Rebore one pot only?

[isham-research.freeserve.co.uk at pop.pol.net.uk]

> Bet people have tried it. It'd probably be ok for some pos engine but I
> assume that we're talking Audi I5? If the bore is really badly scored then
> it'll have to have an oversize piston which will weigh more than the others
> so the engine balance will be wrecked. OK, so OE engines aren't balanced a
> finely as race engines but I'd expect one OS piston to make quite a
> difference.

The piston/gudgeon pin/conrod assembly is counterbalanced by the weights
formed in the crank either side of the big end bearing.  Since nothing
is done to these weights when an engine is rebored oversize, I assume
that oversize pistons weigh _EXACTLY_ the same as standard ones.

Indeed, if you check through ETKA and the Mahle catalogue - one engine's
oversize piston is another engine's standard piston.

I bet all I5 pistons weigh the same.  The lack of balance that will
result from the slightly higher capacity is trivial - negligible -
compared with the "up to two bar" discrepancy allowed in compression
ratios.

Mahle (and Audi) will cheerfully sell single pistons, standard and
oversize.

--
 Phil Payne
 UK Audi quattro Owners Club
 Phone +44 7785 302803   Fax: +44 7785 309674