Thoughts on Crank case evac systems?

[Mars]

Yeah, no probs.



I tapped the rear valve cover hole to 1/2" NPT, Didn't even need to drill the hole larger, the tap just bit right in there... Then used 3/4" heater hose to the valve which is right after the cat on my Fiero.



STUPID BRAKE LINE ! blockin my pic... lol.

On my Camaro the valve is in the downpipe. It works pretty much anywhere in the exhaust. The velocity will create a vaccum. my motor was leaking oil out of EVERYWHERE and blowing the dipstick out of it's hole on the Camaro. This fixed all the issues.

I still have the stock PCV valve, and am going to keep it. You should try to plumb the stock PCV so it will pull a little @ idle then once you're WOT it will really draw through the slashcut and close the PCV off...

[Driver_10]

I wonder how well would this work on a turbo system if placed after the turbo or perhaps after the cat?

[Mars]

Dude did you even read my post? ^

lol

[Superdave]

The turbo Honda guys love this setup.


Thanks for the pics Mars, what kit did you get?


Most of them have that check valve but also have the big breathers for the valve covers.. any reason you aren't using those?




I talked to my dad who was a big muscle car guy back in the day. He said they would use the slash cut tubes under the car so the air moving under it would pull out the vapors, then in the other valve cover they'd put a breather and set up a ram-air system from up front. That would work at high speeds for sure but i think the exhaust setup is a better option for what i'm doing.



When it's all said and done i'll put a vacuum gauge on it, or maybe even wire in a MAP sensor and datalog what's going on at different RPM's/loads.

[Mars]

I think it's just a summit brand kit. I didn't use the larger pieces cause our valve covers already have some baffling in them under the hole there...

[Driver_10]

Dude did you even read my post? ^

lol

My bad... I guess not. :P
So they worked well on your turbo camaro too. Id always wondered whether or not you could produce enough low pressure behind a turbo to get adequate vacuum for an exhaust evac system.

Ill have toss that into my bag of tricks.

[Mars]

Pressure has nothing to do with it. You could have 45psi of backpressure in your exhaust, the velocity will still create a vaccum.

[Driver_10]

Pressure has nothing to do with it. You could have 45psi of backpressure in your exhaust, the velocity will still create a vaccum.

Im sure that there is some funky calculus equations that I would need to observe that... however, Im definitely going to take your word on it.
(gotta wrap my brain around my "oiling system" idea right now)

[Superdave]

All you need is flow across the pipe, the more flow and less static pipe pressure the better they will perform. They're recommended to be used with open headers or open type exhaust because of that.


My system flows around 850 CFM with the mufflers and 1600+ without them.. but the engine only produces about 770CFM@ 350 HP so even with the cutouts closed they should still work very well.

[3400-95-Modified]

I'm glad to see someone using this, I've been thinking about doing this as well for a long time now... Maybe I will ge to that this year... Or maybe next lol

[bob442]

IIRC you have to make sure you have like a 35* angle of the pipe in the exhaust. i guess this is your only option with your intake setup, though, i think you MTB could be improved on in design... with minor modifications

[Superdave]

45 degrees, with any luck i'll have the car out of storage tomorrow morning so i can get to work on it. It's finally starting to warm up around here so things should start moving fairly quick.


We have a local track rental in June so my goal is to have all the big things addressed by then.

[Superdave]

got most of the exhaust together today but realized one thing that we all overlooked... these slash cut tubes need to be mounted after the o2 sensor(s).. if not they're going to cause false readings.


My wideband is mounted in the X pipe, NB is going in the pass side before the X so i'll have to put the tubes in right after it and maybe T the line and run a single up to the "rear" valve cover. Might keep engine vacuum on the other one to see what happens.

[gectek]

They are also recommended because you will oil contaminate a catalytic converter really quick or an O2 sensor.
Here is what I recommend, esp for turbo setups....

http://www.racetronix.biz/customkititems.asp?kc=CEPH&eq=

then use an AIR pump from a vortech or 4th gen and you are good to go.
We have one on our LSx 427 with a TVS 2300 set on kill, comes on at 4lbs of boost. The best part is you can change the hobbs switch to turn on when you want.

[Superdave]

Well, i fired the car up with the evac system hooked up and it's working for sure. There isn't much vacuum at idle in the crank case but with my hand over the oil fill hole it starts to build decent vacuum at about 1500 RPM. I plan on modifying a spare cap so i can put an actual gauge on it though.


gectek, i'll have to look into that a little more later on this year. Thanks