stunthanger.com
Engine basics => Engine set up tips => Topic started by: Lauri Malila on May 21, 2017, 12:24:19 AM
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Hi.
I'm allmost ready with the new piston/cylinder groups. Compared to the previous versions, I have increased the port areas and added 2 boost ports.
Also, the port angles are much steeper towards combustion chamber.
I also made the piston rings (Dykes). They came out blue after my heat treatment :)
Cheers, Lauri
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Impressive work!
Which engine is this for?
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Admirable work my friend!
Martin
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Hi.
I'm allmost ready with the new piston/cylinder groups. Compared to the previous versions, I have increased the port areas and added 2 boost ports.
Also, the port angles are much steeper towards combustion chamber.
I also made the piston rings (Dykes). They came out blue after my heat treatment :)
Cheers, Lauri
Great work Lauri , its looking good , keep us informed on how its going
Randy
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Well, I went flying. Mechanically the engine sounds very healthy, first flick start, no black oil, no overheating and good needle response. So after 10 minutes of running-in I decided it would be less boring to fly the thing.
Fuel is 80% methanol, 15% Aerosave synthetic and 5% Racing Castor #927.
I had a pile of cylinder heads to test, all prepared so that starting point is same (squish area, squish clearance, head volume), and all with the same weird bathtub combustion chamber. So, same layout with 3 main differences:
-Standard with nothing else special.
-With a titanium umbrella a'la Yuriy to protect plug and perhaps pre-heat and stabilize the burning process.
-Twin plug.
It was quite windy and turbulent so I could not fully focus to the engine but it seems to run very well. Much better power at richer mix than with older version, and allmost perfect running symmetry. I still need time to optimize the venturi/head volume ratios and play with tank position, but it looks very promising.
As I guessed, heads with Ti-umbrella and two plugs need slightly bigger head volume and give slightly better running stability, including outside/inside symmetry. I think that kind of proves that with horizontally mounted engines with healthy, efficient scavenging, those issues are closely related to burning stability during load variations.
I also found that Merlin 2004 plug works a little better than Enya #3. I have ordered Merlin flat-coil plugs too, it will be interesting to see if they offer any advantage. L
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Here are close-ups of the weirdest heads. Maybe not absolutely ideal but home-made stuff has allways its limitations. L
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Well done Lauri!
Any ideas with using different plugs in the twin plug head to further aid symmetry?
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I doubt it would make a noticeable effect. It's not about burning being somehow asymmetric, but just inefficient in general. To prove that, you just have to change engine running direction; if it's about asymmetric explosion, why does the error reverse?
I think it would just end up as average heat range of the 2 plugs.
But that's my guess and I'm often wrong. I'll test is one day.
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Good to see a sucsessfull outcome .
Id been a bit sceptical it was a bit to sophisticated , and complex .
" Home Made ' ! %^@ must have a good Black & Decker there . S?P
Whats the fuel consumption like /
Regards , M. S.
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Fuel consumption was like before, about 80ml (2,8oz)/6.30 flight.
I can't see why it would be too complex, there are less parts than in a more conventional engine, thus better stability.
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Fuel consumption was like before, about 80ml (2,8oz)/6.30 flight.
I can't see why it would be too complex, there are less parts than in a more conventional engine, thus better stability.
Less parts???
Randy
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Ok, I was wrong. Backplate assy makes it back to same number, about :)
But what I tried to say was no drop-in liner > no thermal gradients > better cooling > better stability.
Only way to make it better would be a cast cylinder with integrated bypasses and exhaust. Back to drawing board!