Mighty Mouse-RCU

My Feedback: (145)

I have been flying for 7 years now and understand fuel components for Airplanes.
I have tried running and tuning small .15 size cars usually with a great deal of aggrevation.
I gave up about 3 years ago and my son and I went to electric. Now for the quest of speed, my son wishes to get into nitro cars again.
I shutter at jerking the pull start over and over or attempting to tune these finicy rascells. Usually my problems are keeping them running after shutting down the quickly to idle. I finally thought perhaps it was the fuel I was using. It was airplane fuel. 15% nitro 18% oil and also some YS 20 20 from WIldcat. Thinking maybe this was my problem. Too much oil. Anyway I gave up back then and now looking to start back.

But I digress.... The real reason I dropped in was to try and sort out this Air vs car fuel delema. I am getting conflicting stories about the differences between the two. In fact I really don't see any differences other than the stickers. Oil and nitro contents apear the same. When I pointed this out to one owner, he just give the standard answer: "There is a differnce in the formulation" Airplane fuel doesnt work as well as car fuel in cars and vise versa. He goes on to say that I need to run at least 18% oil as these engine really turn RPMs and need the extra cooling. Another shop says no, not so. You run less oil in that will allow more nitro and methenal in the fuel and that will keep your engine from dying. Besides the larger head keeps it cool.

So what's up. I have order an Evader nitro and have purchased a gallon of Dominator or Terminator or something like that that has 20% nito and 18% caster/syn mix. I also order a quart of %15 fuel from Tower with unknown oil content.

So, what should I use to keep things running? I dont need information on breaking in ABC engines or the like, just want to know if there is any thing differnt between airplane stickered fuel and car stickered fuel.

Also What fuel should I use? If I use higher oil content will engine go dead more often. If I use lower oil content, am I more likely to burn it up?


SO I look on the shelf. Now I find Oil contents 10% , 14% and 18% oil.

carrellh

I'd get 'car fuel' (have no idea if it's different or not) and would follow the engine manufacturers instructions regarding oil and nitro percentages.

downunder

What the needle valve does is regulate the amount of methanol/nitro that can flow through each cycle (a very tiny little droplet). The oil takes up part of the volume of this droplet. If you increase the % of oil then you need to make this droplet a little larger so you've still got the same amount of methanol/nitro that the engine needs to run properly. You make the droplet larger by opening the needle valve a little more.

In other words, what the shop told you was quite wrong. About the only thing that reducing oil content does as far as I can see is give you a larger volume of methanol/nitro in the tank so the car will run for a little longer (assuming it doesn't overheat and seize up).

mpalermo

Well I mix 2 batches one for my car and one for my planes...

Use the same oil in both a syn / castor mix.

Plane fuel 18% oil 10% nitro
Car fuel 20% oil 20% nitro

WORKS great, both engines look fine when you tear them down so I will keep on saving the green and mixin my own fuel!!!

Mike

Mighty Mouse-RCU

My Feedback: (145)

Downunder,
I always thought the higher the nitro, the more open the needle valve setting is needed.

I think my assumption is correct in that there is no difference between car and airplane fuel give the same nitro oil combination.
But I find it difficult that they sell alot of 14% and 10% oil content even if it is syn/caster blend. I'll use the 20% nitro 18% oil blend and give a try one more time. Perhaps I am just expecting too much as far as idle and performance in these little size engines.

downunder

Yes for sure, the higher the nitro content the more the needle has to be opened. What I was really talking about before was that if you had some of that horrible car fuel with 10% oil and added oil to bring it up to 20% then the proportions of methanol/nitro won't have changed but you'd have to open the needle slightly to allow for that extra oil. You're then flowing exactly the same amount of methanol/nitro which means you then have the same power you had before but with twice as much oil going through the engine. Too much oil never wore out an engine

049flyer

My Feedback: (18)

Car fuel usually has between 8% and 18% oil and 20% or more nitro. The manufacturers of car fuel almost NEVER state the oil content like they do for airplane fuel. Car engine manufacturers often state preferred oil content between 12% and 18%.

As most "car guys" are more interested in raw power and speed than they are in engine life, the preferred fuel is usually the one that results in the most power. This is almost always the fuel with the lower oil content.

Car guys are usually perfectly happy to buy a new piston and sleeve after running 2 or three gallons of fuel through their engines whereas the "airplane guys" expect their engines to run for years.

