Okay, my last words (thank God?) on this subject.

I agree that a smaller R/S ratio increases side loading. I don't think this is a redline consideration, though, because side loading is highest near max torque rpm, not redline. The high cylinder pressure at max torque rpm is what causes the torque to be high. Up at higher revs, breathing suffers and pressure falls off.

Bigger R/S ratio also reduces max piston acceleration. But it makes a difference whether the bigger ratio comes from a longer rod or a shorter stroke. (I got stumped by the calculus - too long out of school. But through the miracle of spreadsheets, I could analyze very small finite steps rather than infinitesimal ones - close enough.) I varied the S2000 rod length by +/- 5%, and then stroke by +/- 5%. The resulting effect on acceleration was +/- 1% for the rod length variation and +/- 6% for the stroke variation.

I believe the reason high-performance, high-speed engines do tend to have big R/S ratios is because they use very short strokes, not very long rods. They go to the short strokes to minimize max piston acceleration. That's my view, not necessarily the gospel truth.

Jet designer dude

 

MY '04 ENGINE NOTES

 

Thanks for your insight dhayner.

So if we are a tiny bit "challenged" in mathematically proving the limiting factor in max RPM (I get a little exhausted with the calculus as well...! ), can we discover it practically? What usually breaks?

We have the following possibilities:

1) Piston side loading/piston slap, etc.--->cylinder scoring, broken rings
2) Piston/rod acceleration--->shattered rod
3) Crankshaft stress failure
4) Valve float (unlikely)
5) Aspiration issues
6) What did I miss?

The strange thing is it seems that metal failures don't usually happen by increasing stress by 5% or 10%. It seems like you you need to multiply stress to get failures, but that's more intuition than anything. (I say that because manufacturing tolerances themselves must be in the +/- 10-20% range for some forged metal components.)

So what is the failure mode when it is not a mechanical overrev from a mis-shift???

It seems like under very high load it is usually the diff that breaks before a rod or crankshaft.

Billman, you have all the clients with broken engines, how do they break if it's not from a mechanical overrev?

Have you had any clients with blown '04 or '05 engines?

 

Two were blown by supercharging. One was hydrolock, other I'm not sure yet. All are 00-03.

 

If you look at my dyno chart, it appears that Honda isn't telling the whole story... the power does indeed come on 500 or so RPMs sooner, but it also continues, my car made peak power exactly at redline, so an increase in rev limit, even power drops slightly will still produce better acceleration, as it's all about area under the curve.

This is an 02 vs my 04. Clearly the 04 makes more power.



I suspect that an 00-03ecu will run the motor too lean and you'll have more risk of knock.

 

whoa!!! the 04-05 has way more power...hummmm...both cars stock in that dyno chart????

 

this should be well know fact by now...

http://www.vtec.net/articles/view-article?...4&page_number=2

 

hummm maybe i was on the slow bus

time for an 05 upgrade...i always wanted a berlina s2k anyway..

 

So much for all those guys who totally slammed the 04 changes calling them pussy changes 9K redlines notwithstanding.

And we were saps for waiting and wanting the 04+'s

 

Do you know if the '02 was tweaked in any way? The mid range does not show the sag in torque around 5000 rpm that I've seen on other dyno charts. If you shift the lines using percentage of maximum rpm as the horizontal axis (so that both redline at the right end of the graph), the two power lines will lie almost on top of one another except at the very top end - without the difference in the mid range that is supposed to be the main difference between the engines. I wonder what's going on there.