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Old 12-28-2005, 01:50 AM   #14
curtis73
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Re: Re: Re: Re: Re: engine running without exhaust

Quote:
Originally Posted by Black Lotus
Have I ever told you how much stinky, clattery diesels, especially diesel trucks that always tip over, and I can't see around disgust me?
Did you know they stink, clatter and tip over?
Maybe another day.
(Phew) that felt good.
Ha ha. I love a good roast

I'll just show up some day in a popcorn-smelling, biodiesel-burning, E30 and show that little Lotus of your's who's boss

Seriously, your words are wise despite your misguided opinions on the worlds single greatest fuel. In theory the compressed air of which you speak would have more inertia, but the fact that its under pressure makes it less important. If (in your hypothetical example) the intake air charge were doubled in density, it would be doubled in mass, which means for the same intake velocity effect you would basically need half the intake runner length at the same diameter. Since many intake runners are only about 8" long, a 4" runner makes sense for that hypothetical setup. The difference between a 4" runner and no intake at all in the case are neglegible, so that part of the engineering is omitted from its design.

To tie this in with the original question; in the case of turbo exhausts, the pipe diameter after the turbine is often as large as practical. Since the turbine doesn't rely on scavenging or exhaust velocity once its done with it, the best choice for turbo efficiency is often the biggest choice.
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