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Old 05-11-2008, 10:41 AM   #1
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Default motor break in , onroad

give me some thoughts on break in , i know to use a prop stand , what im looking for is what fuel and temperatures, cycles . for 1/8 scale onroad.

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Old 05-11-2008, 01:44 PM   #2
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There are quite a number of different "Break-in" methods used out there.
There's not a huge difference between them.

Heat cycle method.
Wide Open Throttle Method.
Gradual rpm increase.......idle first tank increasing through quarter, half etc to full throttle.

Which ever method you use keep in mind what you are trying to do.
The fuel is the engines lubricant and it's also the motors machining lubricant/coolant during break in.
You are trying to match a piston to a sleave as closely as possible. IE: Size and shape. You are also trying to get the best possible finnish.....ie: Smooth as poss' ! On the cylinder wall as it approaches Top-Dead-Centre. This is the way these motors seal the combustion chamber. You are also trying to get this done with the engine at, or as close as possible to the "Normal" operating temperature of the motor. (Due to expansion rates of different metals used in the manufacture of these motors.
On top of this you are making the other moving parts within the motor as smooth and friction free as possible.

There's alot of agreement on certain methods, and dissagreements on certain things done as to their advantages. Either way, it's your choice.

Me?....I like to use a fuel with a high lubricant content 18%, and low Nitro content 10%. A hot plug and I also add an extra 5% or so of 'Ungummed' Castor oil in the first 5 or 6 tanks that go through the engine. Castor oil has an extremley high film strength. So when tolerences are so very tight, it keeps lubricating and wont allow metal-on-metal contact! I filter my fuel before I put it into the tank.
I heat the motor up with a heat gun to 200 Degrees F, Idle the first tank through VERY rich, keeping the heat gun on the motor keeping the motor at or around 220 degrees.I may also have some Tin-Foil around the motor to keep the heat in.
Second and third tanks, I start to raise a little the engine speed, very rich(!!) so it's almost stalling the motor and keeping the motor up at 220 degrees with the heat gun.

With subsequent tanks, I up the rpm, keep the mixture very rich (!) and keep the engine's temp up with the heat gun. I only start leaning the motor down after around 6 tanks of fuel have gone through it. Then a little at a time!
Up till then, I run it that rich in the first 5 or 6 tanks that the motor can bearly keep running!
I take the foil off and take away the heat gun as the motor is able to keep it's temp' up itself.
You don't have to do all this on a stand, but it helps when trying to monitor engine temps and using the heat gun/ hair dryer.
But when your starting to lean the motor down and the motor does not need the foil and the heat gun to maintain temp, then I would say you need to take the car out on the track.

Usually this is not done all at the same time....ie same day. But if/ when the motor stopped for whatever reason. Its VERY important that you ensure the piston is not stuck at TDC !!!!!!!!!! Ensure the flywheel is free before you do anything else!!!

Some motors will take longer then others due to the amount of "pinch" built into the motor at the factory. So the latter stages of break in, after about 7 or 8 tanks, may take longer to complete and you may find you need to run the motor still rich right upto 14 tanks or more! You will notice the motor needs this extra break in time if, when you start to lean down the motor, the engine temps start going high, say 240, 250 or so, and yet the motor still isn't loosening up/ getting much faster. If this happens keep the motor running very rich and the temps down to 210/220 or so and keep running the motor for a few more tanks. Leaning the mixture down.....gradually! You should see a gradual increase in performance as you keep leaning out the motor. Be patient.........the motor will pay you back!

Just the way I try and do things. Others will tell you of their way and the methods mentioned above to follow....
But, it's your motor!!

All the best

British Menace
So enjoying building cars I sometimes forget to save some "man-time" to race them!?
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Old 05-11-2008, 03:42 PM   #3
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Default Break in

I think that is great info. It makes alot of sense. I found a similar method while reading rb products forum. I used a airplane fuel tank lid then used my body reamer to put a hole in the cap of my gallon fuel jug this way i can run through the whole breakin without stopping the engine. I broke in a rb zenon r running at 220 degrees at about 1/4 throttle with foil around the cooling head and you will know when it gets done because it starts to free up. This engine is the fastest i've ever seen and i think it's because of the break in i used. Anyway go to rb website and look on there forum. I think you will like it. It takes a few hours to complete though.
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Old 05-11-2008, 05:27 PM   #4
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Heat cycling with a load is the best. Without a load the engine wont seat near as fast or as well. The head cycle helps with other things and prolongs engine life. Run it really rich and at 200 degrees.
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