I was thinking about the Civic CVCC engine where it had two chambers, one for the explosion and one for the mixing of fuel. I had the idea of putting a lean burn engine head on a higher displacement engine (1.5L vs. 1.7L D series) because the 1.7L has a longer stroke and would distribute heat over a larger area. Anyways I came across what I think is a potential problem. Let's say for example that the 1.7L had a bigger bore than the 1.5L and I wanted to do really lean fuel mixtures. Well one thing about really lean mixtures is that you want to ignite as much fuel as possible, otherwise you'll end up with a bunch of unburnt fuel, right?

So here is my question: In a 1.5L engine 9.3:1 compression ratio with a 20:1 fuel mixture, the piston is at TDC is the same percentage of fuel "close" to the spark plug as in a 1.7L same design engine but with a 9.9:1 compression ratio with a 20:1 fuel mixture?

Or maybe you could answer this question: What would the compression ratio have to be in either the D series 1.5L or 1.7L engine in order for there to be the same amount of unburnt fuel when running a 20:1 air-fuel ratio? My thinking though I'm wondering if I'm wrong, is that a 1.5L and a 1.7L D-series engine at a 20:1 AF ratio, the 1.7L will have more unburnt fuel because there will be more fuel that is too far away from the spark plug, that the remedy is to make the 1.7L engine have X compression ratio in order to have it match the 1.5L engine in the amount of unburnt fuel.

Hope you guys enjoy my visual of what I'm talking about.




So guys, is it like that? While the compression ratio is higher in the 1.7 compared to the 1.5, you still end up with a larger combustion chamber overall which means that when things get compressed and the spark is ignited, less fuel burns compared to the 1.5L. So back to my question, how do I get the equivalent combustion chamber size as I have with the 1.5L?

Edit: Made it into a picture because this site won't allow for more than one space after another.