Quote:
|
Originally Posted by Dean
And exhaust gas starts contracting pretty much the second it stops combusting(Heat source). There is no additional heat in the headers/uppipe, so anything you can do to retain the existing heat will minimize contraction, and maintain velocity to the turbo.
|
I remember reading somwhere that the gasses are nowhere near done expanding due to the heat of combustion until they're into the headers and on their way up the up-pipe. The expansion of the exhaust gasses isn't instantaneous. However I would agree that the rate of expansion is decreasing from the instant the combustion event occures.
Also, if you have an expanding gas volume between the piston and the turbo's turbine blades, doesn't the math start looking a lot like PV=nRT? Granted it's not totally closed, but it's also not just an open pipe.
Thirdly, what about the exhaust pulses? There is energy in the form of a compression wave traveling down the pipe. I know lots of N/A cars take advantage of this and tune the pipe length/diameter such that the resonance frequency of the pipe matches the opening of the exhaust valves on another cylinder, allowing the low-pressure part of the waveform to assist in extracting exhaust from the cylinder. I think the turbine in the exhaust might limit the usefulness of that effect on a turbo car, unless you went with one of those funky rear mounted turbos.