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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Stewart G Griffin on May 01, 2008, 08:55:13 pm
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Please discuss, in great detail, all the ways to raise compression.
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Raise compression? Or Raise Compression ratio?
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They're not the same thing?
Compression ratio, professor.
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No they are not.
Compression is the measurement of cylinder pressure on the compression stroke. Compression ratio is a comparisson of the swept volume of the cylinder vs the volume of the combustion chamber.
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Stewart, The "All of the ways" list could get pretty involved. It depends on what your trying to do & how many new parts you are willing to buy. The beginning of the list could be: Increase: bore or stroke,lump on the piston. Decrease: piston to deck height,head gasket thickness or diameter,combustion chamber size in the head,valve notches in the piston,distance from top of the piston to top ring,dish in the valves. There may be something I forgot, but that's a start. Lorne
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i don't want increase bore or stroke because i don't want to increase cid.
Basically, as you may know, i'm very seriously on this mpg kick, so i want to investigate raising compression but using water injection so as to be able to run lower octane gas.
The thiner head gasket route and possibly using the L98 corvette heads looks more attractive to me as i don't want to have to take the engine out.
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Stewart once again, are you wanting to increase compression or your compression ratio? You need to specify.
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C/R, baby, C/R.
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I was starting to look into the same thing. This water injection thing seems to be gaining some momentum. At first I thought it was just for diesels or FI, like the water/meth kits. It would be cool to be able to use 87 and save a few bucks at the pump and have the savings add up at the end of the year.
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You could increase the dynamic CR by playing with valve timing events by means of a new cam. Here's a
little something I found on the subject: Dynamic Compression Ratio (http://cochise.uia.net/pkelley2/DynamicCR.html)
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If you don't want to take the engine out, buy high compression heads, the other way to raise the Comp Ratio is pistons.