Firstly, I don't mean to offend anyone with an MY98 that has or is suffering piston slap.

But I was just wondering what changed in the engine design that has caused so many of these late 97 & 98 models to suffer from piston slap.

And that it appears that the earlier models seem to of survived this fault.

Being an Ex-Cosworth owner I know all too well what piston slap sounds like, especially when running chipped (and infact my wifes 1.3 Fiesta is suffering also). I know that the 4x4 Cosworth had the design of the piston changed, which placed the gudgeon pin slightly offset therfore pushing the piston up at a slight angle and hence taking up any slack that may occur.

Is this the modification that Subaru have adopted or do they just fit an oversized piston (I alway thought slap was caused by the bore becoming oval).

A collegue of mine has just purchased (privatly) an MY98 and unfourtunatly has found it is suffering the said fault. Hopefully it will be fixed under some sort of warranty claim. But if not what's the cost of a piston replacement.



[Edited by Scott.T - 11/5/2001 8:24:45 PM]

 

Hi,

The piston skirts were made shorter to reduce frictional losses - maybe they overdid it a bit which exacerbated the piston's tendancy to rock from side to side.

The fixed piston is 60 microns bigger, but no other changes I think - presumably if they did change the gudgeon pin offset they would have to change all of the pistons.

Cheers,

Alex

P.S. My car has been fine since the new piston was fitted, so the bores must have been ok

 

Out of interest when is this 'Noise' noticable,is it when the Block & oil is cold or is it a permanent thing ?

555