RunRyder - OS .91 on 30% and break-in

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Engines Plugs Mufflers Fuel > OS .91 on 30% and break-in

woodscra
Senior Heliman
Location: Texas

How well does 30% run in the OS .91 on a standard muffler? I just happen have a lot of this stuff sitting around and would like to use it.

Also, has anyone bench run their .91 in before putting it in the heli for break-in and to get it to start easier?

Thanks

03-10-2002 Over year old.

z11355
rrMaster
Location: 10000 is enough time wasted.

David,

Are you using some straight 20% or something like a
mix of CP 12.5 & 30

03-10-2002 Over year old.

HOMEPAGE

Safe_Cracker
Key Veteran
Location: Chicago, IL

30% will work.

The reason why the 91 runs rough on 30% is because of premature detonation.You can fix this by changing the ignition timing.You alter timing by using a hotter or colder plug.In the case of the 91 on 30% I would use a slightly colder plug which would allow it to fire later.I don't know which plugs exactly, it will take a little trial and error.

04-08-2002 Over year old.

brentf
Heliman
Location: Woodbridge, Ca

I've been using Wildcat 30% with an OS #8 and it runs great. I'm still on my first gallon with the main needle at 2 turns out.

04-08-2002 Over year old.

Dr.Ben
Elite Veteran
Location: Richmond, VA, USA

There's a lot more to the 91 hammering on 30% than plug choice. Certainly there are timing issues, but even Curtis with an OS upgrade Hyper Head on his motor stated that he noticed far more hammering on the 30% fuel than with the 20% blend. I have also spoken in detail with Bruce Bennett about the 91 head design, and he agrees that it leaves a lot to be desired with higher nitro fuels; he has designed a new head for the motor, as well. Those individuals who have had the greatest success with the 91 on higher nitro fuel seem to be the guys that are willing to keep the model on the rich side. Start leaning the motor in, and things start to happen. I was standing by Curtis in AL when he switched from 20 to 30%. You had to have both fuels on hand to understand the hammering that the higher nitro stuff causes. If you've only run 30% from the start, it's hard to explain the problem. We are NOT talking about the tail jerking all around. The problem is more subtle and perhaps more insidious in the things it can do to your airframe and radio.

I suppose you need to weigh out whether the ability to pull 12-13 degrees of positive pitch vs a degree or two less is worth the trade off of extra shake, extra fuel expense, and in some cases extra smoke.

Ben Minor

04-09-2002 Over year old.

Safe_Cracker
Key Veteran
Location: Chicago, IL

Runs great?

I have never heard of a stock 91sxh running great on an OS#8 and 30%.The most the head would have to do with preignition is weather or not it has raised the compression or not.If you look, it is easier to put an extra head shim and then it will effectively lower the compression ratio.And as far as the plug type, the temperature of the plug controls the ignition timing.If you have preignition problems they can be helped if not cured by changing the ingition timing.There are more than one type of TIMING in an engine.

04-09-2002 Over year old.

Eagle
Senior Heliman
Location: Australia

Jason Krause is using Coolpower 30% with an Enya #4 plug.

04-09-2002 Over year old.

Safe_Cracker
Key Veteran
Location: Chicago, IL

Thankyou..

Now that's what I'm talking about.I would have tried an Enya #3 but what ever works right?

04-09-2002 Over year old.

Sam
Senior Heliman
Location: Chandler, AZ, USA

I went to the Phoenix Fun Fly and saw Steve Helms. Steve is the top man for Futaba RC and, as I'm sure you know, Futaba owns OS. He is running an OS91 and has a special fuel mixed for him by Powermaster. It is 15% nitro and 14% oil. I asked him about it and he said that is what he has come up with as the best for his use in an OS91. He advised the engine WILL NOT TOLERATE A LEAN RUN on 14% oil so be careful if you try it.

Sam

04-17-2002 Over year old.

mfendley
Senior Heliman
Location: Saint Marys, GA

I'm running the CP pattern fuel (20% nitro/20% oil) with pretty good results. I'll switch to the 20/18 when it becomes available in this neck of the woods.

Mike

04-17-2002 Over year old.

Safe_Cracker
Key Veteran
Location: Chicago, IL

Plug?

What plug was he running?

04-18-2002 Over year old.

Sam
Senior Heliman
Location: Chandler, AZ, USA

Safe Cracker,

If your question about the plug was for me I have to say I didn't ask. Perhaps I can find an email addrress for him and ask what he suggests. Years ago, in the mid 80's, whe he was flying pattern I think I remember him using Enya plugs but I'm not even posative of that.

Sam

04-19-2002 Over year old.

Sam
Senior Heliman
Location: Chandler, AZ, USA

91 with no nitro

I bought a Henseleit 3DNT. It is set up to use an OS91FX-HGL. It's my understanding it is an OS 91 airplane engine that Graupner modifies for use in a heli. It has a real big round head and there my be some other things that are done but I can't see them. To make a long story longer, Henseleit sez you must change the carb to a Lotterle carb. and suggests no nitro and 12% oil! This combination is run with a Hatori 700 pipe and an Enya 4 plug. I haven't even started to assemble the heli yet but there is an article about it in the April 2002 issue of Model Helicopter World that speaks favorably of the set up. If I can't find FAI fuel I will run 5% nitro but one thing for sure is there is no way I'm going to run 12% oil. I'll start with the normal 18% mix and then try to find some that is down in the 15 to 16% range with a little castor - just in case.

Sam

04-20-2002 Over year old.

EChapkis
Veteran
Location: Tampa, FL

PowerMaster

At Toledo I was talking with PowerMaster about the new fuel Steve Helms is testing. I am a PowerMaster sponsored pilot. The comment above is correct about the oil content. My suggestion to PowerMaster was to increase the oil from 14% to 16%, only for the reason to protect themselves from the guy who does run it on lean side.

Don't be too concerned about the oil %, as you have no idea what oil PowerMaster is using. 14% maybe plenty, but the only downside is heat removal, not lubrication as most people think high oil percentage is used for.

I personally run PowerMaster 15% 23% oil. Smokes alot, but I know my engine (OS 46FX) is well protected. The 46's are known to run hotter so I wanted the extra protection. My intention was to run the same 23% 15% nitro in my OS 91, but before I do I will hook up with Steve Helms and discuss the new fuel.

Evan Chapkis Tampa, Florida

04-20-2002 Over year old.

Safe_Cracker
Key Veteran
Location: Chicago, IL

%'s

There are many variables to consider when trying to figure out oil percentages.You have to look at nitro content, synthetic,non synthetic content,application, engine type(abc,ring,aac,etc.) climate type of flying etc,etc,etc...That's why the big companies do a-lot of research to get us top performing fuels.A synthetic fuel will not lose it's viscocity as much as a non-synthetic in a high nitro application.Depending on the use, a larger engine would probably be able to handle a lower oil content in a lower nitro fuel.I prefer synthetics because of the added protection, never can be to cautious.Also one other thing that might be affected is the carb.The carburetor on any given engine was designed to use a specific type of fuel.That's why you can't just go ahead and run gasoline through it.There are too many variables and it gives me a head ache thinking about it, but it is a very good topic though.

04-20-2002 Over year old.

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Engines Plugs Mufflers Fuel > OS .91 on 30% and break-in

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