yo_marc

Yesterday, I was able to finally install a PCV catch can on my 3.8. I used an Accurate Machine Works (AMW) unit I had run on a previous vehicle.

I hard mounted it to the bracket that holds some major engine/ECU cabling on the drivers side firewall. I had to relocate one of the cable bundles to the bottom of the bracket. Had to re-route it slightly.

I used 3/4" to 1/2" barb fittings to 'splice' into the existing PCV hose. (both of those specs are for the ID of the hose).

Here's a pic of it mounted, prior to plumbing up. Will get more pics and updates in later today or tomorrow...

ReconJeep

That's something I definitely want to do. Will be following this. It's amazing how much it affects the sensors in the throttle body. Keeps everything much cleaner. Thanks for doing a write up.

tattedfire

Can someone enlighten me on what exactly this does?

baron

X2...What is the benefit?

Ryan0260

Looks nice. That is definitely on my to do list. Anyone with the oil consumption issues should look into one of these

Bradlybob

It collects the oil mist/vapors that come from the PCV system. The PCV system basically sucks all of the blowby gasses and oil vapors from the crankcase back into the intake manifold to be burned and sent out the exhaust. If your engine has a lot of blowby it can clog the PCV system to the point where it is no longer able to suck the gasses out of the crankcase and they end up backing up into the crankcase vent ahead of the throttle body. This causes all kinds of nasty buildup on the throttle body and sensors. The catch can collects the heavier oil mist and goop so the PCV system doesn't get clogged. I had to do the same thing on my XJ years ago. Works good.

jugast

This. Catch Cans are great. I ran one on my GTI and it was awesome. I'm definitely going to look into this.

yo_marc

Hi Guys,

So some more updates:

I got the catch can fully plumbed up and got some driving time with it. I burned through about half a tank of gas with mixed driving. It was definitely starting to collect some oil. Pretty clean oil too - not burned combustion byproducts. I've got some observations and concerns I'll try to walk though clearly...


1st) The negatives: I am concerned about the "throughput" of the catch can; the amount of air it's able to flow and process.

As seen in the OEM-PCV-Valve-Study thread, the valve resides inside a ~3/4" ID hose, and the valve itself has a nipple that looks like it would accept a 1/2" ID hose. So that nipple is just hanging out inside quite a large space inside the main PCV hose. The catch can is setup with 3/8" ID fittings and tubing; significantly smaller than the main tubing and the ID/OD of the PCV valve nipple.

There is a noticeable hiss inside the cabin as the motor is running and the catch can is processing air. It's processing at idle and lower RPM's, up to about 1/4 throttle. It typically closes (or at least the noise goes away) above 1/4 throttle, or under heavy deceleration. (note that I have a 6-speed)

Throttle response right off idle and the first bit of pedal travel has softened. I'm led to believe (just like the PCV Valve Study suggests) that the PCV valve should be closed at idle and during lower throttle usage. I believe the throughput of the catch can and the 3/8" tubing is not allowing enough airflow to snap the PCV valve shut when it's supposed to be.

I'm considering drilling and tapping the catch can to accept 1/2" ID fittings, but, I'm not sure if the can is designed to handle that much airflow without the oil walking up the walls or losing processing efficiency.

My other thought is to consider trying different PCV valves. That could be a can of worms though.


2nd) The positives: Greatly reduced engine knock, pinging, or detonation. I'm running a 87 performance tune that is prone to produce knock with the 87 octane fuel in my area. The motor has been nice and quiet and almost knock free. That's a big win.


3rd) A side observation: Looking at the setup of the stock PCV valve, I believe it is deigned to be a mild catch-can in itself. Like I said, the PCV valve only has about a 1/2" nipple on it, but it resides in that 3/4" ID plumbing. You'd think, why didn't Chrysler just use 1/2" ID tubing attached straight to the PCV valve nipple?! That's how it's done on other vehicles. Well, the PCV valve has a small hole drilled in the top of the valve body at the base of the nipple. I believe the valve-in-larger-hose-setup is designed to encourage the oil to fall out of suspension inside the larger tube and drain back into the valve cover through that small pilot hole. I'm wondering if this can be improved upon.


I originally posted this in the Modified Tech section knowing I'd get technical and likely need to pick peoples brains. Hoping I can still get a good amount of feedback from this section of the forum.


Anyhow, here's some more pictures:

ronjenx

Nice set-up.
How do you monitor the oil level in the can? I have seen lots of cans that will drain back into the crankcase when the engine is off.

If the small hole you mentioned is there to allow oil to drain back, it would only do that when the engine is off. Otherwise, there is no feature of the system to sling out the oil and hold it, (as with a catch can), while the engine is running.

yo_marc

Thanks! Unfortunately, yes, it's a manual process to monitor the oil the device catches. On this unit, there is a valve at the bottom that is used to drain the caught oil. It will hold a fair amount of oil - about 2oz pretty easily.

Regarding that small pilot hole... During my install here, I had fully removed the stock PCV valve, taken a look at it, and put it back in. I completely cleaned it up while doing so. I took to JK for a trip to the hardware store for some fittings, returned, and disassembled the tubing again. This time, there was a small puddle of dirty oil forming at the top of the valve. That's about the first time I paid attention to that hole. I happened to put the valve in with the hole towards the front of the block. Oil pooled at the rear of the PCV valve recess in the valve cover (due to the slant of the motor). I took the valve out and spun it around so the hole was facing the rear of the block.

I'm not good with fluid dynamics or whatever science is involved here, but I thought the difference in pressure from the nozzle (PCV valve nipple) to the larger void (the main tubing) would promote the oil to condense in the tube. If it doesn't maybe it's just dumb luck that oil is getting caught there