DC2R: Hand balanced crank.. with flywheel attached?

[00dc2]

I remember hearing about the DC2R engines being hand finished including hand balancing of the crank. Is this true?

And if it is then does anyone know if it was done with the flywheel attached?

if it was then would changing the flywheel (for say a Toda 4.1kg) offset the balance?

[szymonsta]

i'm guessing it wouldnt, since the new flywheel would also be balanced?

re: hand-finishing the engine, i beleive that is true, the engines were hand-finished, and differed signifficantly from the standard production line b18 (bracing of the block to withstand higher rpm, signifficant alterations to the head work etc).
apparently the '96 jdm models had an even higher percentage of engine work which was done by hand, however honda progressively introduced machines to do some of this work as they were able to obtain higher accuracy of work (i think there was a thing on this in BMi vol1).

[tinkerbell]

it is not balanced left to right,

it is balanced for the lateral centre...

the flywheel will also be balanced for the lateral centre, as will the crank pulley...

[00dc2]

err... when you say left / right you mean long ways.. i agree its not balanced long ways as that is pointless.. its balanced such that it spins evenly/smoothly..

so you think the flywheel and crank etc are all balanced seperately then?

do people understand what i am on about? how if they are balanced together then potentially replacing the flywheel with a different one will result in bad balance?

[tinkerbell]

yes, all parts are balanced.

bad balance depends if the laws of physics change from the geographic location where one part was balanced to the geographic location of where the other part was balanced...

in my experience, the laws of physics hold true everywhere on earth...

however, there are differences in the "level" of balancing,

e.g. balanced to 1gram or balanced to 0.00001 gram

if the crank is balanced to 1 gram and the flywheel is balanced to 0.1gram, then the flywheel is more balanced than the crank, so it is fine...

i personally feel that honda does acurate balancing, so there should not be a problem.

[tinkerbell]

http://www.babcox.com/editorial/ar/eb10330.htm

[00dc2]

so the bit that i am interested in is this

"With inline four and six cylinder engines, and flat horizontally opposed fours and sixes (like Porsche and Subaru), all pistons move back and forth in the same plane and are typically phased 180° apart so crankshaft counterweights are not needed to balance the reciprocating components. Balance can be achieved by carefully weighing all the pistons, rods, wrist pins, rings and bearings, then equalizing them to the lightest weight.

On V6, V8, V10 and V12 engines, it’s a different story because the pistons are moving in different planes. This requires crankshaft counterweights to offset the reciprocating weight of the pistons, rings, wrist pins and upper half of the connecting rods.

With "internally balanced" engines, the counterweights themselves handle the job of offsetting the reciprocating mass of the pistons and rods. "Externally balanced" engines, on the other hand, have additional counterweights on the flywheel and/or harmonic damper to assist the crankshaft in maintaining balance. Some engines have to be externally balanced because there isn’t enough clearance inside the crankcase to handle counterweights of sufficient size to balance the engine. This is true of engines with longer strokes and/or large displacements.

If you’re rebuilding an engine that is internally balanced, the flywheel and damper have no effect on engine balance and can be balanced separately. But with externally balanced engines, the flywheel and damper must be mounted on the crank prior to balancing.

Customers should be told what type of engine balance they have (internal or external), and warned about indexing the position of the flywheel if they have to remove it later for resurfacing. Owners of externally balanced engines should also be warned about installing different flywheels or harmonic dampers and how it can upset balance."

So we assume our engines are internally balanced and the flywheel was not on the crank when it was balanced and that replacing the flywheel (as long as its balanced) is fine..

tinkerbell you need to be more accurate with what your saying.. you say "all parts are balanced" but your forgetting 1 important word.. "all parts are balanced separately" if this is the case then fine i am happy. but if the parts are balanced together (crank and flywheel) then replacing the flywheel could cause a problem.

so we are conclusively saying that the crank and flywheel are balanced SEPARATELY then?

[tinkerbell]

On internally balanced engines, the flywheel and damper can be balanced separately, or installed on the crank and balanced as an assembly once the crank itself has been balanced.

did you read that bit?

this implies that it doesnt matter if they are balanced separatly or together..

[00dc2]

lets just say the stock honda flywheel isnt very even. and by even i mean that by itself its not very balanced. And lets say that the crank and the flywheel were balanced together. so they did what they needed to do to get the crank+fly to spin perfectly together.

now you take that uneven flywheel and replace it with a perfectly balanced toda flywheel and what do you get? an unbalanced engine.

do you see what i am trying to say?

[bennjamin]

Possibly so. But engines in mass production , would be balanced with certain tolerances. Otherwise aftermarket parts , as they are would not exist ( if they didnt work or led to premature wear etc).

Its fact that stock ITR flywheel i cast , while some aftermarket lighter are forged.They are lighter , but retain the same degree of "balance" at all RPM's. Its the energy they store which is different

[TODA AU]

Regarding fitting a lighter flywheel to a std engine,
Should you fit a lightweight flywheel to a std engine, which we will assume is balanced very well, the net result is it will raise the harmonic frequency that problems could occur.
If there is currently not a balance problem with the engine, reducing the balanced rotational mass at the rear won't make matters any worse.
Rather, you'd be less likley to encounter a problem as the harmonic is increased with the reduced mass.

[00dc2]

did they balance the B18CR engines with the flywheel attached?