Quote:
Originally Posted by payne171
And at 400C, isn't exhaust manifold pressure going to be almost 65% over atmospheric pressure?
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Nope, it depends on the exhaust system. If it's a restrictive exhaust, sure it could be that high under high power situations. You are right that a slightly more restrictive turbine could replace the muffler requirements, and that's a great idea, but in a well designed exhaust system there is very little backpressure. Think about a compressed air bottle, if you attach a pipe to the outlet and let the gas out, the gas is not going to be at the pressure in the air bottle. The pressure has turned into "kinetic energy", as the gas is now travelling at a higher velocity but with lower static pressure.
The pressure isn't constant. The "static pressure" shall we say, inside the pipe, is what the pistons have to push against. The reason the exhaust valves open early is so the gas blows itself down the exhaust pipe instead of using the piston's energy to do it.
drmiller100, no, a turbine does not convert heat energy. A turbine can only work across a pressure gradient. If you have a straight pipe with air blowing through and a flame, and you place a turbine downstream, it will do absolutely nothing. A turbine can use heat energy only when the heat is used to heat a gas in a closed chamber, which increases its pressure and allows the turbine to extract some of the energy.