mtsubishi v6 balancing

[zrp]

i was wondering if anyone knows what the factory percent of the bob weight is on a mitsubishi 3000gt vr4 engine(twin turbo)

the machine shop is asking for this info so they can balance the crank corectly due to that i have much lighter pistons going in the engine.

any type of help is appreciated, or if anyone knows where i can get this info from.
thnks joe

 

[ivymike]

You've got the old hardware, right? How about measuring and calculating?

 

[zrp]

well actually the crank has been replaced from a cast crank to a forged piece witch mitsu has changed for all the years, regardless what originally came with the car.
i know that i can get a number as you said but i need to know what %of that weight actually is needed like chevy v8 take 50%, buick v6 are 35% i think, i need to find out what does mitsubishi require.
tnx.

 

[magnograil]

ZRP - It does not matter if the crank was changed, the reciprocating weight is what matters. If it is a 60 degree V then stock formulas work within a couple percent. The old weighing the piston/rod at both ends approach is close but does not take into account the rotational inertia of the rod.
If it is other than an even firing 6 then you have to go through the balance equation for the whole engine.
I would not go by what american manufacturers do. You might end up with a V8 chopped down to a V6 balance factor and it will run like a dodge.

 

[Milanoguy]

Joe

Tell us a little more about this engine. Is it a 60 degree V6? Does it have three crank throws(shared crankpin) or six crank throws(one crankpin per cylibder)?