Originally posted by Eric2004
So do you think there is a real significant difference in terms of power output between the old and new engine? Or was the effect only placebo ( you know, nova produce a new engine, people think it is "new" and must be more powerful, so when they run it, they think it is more powerful where in fact it is the same. or the difference is insignificant.)
By the way what is the conrod length and stroke ratio? Haven't heard of it? How does it effect the performance?
In technical terms there is no conrod length to stroke ratio. Basically, providing you are within the 2.11cc anything can go.
As was already mentioned a longer stroke will produce more torque because the rod moves up and down at a slower pace over a fixed rotation due to having to rotate a larger distance.
With short stroke the vertical movement is much faster on the same given rotational speed as it doesnt have as far to travel to complete a full circle.
The myth of the long and short stroke engine is mainly hype. All the current engines on the market are longstroke because the stroke is greater figure than the diameter of the bore. An engine only becomes short stroke once the stroke length becomes smaller than the diameter of the bore. When both are equal we usually call this a box engine.
Now, rod length is a different issue. A shorter rod means there is a more acute angle of the conrod in relation to the piston at TDC and BDC. This places excess wear on all the moving components as the conrod at first is wanting to push the piston through the side of the sleeve and then pull it back through the same side on the way down. Making the rod longer decreases the acuteness of the angle and helps the engine work less effortlessly.
The problem here is that everyone is continually striving for lower CG's in the car to better the performance. One of the biggest gains is in the engine. Make the engine as low as possible and you vastly reduce the CG. At the same time you make the sacrifice of rod length and longetivity of the engine.