[mhiscott]

For the past three years, I've been tracking my FRS heavily with a dual VTA catch can setup. I modified the original PCV check valve to make it straight flow through, and ran the PCV to one catch can, and the crankcase breather below the AC compressor to the other catch can.

The above setup worked great for years, and only this winter did I make some changes in an effort to move to a sealed system (the VTA setup stunk a little bit under heavy loads).

Unfortunately, I sold the MAPerformance dual VTA can setup I had, and assumed I would be able to use a Crawford AOS I had poked away in its place. Things didn't work out well when I tried using it, however.

The Crawford AOS has four ports, and the two pairs are completely isolated from one another. The side for the crank case breather is working fine, with one side under the AC compressor, and the other hose for that side routed to the turbo inlet tube (before the compressor housing, so not exposed to boost pressure)

The other side of the Crawford AOS is hooked to the intake manifold on one port and the PCV on the other. This is what's causing my troubles. I first tried this as per Crawford's instructions (I e-mailed them to ask specfically about this AOS on a boosted twin). They told me to only use the factory PCV valve, so I ordered a new one at the dealer, and used it as directed. Doing this resulted in a pressurized crank case and a lot of blue smoke.

After doing some research, I tried adding a check valve, a couple of inches up from the PCV valve. I put the hollowed out PCV back in, leaving me just with the check valve on that hose. I verified the direction was correct; blocking air being blown towards the engine block.

This attempt also netted a pressurized crank case and heaps of oil in the intake manifold.

Some further researching for solutions led me to a mix of people suggesting that VTA cans are the only way to go on a turbo track driven twin, and others that said sealed systems like the dual radium is best. Radium themselves even say this specfically:

-Both of these kits are also compatible with all current aftermarket forced induction kits
-Because the Radium catch cans are pressure sealed, they are great for boosted applications as well so connecting to the intake manifold is permitted.
And they also say;
-This catch can runs inline with the 3/8" PCV (positive crankcase ventilation) valve. When the intake manifold pressure is close to or greater than atmospheric pressure, the PCV "check" valve closes and, thus, this hose experiences no flow. Conversely, the PCV hose will experience "metered" vacuum when the engine is idling, steady state cruising, and decelerating.

The OEM check valve is specifically known to not work with boost properly.

From where I'm sitting, I can't see how a sealed dual radium setup would be any different than the Crawford which is essentially two cans in one, entirely divided from one another internally.

I need to get this sorted soon - I am fine with paying more than I'd normally like to get something I know will work, wether it be radium, full blown (which would put me back to vta), etc. Even something like a VTA moroso on the PCV (passenger) side and a sealed moroso on the breather (drivers) side.

Can anyone with track experience and an FI twin with catch cans or aos shed some light?

For what it's worth, Boomba doesn't even sell their 1/2 in check valves anymore...