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| Re: Query on Oversize pistons |
Subject: Re: Query on Oversize pistons
by andos on 2002/10/3 10:58:05
Not sure exactly you're intent here, but l'll try and give you a basic run down.
Compression ratio is just the volume contained in a cylinder at BDC divided by the volume at TDC.
Or a 10:1 compression ratio means that the air (and possibly fuel) get compressed to 1/10th the size... so if it was 500ml its now 50ml.
If you increase the diameter this will just mean that you start with a larger number and end with a larger number, but essentially the ratio will stay the same..
However, this would require that the exact same cavity in the piston existed. So if you got flat tops, or different cavity pistons then this can, and in most cases does, increase compression ratio..
An increase in compression ratio is good as it not only provides greater pressure for combustion, it also increases efficiency of the engine..
The reason it is not increased dramatically is dependant on other factors such as fuel, timing, detonation etc.
So it comes down to the type of oversize pistons that you've used.
Hope this helps 
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