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Old 07-27-2017, 06:14 PM   #172
JMlegacy
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Member#: 341649
Join Date: Dec 2012
Chapter/Region: International
Location: Sun City
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Quote:
Originally Posted by Maxwell Power View Post
here is what I'm trying to explain in a really crappy MS Paint drawn picture.

Point A is the large quench pad that is created by placing a 2.5L bore on a 2L head. Point A on the non enlarged head has a greater quantity of exhaust gas passing that point in addition to a relatively stagnant pocket (B) just below it. When the piston moves to the top, that pocket is cleared out and the hot gasses are pushed up and around the corner at Point A. This causes the heat to be deposited into the head at that point which creates a hot spot that will cause detonation the next time the cylinder is filled and compressed. Also, filling that void around the corner takes more time and energy which can rob power. Someone might argue that the cool charge coming into the cylinder the next time around will cool off that hot spot. That is what I believe happens to a degree under light loads and when the intercooler is cooling the intake charge off significantly. Under high boost and heat soak conditions the spot will not be cooled sufficiently by the intake charge and that point will only get hotter and hotter.

In the cylinder on the left, the point A only has a small amount of gases flowing past it and the very small pocket (B) doesn't retain a lot of heat or stagnant gasses.

This is why Hybrids are so unreliable. You can have a 9:1 compression hybrid with a larger chamber and it would be leagues above a 9:1 compression hybrid with no chamber work in both power and reliability.

So maxwell, I thought the hybrid pistons took care of this problem?

I'm looking to do a Hybrid at the moment, already bought some parts. Need to buy gasket kit, timing belt and the JE pistons.
CNC is not an option at this moment!
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Last edited by JMlegacy; 07-27-2017 at 06:28 PM.
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