Gretch

Bump

Edit, bumped this to get Tim Murphy's take on the idea........................

bcdavis

Tell me about the valve...

Is it a PCV valve?

This seems like a really good setup.

PorKen

bcdavis,

The valve is a 'Standard' brand part number 'AV7 - air pump check valve' (used for cat air injection on GM trucks I think).

I added it to smooth the fluctuations in the vacuum.

It's just a one way valve. I had used for the exhaust dump I tried so I reused it. I would rather use a valve with a more positive/sensitive seal if it could be found. The Standard valve does not hold the vacuum in the crankcase for long after the rpm level is reduced.

bcdavis

See, the thing I am trying to figure out, is how to avoid creating a vaccum leak.

If you plumb the crankcase to a breather, and cap the inlet to the intake, it stinks.

If you add a breather, but keep the intake inlet connected, there is a vaccum leak to the breather.

So it seems like venting directly to the exhaust is the only way to avoid creating a vaccum leak,
or creating a stinky breather...

PorKen

The nice thing about what I've done here is that you can run a hose to a point where it will not be drawn into the cabin.

I dump mine into the passenger side fender well, but I only have steam. The intake is capped.

I had originally a hose that went all the way back behind the passenger seat (zipped-tied to the fuel rails) and it worked fine there too.

bcdavis

Yeah, I only have steam too...

Besides, I have a catch can inline first, to catch any oil, etc...

But the damn breather is stinky and you can see the steam drift out from under the hood area, because my breather was right next to the air intake tube on the passenger's side. So you'd see small trails of vapor coming out from the hood/fender seam. Not appealing or confidence inspiring!

I'd consider the fender, or under the car, but I think if I am going to be venting stinky steam under the car, I might as well plumb it into the exhaust, (post cats) and let the steam and exhaust all come out the tailpipe...

PorKen

I tried using the air pump output going to my exhaust pilot tube, but any restriction in the output pressurized the crankcase instead of making a vacuum.

That was before I installed the check valve; with two check valves, it might work.

I'll try it, if only because I have this ugly capped pilot tube on my exhaust pipe and I feel the need to use it or lose it.

bcdavis

That's what I was worried about...

That exhaust pressure would create reverse pressure.
The air pump seems like it would work to help with flow,
but I do not have one on my Euro.

And yes, I could use a check valve...
But I still wonder if the pressure in the exhaust will be too much to
allow the crankcase gasses to properly vent...

Or if the valve will just stay shut because of exhaust pressure...

PorKen

I tried pumping the final design output into the exhaust via a pilot tube (which I had previously installed while trying to exhaust vent directly - here), through a check valve. This didn't pull any vacuum.

I then removed the check valve at the pilot tube, and ran the output directly into the exhaust. Success! The flow is similar to dumping into the fender well. In theory the flow should be helped by the pilot tube exhaust suction at speed.

I also tried running without the check valve from the crankcase, that is to say, no check valves. Pressure in crankcase instead of vacuum at low rpm's.

...

In short, the air pump/vacuum system pushes the crank vapors into the exhaust stream to be pulled out the back of the car. So, absolutely no stinky vapors now.

Note: I have a very low restriction exhaust (3" single), and I'm pumping the crank vapors in after the muffler. A more restricted exhaust after the muffler/cat may push exhaust back up the crankcase vent hose instead of pulling the vapors out.

Old & New

Ken,

Have you tried running the pilot tube into the exhaust pipe a little ways to create a venturi at that point? (As you have inside the "T") The exhaust stream should pull a pretty good vacuum on it.

PorKen

Old & New,

I had done as you describe previously, and I reused the tube:


(The muffler is in place of the cat.)

How it looks now:



The exhaust vent did not pull any measureable vacuum, but it did vent the crankcase. The first time at the dyno, I had oil coming out of everywhere. The second time, after installing the exhaust vent, no oil was leaked.

If the exhaust vent was closer to the engine (where the exhaust is hotter and faster), it probably would create more draw, but I didn't want to affect my oxygen sensor(s), so I welded in the pilot tube in farther downstream.

Old & New

Ken,

It wasn't clear that the tube extended into the exhaust pipe.

I wonder what cut on the end of the tube would create the most vacuum in the tube? Probably a 45 degree angle to the flow, like what they put on tailpipes...

bcdavis

No issues with heat affecting the tubing?

PorKen

Old & New,

The tube is cut at 45 degree and the tube is inserted so that the opening is just inside the exhaust pipe, facing downstream. I copied the design of a Moroso exhaust evac kit.

bcdavis,

The external exhaust temps drop remarkably through the muffler. 400F+ at the inlet, but 200F+ at the outlet. You can see in the pic above where I added a few inches of 1/2 copper pipe to further cool it down before the 5/8 heater hose. The crank vapors also cool the hose.

For just a plain evac, you can't beat the exhaust tube for simplicity.

drnick

what about an air-oil seperator and feeding this back to the engine? perhaps close to the oil filler tower?