RC Fuels Nitromethane, Castor Oil, Synthetic, heli fuel, 4 stroke, etc...Fuel Q&A is here!


Old 02-27-2004, 10:25 PM
Thread Starter
My Feedback: (2)
Join Date: Sep 2002
Location: HOUSTON, TX
Posts: 895
Likes: 0
Received 0 Likes on 0 Posts

I have purchased the OS PEGASUS a fourstroke four cylinder horizonally opposed engine.
I am about to send it up to C&H IGNITION to update the engine to IGNITION.

Every person I ask, gives me a different answer.......

I haven't yet ASKED either C & H or CLARENCE LEE ( but I will )

ANYBODY OUT THERE care to tell me what I should use for FUEL on this ENGINE ?


IF GAS, what octane is correct ?

IF METHANOL, how much NITRO and/or OIL ?


Old 02-28-2004, 06:30 AM
Senior Member
My Feedback: (16)
Join Date: Apr 2002
Location: Locust Grove, GA
Posts: 12,942
Likes: 0
Received 0 Likes on 0 Posts

Even with spark, you will still use alcohol.
If you try to go to gas, you will have to make changes in the carb.
Old 02-28-2004, 09:13 AM
Sport_Pilot's Avatar
Join Date: Jan 2002
Location: Acworth, GA
Posts: 16,916
Likes: 0
Received 1 Like on 1 Post

The O rings in the carb may not be able to hold up to gas. Even if you change them it most likely will not work. Gas is not as tolerant of lean or rich mixtures and needs a more accurate carb. You may be able to fit a Walbro carb, but I doubt it would be worth it. But at least with ignition you will have more accurate timing and no worries about drowning out glow plugs.
Old 02-29-2004, 04:46 AM
Senior Member
My Feedback: (1)
ZAGNUT's Avatar
Join Date: Feb 2003
Location: tel-aviv, ISRAEL
Posts: 2,635
Likes: 0
Received 2 Likes on 2 Posts

with gas you will still need a very high % of oil as these engines have plain bearings on the rods and rely on blow-by to lube the lower end. with gas it might also run at too high a temperature, remember that methanol is an awesome coolant, gas is not.

but now that you are in total control of the ignition timing you can probably run without nitro at all. just use whatever oil content OS recommends and the balance methanol.

Old 03-01-2004, 11:34 AM
Senior Member
Join Date: Jan 2003
Location: Paris, ON, CANADA
Posts: 183
Likes: 0
Received 0 Likes on 0 Posts

While I have not run the Pegasus on spark ignition , I did run my OS 120 II twin on the CH ignition with mechanical advance for about 5 years and I believe the results would closely match those obtained with the Pegasus.

I started out using 87 oct auto fuel /Amsoil synthetic oil mixed 85/15. Both needles were extremely sensitive with about 4 clicks between too rich and too lean. I started adding methanol in increments displacing an equal amount of gasoline and when I got to 50 % methanol the high speed needle response became acceptable with about 1/3 turn between too rich & too lean. I finally ended up running 5% glo fuel for the best performance. Top rpm using spark ignition and glo ignition on 5% glo fuel was identical.

While the engine started and idled beautifully on fuel with a gasoline component, the midrange was extremely rich in spite of both needles being set as lean as possible. I replaced the airbleed carb with the Pegasus carb which is a metering type with the same venturi area and this helped the midrange slightly on gasoline fuel, and considerably on glo fuel. These carbs are metered for alcohol fuels and when you try to run gasoline fuel, a midrange mixture adjustment becomes necessary.

I played around with different advance curves starting at 4 degrees at idle and 32 degrees at WOT. Advancing the idle setting to 15degrees cured some of the midrange richness but total advance ended up around 45 degrees and detonation became a problem. Kickback on starting also became a problem with this amount of idle advance. With the later electronic advance that CH is selling, the results may be somewhat better than mine were with the mechanical advance.

One beautiful day while flying my Cub, the pulse wheel containing the magnet split and flew apart causing an instant engine failure. I landed and not wishing to waste the day, I stuck in a couple of glo plugs. Using the same 5% glofuel an immediate noticeable improvement in midrange engine operation was evident. When I got home I removed all of my spark ignition system and have returned to glo operation with no regrets.

My recommendation, forget the spark ignition, and accept the higher cost of fuel to operate this engine
Old 03-04-2004, 04:14 PM
My Feedback: (11)
Join Date: Apr 2002
Location: Monticello, IL
Posts: 19,483
Likes: 0
Received 6 Likes on 5 Posts

An engine originally intended for glow fuel operation will have fuel passages that are too large for gasoline operation. That's why the needle became so sensitive on wacodriver's engine. The range from too much to too little was not that much when the glow fuel carburetor was used. O.S. does not have a conversion for their engines to make them operate on gasoline.

Gasoline operation will also make the engine run hotter than glow, and you'll still need a fuel fairly rich in oil because the connecting rods don't have bearings...they're bushed, and the oil that gets to the lower-end of the engine comes past the piston rings from the upper-end.

Basically, the engine wasn't really designed for gasoline operation, and we can't give you a clue about the longevity of the engine when run on gasoline.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are On

Thread Tools
Search this Thread

Contact Us - Manage Preferences Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.