^ Thanks for your input

Guys don't forget the main reason for this project....I originally had 3...now its FOUR guys, with blown F20C's. If I could find an F20C in drop in state, this project would not have started. I'm looking for the most cost effective way to get the guys on the road. They do no wrenching of their own, so getting into major building is not going to help them. There were at the time TEN 2.2L engines, brand new from in-transit wrecks, ready to drop in. If you've ever done an S2000 tranny, you should know that the work that follows to remove the engine is cake.
Bottom line...I can offer these guys one hell of a deal for a new engine. I have been given a special price by the supplier, who has taken on the project.

 

Whoa, I didn't even tell you that..you must have read

 

I stand corrected, regardless, I doubt there will be problems.

 

I still think that it's the R/S ratio that limits revs. That's why squre ratios like the B16 kick ass and that's why F1 cars scream. I don't believe piston speed is the most destructive force when compared to poor R/S ratios regardless of what jet designer dude says

-Matt

 

No offense taken.

I agree that R/S ratio is important as it affects piston acceleration. Remember that Force=Mass times Acceleration. This means the force exerted on the big end and small end bearings depends on the piston's mass and its acceleration. When I said that conrod length was not a major factor, I only meant that any likely difference in F20C to F22C length (I don't have the F22C length) wouldn't affect the acceleration much.

Imagine a very short rod "whipping" the piston as it passes TDC - high acceleration. On the other hand, a very long rod sort of pushes the piston straight up without the "whip."

Let's try slightly more technical terms. Approaching the top of the stroke, a short rod will make the piston move farther per degree of crank rotation than will a long rod. Therefore, for a given stroke and rpm, the piston is moving faster with the short rod. The piston has to stop at TDC (we hope), requiring a greater acceleration to do so from the higher speed.

I hope you don't make me refresh my calculus - it's been a long time. The guy whose spreadsheet I used did do the calculus, though.

Jet designer dude

 

I'm not an engineer, so maybe I'm not seeing this right. It seems to me that the rod length has little to do with the acceleration and the rod length is controlled by the design of the block. The way the crankshaft is machined (journal to center distance) controls the distance the rod travels, and thus (for longer distances) increases acceleration.

 

If when you say rod length you are refering to travel, woulldn't a longer rod move further per degree of crank rotation?

 

Can we clarify that a little to say that max piston acceleration is what limits rev capability in certain failure modes? Those would be in the lower block: rods, crank, etc. There are many other ways that engines fail when turning too fast.

In S2000 reality, we have far more overrev failures up top where apparently valve stem acceleration is what limits rev capability.

Billman has a couple of threads with photos showing the damage that occurs when a valve stem is suddenly stopped by its retainer and how it ultimately busts through the retainer and drops into the cylinder. This failure mode was described earlier by Woodwork as the very specific evidence of engine overrev in the S2000 engine.

More classic overrev damage occurs when the valve floats due to overrev or insufficient spring tension and slams into the piston--those have also apparently happened on the S2000.

It seems like lower block overrev issues are much more rare on the F20C.

Most likely valve springs and cam profiles will be the limiting factors in maximum rev for a F22C when it is placed into a MY2000-03 S2000, just as they are in any other S2000.

 

I think you are right. Rod length has little to do with vertical acceleration or stroke. It is the "radius" of the crank mechanism (journal to center distance, as you said) that primarily controls both the stroke and the acceleration (as a function of RPM). I think there is some trigonometric element that makes the acceleration profile change a little based on rod length, but I think it is minimal.

The two more important aspects of rod length, I think, are mass and angle and they are offsetting when it comes to maximum RPM.

The shorter the length, the less mass, and the less stress on every single rotation of the engine (every rotation = 2 accelerations and 2 decelerations.) But the shorter the length, the greater the rodiston angle, and that puts more stress on the cylinder walls and piston components.

 

Makes sense,

Thanks