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Hi. Im looking to install a catch can on my 12a engine which has all emission system deleted.
Will it be correct to connect the lower fill tube nipple into the in on can and the upper nipple to the out on can?
Thanks!
Why bother? These engines have engine oil squirted into the intake the lubricate the Apex Seals anyway. A little extra oil vapor going into the intake is a good thing.
thanks for reply. I was really looking for directions on how to install, but your opinion is redpected too.
My 12a has a RB intake and no omp so no oil going to intake
Yeah, hopefully you are pre-mixing oil into the fuel, or the apex seals won't last long! As LongDuck mentioned, why bother? A SA/FB/FC engine doesn't have enough compression that oil in the chamber will bother, and a bit of oil in the combustion chamber can actually help.
Unless you're running a bunch of boost, but that's not mentioned.......
Yes you can. I made the one on my race car. It never fills up with anything but it does vent the engine. Rotaries are not like piston engines so the "crank case" doesn't fill up with blow by gases. Having some form of a vent should help keep oil from pushing past the front and rear oil seals. Sort of like the vents on the transmission and rear end on these cars.
Instead of connecting to the nipples on the oil fill tube I bought an Atkins fill cap and drilled/tapped it accept a 3/8" pipe thread fitting. From there I ran a -6 aeroquip push lok hose over to a 16oz Miller Lite beer can that has a breather attached. I installed a -6 bulk head fitting into side of the beer car to attach the hose to. When JPM was building rotaries he would weld a 1" tube to the fill tube and run a hose over to an unused windshield washer reservoir or similar.
Last edited by mustanghammer; Mar 30, 2025 at 10:08 PM.
The nipple on the intermediate housing is IN flow only. If you do not have a PCV system or the stock charcoal canister setup in place to pull air through the one on the oil fill tube, then it must be capped off or oil slinging out of the rotors will blow out of it.
I run a hose from the fill tube to the clean side of the air cleaner and be done with it.
Really, I'd do what I can to reinstall the charcoal canister and a stocklike breather. The stock setup pulls "fresh air" from the charcoal canister to the port on the intermediate housing. The nice thing about having the whole canister setup is that the fuel in the tank won't evaporate when the car is parked, so the fuel will stay fresh and not turn to garbage. I've had seven year old fuel in an intact RX-7 be fine. I've also noted significant fuel loss in a deleted car when sitting, like park it at half a tank and then a couple months later the gauge is near a quarter tank. Gasoline isn't a single chemical, it is a brew of heavy and light hydrocarbons, and the light ones evaporate first, you see. After the light stuff evaporates you are left with barely igniteable liquid in the tank.
The key is the vacuum operated valve inline with the breather to the intake manifold. When the engine is shut off, the valve closes and the fuel tank is sealed to atmosphere.
The nipple on the intermediate housing is IN flow only. If you do not have a PCV system or the stock charcoal canister setup in place to pull air through the one on the oil fill tube, then it must be capped off or oil slinging out of the rotors will blow out of it.
I run a hose from the fill tube to the clean side of the air cleaner and be done with it.
Really, I'd do what I can to reinstall the charcoal canister and a stocklike breather. The stock setup pulls "fresh air" from the charcoal canister to the port on the intermediate housing. The nice thing about having the whole canister setup is that the fuel in the tank won't evaporate when the car is parked, so the fuel will stay fresh and not turn to garbage. I've had seven year old fuel in an intact RX-7 be fine. I've also noted significant fuel loss in a deleted car when sitting, like park it at half a tank and then a couple months later the gauge is near a quarter tank. Gasoline isn't a single chemical, it is a brew of heavy and light hydrocarbons, and the light ones evaporate first, you see. After the light stuff evaporates you are left with barely igniteable liquid in the tank.
The key is the vacuum operated valve inline with the breather to the intake manifold. When the engine is shut off, the valve closes and the fuel tank is sealed to atmosphere.
Always solid advise given by Peejay. e85 is even worse. I spilled some on the ground a within mins it was evaporated and dry. I was amazed!
My center iron is routed to the charcoal canister and my oil fill tube just has a tiny little amazon air filter on it. For a while I just ran nothing on that nipple and I saw the smallest oil residue on my oil filter after a year. So really, the air filter is just going to catch minute traces of oil trying to dirty my engine bay.
-M
Last edited by Relisys190; Apr 1, 2025 at 08:50 PM.
And guess what,... oiled air filters are better air filters because the ionic charge in the oil molecules attracts and traps incoming particles. We're back to square one.
