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Old 03-02-2011, 12:59 PM   #72
because I can
Joined: Sep 2010
Location: San Francisco Bay area
Oddometer: 9,116
As you mentioned, the burn is often going on clear out the exhaust pipe. That obviously isn't pushing on the piston any since the exhaust valve has been open for some time. At higher rpm's, the flame front's usefulness pushing on the piston is actually pretty much over LONG before the exhaust valve opens. The piston is already in a hurry and the flame front has no idea. Many tuners including Yunick, Curve, and Hodgeson think that at higher rpm that piston hanging around longer and waiting for the flame fronts crucial first grunt on the piston is the main source of longer rod ratio's higher rpm torque gains. The advantages and disadvantages of different RLR's vary with rpm. Longer RLR's favor high rpm torque. The physics of longer RLR's also favor higher rpm. Most tuners report longer RLR's netting HIGHER rpm limits despite the heavier rod. Most attribute this in practice finding again to the longer RLR's slower decel and acceleration on both sides of the dead stop. Longer RLR's have greater acceleration and deceleration further into the stokes at TDC but they also have less herk and jerk right at TDC and that is what really effects the situation negatively.

You can get Carrillo rods from Carrillo, San Jose BMW, and Siebenrocks as far as I know. Venolia pistons are available from Venolia and San Jose BMW. Mahle and others make applicable pistons as well.

More data? This narcissist has never taken a photo of any of his work or others that I have worked with. I never owned a camera till just recently and I still haven't taken many photos with it. I never posed with a race bike at the track. I never saved any dyno printouts of experiences I have spoke of on this topic except for ONE of my own. It's all been in the interests of eventually controlling the minds and bodies of airheads! I think all of Yunick's books are a good source. I have never looked to see if any of them are googleable. I will read your link when I get time.

My bike was dynoed on an electric dyno. CC Products dyno was electric if I remember right. It might have been hydraulic. It was a brake dyno. That I remember for sure! My dad's used water. I have never seen any of them read down right off idle for some reason or another. Dynojet doesn't JUST make inertia dynos.
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