Join Date: Feb 2004
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Hot/dry exhaust installation
"You always want to eleminate as mush back pressure as possible. It can burn and/or deposit up the valves."
This is what I have always heard too, but a sailor friend of mine who designs gasoline engines for a living laughed when I told him of my worry that a waterlift system could potentially generate damaging levels of back pressure. I will quote him: "Exhaust backpressure is absolutely not an issue. Period." He says that typical back pressure for an automobile exhaust system is around 3psi. (This corresponds to lifting a solid column of water 83 inches!) He says one year the OEM Chevy Corvette exhaust system, as designed and marketed, gave 7psi back pressure (that''s sixteen FEET of water column). His recommendation was to make the exhaust loop as high as needed to eliminate any chance of back siphoning and to not think about it again. He did say that there would be a slight drop in engine performance, but not anything significant. (We are talking about gasoline, not diesel, engines here, and naturally aspirated, not turbocharged, though even with those, while more of an issue, he thinks backpressure is not a major concern.)
So I now reverse my plans and have begun installing a waterlift system after all!