Raise compression ratio by using different spark plugs?
- Thread starter pulse98
- Start date
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I have never heard of it so, my answer is no, you cannot raise the CR by a worthwhile amount with just a change in spark plugs.
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A worth wild ammount? No.
I guess technically installing a plug that occupied more space in the combustion chamber could raise compression ratio a tiny amount but I do not know of any such plug, the diameter of the plug thread and clearance to the piston top would limit this to a small useless amount, heat range of the plug would be wrong way offsetting any tiny gains from C/R, such a protruding plug would overheat and possibly lead to pre-ignition
I guess technically installing a plug that occupied more space in the combustion chamber could raise compression ratio a tiny amount but I do not know of any such plug, the diameter of the plug thread and clearance to the piston top would limit this to a small useless amount, heat range of the plug would be wrong way offsetting any tiny gains from C/R, such a protruding plug would overheat and possibly lead to pre-ignition
This is a viable tuning option that many folks 
use on some higher strung engines.. many crotch rockets and 4 stroke snowmobiles show an honest 1 - 2hp gain on the dyno. Not bad for a set of plugs on a 600 - 1000cc engine producing anywhere from 120 - 160+ hp.
On such a large engine, the compression gains from extended tip multi electrode plugs may be negligible. There's only one way to find out...
If gains are realized, my best guess is they're more likely to be from the extended tip. By placing the tip of the plug, and thus the spark/flame front closer to the piston that is rushing up to meet it, you are producing the same effect as advancing the timing... Many folks around here bump their distributors a bit and claim gains... so again, there's only one way to find out.
use on some higher strung engines.. many crotch rockets and 4 stroke snowmobiles show an honest 1 - 2hp gain on the dyno. Not bad for a set of plugs on a 600 - 1000cc engine producing anywhere from 120 - 160+ hp.On such a large engine, the compression gains from extended tip multi electrode plugs may be negligible. There's only one way to find out...
If gains are realized, my best guess is they're more likely to be from the extended tip. By placing the tip of the plug, and thus the spark/flame front closer to the piston that is rushing up to meet it, you are producing the same effect as advancing the timing... Many folks around here bump their distributors a bit and claim gains... so again, there's only one way to find out.