"His book has a permanent home in my bathroom, next to the throne."

Some may take that quote as an insult. Let it be known that only the highest
level of literature can find its way from the office library shelf to the bathroom

That is a great write-up. Learned a couple of new things. I've achieved
my goal of lessons learned for the day. I can now retire from automotive tech
and focus on, "The Caramilk Secret".

 

You can't really improve on what David Reher said.....

All though I love Smokey you gotta remember that he was building motors before real head porting and had tiny little ports and stupid high velocities when they tried to twist those things back in the day, anyway he could find to help slow the port velocity down made HP, so hence the long rods were one of those factors. Today we just fix the head port.

Bret

 

That’s really what it comes down to… there is a very minimal (probably not accurately measurable on most dynos) difference in power production (or more accurately, delivery to the crank) with different rod/stroke ratios, the issue in a race car that’s going to see some rpm is what is lighter, and in a street or endurance car is the ratio high enough/side loading low enough for the engine to last long enough. Past that you just adjust cam timing to match what you ended up with and run with it…

 

Alright, this has been bugging me all afternoon. I even made a diagram,
but I can't see how a rod will have different dwell times at TDC and BDC?

A longer Rod influences the piston to dwell a bit longer at TDC than a shorter rod would and conversely, to dwell somewhat less at BDC. This is another area where people often get the information backwards.

The rod to piston angle is going to be the same when this piston is at TDC
and BDC...? I am referring to any length of rod in the same stroke cycle - not
two different rods.

Where am I going wrong? Did I misinterpret the quote?

 

Yea, I don’t either but I didn’t bother drawing it out to make sure. The dwell time should be the same top and bottom, it will change with the R/S ratio, but it should be the same top and bottom for the same ratio.

 

The only difference is the distance from the piston to the crankshaft.

Assuming that the crank maintains a steady rotation, I can't see how it would
change?

EDIT: More thoughts

Maybe we're onto somehting. The crank roation would not be constant.
After ignition, the acceleration of the crank would be faster at TDC because
of the energy of combustion.

At BDC, we're left with a flywheel to carry over to the next spark.

Is that the answer?! We're getting more dwell at BDC because of the changes
in cylinder pressure?

But WHY would a shorter rod have MORE dwell than a long rod at BDC???

F*%K!

 

naw, that's not it unless the crank is flexing or if you had a 1 cylinder engine...

 

I don't know, there's a period of time when all eight cylinders are not firing.

I'm betting there is a fluctuation in crank rotation speed unless the flywheel
is doing an awesome job of storing energy.

I'd love to be Albert for a day! I'd steal his brain and you'd all bow to me.

EDIT:
Come on Jon, Bret, Fred, Brent, Damon, Mindgame, etc.! Get off your Easter chocolate eatin' a$$' and put this to rest.