By acumulated strokes, I meant one for each cylinder, and by compression area I meant the volume between top of the piston at TDC and the Cylinder head.
In a 10-1 compression engine that's something like 10%. And the way car companies like to fudge things, it would be an easy way to call a 2.0L engine a 2.2L. Not that I belive this to be the case for the Ap1 to Ap2 jump.

 

Displacement is just that... It's the volume displaced from the bottom of the stroke to the top of the stroke multiplied by the number of cylinders. It does not include the volumes above the pistons at TDC.

 

I already hoped you guys would notice the at the end

 

again

 

It's amazing how such a simple question has resulted in so much chatter.


The stroke was increased to make up for the power lost when the red line was lowered. Not the other way around. The proof of this is in the other changes that were made, including the heavier flywheel, CDV, and thicker retainers. All of these things work together to minimize the damage done during a money shift. Honda also wanted more torque in their US Spec engines, and stroke is the easiest way to get more torque out of any engine (as the longer crank throws give the pistons more leverage on the crankshaft).

There are some factors involved in the stroking that might result in the F20C stresses being lower at 9K than the F22C is at 8k. The longer stroke requires shorter rods, and that means greater side forces on the crank and pistons. Since our pistons have abbreviated skirts, side forces could easily be a greater factor than peak or average piston speeds.

Have any of you seen any data on the BMEP of the two engines? Since the specific output of the F22C is lower, the additional torque might be entirely due to the extra leverage gained by the longer crank stroke. Does anyone know for sure how the VE and BMEP of the two engines compare?

 

[QUOTE=RED MX5,Jul 20 2007, 03:47 PM]It's amazing how such a simple question has resulted in so much chatter.


The stroke was increased to make up for the power lost when the red line was lowered.

 

These are 2 of the most basic parameters of engine analysis/modeling.

VE is Volumetric efficiency. air flow = diplacement * rpm * VE

BMEP is brake mean effective pressure. HP = BMEP * stroke * piston area * rpm

 

Side forces are the issue with the F22C. Piston sleeves wear appreciably faster above 8500 RPM.

Although Honda kept the official HP output the same for both motors, F22Cs seem to dyno about 10 HP higher stock.

My guess is that there wasn't just one reason for the stroke increase on the F22C. It's likely a combination of wanting more torque and creating more headroom to help against money shifts.

 

I remember reading a release from Honda saying that the reason the red line was lowered on Ap2 is because of piston speed. Because of the longer stroke, the Ap2 piston travels the same speed at its redline as the Ap1 does at its redline. Thats because the Ap2 piston has to travel farther than the Ap1 to make one revolution, thus the pistons in an Ap2 at 9000rpm are moving faster than those of an Ap1 at 9000 rpm. Honda had set a maximum piston speed that they didn't want to go over. Since the Ap2 would have a faster speed than what they wanted at 9000 rpm, they had to lower the redline. QED

 

[QUOTE=carrera4,Jul 21 2007, 01:24 AM]My guess is that there wasn't just one reason for the stroke increase on the F22C.