>I don't know if you misquoted, but the long rod will have more
>dwell time at TDC and BDC.

Nope. Look at the graph I linked above. The red line is the long rod and the blue is stock (short) rod. 180 degrees is BDC. If you were to make a line 5.08mm above BDC (similar to the orange line depicting dwell at TDC) you would see that the short rod has more dwell at the bottom of the stroke.

>I think everyone is missing the
>point with this engine. The RPM gains are a minimal advantage
>to the long rod and the torque to the short, the reason you
>build a long rod engine when you can is to relieve side load
>on the cilinder wall, and transfer more of the energy down the
>centerline of the rod as opposed to diagnally across it. I
>have pulled many of the same race engines apart with the only
>difference being the R/S ratio and rod length and you can see
>the difference in the cilinder walls and piston skirts. To
>visualize this draw a tall letter I and a short letter Z. The
>two horizontal lines are the piston and the crank, the two
>vertical lines are the rods. Even with the longer vertical
>line in the I, which vertical line do you think will bend or
>break first. my example is a little exagerated but I wanted
>everyone to get the point. Everyone was getting a little to
>far in the wrong direction. As far as the long rod turning
>more rpm because of the decrease in piston speed, that benefit
>is minimal. The reason the long rod can turn more RPM is
>simply because it can phisically do it without breaking
>parts.

One interesting thing I looked up... (Forgive me, i'm a Ford guy) Powerstroke diesel has 1.71 R/S which is better than the somewhat buzzy 4.6 liter (1.67 R/S). The 5.4 liter has a 1.6 R/S, which is only marginally better than my favorite motor, the 4.9L (1.56 R/S). When you compare typical life of the gas motors, the 4.9L wins hands down, yet has the worst R/S of the bunch. Yet the buzzy 4.6L has a worse R/S than even a 460 (1.72 R/S). Going through a database of many engines, the largest R/S i'm seeing is on the 4.9L's little brother, the 240cid six at 2.14. That motor peaked hp at less than 4000rpm. Yet you have the Honda H23A4 which put out 195hp at 7000rpm with a R/S of 1.49.

That all said, I think the general consensus is this... Any motor is a compromise. This is just one of them. Would I rather have a long rod over a short rod? Yes. Would I personally pay for that difference with custom rods and pistons? No. If I were already going for custom rods and pistons, of course I would go long rod. Would I consider a short rod to be holding me back? I'd be more worried about tuning.


-=Whittey=-