waterlock

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First of all, what is it? Ever since I got my cold air intake for my 97 eclipse, people have been warning me about having the intake suck in water. How much water would the intake have to suck in before anything major happens?

posted by  Anbuhero

hi i live in ca, and with the recent rains, the roads have had lots of water especially in the hi deserts, couple of my friends have sucked up enough water with their low, long cold air filters to bend their rods, other friends just did not drive their cars and some changed over to the short until the floods subsided. heavy rains will allow enough water into the intake to lock yours up, not worth taking the chance.

posted by  doug wong

"Water lock" is the familiar term for the condition known as hydrostatic lock. As referenced in your question, it occurs when water is ingested by the engine in a certain quantity. The specific quantity necessary varies by engine. The problem is one of basic physics -- liquids are non-compressible. Water, of course, is a liquid.

Your engine is a four-stroke-cycle engine. The four "strokes" are intake, compression, power, and exhaust. Note that compression directly follows intake. The intake stroke occurs during (generally) downward movement with the intake valve open. This causes an air-gas mixture to be drawn into the cylinder. At the bottom of the intake stroke, the cylinder volume above the piston is at its greatest. During the compression stroke, the piston moves upward, reducing the cylinder volume above the piston until the piston reaches its upper travel limit. At this point, the cylinder volume is at its smallest. Under normal conditions, the air-fuel mixture is basically gaseous in nature and is therefore compressible. But... what happens if the cylinder is contains liquid instead of vapor? In this case, at the point when the cylinder volume is reduced to where it is approximately the same as the volume of liquid in the cylinder, the piston will no longer be able to move upward. This is the "lock" point.

Depending upon specifics of operating conditions, engine design, and general engine health, this sudden stopping of the piston by a non-compressible mass can cause damage such as a broken piston, bent or broken connrod, shattering of engine castings, or even breakage of the crankshaft.

As to the question of how much water is needed? Not much -- when the engine ingests into any single cylinder a volume of water greater than the cylinder volume above the piston at TDC, the piston in that cylinder will be stopped on its compression stroke when the cylinder volume above the piston matches the volume of ingested liquid. The smaller the engine (displacement), the less liquid is needed to get to this point. That amount can be roughly calculated for any given engine, so long as the bore, stroke, and compression ratio are known.

posted by  cpprioli

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