AOS or catch can for track use
 

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...

This is the link to the Radium page I was referencing above:

http://www.radiumauto.com/Catch-Can-...RZ86-P374.aspx


Here's a shot of my previous setup, you can see the two cans both VTA and this worked flawlessly.

http://i63.tinypic.com/27zydli.jpg

Here's the Crawford with the lower hose removed as I was refitting it with an aftermarket check valve in hopes it would help...

http://i68.tinypic.com/24qsm1d.jpg

This is what Jackson Racing puts in their kit with their superchargers to avoid crankcase pressurizing.

http://i65.tinypic.com/211mhw1.jpg

I guess what I'd really like to know before trying some other sealed setup, is why some are so adamant that VTA is the only way to do this reliably in a racing application.

Jackson Racing won a many championships without a catch can.

I don't run any catch cans on my GReddy turbo setup.

Since I half fit the description of who you’d like to shed light I’ll give my .02

With a sealed system regardless of how nice/expensive/good of a brand you still run the risk of it failing and giving you problems that could possibly be the death of your engine being that it fails under high load.

With a vta setup you’re bypassing any possibility of getting oil in your intercooler/pipes and your intake manifold due to a possible failure of a valve.

I have a rev works vta setup and it does stink after a good while of heavy use or sometimes just from idling for a while but I’ll take the stink over no stink and possible chance of engine failure due to pcv failure. Also tuner says he recommends vta setup for anybody that FI on this platform just to avoid the problem


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I was catching quite a bit of liquid on the PCV side with the previous setup, so I'd be inclined to keep at least something in line.

On your GReddy car, are you using one of those JR valves in the oem hose from the IM to the oem PCV?

I could definitely see the opportunity to skip a catch can on the breather side. I've never had any accumulation there before.

I can confirm that NA with autocross use, I get oil in my Radium PCV catch can. No more than a teaspoon, but ANY is more than enough to warrant the purchase for me. I've no input on the crankcase side, haven't bothered yet.

I run a Verus Engineering AOS, which services both ends of the PCV system with one can. It comes with an open fitting for the rear PCV port, which I prefer over a soft valve since there is no reason not to let all of the positive crankcase pressure out on a boosted track application, which depending on your build it can be considerable. It's pretty stealthy up in the top left corner of the engine bay and the hoses are all routed under/behind the intake manifold. I have it vented to atmosphere with no pre-turbo vacuum source as doing so before would overwhelm the AOS on track with so much vacuum that it would suck oil into the turbo. So now it's a "catch can" which vents with a longer hose down beside the transmission and points at the ground. It works much better for track use this way and I don't have any liquid oil coming out of the VTA hose, but the can does catch oil as it's supposed to. I have a Fumoto valve on the bottom of the can for easy draining.

https://i.imgur.com/4YKhJ0i.jpg

So you're running a hose to the aos from the crankcase breather, another from the pcv (but with a straight through barb fitting), nothing pre turbo, and a long vta hose. How about the intake manifold? Is the intake mani barb capped off and not connected to the can in any way?

Yes, that's correct.

You can see the different ways to install it here: https://docs.wixstatic.com/ugd/b6c8d...ba9777b4f6.pdf

I'm running a universal 3 port mishimoto catch can (I bought their mounting bracket separately through their customer service.) I also have a straight through pcv valve. PCV and CCV go into my can and the middle port is VTA. I can see oil coming out of the middle port. So I assume it's working as it should. Sorry the pictures aren't catch can focused, but you can see how it's mounted towards the top center of the car. The first picture shows it on the right. The left port on the intake manifold is capped off, as well as the nipple on my intake pipe right before the air filter (not pictured).


https://uploads.tapatalk-cdn.com/201...769f2c2ec1.jpghttps://uploads.tapatalk-cdn.com/201...a002304ccc.jpg

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I don't run any check valves either!

-Mike

It's bazzare that some seem to have no issues at all with crank case pressurization. You've effectively got a 1/2-3/8th hose feeding boost straight into your oem check valve, but if it's working - great. I wish I knew why it's causing trouble for some and not others.

The effect of the pressurization will vary with the condition and state of every engine. While I may not be having any adverse issues, I'd also speculate that I'm much more vigilant with my maintenance than many other owners here on this board, possibly resulting in a better condition.

For example, my S2000, with 140k miles on the clock (and currently at over 17 million vtec activations) has steller compression numbers across the board (within 2% of new), but with very high leakdown numbers (30%+ per cylinder).