This is the Advanced Tech Section but sometimes it helps people if they understand the basics of how things work and then can apply that info to other "Advanced Tech" Racing Projects. I found this web site while looking for an answer to a "Dishing" Pistons vs Balance question on another forum.

Here is the website:

Parts 1,2, & 3 are covered in this link

http://www.eatonbalancing.com/blog/2007/11/

Parts 4 & 5 are covered in this link:

http://www.eatonbalancing.com/blog/2007/11/page/2/

This info caught my eye:

"The use of nitrous oxide, superchargers, or turbo chargers typically also requires a certain amount of overbalance. Using nitro methane in conjunction with a blower is likely the worse case scenario as cylinder pressures are extremely high under detonation which artificially increases the piston weight by a more than a normal amount. Any form of blown engine will benefit from a given amount of overbalance simply due to the weight of the piston averaging artificially heavier not only from the increase in cylinder pressure at ignition, but the increase in cylinder pressure taking place while the cylinder is also filling during the intake stroke. In this instance, the piston is averaging an overall heavier weight when running at speed. A normally aspirated engine has a given amount of pressure counterbalance in that the piston is subjected to negative pressure when the cylinder is filling but is under increased pressure during compression and ignition. If an aspirated engine is working with an extremely well designed induction system and is benefiting from a ramming effect to fill the cylinders at the upper rpm ranges, then overbalancing also helps here. And then there's the rpm factor. Balancing is linear up to a point throughout the rpm range but depending upon the masses at work within your particular assembly, there is a point in which the crankshaft rpm starts to out run the dynamics of the existing state of balance. Overbalance allows these dynamics to stay in tune or 'caught up' to the rpm's of the crankshaft. There are proprietary formulas that calculate these amounts of overbalance for all the different variables and will vary somewhat from shop to shop. Again, talk with your balance shop regarding overbalancing and determine if this would be best applied to your application."

Tom Vaught

 

Thanks Tom. Good stuff.

 

Dude, you are such an asset to this site

Thanks Tom

 

wow.!
Good Stuff.!

 

That was an enjoyable read. I would like to know more about the "proprietary formulas" used to calculate over balance on different applications. But I suppose the name itself indicates a low chance of that happening.

 

Always wondered why the over balance. Thanx Tom

 

I don't understand the 'over balance' at all. Is it a V configuration issue with bearings?
Decent rotating assembly parts will be balanced by the manufacturer, no need to worry about static balance.
Greatest contributor to 'dynamic' balance is A/F per cylinder. They should have the same CFM and fuel for the intake side, and ignition timing and blow down on the exhaust side. Basically the exhaust and intake shouldn't be fighting against each other at the crank. If you have a pressure differential per cycle between them then you're beating up bearings and probably have flow/pressure issues between cylinders. Solve that, then worry about Hz affecting things with resonance breaking stuff.

I come from an inline and flat background, so a V config is different for me. I have a 60* V6 build I'm going after, and would like to know more about how balancing these engines is different from a 90* V8 or V6, as well as an I4 or I6 engine assuming equal air/fuel to each cylinder.
Flate plane V8 vs an LS7? Balance issues with the components assuming equal pressure, temps, timing, etc per cylinder.

Making crank mods is usually due to decreasing windage and freeing up high RPM.