A 4v cylinder head changes bore size limitations dramatically. You can get a whole lot of valve area for a specific bore with a 4v cylinder head. I've been told the move to smaller bores and longer strokes was to do with emissions. Not power.Truckedup wrote:Honda uses a longer stroke than most the competition especially in Acura 4 cylinder engines. Some of 2-2.2 liters fours have strokes near 3.5 inches with a redline of over 8000 rpm. Now there might be emission or packaging considerations... But Honda is known for high RPM engines so they might know something...
Look at how much better the Chevy LS7 head is to what is on the smaller bores of the 6.0-6.2L engines.
People need to remember that when you extend the rpm range you can use a lower rear gear. RPM range and gearing is a huge factor in accelerating the vehicle. A lower rear gear will produce greater torque at the tire. So what seems like a low end torque disadvantage on the dyno can be easily overcome when the appropriate gear is used for the higher rpm engine. The kicker is the lower rear gear will produce greater torque at the tire over the entire rpm range. So you don't just make up for (to whatever degree) the low rpm range but also have the gearing advantage working with a superior upper rpm engine power output.