Engine secrets

How To Break In Your Engine For More Power & Less Wear

One of the most critical parts of the engine building process is the break in !!
No matter how well an engine is assembled, it's final power output is all up to you !!

Although the examples shown here are motorcycle engines,
these principles apply to all 4 stroke engines:

Street or Race Motorcycles, Cars, Snowmobiles, Airplanes & yes ...
even Lawn Mowers !!

( regardless of brand, cooling type, or number of cylinders. )
These same break in techniques apply to both steel cylinders and Nikasil, as well as the ceramic
composite cylinders that Yamaha uses in it's motorcycles .

What's The Best Way To Break-In A New Engine ??
The Short Answer: Run it Hard !em>

Why ??

Nowadays, the piston ring seal is really what the break in process is all about. Contrary to popular belief, piston rings don't seal the combustion pressure by spring tension. Ring tension is necessary only to "scrape" the oil to prevent it from entering the combustion chamber.

If you think about it, the ring exerts maybe 5-10 lbs of spring tension against the cylinder wall ...
How can such a small amount of spring tension seal against thousands of
PSI (Pounds Per Square Inch) of combustion pressure ??
Of course it can't.

How Do Rings Seal Against Tremendous Combustion Pressure ??
From the actual gas pressure itself !! It passes over the top of the ring, and gets behind it to force it outward against the cylinder wall. The problem is that new rings are far from perfect and they must be worn in quite a bit in order to completely seal all the way around the bore. If the gas pressure is strong enough during the engine's first miles of operation (open that throttle !!!), then the entire ring will wear into
the cylinder surface, to seal the combustion pressure as well as possible.

The Problem With "Easy Break In" ...
The honed crosshatch pattern in the cylinder bore acts like a file to allow the rings to wear. The rings quickly wear down the "peaks" of this roughness, regardless of how hard the engine is run.

There's a very small window of opportunity to get the rings to seal really well ... the first 20 miles !!

If the rings aren't forced against the walls soon enough, they'll use up the roughness before they fully seat. Once that happens there is no solution but to re hone the cylinders, install new rings and start over again.

Fortunately, most new sportbike owners can't resist the urge to "open it up" once or twice,
which is why more engines don't have this problem !!

An additional factor that you may not have realized, is that the person at the dealership who set up your bike probably blasted your brand new bike pretty hard on the "test run". So, without realizing it, that adrenaline crazed set - up mechanic actually did you a huge favor !!

Here's How To Do It:
There are 3 ways you can break in an engine:
1) on a dyno
2) on the street, or off road (Motocross or Snowmobile.)
3) on the racetrack


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On a Dyno:
Warm the engine up
completely !!

Then, using 4th gear:

Do Three 1/2 Throttle dyno runs from
40% - 60% of your engine's max rpm
Let it Cool Down For About 15 Minutes

Do Three 3/4 Throttle dyno runs from
40% - 80% of your engine's max rpm
Let it Cool Down For About 15 Minutes

Do Three Full Throttle dyno runs from
30% - 100% of your engine's max rpm
Let it Cool Down For About 15 Minutes
Go For It !!

NOTE: If you use a dyno with a brake, it's critical during break - in that you allow the engine to decelerate fully on it's own. (Don't use the dyno brake.) The engine vacuum created during closed throttle deceleration sucks the excess oil and metal off the cylinder walls.

The point of this is to remove the very small (micro) particles of ring and cylinder material which are part of the normal wear during this process. During deceleration, the particles suspended in the oil blow out the exhaust, rather than accumulating in the ring grooves between
the piston and rings. This keeps the rings from wearing too much.

You'll notice that at first the engine "smokes" on decel, this is normal, as the rings haven't sealed yet. When you're doing it right, you'll notice that the smoke goes away after about 7-8 runs.
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On the Street:
Warm the engine up completely:
Because of the wind resistance, you don't need to use higher gears like you would on a dyno machine. The main thing is to load the engine by opening the throttle hard in 2nd, 3rd and 4th gear.

Realistically, you won't be able to do full throttle runs even in 2nd gear on most bikes without exceeding 65 mph / 104 kph. The best method is to alternate between short bursts of hard acceleration and deceleration. You don't have to go over 65 mph / 104 kph to properly load the rings. Also, make sure that you're not being followed by another bike or car when you decelerate, most drivers won't expect that you'll suddenly slow down, and we don't want
anyone to get hit from behind !!

The biggest problem with breaking your engine in on the street (besides police) is if you ride the bike on the freeway (too little throttle = not enough pressure on the rings) or if you get stuck in slow city traffic. For the first 200 miles or so, get out into the country where you can vary the speed more
and run it through the gears !

Be Safe On The Street !
Watch your speed ! When you're not used to the handling of a new vehicle, you should accelerate only on the straightaways, then slow down extra early for the turns. Remember that both hard acceleration and hard engine braking (deceleration) are equally important during the break in process.
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On the Racetrack:
Warm the engine up completely:
Do one easy lap to warm up your tires. Pit, turn off the bike & check for leaks or
any safety problems. Take a normal 15 minute practice session
and check the water temperature occasionally. The racetrack is the perfect environment to break in an engine !! The combination of acceleration and deceleration is just the ticket for sealing the rings.
Go For It !!

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Yeah - But ...
the owner's manual says to break it in easy ...
Notice that this technique isn't "beating" on the engine, but rather taking a purposeful, methodical approach to sealing the rings. The logic to this method is sound. However, some will have a hard time with this approach, since it seems to "go against the grain".
The argument for an easy break-in is usually: "that's what the manual says" ....

Or more specifically: "there are tight parts in the engine and you might do damage or even seize it if you run it hard."

Consider this:
Due to the vastly improved metal casting and machining technologies which are now used, tight parts in new engines are not normal. A manufacturing mistake causing a tight clearance is an extremely rare occurrence these days. But, if there is something wrong with the engine clearances from the factory, no amount of gentle running will fix the problem.

The real reason ???
So why do all the owner's manuals say to take it easy for the first
thousand miles ???

This is a good question ...



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Q: What is the most common cause of engine problems ???
A: Failure to:
Warm the engine up completely before running it hard !!!

Q: What is the second most common cause of engine problems ???
A: An easy break in !!!

Because, when the rings don't seal well, the blow-by gasses contaminate the oil with acids and other harmful combustion by-products !!

Ironically, an "easy break in" is not at all what it seems. By trying to "protect" the engine, the exact opposite happens, as leaky rings continue to contaminate your engine oil for the rest of the life of your engine !!

PICS of da tested pistons comin up inda nxt post !!!

source: http://www.mototuneusa.com/