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Old 04-14-2015, 03:18 AM   #20 (permalink)
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Quote:
Originally Posted by RedDevil View Post
This has been proven wrong before, but here goes:

When fuel gets burned it produces a lot of pressurised exhaust gas and heat.
The pressure is what drives the piston down in the expansion phase.
It will do that for all of the expansion phase.

The pressure rises sharply when the ignition takes place just before TDC, and that will indeed slow down the engine a little bit.
But the pressure is still there when the piston moves past TDC, and will stay there until it gets released in the exhaust phase.

The heat just increases the pressure, it also heats up the pistons and cylinder walls so that the fuel won't condensate on them once the engine is at operating temperature.
You apparently have such a flimsy grasp on the subject that you're not aware that pressure immediately follows combustion... do you suppose to tell everyone that somehow the flame front travels through the majority of the fuel BTDC, yet the pressure rise somehow magically waits until the convenient point ATDC? LOL

You apparently missed this in my previous post, so I'll provide it again:
Cylinder head design
"The wedge-shaped combustion chamber tapers away from the plug which is at the thick end of the wedge. The valves are in line and inclined from the vertical. This design usually has a smaller surface area than the others, with less area where fuel droplets can condense. Less fuel is left unburned after combustion, which reduces hydrocarbon exhaust emissions."

Do you suppose to tell everyone that fuel droplet condensation only occurs at startup, and hence the manufacturers would undertake to design an entire head just to mitigate a problem that lasts for that short warm-up interval? LOL