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Break in - New Engine Deceleration - under own vacuum or drivetrain brake?

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Old Aug 3, 2010 | 01:54 PM
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Default Break in - New Engine Deceleration - under own vacuum or drivetrain brake?

I have read controversial engine break-in information. Some say, to let the engine decelerate on it's own, ie., put it in neutral and let it fall to idle naturally. Others say, go 1/2 or 3/4 or WOT throttle with it, depending on tune, detonation, etc, up to around 60% engine range, around 3500-4000 RPMs and then let off the gas and use the engine/drivetrain as a brake.

A little background. I do not regularly downshift when I drive. I will usually just throw it in neutral and when I am ready to go again, select a proper gear for the new speed and head off. All I have ever heard during break-in process is not to downshift the engine, let it fall to idle under its own vacuum. So, naturally, being raised that way, that is what I thought. Engine technology, theory, design, and clearances have changed greatly over that past few years. So, instead of just blindly following what I have heard growing up, I did some research. That leads me to where I am now.

The theory behind door #2, downshifting, engine braking, etc, is to remove the ring and cylinder material out of the exhaust instead of letting it collect between the grooves of the rings.

I do not know the reasoning for door #1. What are y'alls thoughts/opinions/theories for letting the engine fall to idle under vacuum or loading?
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