fuel question,,,,
#1
Thread Starter

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as you guys know I have had a hard time starting my MVVS 35cc gasser (I just haven't flown it in 3 months), and I still have a hard time starting it even though the new carb works great, and the motor runs beautiful/fantastic-O once it starts,,,
but what I have noticed about this motor is it has a higher compression ratio than many US made motors, in-fact it has a lot of compression~ although my MVVS 35 is a smaller motor it has a higher compression ratio than my friends BME 105cc,,,
question,,,
so I have been burning 89 octane in it, do you guys think it would start better with a higher octane of 93 or 94 ???
I just though I would ask before i try it...
Jim
#2
Senior Member
Octane ratings around the globe are not the same. Some countries use RON ratings (Europe), some use MON ratings (US, partly or all states?) MON is typically 5 point lower than RON, so you should use at least 90MON octane leadfree gas.
Running too much octane rating does not harm an engine. That is why some modellers use AVgas, which I believe to be 95+ MON octane, a special brew for airplane combustion engines that have to perform at altitude..
Then there also is the gas mix. Depending on state, and state laws, some high octane numbers in leadfree gas are obtained by adding up to 15% ethanol. which may influence oil mix stability and Walbro membrane life.
If you can get 94 octane, by all means use it, as MVVS presribes a lower limit of 95RON octane, which equals 90mon octane. I use 98RON octane with good results.
Using a low 89rating is a risk for your engine, because detonation can set in long before you hear it. These detonation pressure peaks, also known as ping or knock, can seriously harm piston and conrod bearings.
Running too much octane rating does not harm an engine. That is why some modellers use AVgas, which I believe to be 95+ MON octane, a special brew for airplane combustion engines that have to perform at altitude..
Then there also is the gas mix. Depending on state, and state laws, some high octane numbers in leadfree gas are obtained by adding up to 15% ethanol. which may influence oil mix stability and Walbro membrane life.
If you can get 94 octane, by all means use it, as MVVS presribes a lower limit of 95RON octane, which equals 90mon octane. I use 98RON octane with good results.
Using a low 89rating is a risk for your engine, because detonation can set in long before you hear it. These detonation pressure peaks, also known as ping or knock, can seriously harm piston and conrod bearings.



