Runwell vs Zeda crank

[Lukesky36]

Even though it's only 2mm difference between the strokes that 2mm equates to quite a few degrees in rod angularity and that allows higher power density to be attained due to the extra dwell at the top and bottom.And a long rod takes advantage of this aswell and having both a long rod and longer stroke is better again to take full advantage of this.

So in a sense a longer Rod has more leverage on the crank witch in turn could mean more torque produced from it but we are talking minor differences of 2mm

 

[gary55]

So if I'm getting this right the long rod with the short stroke would be the best for the least amount of angularity of the rod as opposed to the cyl.which reduces friction and increases cyl. life and the long rod long stroke would have the most static time at TDC along with 3+ extra ccs? Is the extra dwell time just allowing the charge to be fully compressed for a millisec. longer creating better bang?

 

[Lukesky36]

So if I'm getting this right the long rod with the short stroke would be the best for the least amount of angularity of the rod as opposed to the cyl.which reduces friction and increases cyl. life and the long rod long stroke would have the most static time at TDC along with 3+ extra ccs?

Yes a longer rod will lower Peak piston speed Peak piston speed is higher with a short rod compared to a long rod(stroke being the same), because the shorter rod creates a greater angle. a rod will not change your cc count unless the piston pinion location to match the rod length is different or head is changed

 

[gary55]

Yes a longer rod will lower Peak piston speed Peak piston speed is higher with a short rod compared to a long rod(stroke being the same), because the shorter rod creates a greater angle. a rod will not change your cc count unless the piston or head is changed

Changing the piston will help if it's a larger piston. the head will not chance the displacement. You need to change the stroke or piston size for that.

 

[Street Ryderz]

So if I'm getting this right the long rod with the short stroke would be the best for the least amount of angularity of the rod as opposed to the cyl.which reduces friction and increases cyl. life and the long rod long stroke would have the most static time at TDC along with 3+ extra ccs? Is the extra dwell time just allowing the charge to be fully compressed for a millisec. longer creating better bang?

Yes all true!Also at bdc the dwell allows the return wave a bit more time to aid in cylinder fill.

 

[gary55]

I didn't think about the BDC part. My thoughts on the rods effect on the piston speed (which could be wrong) is more a factor of the longer rod being heavier rather than it's length. If the 2 were of equal weight they would travel at equal speed. Or do you think the angularity has more to do with it than the added weight? Got me curious.

Yes all true!Also at bdc the dwell allows the return wave a bit more time to aid in cylinder fill.

 

[Street Ryderz]

My thoughts on the rods effect on the piston speed (which could be wrong) is more a factor of the longer rod being heavier rather than it's length. If the 2 were of equal weight they would travel at equal speed. Or do you think the angularity has more to do with it than the added weight? Got me curious.

The piston speed is lower with the long rod due to the time it takes to cover the same distance and that kinda explains why PK's are known to be good at higher rpm and Zeda's make more torque.

 

[Lukesky36]

Here are some comparisons of what Pistons go with what Rod Type if you want to watch the video ill put a Link Link 2 it is pretty informative video.

 

[gary55]

The piston speed is lower with the long rod due to the time it takes to cover the same distance and that kinda explains why PK's are known to be good at higher rpm and Zeda's make more torque.

Silly rabbit. LOL of course it's slower due to the increased time it takes to cover the same distance. What I was getting at was is the cause of the slower movement due to the increased weight of the longer rod ? I think it's the weight since the PKs have the same stroke but a short rod so it can't be the angularity slowing it down if the PKs crank higher RPM cause their short rod would give them greater angularity. Ha with a little help I answered my own question. I'm a freakin genious. In reply 23 greater angle was said to be the reason for greater piston speed. If they are traveling the same distance increasing the friction can't increase the speed so it has to be the decreased weight.

 

[gary55]

Here are some comparisons of what Pistons go with what Rod Type if you want to watch the video ill put a Link Link 2 it is pretty informative video.
View attachment 84152
View attachment 84151

Good ol Fred. I've written this stuff down in a notebook, and refer to it as needed which with my memory is a bit more often than I would like to admit.