Small Breather Pipe?

Small Breather Pipe?

Author
Discussion

MPO

Original Poster:

264 posts

111 months

Wednesday 18th May 2016
quotequote all
Does anyone know why we have this small breather pipe that connects to the Trumpet Base?




Cheers

MPO

Sardonicus

18,928 posts

220 months

Wednesday 18th May 2016
quotequote all
Yes, it's a vital part of the positive crankcase ventilation system

Alan461

853 posts

130 months

Thursday 19th May 2016
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I was rather hoping and looking forward to someone explaining this.
It's the tee arrangement I don't get,
there's strong vacuum behind the opening to the small pipe, exhaust gasses passing from the flame trap and the other end goes to a port right next to the throttle butterfly.
The only thing I can guess is maybe when vacuum is lost due to open throttle the breathing is taken in at the throttle butterfly port.
And even if that was the case why is the flame trap not on the n/s rocker cover adjacent to both vacuum feeds?

MPO

Original Poster:

264 posts

111 months

Friday 20th May 2016
quotequote all
Sardonicus said:
Yes, it's a vital part of the positive crankcase ventilation system
Sardonicus


Thanks for your reply, it got me researching a little more smile It seems that the small pipe is to give positive pressure when the engine is idling and the butterfly closed (the larger vent pipe would be inoperative at this time). Makes sense now! smile

Thanks

MPO

MPO

Original Poster:

264 posts

111 months

Friday 20th May 2016
quotequote all
As an update, I purposely blocked this crank case vent system (that would stop the large and small breather pipe operating) last year and tweaked my 14CUX maps accordingly getting the AFR I’m looking for.

I have seen no adverse effects in doing this, no lifting of the oil stick no oil seepage either smile. So, I will be blocking off both the small and large pipe on a more permanent basis to prevent it entering the combustion chambers and probably effecting performance. Everything will be reversible…

Temporarily, I am venting to the atmosphere with the original flame trap in place and a suitable filter on top. I may add a catch tank this year…

Cheers

MPO