nelziq

Does any one know the rod ratios for the 2.0 and the 2.2 liter s2000 motors? What about the Toda 2.2L stroker kit? Same as the oem 2.2 or do they move the wrist pin higher and use a longer rod? Any info on this 2.5L kit i keep hearing about?
How high can these motosr rev with a built bottom end? Im curious as to which would have the greatest power generating potential.

nelziq

anyone? Is the f20c based on the same block as the K20 series? Maybe ill go ask in their forum.

xviper

I can't say for anyone else, but I have no idea what you mean by "rod ratio".

RazorV3

possibly, they both spin backwards.

Feezy

I believe he means rod to stroke ratio. Perfect is 1.75 and the B16 has a RS of 1.74. Those suckers can be build to rev to the moon.

hukares

Rod ratio is rod length : crank throw. Basically, as the ratio increases, the less side loading the piston places on the cylinder walls and the higher you can rev without breaking something (all other variables equal that is).
ROLLININMYS2000 - I don't know why you say 1.75 is perfect. The higher the number, the less load placed on engine components, so long as rotating weight isn't increased to the point where that benefit is nulled.
Also, the longer the ratio the longer the piston will spend near the ends of it's stroke thus making a slight increase in torque and power as the expanding burning gas has a chance to reach a higher pressure before the piston moves down the bore. Sort of the same advantage as raising the compression ratio.
-Brian

03spa

Because it is the cut off for sort rods and long rods. With 1.75 you basically have your cake and eat it too.

Ideally speaking the engine will be optimized to breath with that ratio. It will be able to perform both high RPM and low RPM. It will not lose a flame front at high rpms, nor will it impeede good cylinder filling at low to moderate engine speeds due to reduced air flow velocity.

Although you can still use a lighter piston rev higher and you'll see good intake and exhaust velocities at low to moderate engine speeds causing the engine to produce good low end torque.

1.75 is considered ideal for race engine builders.

03spa

I think the chevy 327 may have had a 1.76? 2 great motors of their time!

hukares

What magazine are you quoting from here? I can see that you don't really know what you're talking about especially once I read some of your other posts. 1.75:1 is a good practical ratio, to say it's ideal is wrong. There are so many more things involved in cylinder filling than just rod ratio. Also, rod ratio does not determine piston speed, a combination of rpm's and stroke do that. The ratio only determines the acceleration curve of the piston. It won't travel faster than the flame front unless rpms are ridiculously high. Going back to cylinder filling, a longer rod ratio will increase vacuum some, barely noticable in a car like ours, but better in an engine that is more restrictive on the intake, so yes, low end power and throttle response too will be improved.
There are many race engine builders that don't use 1.75:1. Maybe it works well in the height of a stock Honda block, but I have to admit, I'm new to 4-cylinders. I've been building v8's and working with top builders for a while though.
-Brian