Car engines do seem to run more reliably with reduced oil content though. I think that they tend to load up with higher oil concentrations.

Actually aiplane engines will run fine with reduced oil content, but a lean run will probably cause major damage before you notice it or get the thing on the ground.

Buy car fuel and a little castor. Use the car fuel as is in the car and add some castor to some that you use for the plane.

Mighty Mouse-RCU

My Feedback: (145)

Well I just ran out of the quart of fuel I purchased from TH. It was 10% with unknown oil content.
The engine ran perfect with a somewhat rich setting. Did not smell any castor in it. I will be switching
to "Terminator" or something like that. It has 20% nitro and 18% syn/castor blend. I am sort of expecting
a problem with it having too much oil. If this is the case, I'll use it for air and buy less oil content in the fuel.
Using airplane fuel , I think the engine was drowning on the oil and the plug could not stay lit. I never run too rich
in my plane, but I do tune to the very safe side. I suspect this is my problem. I'll let you know how the new
fuel runs in a day or so. Thanks for the comments.

memjsims

My Feedback: (33)

Hello Craig,

I've had great luck running O'Donaolds 20% car fuel. Clear and clean running with great power.
Working at a large hobby shop in Phoenix, AZ, I talk to the racers who won most and had the best engine lives what they ran and 90% ran O'Donalds fuel. Duratrax is now making the O'Donalds fuel. TH, Hobbytown USA and many others stock it.
Good luck.

Sport_Pilot

If you are haveing trouble keeping the plug lit with higher oil content, then a hotter plug would probably do the trick. There is no reason the car engines cannot run on airplane fuel, the airplane guys run the higer oil content without any problems, even hot .15 sized engines. You could always run a high oil content and hot plug for practice, and a cooler plug and low oil for races.

Mighty Mouse-RCU

My Feedback: (145)

So what is a good hot plug, tha A3?

memjsims

My Feedback: (33)

The A5 is the better plug. A3 is a cooler plug.

bentgear

Actually OS lists their plugs from hottest to coolest as A3 - #8 - A5 and my experience with them tends to think the list is right.

Ed M.

memjsims

My Feedback: (33)

I had it backwards. But the A5 for off-road and R5 for on-road are better than the A3 or #8 which are better for airplanes.

bentgear

Lighter loads, cooler operation, higher oil, lower compression, lower nitro would tend to use the warmer plug. As you change in the other direction you will find the cooler plug comes into play. Many times its a tradeoff between performance desired and the ability of the plug to stay in one piece.

Ed M.

adamkerrnz

i race nitro cars and at the moment i am running 15% Nitro with 20% oil, seems to run fine.
and ditch those damn pull starters, get a better car with a starter box!!!

Bax

My Feedback: (11)

So-called 'RC Car" fuels usually have lower oil content because an engine will clear out and accelerate faster than if it used higher-oil content fuel. We've seen "car" fuels with oil content as low as 10%-12%. DO NOT get any bit lean with these fuels or your engine's piston/cylinder fit will go bad very quickly. One manufacturer even states that a lean run will cause the engine to go into :thermal overload" if it's too lean, and it will quit and not become scored. Well, sure. The cylinder liner will expand away from the piston and compression will be lost. The engine will quit. You'll still need a new piston/liner assembly to get any kind of reliable operation after that. Once an engine's had an overheat and then cooled down, the parts fit will never be right again.

DualdudE

Friend of mine runs his 3.5cc car engines on 10% Nitro Heli-fuel (15% oil) This works perfect

hitman45

Yeah Im doing the same. Im gonna run 15% nitro and 20% (mabey more) oil content of Heli Fuel.

I'v heard that Heli fuel works good in car engines and its an extra bonus that Heli fuels DO have more oil in them, so you will expect more engine life.

downunder

I don't know if it's just me but for a while now I've been noticing that a lot of people are saying X brand is really great but add a little oil...or Y brand is really great but add a little more oil. Now we're starting to see car guys saying they use aircraft fuels instead of car fuel because it's got more oil in it. Don't get me wrong, I think this is a step in the right direction. The strange thing is that a couple of fuel manufacturers make a range of fuels with considerably more oil than others but they generally only list it as CL fuel. This is because CL fliers in general will never use anything less than 20% oil. But of course the average RC flier won't look twice at anything labelled CL. Check it out, you might be surprised at what's available