In discussing two active topics "why are guys dumping air into their cai's" and "lets talk crankcase ventilation" I have come to learn far more about the SRT-4 PCV system than I every thought I would.
Ok heres the deal/warning.
The 3/8" hose that runs from the factory airbox to the crankcase cover is called "make-up air hose" (reference SRT4 service manual page 1022). The hose is there to provide fresh make-up air to the crankcase as a subset of the PCV system and allow for crankcase pressure to exhaust while the engine is under boost.
Reference these links for a description of "make-up air" or "fresh air" in on PCV systems
The crankcase make-up air vent connection brings filtered air (filtered by little sponge in airbox) to the crankcase to establish and maintain a flow through the crankcase necessary to correctly remove the blow by waste vapors. The flow is created by the throttle body/intake track pulling a vacuum in the pcv valve outlet line. This vacuum opens the pcv valve. Continuous flow is maintained by the introduction of fresh air through the line in question.
This is the case with the engine under no or light load and a vacuum on the boost gauge. When you put your engine into a boost condition the SRT PCV system temporarily chages the way it operates. The vacuum source is no longer present in the intake manifold, but rather is replaced by positive pressure (boost). This pressure/boost forces the PCV valve shut. The pressure that now builds up in the crankcase from ring blow by is forced to backflow up and out the crankcase make-up air vent line. This is why the sponge element in the factory airbox gets oily after periods of heavey or prolonged boost.
Ok heres the problem with hooking the make up air line to a CAI.
The engine is drawing all its fresh air through the air fliter/CAI main tube. This air rushing up/through this tube creates a vacuum lifting or pulling air out of the smaller tube (make up air connection on the side of the cai) by virtue of Bernoulli's principle.
When you hook your crankcase make up air line to your CAI you inadvertantly reverse the flow through this line and thereby starve your PCV system of its vital make up air.
Another very bad thing is the fact your pulling of crankcase oil vapors into your turbo and innercooler leading to damaged turbo blades and fouled iC tubes, and also some degree of detonation from the oil vapor that is delivered to the intake track. When the engine is under boost you send not just vapor but actual oil into this path.
In my opinion you need to cap the connection provided on the CAI tube and install a breather filter element on the cranjcase make up air vent. This provides for the necessary clean air supply to the PCV system, allows pressure during boost to escape to atmosphere (aka original design save the fact its not dumping into the airbox), and keeps oil and oil vapor out of your turbo and innercooler.
I am concerned that someday a person will have a powertrain warrenty claim denied because of a CAI being installed that has re-engineered the factory PCV system (by accident or not). I am also concerned that SRT owners with CAI systems will eventually suffer premature engine damige or failure from operating with their PCV systems greatly impaired.
I offer this information to help the SRT4 community, not start any arguements, knowlege is power so take it for what it is worth.
Heres an example hookup
__________________
John 3:16
"For God so loved the world that he gave his only Son, so that everyone who believes in him will not perish but have eternal life."
Its early and I was out late so my brain really has not woken up just yet but superficailly this all makes senes to me and should be a concern to all SRT4 owners.
Well, I'm convinced, and even if you are wrong, or just being a little too safe, it's only like 10-12 bucks for a little filter and some tubing.. Can't hurt!
That is all good. When the motor is revving up, the motor is accually making pressure in the crank case, that can hurt performance as well as many other things. If you use a REAL oil catch can, it will accually pull a vacuum on the crank case causing all of the pressure to be releaved. That is a good thing. If anyone looks at high horse power crate motors or drag cars, they will accually use a vacuum pump, or some people us a old smog pump to pull a vacuum on the crank case. On Jim Butlers 800++ horse power big block Pontiac, he picked up 15hp by using a vacuum pump on that motor.
I am not sure if this was helping your post or hurting, that is my 2 cents. Everybody has their own take on PCV, and their own ideas on how to fix it.
On my car I use a Perrin oil catch can, & I think it works great. IMO.
I have a breather hooked up the same way. My question to you is where did you find a cap that fits the intake? I can't find that size. I've got a small piece of hose with a bolt in it and a hose clamp, until I can find one.
