Have a local HD guy tell me thatI should have a one way valve on my crankcase vent. Says dyno results have showed hp gains from adding this. Anyone else heard of this?? Mine is just open.

 

I would think it wouldn't make ,any big difference, was he trying to sell you a one way valve?

 

No.

 

I was talkin to my wrench , he said he thought thta sounded legit. Its like a pvc on a car engine I guess.

 

Sounds like another guarenteed7 to 10 horsepower to me.......

 

The Doherty Power Vents that come with their intake setup are one-way valves.

Think about the displace air that is pushed away from the back side of either piston as it descends... It's like a sudden positive pressure pulse inside the crankcase. Then think about the "negative pressure" scenario that occurs when the piston(s) ascend. The net result would look something like a sine wave if it were graphed.

What the one-way does is basically "chop off" the negative part of that pulse, thus reducing the overall amount of air that is being forced to move about inside the crankcase.

Does that translate to tangible or measurable power??? F... if I know. It does seem to make sense, at least in my pea brain...

And, yes.... I do have those vents on my scoot...

 

Niterider has some interesting reading on this issue. I think it was niterider, anyway, the scoot was dynoed with the vents open, with a one way and sealed off, according to the graphs, no difference on any of the runs. I took it for what it was worth.

 

put a check valve on '98 dyna, no differance. left it on anyway

 

you have crankcase breather check valves that are one-way in each head and port to the air cleaner banjo bolts, what are you guys talking about?

 

I think he may mean the one that exits the back of the engine at the bottom.