rods, was it core?

Second, if all the ancillaries are critical to keeping the prop spinning, and it stops doing so, does it really matter? Ross, did you crash any less, because the core was still good. David, did you?

Third, 23 power failures out of a fleet of 500 or less flying versus 75 failures in all GA using recipe engines...how is this a sobering statistic about the choice of a certified engine? You should also add yours to the number Ross, because as you know, the NTSB database does not include yours or any of the other Canadian crashes, although my fleet number of 500 does include all of North America, and is probably generous, at that.

I had previously posted general MTBF numbers, which you did not respond to, I will say that the very instant the fleet generates a MTBF in terms of flight hours which is half of the "sobering" failures statistics of the traditional piston recipe, I might try it.

These two statements contradict each other. The delta t is probably the same for both engines the only difference is the mechanism to remove this heat. The liquid cooled engine engulfs the cylinder and removes the heat directly from the area around the cylinder where as the air cooled engine dissipates the heat through the fins. My guess is that the cylinder head temps are similar in both engines and the outside air is constant in the "test" environment therefore you delta t is similar. Where a radiator excels is in its exposed surface area which will help extract more heat energy out of the engine or cooling out of the air.

I have no doubt mind you that my plane will probably be the heaviest RV-10 out there. Not just because of the engine. I probably have 40 tubes of sealant on my plane. Every two pieces of metal have sealant between them. Every piece is primed. I have two batteries and an air conditioning system. I believe the Sub(the original purpose of this thread) system will be a lot lighter than mine. But there will probably be nothing(RV-10 wise) out there that will be able to out climb mine. Notice I don't say fastest because anybody is foolish to go faster than Van's posted numbers for Vne.
 
Todd, the cylinders are aluminum, the air is air, the rads are aluminum, so the coefficients are constant. Given that, and given a similar quantity of heat to dissipate, at lower Delta T it takes a higher quantity of air.

Of course if you could design a ducting system which was enough better to make up for all of it, you would have an overall system which was better. However, such a design has been elusive for decades now. In all probability Ross's 10 will be a good test of a dedicated duct design approach.

In the end, you may get to laugh last here....when your plane is weighed and flown, we will easily be able to tell the drag/power/fuel issue.

But, pumping water through an engine, and then into a radiator does not magically change the quatity of air required to dissipate a given quantity of heat, nor does it magically reduced the amount of heat there is to dissipate.

For Subaru, we find 23 in the same period and zero internal catastrophic failures. All these failures were due to supporting systems and poor maintenance- very similar to the majority of certified engine failures. The point here is that there were no core failures.

First, when the supercharger blows the engine up, is that a core failure? When an overheated sub went down with cooked rods, was it core?

Second, if all the ancilliaries are critical to keeping the prop spinning, and it stops doing so, does it really matter? Ross, did you crash any less, because the core was still good. David, did you?

Third, 23 power failures out of a fleet of 500 or less flying versus 75 failures in all GA using recip engines...how is this a sobering statistic about the choice of a certified engine? You should also add yours to the number Ross, because as you know, the NTSB database does not include yours or any of the other Canadian crashes, although my fleet number of 500 does include all of North America, and is probably generous, at that.

I had previously posted general MTBF numbers, which you did not respond to, I will say that the very istant the fleet generates a MTBF in terms of flight hours which is half of the "sobering" failures statistics of the traditional piston recip, I might try it.

For a given mass flow, the rate of heat transfer is not only dependent on Delta T but the surface area, turbulence within the boundary layer next to the fins, turbulence within the tube (radiator), the amount of time the air is in contact with the fins (which we can adjust with duct shape and exit aperture) and temperature gradient.

Drag is a result of pressure drop across the system. Coincidentally, I was actually running some flow bench tests on different radiator cores today for a magazine article and I'll add to this some data for air flowing around a typical air cooled cylinder. My hunch is that the cylinder will offer much higher pressure drop than a rad core even with no diffuser, but I'll wait for the scientific confirmation on this one. Any time you turn air sharply, you have a pressure drop. Air goes straight through a rad but turns 180 degrees in most air cooled setups.

Duct shapes have been well understood for decades just not applied on civilian aircraft for the most part. Reg Clarke in particular has done some fine work with belly mounted diffusion ducts on his turbo Sube Dragonfly showing how little air and how little rad is required to cool an engine if done correctly.

Core means just that, engine core. I was trying to be fair to the certified engines as well by not counting external parts like mags, carbs etc. or pilots operating the engine with no oil. The 72 I came up with were 90% rod failures and crank failures, unrelated to oil starvation or improper maintenance.

