Crankshaft balancing and lighting is it worth it?

sdbutler10

So really as the title says is It worth it??

OAKMERE

I have been told by my local machine shop it will be worth balancing the crank rods and pistons if planning to remove the balance shafts. If the engine is out then is is not hat much extra work (I hope). Vocky will know what is involved and what new parts are required to replace the Crank.
Don't think I will bother lightening the shaft unless the machine shop feel confident. The shaft doesn't sit in the oil so no point knife edging etc.

Cheers Oakmere

sdbutler10

Ok thanks for that. I was at the machine shop earlier and he said about the knife edge. I will just wait and see how it all goes.

OAKMERE

Vocky said the Crank doesn't go near the oil so don't now if knife edging is worth it? But I am far from an expert.

Cheers Oakmere

vocky

the z22se crank is balanced very well, several have required no further balancing work :clap:

the standard rods and pistons might need a bit of work, but the eagle rods and wiseco pistons are also perfect from the factory :thumbup:

The balancer shafts are designed to cancel vibrations due to the long stroke of the z22se engine, they are extremely UNbalanced and weigh 2KG EACH, most of that weight is on one side :crazy:

I've never seen any horrid vibrations from removing the balancer shafts dunno..

FLD

Bull nosing is more popular to avoid issues of crank drag through the oil. The Z22 crank is bull nosed as standard. Its fully counterweighted (gives a mega smooth idle!!) so I think theres room for removal of loads of weight. This could be by removal of two opposed counterweights (to maintain balance) or four. Or by knife edging the existing counterweights all the way along. This is to remove rotating weight kinda like fitting a lighter flywheel. It depends what your after really, stripping out lots of weight will make the throttle response better but may make it prone to stalling. I'll be knife edging mine but only because I have a friend with a lathe big enough to turn the crank.

WRT balancing, my reckoning is to be within 1g. This makes things smooth enough. The eagle rods I have hit this target.....just. I might go a bit closer but only because I'm anal!

TheHood

Coincidently I picked up what appears to be a very good bottom end for a steal yesterday and was intending to discuss crankshaft modifications amongst other things when I speak to a machinist that's been recommended to me.

In terms of removing material from the counterweights would there be a very rough % figure that would make a worth while difference to response wise whilst not making it stall too easily?

alanoo

Yes... do not remove anything !

TheHood

Thanks ananoo, probably just saved me making an expensive mistake :thumbup:

I remember the youtube clip of your car running and it sounded very "blippable" I assume this was with a standard crank?

FLD

alanoo said:
Yes... do not remove anything !

Interesting. On the 2.0 turbo isn't the crank only half counterweighted? Rough idle and stalling can be countered by having a flywheel with the weight round the side, not neccessarily heavier just redistributed. These usually have to be billet to take the stresses. IMO doing this can be worth while depending on the car, how / where it is to be driven and what you want to achieve. A track VX is a good candidate whereas a roadgoing vectra I'd leave alone.

OAKMERE

alanoo said:
Yes... do not remove anything !

Alanoo how was your Crank balance as standard? was much balencing required?

Cheers Oakmere

alanoo

FLD said:

alanoo said:
Yes... do not remove anything !

Interesting. On the 2.0 turbo isn't the crank only half counterweighted? Rough idle and stalling can be countered by having a flywheel with the weight round the side, not neccessarily heavier just redistributed. These usually have to be billet to take the stresses. IMO doing this can be worth while depending on the car, how / where it is to be driven and what you want to achieve. A track VX is a good candidate whereas a roadgoing vectra I'd leave alone.

The Z20LET crank is heavily UNDERcounterweighted ! It has to be tungsten inserted if you want a perfect dynamic balance and low bearing load.

On both engines you could get the engine more revvy and with a better throttle response by removing inertia/weight from the crank, this is just bad for power and bearing wear.

Eventually I'd like to get a spare Z22se crank to be cutted and having its counterweights benchmarked but well... costs a lot 😃

OAKMERE, I had two OE cranks balanced to F1 spec, almost nothing to do... in fact on a normal race spec there was nothing to do.
The Eagle forged crank was not as good, the LSJ one even worse (and only a 4 counterweight part) and the Bastuck/Courtenay flywheel was heavily out of balance :crazy:

FLD

Hmmm, interesting stuff. Perhaps I'll hang on for a spare before I cut the hell out of mine then! I thought removing weight would be OK given its essentially a flat crank.

vocky

both courtenay flywheels that I've had done required balancing work, but they are very good value for money and hardly anyone balances their bottom end dunno..

FLD

Thats shocking! I always balance the bottom end, it can often save an engine. Last one I did was to 0.1g and it didn't even ripple the mug of tea I sat on the top of it. I felt smug after that one.

Back on topic...I thought the balancing was just rotational and as such if I remove weight both sides it would remain in balance. I make no claim to be able to balance a crank this is just my understanding of it. have I missed soemthing??