Race Engine Forum UK

Guy,
I decided to vent my crankcase breather straight to atmosphere for 3 reasons. 1)I was sick of the plumbing cluttering up my engine bay, 2)I don't like all those dirty vapours going into my inlet thank you very much, 3)I've heard oil vapour actually lowers your octane rating.
I made a pipe with a bore that is slightly larger than the restrictor washer that was brazed into the original breather pipe. When it is plumbed into the inlet it is "sucked" in, but out to atmosphere it doesn't get any help, hence the slightly larger bore.
I know its probably hard to tell, but in your opinion have i got it anywhere near right?
Thanks,
Guy

You better put a pressure gauge on the engine somewhere and measure with/without that small pipe!

G

Would a pipe that's too large give problems do you think? Or is it a case of "no such thing as too large" and only too small will cause problems? What kind of pressure (if any!) would i expect from a crank case and at what revs?
Thanks,
Guy

I've never measured the pressure in a crankcase, wet or dry sump but excessive pressure due to blocked breather and worn rings does, I know, blow oil out of the cam and crank seals, based on the assumption that it was sized 'right' by the designers in the first place (which is true in my exp) I've always run with the OE sized breather pipe. I don't know what will happen if you restrict that with a smaller diameter..


G