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  #1  
Old 05-22-2008, 09:02 AM
leeschaumberg's Avatar
leeschaumberg leeschaumberg is offline
 
Join Date: Apr 2005
Location: Northern Wisconsin
Posts: 131
Post Lycoming vs Alternative Engine

Vans recomends the Lycoming 320 & 360 engines because they work so well. This is an undisputed and true fact. The knowledegable knows you can break any thing when every thing is done right. The two main piston aircraft builders are working on the next generation of piston aircraft engines. The flat four engine is the choice for these two. A low fuel consumption is very desireable. The use of petroleum for fuel will be obsolete in the near future. The alternative is a fuel made from plant oil. So considering this the ideal engine would be a flat four, same weight and size of the Lycoming, and capable of burning plant oil for fuel.
Lee
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  #2  
Old 06-16-2008, 07:24 AM
cujet cujet is offline
 
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Location: West Palm Beach, Florida
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Quote:
Originally Posted by leeschaumberg View Post
The alternative is a fuel made from plant oil. So considering this the ideal engine would be a flat four, same weight and size of the Lycoming, and capable of burning plant oil for fuel.
Lee
I would suggest that the opposed 6 cylinder direct drive diesel, of similar HP/displacement as your above 4cyl, is a better choice for prop resonance and crankshaft torsional issues. Including the all important seat of the pants "feel" of vibration issues.

I have 2 Volkswagen diesel cars. Both have serious vibration issues. Yes, the engine mounts hide the vibes. But, the vibes are still there.

I had always wanted to convert a 6 cylinder lycoming 540 to a diesel engine. My thoughts were to produce a water cooled, 4 valve cylinder assy (3 integral cylinders) with much less bore diameter than the Lyc. It would bolt right on. The 2 mags would be replaced with 2 injection pumps. Each cylinder would have 2 injectors.

To the bottom of each "triple cyl" assy would directly mount a small turbo, this would place it high enough to drain into the sump without a scavange pump.

The twin turbo, 400 cubic inch, 6 cylinder diesel engine would produce about 250HP at 2500RPM and maintain that HP up to a fairly high altitude. Giving excellent cruise performance and economy.
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  #3  
Old 06-16-2008, 07:44 AM
rtry9a rtry9a is offline
 
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Location: Bountiful, Utah
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I think your basic assumptions are faulty ...

Why pistons at all- they result in vibration and unneeded internal stress compared to other alternatives?

Why diesel? It requires a lot of engine weight to withstand the torque reversals, it is polluting (dirty burning under high loads, and it is significantly more expensive than avgas and mogas.
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  #4  
Old 06-16-2008, 10:27 AM
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John Clark John Clark is offline
 
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Location: Santa Barbara, CA
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Default Assumptions

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Originally Posted by rtry9a View Post
I think your basic assumptions are faulty ...

Why pistons at all- they result in vibration and unneeded internal stress compared to other alternatives?

Why diesel? It requires a lot of engine weight to withstand the torque reversals, it is polluting (dirty burning under high loads, and it is significantly more expensive than avgas and mogas.
I think you missed Lee's point. The assumption he is making, and I agree, is that there might not be any avgas or mogas to use in the future. The diesel will run on a variety of fuels including Jet-A (which will be around longer than Avgas due to economic realities) or vegetable products.

John Clark
RV8 N18U "Sunshine"
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  #5  
Old 06-16-2008, 10:42 AM
cujet cujet is offline
 
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Quote:
Originally Posted by rtry9a View Post
I think your basic assumptions are faulty ...

Why pistons at all- they result in vibration and unneeded internal stress compared to other alternatives?

Why diesel? It requires a lot of engine weight to withstand the torque reversals, it is polluting (dirty burning under high loads, and it is significantly more expensive than avgas and mogas.
OK, I see your point. I wish you all the best luck with your engine design. One day, someone (it could be you!) will come out with a great solution. I am old school, and my thinking clearly shows that.

However, in today's environment, fuel economy is quite important. It is kind of hard to beat the BSFC of a diesel, not to mention the MPG. Remember that diesel/jet fuel has more energy per gallon and diesel engines have better BSFC per pound. That is a double positive.
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  #6  
Old 06-16-2008, 10:48 AM
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Mike S Mike S is offline
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Quote:
Originally Posted by cujet View Post
I had always wanted to convert a 6 cylinder lycoming 540 to a diesel engine. My thoughts were to produce a water cooled, 4 valve cylinder assy (3 integral cylinders) with much less bore diameter than the Lyc. It would bolt right on. The 2 mags would be replaced with 2 injection pumps. Each cylinder would have 2 injectors.

To the bottom of each "triple cyl" assy would directly mount a small turbo, this would place it high enough to drain into the sump without a scavenge pump.
Good thinking, I like it.

Not too sure if water cooling is needed------lots of air cooled diesels currently in existence for a variety of uses.

My biggest concern would be the strength of the remaining Lyc parts.
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  #7  
Old 06-16-2008, 10:59 AM
cujet cujet is offline
 
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Quote:
Originally Posted by Mike S View Post
Good thinking, I like it.

Not too sure if water cooling is needed------lots of air cooled diesels currently in existence for a variety of uses.

My biggest concern would be the strength of the remaining Lyc parts.
Water cooled to allow the 4 small valves, without overheating between the exhaust valves.

The smaller bore would reduce the loads on the remaining Lyc parts by quite a bit. However, you are right, high compression puts higher loads on the parts. Going from a nominal 9 to 1CR with a 5.25 inch bore to 17 to 1 with a 1/3 less displacement (due to bore) would still produce higher loads during the compression stroke. However, compression is not the highest load the rods/bearings experience. Inertia is, by far.

The reason for dual injectors was not for redundancy (although that could be incorporated). It was for a mechanical means to provide a small pilot injection to reduce stress. In other words, the first injector would be smaller, atomize better, inject earlier and provide only a fraction of the required fuel.

The 2500 RPM limit was also to reduce stress.

I suppose the goal would be to use as many off the shelf components as possible. Cummins turbo diesel parts maybe?
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  #8  
Old 06-16-2008, 11:32 AM
gasman gasman is offline
 
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IS NOW A GOOD TIME FOR THIS MOTOR?........ http://bourke-engine.com/ani.htm
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  #9  
Old 06-16-2008, 01:24 PM
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John Clark John Clark is offline
 
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Default Twenty two percent!

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Originally Posted by gasman View Post
IS NOW A GOOD TIME FOR THIS MOTOR?........ http://bourke-engine.com/ani.htm
Mmm, right. Brought to you by the fellow who's patents expired before anyone showed any interest. But not to worry, he has a new product "that will increase your fuel mileage by at least 22%. Please excuse me if I don't hold my breath waiting for this breakthrough.

John Clark
RV8 N18U "Sunshine"
KSBA
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  #10  
Old 06-28-2008, 06:07 PM
smenkhare smenkhare is offline
 
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Location: Sydney Aus
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Why not plug in one of these from Sandia national labs?

http://www.switch2hydrogen.com/
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