Ok, so I have a stainless catch can. I'm 652hp currently and I have both breather hoses going to the catch can and then the catch can is just open breather. This hasn't provided any problems except when I'm cruising on the highway with the a/c, heat, or vent on I smell nothing but exhaust gases. This sucks on my 3 hour drive home to Indiana.

So I purchased some 3/8" check valves to plum a recirc system that will draw off the fumes while i'm in vac. I double checked all the arrows and physically checked the air draw with my mouth to make sure everything was working correctly.

So I got out onto the highway and did a single pull. Drove it on over to a friends house and oil was pouring out of my front seal. Front seal is done. When the car idles oil is just dripping out the front. PITA.

I think the check valves are too restrictive. I was trying to keep it from drawing fresh air through my breather filters on vac. I realized something this morning though. I'm tuned to MAP and not maf therefore even if my vac draws air in through my catch can it won't affect my tune because my air isn't metered (no maf).

So, i might just leave the check valves out (except for the one off the plenum that keeps me from losing boost into the catch can) and go from there. Otherwise my option would be to put longer hoses on my valve covers and just route them down under the car so when the fumes come out they are under the car and not being drawn into the cabin air system.

Any thoughts? Here is a diagram of my system. The red arrows show the check valves and they are pointing the direction. It is setup so under boost the plenum check valve is closed and the filter check valve is open. Under vac the filter check valve is closed and the plenum draws air through the catch can.

 

yah bro really shouldnt be any need for the second check valve but thats amazing you have enough blow by to blow out the front seal

 

Eh, I dint think it's that much. I really have never had an issue so I'm almost positive the check valves are restrictive.

This engine went in last and since then after multiple dyno days with wot I have barely any oil in my catch can. Blowby does create some crank pressure but it's not the sole reason. Pistons on the down stroke will create pressure as well. I have zero other signs of blow by and my compression numbers were dead on in January after my tune.

 

If the smell is a problem, why not plumb the blow by and crank case gasses into the exhaust? Not only do you get some vacuum but would be less messy then open tubes under the car.

http://vibrantperformance.com/catalo...1022_1035_1069

 

I saw one of those before. I guess I could do that right at my headers. Problem is I don't have my welder here and that requires me to remove my turbo again. I'm just getting lazy these days with all I have to do besides my car

 

You feel that the front seal was caused by your check valve restriction? It seems odd to my that a pressurized crank case would be bad enough to make it to the front seal.

 

I know supra have the same problem. The only thing I changed was to catch can. It was either the changes for random chance. Seems off that it was fine for hundreds of pulls and now it blows first drive after the changes.

 

You still had a breather on the rear port though, right? If you had boost going straight into the crankcase through a drilled out PCV, then that would be the only way I can think you'd blow a seal. Use 2 check valves in series if you don't trust the valves. Even if you ended up blocking the port entirely because piping/valves were too restrictive, I don't think you'd build enough crankcase pressure to blow a seal. I would think your dipstick would blow out first.

You could monitor peak boost going into your crankcase with a cheap mechanical boost gauge and another check valve if you wanted to (just plumb it into your catch can plumbing). Or you can temporarily reroute your actual boost gauge from the manifold to your catch can. I originally put a $17 vac/boost gauge on my catch can to make sure everything was working ok and ended up leaving it on.

 

wouldnt the exhaust plumbing require it to be post turbo? i would think pre turbo might run into issues due to low velocity, and would require a check valve as well since pre turbo is going to pressurized during high boost situations.

i know windage makes some of the pressure inside the crankcase as well but i would have figured blow by in boost would be significantly more, even with great compression numbers theres going to be a tiny amount getting past the rings still. untelling though but that one check valve isnt needed since anything the engine draws in is going through the breather filter so might as well pull that and see if it works. mayby upgrade the other one to a size bigger as well?

 

Well, i don't think the valves failed. I took them off the car and tested each of them with my air compressor and they held 30 psi. I double checked to make sure it was all plummed correctly for flow and it is.

