Quote:
Originally Posted by PFM
Some more input to compression and knock.
Below is a quote from David Redszus, a racing engineer. Clearly he is describing the 3.6 piston. The underline I provided. Makes you want to look a little harder at some of the aftermarket pistons.
True hemi chambers have a real problem with compression ratio and squish velocity. The resulting combustion chamber shape does not lend itself very well to flame front travel and is often quenched on contact with a chamber or piston surface.
The best solution I have seen was a design by Porsche. They used a full dome piston nested closely against the chamber wall to provide a high squish velocity. The actual combustion chamber was actually a bowl cut into the top of the piston. This combination produce extraordinary high flame speeds, and a compact chamber to prevent detonation. I could see where they could run very high turbo boost pressures and still prevent detonation.
Regards,
PFM
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Good post,
The principal is the same as the earlier CIS pistons which "Quench" the non sparkplug side of the combustion chamber. This yielded a smaller combustion area, pushing the mixture to the ignition source. Combustion management is much easier. It is incorrect that people say these pistons were designed to promote swirl...at least in the initial design, I guess it's plausible that it could. The piston was again for emissions/efficiency. The piston design changed on the 3.6 because of the incorporation of twin plugs