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Old 09-25-2005, 13:01   #1 (permalink)
unknown
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Break in period?

In ancient days one would drive a new car like a maniac, helping it to
"break in" for about 5000k, then do a full tune-up.

I have a new 05 ZX4, and the manual recommends NOT stressing it for
~3000K, in order for the rings/pistons to work themseleves in. Is this
really necessary?
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Old 09-26-2005, 10:01   #2 (permalink)
Mike Hunter
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Re: Break in period?







Read this



What's the Best Way to Break in a New Engine?


The Short Answer: Run it Hard! Why? 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
that small amount of spring tension seal against thousands of pounds of
combustion pressure on the way down? Of course it can't. How do rings seal
against massive combustion pressure? From the actual gas pressure itself!
The pressure takes the path of least resistance, which means 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 too completely seal around the bore. If the gas
pressure is strong enough from a wide-open throttle, and then the entire
ring will make contact with the cylinder surface, and it will wear perfectly
into the right shape. The problem with "Easy Break In" ... The rough
crosshatch pattern in the cylinder bore acts like a file to allow the rings
to wear. The rings quickly "use up" the 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 ... only about 20 miles! If the rings aren't
forced against the walls, 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. An additional factor that you may
not have realized is that the person at the dealership who set up your
vehicle probably blasted your brand new car 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: Warm the engine up completely.
The main thing is to load the engine by opening the throttle hard in 2nd,
3rd, and 4th gear. The best method is to alternate between short bursts of
acceleration and deceleration. You don't have to go over 65 mph to break in
your engine. Also, make sure that you're not being followed closely by
another car when you decelerate! The biggest problem with breaking your
engine in on the street (besides police) is 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 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. I know 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 may be tight parts in the engine
and it might do damage or even seize if it's run hard." Consider this: If
there is something wrong with the engine clearances from the factory you'll
find out about it soon enough no matter how easy or hard you run the engine.
As long as the engine is fully brought up to temperature before it's run
hard, you'll never have a problem. If there are any parts that are tight
enough to cause seizure, no amount of running will loosen them up and fix
the problem! So why do all the owner's manuals say to take it easy for the
first thousand miles? Good question ... 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? An
easy break in! Because, when the rings don't seal well, the blow-by gasses
contaminate the oil with acids and other harmful exhaust 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! Blow by
is reason why it is necessary to change oil MORE often on a high mileage
engine. The reason is that brand-new rings don't seat all the way around
the 360 degrees of their circumference. The gas pressure from hard
acceleration forces the rings to contact the cylinder around their entire
circumference, which is the only way the rings can properly wear into the
exact shape of the cylinder and seal the combustion pressure. Avoid idling
the engine. There is no load on the engine, so the rings are just going up
and down "along for the ride". Only a small portion of their surface is
actually contacting the cylinder wall. The ring area that does contact the
cylinder wears down the roughness of the honing pattern on the cylinder
walls. Once the roughness of the cylinder is gone, the rings stop wearing
into the cylinder. If this happens before the entire ring has worn into the
cylinder and sealed, you will have a slow engine no matter how hard it gets
ridden after that point. The difference between an idling an engine driving
it easy, versus one being driven hard is that the rings don't get loaded for
more than a split second and don't seal, and an engine is in 100% ring
sealing mode.


mike hunt


> In ancient days one would drive a new car like a maniac, helping it to
> "break in" for about 5000k, then do a full tune-up.
>
> I have a new 05 ZX4, and the manual recommends NOT stressing it for
> ~3000K, in order for the rings/pistons to work themseleves in. Is this
> really necessary?



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