Piston and rod size of the D14A3/A4/Z1/Z2

[saxophonias]

so maybe, more compression leads to cleaner fumes right?

[Dodo Bizar]

Well... that's the first basic step when looking at CO2 emissions I guess, but from there I think it gets really more complicated and I am afraid things like local wall temperatures are starting to play a role.

[mynameisowen]

Starting to sound like one of my "Automotive Engines" lectures in here =P

I can add that increasing the compression ratio of the engine is done to increase the thermal efficiency of the engine, in an ideal world you would have it as high as possible without the engine knocking (this is why diesels have higher thermal efficiencies than petrols). However like Joris said there are a load of factors than influence the types of emissions from the engine (like fuel burn rate, turbulence in the chamber, and very much so temperature of the engine), much of this can be controlled by changing the cylinder pressures and temperatures which are controlled by comp. ratio among other things.

I can see why Honda would have a load of different pistons for similar engines (piston is quite an easy part to change compression ratio compared to boring or skimming), that way they can change the specs of the different engines in one family without too much trouble.

Remember different countries have different laws on emissions, etc, so a d16 in Japan might be okay but take the same engine to UK (for example) and it might not pass emissions, or the market may want more powerful engines (like what happens when Jap firms take their cars to america, they make them bigger and more torquey (cos americans are dumb )).

[Law_]

I got the PHXG pistons for my car
I am quite concern though that the Honda compression ratio calculation would not fail:)
on the other side, why would Honda also fake, and tell us 9.0 instead of 9.8?
Do the pistons sit at the same height?

BR