Run_Away
Run_Away Reader
10/31/11 8:03 p.m.

Hello all, So I've decided I'd like to improve my PCV system.

I've read this article and I'm intrigued by the idea of using the exhaust flow to create a suction. In the comments someone mentions they can't find a good source for long-lasting one way check valves to keep exhaust blowing back into the crankcase. Does anyone know of an application or source for a valve that will be effective and last?

I also don't like the extra pollutants factor of this method, I'm hoping a good catch can will be effective in removing the majority of the oil mist, and maybe introduce the PCV gasses pre-catalytic converter? Would the cat catch and burn the majority of pollutants, and would a pre-cat placement be less effective due to increased backpressure?

Or if anyone has experience with an electric pump that could move enough air to be effective and not weight/draw a ton of power? I don't quite have the $$ for a dry sump....

alfadriver
alfadriver SuperDork
10/31/11 8:07 p.m.

What car?

Most modern cars have an engine in that comes from the air box, and then and engine out that goes to the intake (downstream of the throttle).

They also have some kind of oil separator in the engine outlet area- so that the drops are caught.

The gas burns best in the combustion chamber.

N Sperlo
N Sperlo SuperDork
10/31/11 8:10 p.m.
alfadriver wrote: The gas burns best in the combustion chamber.

Hold on, I better write this down.

Taiden
Taiden Dork
10/31/11 8:11 p.m.

I am curious to see what peoples thoughts are on this.

Is there data that suggests reasonable gains with a high performance PCV system?

tuna55
tuna55 SuperDork
10/31/11 8:16 p.m.
alfadriver wrote: Most modern cars have an engine in that comes from the air box, and then and engine out that goes to the intake (downstream of the throttle).

I saw that you posted, and expected some good info, but I don't understand this sentence. At all.

Run_Away
Run_Away Reader
10/31/11 8:27 p.m.

Car is a Honda Civic (B-series motor, see my garage for specifics). Factory there is a tube from the valve cover to the intake arm before the throttle body. Currently there's a generic vented to atmosphere filter the previous owner installed there. The car has also has a oil separator box at the back of the block which drains into the bottom of the block, at the top of the box there is a hose that goes to the PCV valve, and from there another hose to the intake manifold (to manifold pressure).

I've got a new PCV valve on there but I need to figure out something better as the aftermarket intake manifold makes the fitting from the oil seperator box to the PCV hose not sit properly...hard to explain in words.

N Sperlo
N Sperlo SuperDork
10/31/11 8:30 p.m.
tuna55 wrote:
alfadriver wrote: Most modern cars have an engine in that comes from the air box, and then and engine out that goes to the intake (downstream of the throttle).

I saw that you posted, and expected some good info, but I don't understand this sentence. At all.

I think what our friend here is trying to say that most modern cars have a pcv line (Not pvc like i usually say) that goes from the air box and... lets just say its 50/50 or 25/75...

mad_machine
mad_machine SuperDork
10/31/11 8:40 p.m.

how about a catch can... large enough to hold a large amount of oil.. with a filter on top to keep the crap out (or in) and a one way check valve that allows the oil to drain back into the sump when the engine is turned off?

Run_Away
Run_Away Reader
10/31/11 8:44 p.m.

See a catch can just reduces the amount of oil that enters the intake manifold (and without a drain keeps the acids/sludge from going back into your oil), it doesn't actually reduce pressure in the crankcase. Still a good thing to have and will be part of my upgrades but I'm looking to actually lower the pressure in my crankcase.

fasted58
fasted58 SuperDork
10/31/11 8:51 p.m.

are you talking about something like this:

http://www.jegs.com/i/JEGS-Performance-Products/555/52210/10002/-1?parentProductId=924093

Run_Away
Run_Away Reader
10/31/11 9:00 p.m.

Wow - that looks exactly what I'm looking for. Thank you!

Streetwiseguy
Streetwiseguy Dork
10/31/11 10:18 p.m.

Yep. Thats the deal. If you want to GRM it, go find a car in the junkyard that still has an airpump on it. Volvo used those valves on their air pump and pulsair systems for a decade or so- 75-85 vintage. Many of them have rotted out since then...

You can also hook up the air pump to the crankcase to create a vacuum in the pan. Drag race cars that require every last horsepower use them- the pistons go down easier in a vacuum than pushing the air in the crankcase.

81cpcamaro
81cpcamaro Reader
10/31/11 10:26 p.m.

That drag race setup in the Jegs link works best with open headered engines. Cars with mufflers end up with oil building up in the muffler. A good separator could help out.

For a low cost electric air pump, just find a 93-97 Camaro Z28/Formula/Trans Am with the LT1 in the junkyard, they all had them. Many racers have used them just for what you want to do. Look here for images: http://www.camaroz28.com/forums/showthread.php?t=702735

novaderrik
novaderrik Dork
11/1/11 12:39 a.m.

you don't want any backpressure in the exhaust if you go with the style in the Jeg's link up above.. if you have any backpressure at all you will just end up with an overpressurized crankcase and oil seeping out of every gasket and seal. it will also pull a lot of oil up past the rings and cause to to burn a lot more oil than it should.

the factory engineers generally knew w at they were doing when it came to crankcase ventilation.. you want a big breather to let a lot of fresh air into the crankcase and a good pcv valve with a baffle between it and the oil to suck the air into the intake plenum to be burned in the combustion chamber.

