Converting Nitro engine to run Gassoline - HeliFreak
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Old 08-20-2010, 04:29 PM   #1 (permalink)

Join Date: Feb 2009
Location: USA
Default Converting Nitro engine to run Gassoline

First - Let's keep the flack and any "versus" to a minimum folks!

I was browsing my local Kijiji classfields today while sitting about waiting, and I came across a typical 90 sized Nitro engine that has been converted to burn gasoline. None of the specifics were outlined but it really perked my curiosity. So I did email the gentlemen for some information regarding it.

From the picture though, he has a typical gasoline carburetor fitted to the engine and a gasoline sparkplug, not sure how he's got the ignition system engineered but I will find out in due time on how he achieved it. Additionally the next issue would be fuel mixtures, IE what his oil to gas ratio is, this would be paramount that it's nailed to ensure consistent running, and good performance without causing damage to the internals.

So sitting here thinking, I got a spare OS50 Hyper engine sitting in a box I have no intentions of using because I'm have outstanding luck with my TT Redline .53 engine. It'd be a very cool project to see if I can modify it to run gasoline and see what exactly it can deliver in terms of results, and honestly if it can even be considered something that will last.

Any experienced folk or non-experienced folk that would love to share some thoughts, concerns or stories on this?

Given it's possibilities for unsatisfactory real world use, it does prove to be an interesting way to combat rising nitro fuel costs and go the ability to go gasser without the need of a new more expensive engine and necessary equipment.

**EDIT I attached a picture of the engine as I found it pretty neat.
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Old 08-20-2010, 04:45 PM   #2 (permalink)
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interesting, there appears to be a pick-up on the crankshaft for triggering the ignition system. Not sure that the port timing and compression ratio would be correct but I'm afraid I'm not that hot on 2 strokes so I can't really comment. Would be nice to be able to gass up a cheap old nitro engine!
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Old 08-20-2010, 05:47 PM   #3 (permalink)
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The basic rule of thumb is that you will get somewhere between 1/2 to 2/3rds of the power out of gas vs what you had with glow.

In other words a gas OS 50 will have about the power of a 30.
A gas 90 has about the power of a 60.
If you dig back a few years, you will find articles and posts about the BME 90 gas conversion and a Webra 90 gas. They both had about the same performance as a 60.

Regarding the fuel mix. you will need to stay near the 20% oil. The reason for this is that the bushings on the con rod need this much oil for proper lubrication. In the BME and Webra the changed the con rod to a Roller bearing to be able to run a more normal 25:1 2 stroke gas mix.

As long as you keep these facts in mind, it is a LOT less expensive to run a gasser than a glow machine.

If I were converting a 50 size machine to gas, I would base it off of a 90 engine and you should be good to go.
Jeff Borowski
RAMS Club President
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Old 08-20-2010, 06:19 PM   #4 (permalink)
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thats likely a BME engine, they do a conversion on a super tiger motor

you need to change the rod bearings from plain to roller and come up with a way to harden the crank pin. Those parts get a lot hotter when you run gasoline.
Carey Shurley
Proprietor - Gas Powered Helicopters

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Old 08-21-2010, 02:57 AM   #5 (permalink)
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The motor pictured is a 90 Super Tiger. Likely a Zama Carburetor (pretty much the same as a walbro). This engine is suppose to have marketed conversion kits around (many do). But as pointed out they don't perform quiet as well as if you were running nitro fuel.

From what I recall there is some porting modifications needed to be done to get the right flow (to much or to little = no good!). You'd need the proper equipment to test these things too.

So it's do-able, but not practical.

Pick up that motor and slap it on to a .50 sized bird and let us know how you make out!
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