Question about Fixed Orifice PCV valve
Thread Starter
Burning Brakes
Joined: Oct 2004
Posts: 931
Likes: 35
From: Rowlett, Texas
Question about Fixed Orifice PCV valve
I decided to try the new Fixed Orifice PCV in my 2000. Some of the guys have reported a bit less oil drawn through the intake with this setup, PN 12572717. So, why not; the '04 has the same type system with the same 2.5mm orifice.
I installed it, and recorded the exact same manifold vacuum and fuel trims under normal driving, so it seems compatible with my 2000 engine.
BUT, one question regarding WOT and crankcase blowby pressures:
During WOT, when blowby is at maximum, and intake vacuum is greatly reduced, these gasses are pushed back through the 3/8" crankcase intake hose, and they can also escape forwards through the PCV valve (when the spring is not pulled closed by the intake vacuum). My OEM PCV apparantly allows pretty significant flow from the crankcase under this low-vacuum condition - much more than the small hole in the Fixed Orifice PCV. Super scientific test - I blew through it.
So, the question is; with one of the escape routes partially reduced, will the blowby gasses build positive pressure in the crankcase during WOT, and possibly cause oil leaks?
The '04 seems to work fine; and I assume the C6 is similar. Am I worried about nothing?
DG
I installed it, and recorded the exact same manifold vacuum and fuel trims under normal driving, so it seems compatible with my 2000 engine.
BUT, one question regarding WOT and crankcase blowby pressures:
During WOT, when blowby is at maximum, and intake vacuum is greatly reduced, these gasses are pushed back through the 3/8" crankcase intake hose, and they can also escape forwards through the PCV valve (when the spring is not pulled closed by the intake vacuum). My OEM PCV apparantly allows pretty significant flow from the crankcase under this low-vacuum condition - much more than the small hole in the Fixed Orifice PCV. Super scientific test - I blew through it.
So, the question is; with one of the escape routes partially reduced, will the blowby gasses build positive pressure in the crankcase during WOT, and possibly cause oil leaks?
The '04 seems to work fine; and I assume the C6 is similar. Am I worried about nothing?
DG
Tech Contributor
Joined: May 2008
Posts: 3,100
Likes: 17
From: Somers, CT and Clermont, FL
St. Jude Donor '09-'10-'11-'12-'13-'14-'15-'16
Here's some interesting reading on the concept.
http://forums.corvetteforum.com/c5-t...2572717-a.html
Last edited by Quicksilver Vert 01; Feb 9, 2009 at 11:47 AM. Reason: added link
Thread Starter
Burning Brakes
Joined: Oct 2004
Posts: 931
Likes: 35
From: Rowlett, Texas
Thanks guys. Yeah, I saw posts where the superchaged guys definitely had to add more blowby escapes in the form of an oil cap breather.
I did a little checking on my other cars, and found my new '08 Caddy has the exact same fixed orifice PCV and small inlet tube. And even my old '91 Benz has the same setup.
So, I guess on a near-stock car like mine, the blowby can work out through the inlet tube okay. I'll drive it awhile and see if I detect any weirdness, like oil mist around the seals.
But, this setup has to be worth at least the same HP increase as the coolant bypass or performance hood seal, correct!
DG
I did a little checking on my other cars, and found my new '08 Caddy has the exact same fixed orifice PCV and small inlet tube. And even my old '91 Benz has the same setup.
So, I guess on a near-stock car like mine, the blowby can work out through the inlet tube okay. I'll drive it awhile and see if I detect any weirdness, like oil mist around the seals.
But, this setup has to be worth at least the same HP increase as the coolant bypass or performance hood seal, correct!
DG
Tech Contributor
Joined: May 2008
Posts: 3,100
Likes: 17
From: Somers, CT and Clermont, FL
St. Jude Donor '09-'10-'11-'12-'13-'14-'15-'16
