Best ways to lower the engine compression ratio

I guess the questions we need definitive answers to are just that PG and will a stroker kit or piston profile alone be enough to lower the compression ratio?
 
Thicker/more gaskets is the CHEAPEST hence the most popular, but it's a bit of a bodge imo. Also I wouldn't use shorter rods or skim the pistons either, for the same reason; the pistons won't be reaching TDC! Thus reducing the "squishing" of the mixture.

The best way to do it without a doubt is using low comp pistons. Off the shelf or custom.
 
Displacement will only change of you change the crank throws. Conrods will just make the same displacement take place lower down the bore.
 
Hi,sorry used to every body running turbo cars which already have L comp pistons,so only option is steel head gasketts so you can increase boost,these are not cheap to buy and a few hours labour if you can't do it yourself.Cheers.
 
Theres nothing wrong with using shorter rods!

Youre changing the squish with different pistons anyway...there is no other way of lowering CR than by changing squish.
 
Munday said:
Theres nothing wrong with using shorter rods!

Youre changing the squish with different pistons anyway...there is no other way of lowering CR than by changing squish.
Click to expand...

Less so though. Using low comp pistons at least the piston reaches TDC, the squish is only reduced in the dished area of the piston and not over the whole area as with shorter rods etc. They also help to keep combustion in the centre of the cylinder, exactly where you want it, as I'm sure you know.

I didn't say there was anything wrong with shorter rods. Read it again. I said I wouldn't use them.
 
Normally,

there are three options to lower the static CR in any piston engine.

1] A thicker head gasket (some manufacturers and after market companies make head gaskets for a particular type of engine of different thicknesses and material).

2] A different cylinder head from the same type of engine which has a larger combustion chamber.

3] Fitting pistons with a dished or bowl-shaped crown ( a lot of after-market companies that make pistons will offer them with different sized dished and domed crowns to suit different CR requirements).

Most production pistons now are of the cast alloy hyper-eutectic type which don't lend themselves to have the crown shape altered in any way. It can weaken them considerably and cause overheating issues as the thickness of the crown helps absorb the heat generated from the combustion process.
 
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Thanks for all the input, that is really helpful and has given me some new avenues to explore (article coming soon.)

How much difference would a thicker gasket make? Has anyone got the maths involved here?
 
here is 1 idea i came up withi put a turbo on my gsx 750 slabside to lower the compreshion i put shorter spark plugs in it worked quite well
 
TDC will always be reached no matter what pistons or rods are used, otherwise the engine wouldn't turn over!

Using shorter rods increases pressure on rings and cylinder bores due to increased sideways forces and reduces torque duie to the angle of the rod relative to the crank journal. It also changes piston speed, the amount of time piston is near TDC, etc. Very complicated subject. Upside is that engine may rev easier.
 
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