Guest wrote:But a short stroke engine has lower values than a long stroke engine of comparable displacement.
No, the old “for a given displacement short stroke means less leverage hence less torque” is a false myth, for a given displacement the amount of peak torque is pretty much independent by the bore/stroke ratio. To be more precise, there are secondary effects, but they aren’t directly related with the leverage, they are related with the shape of the combustion chamber, over a certain value of the bore/stroke the shape could be very poor and cause a reduction of the combustion efficiency, hence of the mean effective pressure, that is proportional to torque.
Same goes for the myth of “a V8 has more torque than a V12”, simply false, or, as Marmorini once said with notable brevity : “balls”.
Guest wrote:Why do they not just use a higher compression ratio? This would achieve a greater density of air/fuel in the cumbustion chamber, would it not?
Compression ratio has nothing to do with the amount of air (hence mixture) entering in the engine, CR is the ratio between the volume with piston at BDC and the volume with piston at TDC. The influence of the CR is on the thermodynamic efficiency of the engine, but efficiency doesn’t growth linearly with CR, the slope of the curve actually decreases with CR, so above a certain value there’s little to gain.
bcsolutions wrote:The problem arises when the compression ratio becomes so high that the fuel/air mixture within the combustion chamber detonates uncontrollably
Detonation was certainly a huge issue during the turbo era but at current F1 rpm isn’t, there’s no time enough to have it. In the current F1 engines the CR is in the order of about 13, limited mainly for geometrical reasons. If you consider that for a unitary displacement of 300cc the combustion chamber volume at such CR is little more than 20 cc, with a bore of little less than 10cm you rapidly understand that the combustion chamber volume at TDC is largely formed by the hollows for the valves on the piston upper surface and these also depend by valves size and lift. Further reducing the volume of the hollows would limit the valve design, the reduction of the volumetric efficiency would likely offset the increment of thermodynamic efficiency.