The pcv valve isn't drilled out. It's stock. I have both vents going to the catch can. It might be fun to see how much pressure is in there but i'm not sure i want to test the waters again. I hate changing that front seal and cleaning all the oil off my car. I can use my internal sensor from the haltech so I "might" do it if i'm bored.

I'm going to just remove the check valve on the filter since jerry pointed out that i'm map tuned and i completely overlooked that. I think that check valve was my downfall allow enough venting. I'm also going to put a T in the 3/8" line that connects the valve covers and vent through them as well. Those are much bigger than the tiny hole on the pcv valve and the tiny hole in the drivers rear port.

I was driving back to indiana last night and realized after i posted that pre-turbo wouldn't work since it builds pressure. So for it to be post turbo for me that would be a long hose down there. I don't think i'm going to mess with that. I might, however, go to a larger sized check valve. Maybe use 1/2" or 5/8" hose and find a check valve that size. I'm only going to use a check valve on the plenum now to keep boost from going into my catch can. The other breathers i'm probably going to just leave open since pulling in fresh air on vac won't affect my tune.

Thanks for the info guys. McMaster has some nice ball check valves but they are in the 20-50$ range each. Anyone know of cheaper ones or have some extras they might want to sell?

 

Binder- do you feel the crankcase is pressurized on decel or accel? It makes a big difference on the approach you are taking.

 

my car doesnt smell as long as i have the ac set to recirc air, not fresh air.

 

You may want to consider drilling out that PCV - it's very restrictive. It caused my turbos to start leaking oil into the IC piping. FI blowby is definitely higher than NA and I think our valve covers require this modification once you are into boost. Mine actually got stuck so maybe just replacing it would've worked...

 

boost. During idle there wasn't anything coming out of the catch can vents.

mine wasn't bad until i switched to e85. Now if anything is on it smells pretty bad.

Ya, i think i'm going to just open up the 3/8" ports that connect the 2 valve covers. Those are the biggest holes on those valve covers and should provide the best flow.

 

if you truly believe its during boost then the check valves were a mistake if they are connected post throttle body. The check valves are closing off your only form of evacuation in this instance.

The correct thing to do in my opinion is remove the valves and connect the suction line to the exhaust or to the inlet of the turbo. Both will provide continuous vacuum. I personally did mine to the intake on both my supercharger and my turbo and had good success with scavenging.

 

interesting. my 350z always had a stock PCV system... the drivers side VC always went to the drivers side turbo filter tube. passenger side stock. drivers side VC i grinded open the PCV outlet a little since back there inside where the hose connects it gets really small.

i would say that in the 7+ years of the car being boosted, it never had a problem nor did I get enough oil in the intake to bother me.

but now based on your experience, perhaps I can finally think of a good reason why my 350z could never keep a rear main seal intact... after the 3rd one went I just said forget it and I let the thing drip (it wasnt fast enough to notice level drop between oil changes, but the bottom of my bell housing was always wet with oil and it would leave a few drops on the garage floor when I parked it after running).

 

I added this to my system to keep fumes out of my car at the recommendation of Sasha. I had the bung welded on past my 02 sensors. Then I ran ~6 feet of -10 hose to my catch can. That was the expensive part.

 

I had to replace the seals on my Vortech a few times, and I finally drilled out the PCV and no more oil in my pipes. I think the PCV is too restrictive for boosted Z's if you just want to vent the crankcase into a can or not. This is just my experience. I vented both sides to the atmosphere and haven't noticed any fume smells in the cabin.

 

Weird. i just went back to mainly pump gas to dial in the ID2000s and it smells a million times worse than E85.

But I am also running alot richer at cold idle as well, which doesnt help

 

In the quest of simplicity... if plumbing the crankcase to the exhaust is a catch can really necessary? Could you plumb each bank to the respective exhaust bank?