Trans_Maro
Trans_Maro Dork
11/1/11 1:10 a.m.
Run_Away wrote: In the comments someone mentions they can't find a good source for long-lasting one way check valves to keep exhaust blowing back into the crankcase. Does anyone know of an application or source for a valve that will be effective and last?

You mean like the factory equipped smog pump check valves that GM has used on their cars for the last 30 years?

They just happen to be the same ones that are in the Jegs kit.

That kit is installed on a blown SBC equipped '67 Camaro dragster that is sitting in the shop at work right now.

By all accounts it works well but as someone mentioned, you want zero backpressure in the system.

Ours works well but it's running open headers. A factory system may have its limitations.

Shawn

alfadriver
alfadriver SuperDork
11/1/11 6:53 a.m.
tuna55 wrote:
alfadriver wrote: Most modern cars have an engine in that comes from the air box, and then and engine out that goes to the intake (downstream of the throttle).

I saw that you posted, and expected some good info, but I don't understand this sentence. At all.

Yea, I'm not sure what happened there, but the wording isn't exactly clear. I know what I meant, but that didn' translate into anything u.... well, anything.

What I meant to say was that modern engines have a fresh air inlet to the engine, which is normally in the air box, and then a return line to the inlet manifold- which has both an oil separator as well as a PCV valve.

I think I was distracted last night- I made 5 terrines for a Firday breakfast. Not exactly like spending an evening fixingn rust or rebuilding an engine.

To the OP- if the desire is to lower crankcase pressure enough to make more power, you need to go dry sump. That both reduces pressure and will also give you better low end aerodynamics.

Using the exhaust to make a vacuum (which only would work well at high loads) which is interrupted by a catch can will only make a few in Hg pressure drop.

But if you really want to do it, go with any decent stock car race store, or circle track store- they will have what you are looking for.

Sky_Render
Sky_Render New Reader
11/1/11 8:03 a.m.

I'm glad to see our articles are making their way around the intarwebs.

Here, in my opinion, is the best setup for an N/A motor. Start with the valve cover and install a "T" fitting onto the port.

Your first line should look like this:

T--->PCV Valve--->Catch Can #1--->Intake Manifold

And your second:

T--->Catch Can #2--->Air intake tract pre-throttle-body

The PCV valve can be from any N/A engine that fits in your vacuum line setup. Now, here's how this system will work:

When the engine is operating under vacuum (such as driving on the street or coasting), the PCV valve will open, and the vacuum in the intake manifold will suck vapors out of the crankcase. When the vacuum decreases (such as under full- or almost-full-throttle conditions), the PCV valve will close and the air intake tract (which is sucking a lot of air at full-throttle) will be sucking vapors out of the crankcase.

Using this setup will ventilate your crankcase in all driving conditions.

The only differences between this setup and a forced induction one are: 1) Using a PCV valve designed for a boosted motor that will hold its seal under boost. A good one to use is an OEM one from a Mk IV turbo Supra. It's a stainless steel one. 2) Routing the "airbox" PCV hose pre-turbocharger (or supercharger) so that it is not putting boosted air into the crankcase. The best location for this is in the air tract immediately after the air cleaner and before the turbocharger.

4cylndrfury
4cylndrfury SuperDork
11/1/11 9:17 a.m.

Welcome Mr Render, yes, your articles are very widely regarded here...many of us are Moto-IQ members as well...

I am particularly enamored with the Miaabusa, and the P10 race car. IMHO though, P11>P10, but you guys cant always hit the nail square on the head

Sky_Render
Sky_Render New Reader
11/1/11 9:23 a.m.
4cylndrfury wrote: Welcome Mr Render, yes, your articles are very widely regarded here...many of us are Moto-IQ members as well... I am particularly enamored with the Miaabusa, and the P10 race car. IMHO though, P11>P10, but you guys cant *always* hit the nail square on the head

Note that I didn't write the article the OP linked to. I'm the one responsible for the electrical stuff and most of the Mustang content over there.

4cylndrfury
4cylndrfury SuperDork
11/1/11 9:35 a.m.
Sky_Render wrote:
4cylndrfury wrote: Welcome Mr Render, yes, your articles are very widely regarded here...many of us are Moto-IQ members as well... I am particularly enamored with the Miaabusa, and the P10 race car. IMHO though, P11>P10, but you guys cant *always* hit the nail square on the head

Note that I didn't write the article the OP linked to. I'm the one responsible for the electrical stuff and most of the Mustang content over there.

Noted...but you know what they say about guilt and association...Im just sayin

iceracer
iceracer SuperDork
11/1/11 10:45 a.m.

You could always dry sump it.

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