Basic design

Basic design

A few months back I started building a breather tank (known in the Club RSX community as an “oil catch can”), based on the design in this thread. The prototype image is over on the right side.

An overview of the finished product

An overview of the finished product

I ran out to Home Depot, picked up some 3″ diameter PVC pipe, a couple end caps, a PVC weld two-pack (one can of the thick, clear chemical and one can of the thin, purple, toxic one), a handful of various brass fittings, and a length of thin clear hose – like what you’d use on a home freshwater fish tank. I made all the markings with some black Sharpie, then cut the pipe to the proper length (I did about 7 inches), and drilled all the holes. It’s important to make sure that the holes, which are drilled into the end caps, aren’t drilled in a position where they’ll be blocked once you insert the pipe.

I also picked up some liquid Teflon (for a thread sealer) and QuikSteel from AutoZone. I figured out which side port I’d be using to connect the can to the atmosphere, used some coarse sandpaper to roughen up the area around that hole (on the inside of the end cap), then used the QuikSteel to adhere a little piece of window screen to it – just as sort of a coarse secondary filter.

Once this was done, I grabbed the PVC weld and attached the end caps. Double check everything before you do this – PVC weld is permanent, and the PVC pipe itself isn’t real cheap. After letting the weld sit for a little bit, I spray painted it flat black and let it sit for a day so everything could dry and set up. Then I started on the brass fittings – put a little bit of the liquid Teflon on the second thread in, for about a 3/4 turn, and then get it in the PVC. This is a bit of a pain in the ass, because PVC isn’t really meant to be drilled and threaded – close to the outside it’ll fall apart, then it’ll go in crooked, and not get in all the way. Get it in there as straight and far as you can – it won’t be perfect.

Attach the clear hose to the two brass fittings that are facing each other – this is going to be your gauge to see when you need to empty it. This tank is pretty big, so you won’t need to do it real frequently. The clear hose might not want to stay on its own, if it doesn’t, grab some silicone sealant and get it in there with that.

At this point I was broke and sort of let the project fall by the wayside for a few months – I finally picked it back up last week. I grabbed a little breather filter from Pep Boys, and got six feet of 1/4″ vacuum hose from a friend. Attached the breather filter to the top, hooked up one of the brass fittings (the lower-elevation one) to the PCV valve using the vacuum hose, and hooked the other one up to the PCV port on the intake manifold, like this (sorry it’s hard to read, click to enlarge):
Oil catch can - wrong setup diagram

Wrong setup - overview

Wrong setup - overview

The mounting location from the wrong setupThe PCV connections from the wrong setup

The mounting location and PCV connections from the wrong setup

I kept the tank next to the battery – actually it wasn’t being held in by anything, I just used the tension of the positive battery cable to keep it in place. I don’t recommend this, as it’s a great way to destroy your positive battery cable pretty quickly, but I was only planning on doing it for a day or so to test and make sure everything worked, before mounting it properly.

As it turns out, it didn’t work – the problem is that it caused a massive vacuum leak. I knew that this would be the case when I gave the intake manifold a direct, unthrottled connection to the atmosphere – but I was under the impression that, as long as I let the car idle for ten minutes or so (for the ECU to “get used” to it), it wouldn’t be a problem. That wasn’t the case. It kept throwing a check engine light, code P0505 (“idle system malfunction”) – which makes sense, as the idle controller no longer had any real control over the idle. A fully closed throttle would still leave a source of air.

Logically this would probably have improved my gas mileage due to the reduction of pumping losses from the throttle plate, especially with my foot off the gas, but I wasn’t happy with the way the car ran when it had the code up – it would go between running fine to running like ass. So I reconnected the PCV system as normal and went back to the drawing board to change my setup a little bit, like so (again, sorry it’s hard to read, just click to enlarge it):
Oil catch can - correct setup diagram

The PCV system, post-modificationsOil catch can - intake manifold and hose

The PCV system, post-modifications

There was a problem with this though. First of all, I didn’t know what to plug the intake manifold and pipe with. After a little assistance from the guys at CRSX, I discovered vacuum caps ;) so I hit up Advance Auto Parts to get an assortment of them. Another problem though – the largest one they had wasn’t big enough for the valve cover breather. The guys at AutoZone, however, made a suggestion – get a piece of hose to go over the breather port, and plug the hose with a bolt or something.

So I did exactly that – got a foot of 3/4″ gauge heater hose and the only 3/4″ bolt I could find at Ace Hardware, put the bolt in the hose, tightened a hose clamp around it, and zip tied it up near the battery so it doesn’t flop around. I also needed to change the port arrangement on the tank around a bit – I had the filter on the top port; the valve cover needed to be connected to that now, and the filter to one of the small ports. So I took the casing from a pen (1/4″ or 3/8″, I forget which), clamped that into the end of one of the lengths of 1/4″ PCV-compatible vacuum hose, and clamped the filter onto the other end of the pen casing. Problem solved.

A close-up of the tank's mounting location

A close-up of the tank's mounting location

I hooked everything all up, positioning the tank on top of the transmission – the bottom’s ziptied to one of the stock airbox mounts, and the top’s ziptied to the brake booster. It’s not going anywhere. I put the filter right where the back part of the hood meets the body – basically right in front of the driver side mirror – and made sure the hood closed; it did. However, there was one other problem with this – I went to wash the car and realized that all kinds of water would get into that spot when it rained or when I washed it. So I moved the filter so that it just hangs down in front of the battery now.

Old location of the breather filter outlined in blue

Old location of the breather filter outlined in blue

Again, it’s not going anywhere.

A couple close-ups of the breather filter's final locationOil catch can - filter location (2)

A couple close-ups of the breather filter's final location

I expected it to have a negative impact on my gas mileage, since the blowby that this thing’s catching consists mostly of unburned fuel and oxygen. However, it hasn’t – I’m guessing that without the intake manifold sucking on the crankcase, blowby has simply been considerably reduced. I haven’t noticed a power difference, but I don’t expect to – I’ve heard of people getting 5hp out of these things but that seems like a fish story to me. If I got 2-3whp I’d be ecstatic. I’m going to get it dyno’d with this and a handful of other small mods that I’m doing just to keep the intake charge a bit cooler, so we’ll see what happens.