Crankcase vent VALVE question
Thread Starter
|
Road Warrior
Joined: Sep 2007
Posts: 1,827
Likes: 34
From: Iowa
Crankcase vent VALVE question
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.
Ultimate HDF Member
Joined: Feb 2006
Posts: 5,939
Likes: 3
From: TX
RE: Crankcase vent VALVE question
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...
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...
Stellar HDF Member
Joined: Dec 2006
Posts: 2,906
Likes: 11
From: Grottoes Va.
RE: Crankcase vent VALVE question
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.
Trending Topics
Elite HDF Member
Joined: Apr 2008
Posts: 3,900
Likes: 4
From: way down upon the Suwannee River
RE: Crankcase vent VALVE question
put a check valve on '98 dyna, no differance. left it on anyway
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
7 Surprising Harley-Davidson Products that Are Not Motorcycles
Verdad Gallardo
8 Best Harley-Davidson Motorcycles Ever
Pouria Savadkouei
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
10 Things Harley-Davidson Needs to Fix in 2026
Verdad Gallardo
Thread
Thread Starter
Forum
Replies
Last Post
