To: | spridgets@autox.team.net |
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Subject: | RE: Ugh |
Date: | Tue, 07 Jan 2003 15:28:33 -0500 (pop-3.dnv.wideopenwest.com) |
Longer connecting rods DO increase compression, but they reduce displacement. Maybe some ascii art will help: ___ ___ Combustion chamber ___| |___ ___| |___ | | |___| Piston up | | | | | | | | | | | | | | | |___| | | | Piston down | | | | | | (Assume that the diameter of everything is constant) Swept area of piston = 4 Compbustion Chamber with piston up = 2 Compression ratio = 4:2 or 2:1 Displacement (Piston Sweep + Combustion Chamber) = 6 Longer conrod moves "stroke" of piston higher (as you noted): ___ ___ Combustion chamber ___| |___ ___|___|___ | | | | | Piston up | | | | | | | | | | |___| | | | | | | | | | Piston down | | | | | | Swept area of piston (still) = 4 Compbustion Chamber with piston up = 1 Compression ratio = 4:1 Displacement (Piston Sweep + Combustion Chamber) = 5 Now, nobody increases the conrod length by 1/4 of the stroke, but you get the idea... A longer crank journal (with the same conrod) increases both compression AND displacement (sweep of the piston goes lower down AND comes higher up). That is why "stroker" crankshafts are usually supplied with matching conrods (a touch shorter than stock to keep the compression from becoming insane). > > I don't think longer rods will give you more compression > -- they'll just move your exact same compression stroke > higher in the cylinder. For higher compression, you need > to change the crank to get the pistons to travel farther. > Right? > -- > Chris Eck > 59 Bugeye /// unsubscribe/change address requests to majordomo@autox.team.net or try /// http://www.team.net/mailman/listinfo /// Archives at http://www.team.net/archive/spridgets |
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