Catch Can Part Deux

Bigger is better!

Parts for a BIGGER catch can.

Time and time again issues with oil control during hard cornering have resulted in either an oil swamped intake system (the stock pan vent enters in one location upstream of the primary turbo) from turbo to IC to TB or, if you have one, an overflowing catch can that then proceeds to oil down the entire engine bay, underside of your car, and most importantly your rear tires!!!! Over the years I’ve had various plumbing arrangements to my catch can setup and even gone so far as to fully baffling a deep well oil pan with all kinds of traps doors to control oil movement in the pan. I finally came to the conclusion that, short of going to a dry sump setup or replumbing the can back to the pan, that the catch can I was using was simply too small.

Where to Mount a Big Can??? Solving Problems

Time for a bigger catch can. The problem being, where to install it in my already very crowded engine bay? (problem #1) After much deliberation I concluded that without an airpump that location could accommodate a fairly large can. A secondary issue was that the size of the hoses to the catch can were also a factor in the original problem – essentially it was not allowing the oil pan to breath. Oil pushed into the line would act as a plug with only one way out and could never drain back into the pan. So the new arrangement would have to have some fairly large hoses, -8 AN at a minimum. (Problem #2) With the need for larger vent hoses the oil filler neck would have to be modified to accommodate connection of a larger hose and the little 5mm vent nipples on my existing oil filler neck were far too small. (Problem #3)


Where to place a quart and a half sized catch can? The zeeshan filler neck (which is also GZ LIM compatible) The
Fabrication and Installation

A solution to problem #3 was provided to me when a run of SS oil filler neck was offered (zeeshan from the RX7Forum) with larger vent connections. In my case a two 3/8” NPT fittings, the perfect size for a -8AN line. A shame it wasn’t aluminum and a shame I’d have to part with my current one but it was reasonably affordable and it fit the need. After examining the location vacated by the airpump I determined the maximum can dimensions I could install there. Not easy as it was primarily a long vertical can. Then after much shopping through eBay, Jegs and Summit Racing I located a vented billet aluminum can size that would fit, had a breather, and also a drain in the bottom. (Moroso: billet aluminum 1.5quart transmission expansion tank (PN 41221) w/breather - $102.95) It would need fittings welded to it and a level indicator installed but that could be managed later. With the actual can in hand I then fabricated a custom mounting bracket using the stock airpump top mounting bolt location. This solved problem # 1. I also made sure that the routing path for the fat -8AN braided SS hose was at least feasible. Routing behind the alternator seemed like it would work.


With the two main bungs welded to the can the level indicator is located and fitted. And of course I polished the can.

With a mock up in place I determined locations for two AN bungs on the can and had Piper Motorsports weld them on for me. Why two bungs? In case at some later time I wanted to hook up an additional vent to the left side of the motor. I also located the optimum place for the sight level tube and fittings and drilled and tapped holes for the two fittings. The billet can had walls thick enough to accommodate this. All parts were polished of course. I then installed the new SS oil filler neck and discovered a problem when routing the hose. The AN fitting on the oil filler neck dumped directly out in line with the alternator electrical connector and there was not enough clearance to fit the hose past it! Well rats! The oil filler neck had two bungs but the idea of a big SS hose coming off the front and looping around in front of the belts and pulleys..unsupported…did not sit well with me. So I had to figure a way to route the hose behind the alternator. The 90deg fitting and NPT to AN adapter I had originally envisioned would not fit…not even close. I was able to reclock the electrical connector to afford some more clearance but the only alternative was to buy the $42 hose end to fit this location which was a -8AN 45degree hose end to 38” NPT fitting. With the right fitting in hand I was able to make the hose and complete the installation.


A problem with the hose routing - no clearence past the alternator connector. Solution? One $42 hose end fitting!

Not a whole lot of room in there for the can but it fits. The custom made mounting bracket.

Some difficulty with hood clearence but just enough existed. The final installation.

All told cost of the setup was about $350. This included the filler neck ($137), the billet can with breather ($102), fittings, braided SS hose, and welding fees ($65). Upon reflection it is understandable why my previous setup was always overflowing, it is so tiny! As for the now missing airpump, I will no longer need to subject the car to emissions testing as it satisfies the criteria for *historic* status and as such all the emissions equipment can now be removed PERMANENTLY!


It's no wonder the original JAZ catch can would overflow...look how small it is! The new catch can is hardly noticeable and looks right at home.


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This page last updated July 7, 2012


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