S2000_Europe

I am a bit curious to know which is the cause, I though it was the piston but recently heard that is the engine head due to the valves floating, which limits the capacitiy to rev higher.

If this is true why F20 owners do not swap their cranks for a F22 crank to have a 2.2L able to rev to 9.000 rpm? I think it is some more that I try to explian above who limits the abilitiy to rev higher safetly





J

yeliaB

Well, my take on it is that it's neither -- it's the crank. Honda went from 2.0 to 2.2 liters by using what hot-rodders call a "stroker" crank. As the name implies, it increases the length of the piston's stroke.

The problem is, increasing the stroke means that, for a given RPM, the pistons in a "stroked" engine have to travel farther than the pistons in a non-stroked engine. This means that each piston reaches a higher speed as it moves up and down in the cylinder, meaning that higher forces are placed on it as it changes direction, as well as any friction-related issues caused by its higher speed as is passes through the cylinder.

With all engines (stroked and non-stroked), piston speed increases with increases in RPM, until eventually (assuming all the other parts of the engine -- like the valves -- can handle the higher RPMs) the piston is just going too fast.

With an engine designed as "close to the edge" as the F20, the higher piston speed caused by using a stroker crank (essentially turning it into an F22) is just enough to put the piston speed too high. Therefore, the only thing Honda could do to bring the F22's piston speed back to a reasonable level would be to reduce the redline.

Just my $0.02,

Ed

apex2k

In the 2.0 the limitation seems to be the head with retainers failing due to missed shifts. Valves start floating in the 9,200 range with piston contact around 10,000, if memory serves me correct. Once the valves start to float the retainers take a real pounding, leading to fractures. The bottom-end on the 2.0 seems pretty tough.

Conversely, the 2.2 is probably better off up top with the 8,000 redline. Most concern seems directed at the bottom end due to the piston speed, but another concern is side-load. With the stroked crank the con-rod angle is greater increasing the side load on the piston and cylinder. I suspect it is the combination of the two that lead to to lowered redline.

Honda knows what they are doing. If they could have built a reliable 2.2L-9,000 rpm motor, they would have. I wouldn't do it unless you like blowing up motors, and can afford to.

S2000_Europe

I do not have plans to do it, I read that alaniz has a crank capable of 9000 rpm in a 2.2L.. maybe in a bored F20? if not I do not know where is the difference with F22 crank

CrazyPhuD

The biggest concern that has been raised is with the bottom end. Yes the valve springs have been changed. But to my knowledge there has been no proof that they are stronger or weaker...just different part numbers. The bottoms is more of concern that the top.

jzz30

the f20 and 22 heads are basicly the same thing with the exception of different cams. the valves actually start to float at 10,700 rpm so you really need to over rev to kill a valve. As apex2k had stated the side load is of main concern. when honda stroked the f22 they shortened the rod, which in turn made the forces in the x direction or the horizontal greater than the f20, if you do simple physics on the forces on the x and y directrions you can figure out how much extra side load or wasted energy is in the f22 compared to the f20.
if you want to rev to 9000 safely then you can do a few things to help do that by first using f20 rods which are longer than the f22 and getting custom pistons made which are the rods difference shorter in the distance from the top of the piston to the piston pin. along with a custom piston you will also have a lighter piston which will help with reducing friction.

Emil St-Hilaire

The rev.limiter.!!!