Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
Normal
You've changed the rod ratio but the stroke is still the same as before, that is set with the crankpin offset.Honestly after heaps of reading, I don't think a minor change in rod ratio makes much difference at all. There are as many experts in favour of the lower ratio as in favour of the higher ratios. The really high RPM screamers tend to use a higher ratio, there could be something to that.Supposedly lower revving engines like the Norton get more midrange grunt with a lower ratio.But I'll wager it's not much!In one article a hotrod shop changed the rod ratios quite dramatically while keeping everything else the same. They dynoed before and afterIt made a very small difference, something like 5 HP on 450, more or less margin of error.For the pistons to be light they need to be short and that moves the wrist pin up a bit. Gotta have a longer rod then to make it all work in the same old engine.Glen
You've changed the rod ratio but the stroke is still the same as before, that is set with the crankpin offset.
Honestly after heaps of reading, I don't think a minor change in rod ratio makes much difference at all. There are as many experts in favour of the lower ratio as in favour of the higher ratios. The really high RPM screamers tend to use a higher ratio, there could be something to that.
Supposedly lower revving engines like the Norton get more midrange grunt with a lower ratio.
But I'll wager it's not much!
In one article a hotrod shop changed the rod ratios quite dramatically while keeping everything else the same. They dynoed before and after
It made a very small difference, something like 5 HP on 450, more or less margin of error.
For the pistons to be light they need to be short and that moves the wrist pin up a bit. Gotta have a longer rod then to make it all work in the same old engine.
Glen