That is all good. When the motor is revving up, the motor is accually making pressure in the crank case, that can hurt performance as well as many other things. If you use a REAL oil catch can, it will accually pull a vacuum on the crank case causing all of the pressure to be releaved. That is a good thing. If anyone looks at high horse power crate motors or drag cars, they will accually use a vacuum pump, or some people us a old smog pump to pull a vacuum on the crank case. On Jim Butlers 800++ horse power big block Pontiac, he picked up 15hp by using a vacuum pump on that motor.
I am not sure if this was helping your post or hurting, that is my 2 cents. Everybody has their own take on PCV, and their own ideas on how to fix it.
On my car I use a Perrin oil catch can, & I think it works great. IMO.
A catch can with a breather filter routed to the intake is a solid choice but its hard to say if that arrangement starves crankcase makeup air when the engine is not under boost (most of the time). A breather filter is the choice that most closely retains the procibles of the stock/factory design
I have a breather hooked up the same way. My question to you is where did you find a cap that fits the intake? I can't find that size. I've got a small piece of hose with a bolt in it and a hose clamp, until I can find one.
I stretched a 3/8" vacuum cap over it. Bought it at an Advance store
Last edited by Romans8:28 : 07-10-2004 at 12:58 PM.
if your gonna put a vacuum cap on the intake, make sure its nylon and not rubber! the rubber will tear away and eventually cause a leak. the nylon ones work great with a zip tie on it. The easiest way to get it on is to spray a little wd40 on it first
I'm glad that someone has finally addressed this issue with some good logic.
Thanks for the post Roman, but don't you think 3 threads for the same topic is a bit excessive?
__________________
"I love this job more than I love taffy... and I'm a man who enjoys his taffy."
-Mayor Adam West, Family Guy
Didn't I say, put a filter between the two points?
Can some one tell me what exaclty is going on in that picture? I get the basic idea... but I am not sure what I am looking at..
OK I took a closer look at the pick... what exactly is that hose coming off the Intake? It doesn't look like it connects to anything.. What's the 90 degree plastic piece on the end of it?
Roman, place an open air filter between the inlet nipple fo the CAI and the relief vent valve on the driver's side of the valve cover.
Under WOT, the pressure is release via this relief valve and spills oil into the CAI unit, which gets swallow up via the turbo compressor. Placing a filter on that line prevents the oil being swallow up under WOT conditions.
Can some one tell me what exaclty is going on in that picture? I get the basic idea... but I am not sure what I am looking at..
OK I took a closer look at the pick... what exactly is that hose coming off the Intake? It doesn't look like it connects to anything.. What's the 90 degree plastic piece on the end of it?
ok photo explained:
The intake in the picture has the infamous make up air connection capped. The 90 elbow (plastic piece you speak of) is part of the stock emissions system vapor cannistor vacuum assist and is hooked up like the facory arrangement between air filter and turbo in main intake line (this line if often plugged too reference the "plug line mod" or "to cap or not to cap" threads from the past)
The crankcase makeup air inlet vent in the picture, has a length of hose with a breather filter installed at the end.
Roman, place an open air filter between the inlet nipple fo the CAI and the relief vent valve on the driver's side of the valve cover.
Under WOT, the pressure is release via this relief valve and spills oil into the CAI unit, which gets swallow up via the turbo compressor. Placing a filter on that line prevents the oil being swallow up under WOT conditions.
No good as far as I am concerned because its still redesigning the factory PCV system. The drivers side crankcase vent is FOR FRESH AIR IN most of the time, its only blowing out during boost. I dont want the oil blown out going to my turbo thats the whole point,
The AutoGuide.com network consists of the largest network of enthusiast-owned enthusiast-operated automotive communities.
AutoGuide.com provides the latest car reviews, auto show coverage, new car prices, and automotive news. The AutoGuide network operates more than 100 automotive forums where our users consult peers for shopping information and advice, and share opinions as a community.
Warning about installing cold air intakes!
Linear Mode
