Breather to Exhaust - Venturi PCV System (2 Viewers)

[dadinabarrel]

2 - Route down, and into exhaust via a slash cut pipe. The theory is that by introducing a slash cut pipe into the exhaust, a venturi is created by the exhaust gases, which pulls a vacuum on the crankcase. The fumes go out the tailpipe and, due to the heat of the exhaust, are likely partially dissipated. Due to the under hood arrangement, this is the cleanest option, and requires no maintenance. The intercooler and turbo stay clean. Downside is that if there is too much back pressure, it can pressurise the crankcase. If I was using straight through exhaust, I could see this being the best option, but with a stock muffler I think there might be a bit of back pressure.

Hi
Is there anyone with info about the slash cut pipe? I want to route my breather to the low pressure side (down stream of muffler) of my exhaust, I'm particularly interested in generating a small vacuum for scavenging the gasses from the crankcase.

 

[ForealBoreal]

why not just put it into your frame rail?

 

[dadinabarrel]

???? What about the oil droplets

 

[ForealBoreal]

they collect in your frame rail and prevent the inside from rusting.
I would be scared to plumb it into exhaust mainly because exhaust will always find its way up s***.
Either a catch can or run it to atmosphere.

 

[gerg]

Frame rail routing has shown to cause some kind of corrosion problems I guess due to the corrosive gasses. The venturi in the exhaust is commonly used in racing to get better ring seal and lower crank air density to gain a couple HP. I seoulsly doubt you would realize the HP gain, but I like it for the ring seal and not sucking that junk into my air vents at the stop lights.
Moroso part number 97800 or just cut your own from a pipe.
http://www.summitracing.com/parts/mor-97810
Run a check valve and you wount get your exhaust backing up into the case.

 

[dadinabarrel]

Yep, that's me, weld that sucker in, use a PCV if need be. Thanks Gerg

 

[dadinabarrel]

Just bought this v8 kit (2 of everything) http://www.ebay.com.au/itm/140914382867?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649 only need half, if anyone in Brisbane wants to buy half kit for $35 (cost me $70 posted) call me on 0423 628 370

Must enter the pipe at 45' so that it faces the gas flow with the diagonal end parallel with the pipe wall for maximum venturi effect.

 

[ozwallaby]

Must enter the pipe at 45' so that it faces the gas flow with the diagonal end parallel with the pipe wall for maximum venturi effect.

I hope somewhere in the instructions it says to point it away from the motor end of the pipe...... the above instruction is ambiguous if you know nothing of venturi effect....

 

[dadinabarrel]

I got that from a couple of sources, but yep, the pipe needs to be pointing towards the downstream flow so that the gas blows past the end of the tube, this creates a vacuum when it passes the opening (venturi effect The PCV allows the created vacuum to draw vapour from the block but is a one way valve so gas can't be pushed back into the engine.

 

[gerg]

As usual there is a lot of conflicting info on the placement of these things. I would agree that basically faceing the slash to the downstream flow would net you the greatest Vacume, but I would test placement with a gauge myself as depth into the stream plays a part as well as angle of attack. The closer to the pipe wall you get the slower the exhaust stream. Course I'm pretty sure you could design a nice exhaust restriction with one of these if you over did it.

 

[dadinabarrel]

I'm thinking 25mm into a 75mm pipe

 

[dadinabarrel]

Here it is, welded it in just on the low pressure side of my muffler. Works really well, you can hear it sucking away when you drive with the window down. I think I'll put a catch can in between the RC and the Venturi/PCV as I'm getting a bit of smoke and an oil drip at the end of my tailpipe. I definitely want that oil to stay in the motor.

 

[maat]

if you were to put it say a foot after the turbo/dump pipe wouldnt it burn alot of the oil vapour up so you wouldnt get the oil drips? or would the venturi effect be too strong making it suck too much?

loving your build btw, spewing you moved to brissy, i would have loved to have seen it in person!

 

[dadinabarrel]

Thanks dude, I put it downstream because I was worried the pressure would be too high closer to the turbo. With this much pressure, there is a possibility of it blowing right through the non return valve, because it's welded in, that'd be a disaster. The other thing is, right after the dump is a flexible section then the O2 probe for my AFR meter, then the muffler so there wasn't really any other point except downstream anyway.

Surprisingly the tape hasn't melted

 

[gerg]

That is a pretty exhaust pipe. Get it dirty is I don't feel so bad about mine ok. Your right to put it post turbo as for sure the pressure would back up. In fact downstream of the muffler would be perhaps better yet, but your exhaust looks pretty free flowing. How did you orient it internally? I'm Cureous as this is on my to do list and I'll model yours if it creates good Vacume. Nice install by the way.

 

[dadinabarrel]

It's about 150 mm downstream of the muffler coming in from the top so it's protected. It also lines up nicely with the chassis rail so I have a tidy run back up to the motor.

 

[gerg]

Isn't the braded thing just a flex pipe and the black thing your muffler? Or is your muffler immediately before your flex pipe? I might have misinterpreted your pics sorry.

 

[dadinabarrel]

Yep, turbo - flex pipe - muffler - tailpipe

 

[gerg]

Ahh sorry I mistook your o2 sensor for the Venturi. Mystake. I see it's 45degree to the pipe, is it perpendicular facing downstream inside like you spoke of?

 

[Dougal]

So what's the advantage again over a catch can and breather into the intake pre-turbo?