AceOfDiamonds0 Posted March 25, 2014 Author Report Share Posted March 25, 2014 I haven't got a chance to check it yet. I have to go pick up a compression gauge so I can. I'll post what all 4 cylinders are once I pick one up. Quote Link to comment
Russell Posted March 25, 2014 Report Share Posted March 25, 2014 I haven't got a chance to check it yet. I have to go pick up a compression gauge so I can. I'll post what all 4 cylinders are once I pick one up. you can have good compression in all cylinder but still have a low compression ratio, you know what the difference is right. Quote Link to comment
AceOfDiamonds0 Posted March 25, 2014 Author Report Share Posted March 25, 2014 Yeah, the compression in the cylinders should be between 175 and 195 right? I don't remember how to calculate the ratio though. Quote Link to comment
Russell Posted March 25, 2014 Report Share Posted March 25, 2014 I believe so but compression ratio is the amount of volume from bdc (bottom Dead center) compaired to the volume of TDC (top Dead center) Ex.1 Bdc 100cc TDC 10cc 100:10 = 10:1 compression ratio If you compression is usually lower than 8.5:1(for naturally aspirated engines) excessive timing is needed to get optimal power out of the motor. Quote Link to comment
Doctoraudio Posted March 25, 2014 Report Share Posted March 25, 2014 I am working on a LZ 22 engine now.The L18 work great, but it not for daily driving! So I am going larger displacement. Quote Link to comment
datzenmike Posted March 26, 2014 Report Share Posted March 26, 2014 Many things are needed to calculate the correct CR. The Swept Cylinder Volume is the bore x Pi R2 X stroke. Basically how much air is moved by the piston from BDC to TDS. Everything above the piston is the combustion chamber and includes the piston dish or a minus amount if a domed piston. Next the piston may not reach the top of the block. This is another bore x Pi R2 X (the distance from the piston top to the block or deck surface) this volume is added to the combustion chamber. If the piston protrudes slightly above the block this volume must also be calculated and removed from the final combustion chamber volume. Last is the crushed gasket thickness which is between the block and the head. And one more time bore x Pi R2 X (1.2mm is the norm for our motors) This volume is added to the combustion chamber. The head combustion chamber must be determined by filling with a known amount of water. Combustion chamber volume + gasket volume + deck height volume (- if above the deck) + piston dish volume (- if a domed piston) = Total combustion chamber volume. Swept Cylinder volume + Total Combustion Chamber volume divided by Total Combustion Chamber volume = Compression Ratio Quote Link to comment
Russell Posted March 26, 2014 Report Share Posted March 26, 2014 ^ well that is the exact way to calculate you compression ratio I just was giving him a simple to understand it . 1 Quote Link to comment
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