Nobody is debating that ancillary systems are important to keep engines running, more so in the case of auto engines but if you wish to count non core failures bringing down certified engines, then the figure is about quadruple with magneto, carb and carb icing thrown in as reasons the prop stopped turning. For the 5 year period, the following search strings are related with numbers of accidents (connecting rod 143, power loss 195, engine failure 278, carb ice 141). Clearly while there are tens of thousands of piston powered aircraft flying in the US accumulating hundreds of thousands of flight hours, there have been at least 278 accidents caused from engine failure in the last 5 years.

There have been over 650 RAF gyros sold, nearly 200 Groen Gyros sold and there are several other designs out there, most of which are Subaru powered. Add to this all the NSI, Eggenfellner and private Subaru powered creations and we have closer to 750-1000 probably flying today. There were only 16 actual power loss conditions (out of the 23 total Subaru accidents) and several of these were undetermined for reason.

I don't think either stat is particularly comforting. I would say that given the numbers of the two engine types flying, you do appear to have a higher likelihood of a power loss condition with a Subaru than a Lyconental but a much lower likelihood of a core engine failure. (not that that matters when it happens to you!)

There are no accurate MTBF stats for either engine type. Should anyone wish to compile this information somehow, it would prove very interesting.

My original point of the exercise was to was to counter the notion that turning Subarus at 4000-5000 rpm was in some way detrimental to the engine. Can't find a single case here to support that idea. The bulletproof term may be more deserved by the Subaru than Lycomings and Continentals.

I think much has been learned and applied in the last 5 years to make auto conversions more reliable overall, backup batteries, standardized fuel systems, better PSRUs. The biggest problem I see that may forever remain is poor wiring practices and electrical design. This is very critical with EFI/ EI and electric fuel pumps.
 
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Please Close This Thread!

I find this thread so drifted that there is NO reason to keep it open. First this is labled "A Little Eggenfellner History." All the air vs. water-cooled arguements simply DO NOT BELONG HERE. The attitudes of some of the posters borders on juvenile.
Eggenfellner is providing one of the best FWF conversions available to the market right now. The systems have not been TOTALLY trouble free, but reguardless of performance claims or engine leanings the Egg systems are working well, and the updates that some complain about are MAKING THE SYSTEMS SAFER, so what is the problem? This is a retorical question by the way, I really don't want to hear your answer. We should start a proper air and water cooled thread for the people actually interested in the subject. The back and forth of the arguements here bear no relevance to the previously mentioned conversions. LETS MAKE THIS SIMPLE for everybody OK?
Subarus aren't perfect. Lycomings aren't perfect. Contentals aren't perfect. Chevrolets aren't perfect. Anyone noticing a trend here? I'm starting a AC vs. WC thead. BFN
Bill Jepson
 
Great idea Bill- Id like to see more emphasis on technology design aspects vs opinions in your new thread...
 
Eggenfellner

2008 engines are better than 2007 engines. 2007 are better than the previous years engines, and so on. This is the only thing that matters to us and all profits go to this. In addition, even though engines, sold 16 years ago, have changed significantly, the much improved parts made for the 2008 engines will fit. We continue to fine tune the process and to sell the best conversions we know how. I still don't have money for a house though. Maybe with some more history, I will :)

Jan Eggenfellner
 
No Easy Task

2008 engines are better than 2007 engines. 2007 are better than the previous years engines, and so on. This is the only thing that matters to us and all profits go to this. In addition, even though engines, sold 16 years ago, have changed significantly, the much improved parts made for the 2008 engines will fit. We continue to fine tune the process and to sell the best conversions we know how. I still don't have money for a house though. Maybe with some more history, I will :)

Jan Eggenfellner

Jan,
As someone who has built and provided a complete product to the public I can really appreciate how difficult your task can be. I think you are doing a good job and providing a solid product to people that can't do it themselves. I'm not a customer, and since I'm building a rotary powered RV-10 I won't be one, but I believe you are providing a excellent service. It is always easy to be an armchair engineer and second guess someone elses work. Putting anything together that has more than 10 parts can be an incredible hassle. I've seen 2 of your packages up close and personal. One a six cylinder and one four in an RV-9 both flying well and the owners happy. With all the sniping that goes on on these forums I figure that some positive feedback couldn't hurt!
Bill Jepson
 
Well, after 17 pages, I think it is time to end this. Actually, I thought it had died from lack of interest.

Even though the last couple of posts are sorta back on track, the thread has gotten so far off from the original post it isnt even recognizable anymore.
 
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