Small Dispacement Nitro/methanol NA 2S engine questions

[Nesikachad]

Greetings!

I build/race model airplanes. My latest project is to attempt to bump up the power delivery and RPM of an engine I'm using in a particular airframe.

It's called a Moki 210. 2.10cid (34.4cc) with a 36mmbx34mms.

These engines come from Europe where nitromethane is next to impossible to get. That being said they are designed/intended to run on a blend of methanol and bean/castor oil. Here in the states we can buy nitro but due to the compression ratio only about 10% will work with the stock CR.

I own a full service CNC machine shop. I am making a new crank (stock ones don't last much past 10K rpm) new rod, and a piston using no rings. I plan on running a tapered bore with a choke near TDC that'll open up once the engine warms up to operating temp.

I'd like help with configuring a good CR for a 50% nitro/50% methanol blend. I'm guessing around 8:1-9:1.

The end goal is to spin a 16" X 16" pitch prop at 15,000rpm. Right now the engine will run it at 7400. At 15K this gives me a round about speed potential of 225mph. That's ignoring things like drag. I'm guessing 170-180 is more likely. Plenty fast for this airframe. (terrifying fast for this plane actually)

Thoughts, comments, suggestions, and help is much appreciated!

C

 

[Nesikachad]

More info. The engine uses a glow plug for ignition. It's a platinum coil that reacts with the methanol in the fuel. Heat is the catalyst. Varying the platinum percentage alters the timing like on a distributor.

 

[MikeHalloran]

What prop material?



Mike Halloran
Pembroke Pines, FL, USA

 

[Metalguy]

>"I'd like help with configuring a good CR for a 50% nitro/50% methanol blend."<

Good luck, you're going to need it. BTW, nitro is widely available in Europe, it just costs a lot. 50% pop is what Fox Blast was, and a lot of guys ruined a lot of engines with it.

A 50/50 blend doesn't have any lube. Castor doesn't mix well with NM, and with 50%NM, 35% meth and 15% castor you can expect mixing problems, especially in cool weather.

You can blend in ~10% nitrobenzene which will dissolve the castor and/or use some synthetic oil in place of some of the castor, but 50% with a big model engine is asking for problems. NB is also quite poisonous, unlike NM.

What material did you make the crank and rod from?

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