Thats not quite true.porndoguk wrote:yeah i had 2 spare piperX filters i had from an old car, i gave the other to curt,vfrderek wrote:Didnt you fit a pipercross filter or summat Rick?
doesnt make any noticible difference but i guess in theory it should help, and maybe lower emissions! after all only clean air is going into the induction and not dirty oil vapour,
The crankcase has a breather (like all engines do) as the pressure of the combustion often leads to minor 'blow by' where in minor amounts (or major if you have knackered rings / cylidners) of the air/fuel mix burnt get past the piston rings and into the crank-case.
If the crankcase was sealed this pressure would send the gas along with some oil out through the weakest point, probably a joint / gasket or an oil seal somewhere.
Anyhow... some of these gasses are only partly combusted when they enter the crank-case, also water from condensation and unburned fuel gets into the engine oil.. when this oil is upto tempurature these 'burn off' (they evapourate)
Venting these out to the atmosphere was common on older cars as they didn't care too much.
Modern vehicles vent the crankcase back through the inlet, it's only a tiny fraction of the actual air/mix that is reused per given stroke but this helps to burn off any unburned fuelvapour thats come from the crank-case, and giving cleaner overall emissions.
There are cases when running high turbo pressure that the crank-case breather no longer works properly which is why some people vent them to atmosphere but theres no real reason to do so... it's not like your running the bike on 100% oxygen...