[BADDASSC6]

A turbine (exhaust side) is a machine designed to convert the fluid and thermal energy in the exhaust into mechanical energy in the form of the rotating shaft. In order to do this it needs a pressure differential across the turbine wheel. That means you want the turbo to be as close to the exhaust ports with no restrictions (i.e. wrx cat). and have as free flowing exhaust afterwards as possible. This means the pressure and heat before the turbo are as high as possible and the pressure after the tubro as low as possible. This will make the turbo spool up as fast as possible.

A venturi works by reducing the cross section in a pipe band. Mass flow rate is constant and there there is no work in to compress the gas so volumetric flow rate is also constant. This means that the fluid (exhaust gasses) must accelerate through the restriction. The high speed of the fluid will "molecularly entrain" the gasses in the cavity you are trying to draw a vacuum in thus removing the unwanted fluids. The problem is that you can't get anything for free. So you need a differential pressure in order to get the exhaust to accelerate across the venturi. Well you final pressure is atmosphere so it can't go down. That means that the differential pressure is generated by a pressure increase before the venturi. Essentially you are increasing the system head losses.

Now the venturis that I have seen are all medium to small diameter convergent divergent nozzles. They draw almost perfect vacuums of 14.7 psiv. Since you don't need that kind of vacuum then you can run a much larger I.D. on the venturi and not cause as much of a restriction.

How about trying to just tap the pipe and seeing if the exhaust has enough velocity to draw a suction without a venturi. Also if you do this make sure to put the tap behind any restrictions like the turbo or the cat because if the pipe is under pressure then you could end up pumping gasses into the crank case.

[BlacknBoostn]

^^^ gettin my head around this. Thanks BADDASSC6, I'm on my phone so I'll respond later in full.

[enkeivette]

Chrysler motors burn oil. My friends Turbo 420A burns oil and my Neon consumes more oil than my Vette motor does. How much oil does your motor consume? Are we talking rotary consumption? Or like only a quart every other month?

I don't like the idea of modifying your exhaust to scavenge crankcase pressure. First of all, I doubt you'll pass smog like that, especially with your luck. Second of all, you don't need it. If you're that concerned with it and you're too poor or lazy to find the real problem, go with a vacuum pump. If you can't suck enough air with the intake.

BADDASS, btw, when my HG/ intake was leaking boost, my heater hose popped off at about 100mph WOT. Sprayed directly on my header. I've never seen that much steam before in my life. And I've been to Yellow Stone.

[enkeivette]

I have a simpler explanation for a turbine, and it's more fun, but probably less accurate (btw I don't know why you guys are talking about turbines because I didn't read most of this post).

Turbine = Turbocharged rocket engine.

Just like a rocket engine, a turbine ignites fuel mixed with oxidizer in a chamber. It blows out of the chamber through a fan at the back of the turbine, (like an exhaust wheel in a turbo) which spins a shaft which spins the fan in front of the turbine (like a compressor wheel in a turbo) that sucks the air into the rocket chamber. (Technical term, hahaha).

[enkeivette]

Oh you guys are just talking about turbos, nevermind. Thought you were talking about turbine engines.

[Damian]

I don't understand this but a catch can on an existing line is actually illegal. Just run one inline of your vacuum line and call it a day. Or even cap off the nipple on the t/b and vent it after the catch can.

I run a catch can on my Eclipse and it's just a air filter from Lowes and works great.

[enkeivette]

Originally Posted by Damian

I don't understand this but a catch can on an existing line is actually illegal. Just run one inline of your vacuum line and call it a day. Or even cap off the nipple on the t/b and vent it after the catch can.

I run a catch can on my Eclipse and it's just a air filter from Lowes and works great.

You can't use manifold vacuum to vent the crankcase on a boosted motor. You're supposed to move it to the air intake. There is always suction there.

[GTTS > Some]

I had a variation of this problem, crankcase pressure, I was James Bond putting out as much smoke as the 7th fleet. I'm running a 3.7-TT mounted below the exhaust manifolds. I used a scavenge pump set up with 3/4" return lines and a "T" link between both .86 Turbos, works like a charm. The pump is sold local (RB Racing-Long Beach) for about $275, the fittings and hose parts run about $80.00. The upgrade gives out a slight hum like a fan set up, the RB Racing site is attached with the write up. Good luck.

http://www.rbracing-rsr.com/oilsystems.htm

Originally Posted by BlacknBoostn

Lets talk about some ways to get rid of excess crankcase pressure and ways to set up catch cans etc. Whos currently running a catch can system? How is your PCV system set up? Where do you vent the extra pressure and gases to? Do you use breather filters, a breather on the oil cap, anyone using a Venturi Style setup to the exhaust, check valves... etc etc etc.

My eventual setup will consist of:

PCV valve on valve cover to Catch Can (CC)to Throttle Body (this is how the factory system is set up minus the CC) and then the drivers side valve cover port will be linked up to a catch can and then either be routed to atmosphere with a filter or port to CC to exhaust using the venturi method. The idea of this is to be able to pull an appropriate amount of vaccum from the crankcase to remove any excess gas/oil etc from the crankcase and allow it to be replaced with good clean fresh air while at the same time filtering out any oil or blowby. My car requires a constant vaccum to perform at it's best.

Discuss. I'm particular interested in turbocharged/supercharged applications.

[Damian]

Originally Posted by enkeivette

You can't use manifold vacuum to vent the crankcase on a boosted motor. You're supposed to move it to the air intake. There is always suction there.

Right, it has to go to the suction side of the turbo. At least that is what I'm going to do mine when i finally get my turbo in.

One thing I never understood is why does my v6 have a pcv on the front bank and not the rear bank.

[kdracer73]

Originally Posted by Damian

Right, it has to go to the suction side of the turbo. At least that is what I'm going to do mine when i finally get my turbo in.

One thing I never understood is why does my v6 have a pcv on the front bank and not the rear bank.

Most cars have one vacuum side at the pcv valve, another "breather" line to let clean air in. Both banks are open to the same pressure through the block.