KrankVent
Thread Starter
Registered User
Joined: May 2002
Posts: 3,178
Likes: 0
From: Washington State
The KrankVent maintains a vacuum in the crankcase. In order for this to happen, the forward KrankVent valve must be positioned to prevent flow from the intake to the valve cover.
Registered User
Joined: Feb 2002
Posts: 2,071
Likes: 0
From: PDX
I'm more interested in the KrankVent system if, indeed, the PCV is likely to fail under boost AND that failure is somehow going to cause a problem. Given that I have a breather on the front of the block (where Speedcraft replaced the "breather" line that used to run to the intake, upstream from the throttle body), I don't see how I can have much positive OR negative pressure in the crankcase. But maybe I'm missing something. Any thoughts?
CB
CB
Thread Starter
Registered User
Joined: May 2002
Posts: 3,178
Likes: 0
From: Washington State
If the PCV valve fails or sticks open, under boost, I doubt the front breather will be able to relieve the pressure fast enough to prevent pressurizing the crank. Granted, there will be some relief of pressure, so I guess it depends on how much boost you are running.
Registered User
Joined: Feb 2001
Posts: 2,895
Likes: 1
From: You wish
Creating a vacuum in the crank is not a bad thing in most ways.
Many drag cars will run an actual vacuum pump to draw down the crank (even NA cars) pressure.
A lower pressure in the crank means less resistance to movement. Additionally, even on the "up/down" type engines, you still have to move the air around in the crankcase and that takes energy.
Finally, a vacuum in the crankcase can promote better ring seal. This can improve power, but usually works best if you design the ring package to work with it.
UL
Many drag cars will run an actual vacuum pump to draw down the crank (even NA cars) pressure.
A lower pressure in the crank means less resistance to movement. Additionally, even on the "up/down" type engines, you still have to move the air around in the crankcase and that takes energy.
Finally, a vacuum in the crankcase can promote better ring seal. This can improve power, but usually works best if you design the ring package to work with it.
UL
Registered User
Joined: Feb 2001
Posts: 2,895
Likes: 1
From: You wish
Rings are the source of about half the internal friction in a piston engine. That friction easily amounts to several tens of hp on something like the F20C, and it gets worse the higher you rev.
A partial solution is to run lower tension rings (they don't push as hard on the cylinder walls). However, such a ring package doesn't seal as well, reducing combustion pressure, allowing blow by, etc. A vacuum aided ring package can run a lower tension ring while still sealing effectively, which frees up more power.
UL
A partial solution is to run lower tension rings (they don't push as hard on the cylinder walls). However, such a ring package doesn't seal as well, reducing combustion pressure, allowing blow by, etc. A vacuum aided ring package can run a lower tension ring while still sealing effectively, which frees up more power.
UL
Registered User
Joined: Aug 2001
Posts: 41
Likes: 0
From: Pleasanton
I have a Vortech SuperCharger. Before I added the KrankVents I would peg my oil pressure meter above ~ 1.5k RPM (end of meter scale is 100 PSI, needle pegs somewhere between 1/8" & 1/4" past that). Now after installing both KrankVents I can't get the meter to read past 100 PSI.
Thanks fperra
Mike
Thanks fperra
Mike
