Gutting PCV valve with Mishimoto catch can?

[dbmonster]

A little backstory - Like everybody else I had the smoking at idle issue after installing my cat-less DP. First thing I did was change to better oil and then install the Mishimoto catch can, neither made any difference. I then had Adam raise my idle and voila! problem solved.

A few months later I installed the MAP turbo kit, and the idle was set back to normal. I've had the turbo kit on for over 5000 miles now and have had ZERO smoke, until now. Over the last 2 weeks my car has started smoking again (only at idle) and it seams to be getting worse.

So now I'm looking into gutting my PCV valve, but I've seen a few people mention that you need the dual valve catch can from UPR in order to not have issues with the gutted PCV. is that correct? and if so why?

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[wmsky33]

So now I'm looking into gutting my PCV valve, but I've seen a few people mention that you need the dual valve catch can from UPR in order to not have issues with the gutted PCV. is that correct? and if so why?

One of the functions of the PCV valve is to work as a check valve to keep boost pressure from the manifold from getting into the crankcase. If you gut the PCV valve it can no longer do this, so you need to put a check valve somewhere in the line between the intake manifold and the gutted PCV valve. The UPR dual-valve catchcan has checkvalves built in for this. However, you can just add a check valve in one of the hoses of the Mishimoto catchcan you already have so that it will allow oil vapors from the crankcase to flow into the catchcan but will stop boost pressure from flowing the other direction into crankcase. I believe that one or more posts in the "blue smoke" thread even suggest which check valve to get.

 

[dbmonster]

One of the functions of the PCV valve is to work as a check valve to keep boost pressure from the manifold from getting into the crankcase. If you gut the PCV valve it can no longer do this, so you need to put a check valve somewhere in the line between the intake manifold and the gutted PCV valve. The UPR dual-valve catchcan has checkvalves built in for this. However, you can just add a check valve in one of the hoses of the Mishimoto catchcan you already have so that it will allow oil vapors from the crankcase to flow into the catchcan but will stop boost pressure from flowing the other direction into crankcase. I believe that one or more posts in the "blue smoke" thread even suggest which check valve to get.

Thank you! I wasn't aware the upr catch can had check valves, that explains a lot. I understand the basic operation of the pcv system and that is why I don't really want to gut the valve, but it seems to have solved the issue for those that have done it.

 

[Mishimoto]

One of the functions of the PCV valve is to work as a check valve to keep boost pressure from the manifold from getting into the crankcase. If you gut the PCV valve it can no longer do this, so you need to put a check valve somewhere in the line between the intake manifold and the gutted PCV valve. The UPR dual-valve catchcan has checkvalves built in for this. However, you can just add a check valve in one of the hoses of the Mishimoto catchcan you already have so that it will allow oil vapors from the crankcase to flow into the catchcan but will stop boost pressure from flowing the other direction into crankcase. I believe that one or more posts in the "blue smoke" thread even suggest which check valve to get.

Nice clear explanation here! Many prefer to gut the stock PCV and replace it with a more robust check-valve to reduce the chance of pressurizing the catch can and crankcase. The lines included in our direct-fit kit feature an ID of 1/2". This should help locate an appropriately sized valve.

-John

 

[JungleG1337]

So if we decided not to gut the PCV and add the check valve into the Mishimoto Catch can line, would that stop the smoke?

 

[dbmonster]

Nice clear explanation here! Many prefer to gut the stock PCV and replace it with a more robust check-valve to reduce the chance of pressurizing the catch can and crankcase. The lines included in our direct-fit kit feature an ID of 1/2". This should help locate an appropriately sized valve.

-John

Thanks for the info! My next step was to find out the hose size, you saved me some work.

Would it be best to put the check valve inline with the hose going from the pcv to the can? Or the hose from the can to the intake manifold?

 

[UPRSteve]

A lot of people with our catch cans using our check valve and eliminating the factory pcv are getting NO smoke. With with pulling oil and moisture out from the turbo and valve cover with our system, you have nothing else to worry about.

 

[higdominator]

[MENTION=13019]UPRSteve[/MENTION] UPR CC and gutted PCV fixed my smoke 100%. I don't even get a hint of burning oil smell anymore. All I get is the sweet scent of ethanol rich, un-catted, turbo farts.

 

[PewterCam]

So if we decided not to gut the PCV and add the check valve into the Mishimoto Catch can line, would that stop the smoke?

.

No it won't. The stock pcv is the problem so leaving it as is and adding a check valve will not change the situation. By gutting the stock one you are using the added check valve as the replacement to the stock piece.

 

[NewSVO]

I thought by adding a Boomba check valve would help the issue 100% because it only opens at .1 PSI and when you're idling you're not in boost.

 

[dbmonster]

A lot of people with our catch cans using our check valve and eliminating the factory pcv are getting NO smoke. With with pulling oil and moisture out from the turbo and valve cover with our system, you have nothing else to worry about.

Do you guys have plans for a catch can setup that will work with aftermarket turbos? My turbo sits right where your catch can is supposed to mount.

 

[dbmonster]

I thought by adding a Boomba check valve would help the issue 100% because it only opens at .1 PSI and when you're idling you're not in boost.

Did it not work for you?

That's exactly what I was looking at doing, putting the boomba check valve inline with my catch can and gutting my pcv.

 

[wmsky33]

Did it not work for you?

That's exactly what I was looking at doing, putting the boomba check valve inline with my catch can and gutting my pcv.

NewSVO might be thinking that the check valve alone is the answer, that you don't need to gut the PCV valve if you add a check valve. But a check valve by itself won't solve a smoking problem, because the smoking problem is occurring at idle, when the check valve will be open anyway. I think that the problem may be that some factory PCV valves may not be performing their 2nd function properly, that is to regulate the vacuum at idle. If I've got it right, vacuum is highest at idle. Too high a vacuum can allow too much air into the intake manifold, causing a lean condition, like a vacuum leak. On many cars, maybe most, the PCV valve is supposed to close somewhat to keep the vacuum from getting too high. On the EBM, it might be that the PCV valve is closing down too much, causing pressure to build up in the crankcase, forcing oil past seals it's not supposed to get past. When I first heard about someone gutting the PCV valve, I expected that they would get a CEL. That hasn't happened, so it seems that a gutted PCV valve is not allowing too much vacuum to flow, and would seem to be a safe mod. And it has solved the smoking problem for many.

 

[Edkiefer]

NewSVO might be thinking that the check valve alone is the answer, that you don't need to gut the PCV valve if you add a check valve. But a check valve by itself won't solve a smoking problem, because the smoking problem is occurring at idle, when the check valve will be open anyway. I think that the problem may be that some factory PCV valves may not be performing their 2nd function properly, that is to regulate the vacuum at idle. If I've got it right, vacuum is highest at idle. Too high a vacuum can allow too much air into the intake manifold, causing a lean condition, like a vacuum leak. On many cars, maybe most, the PCV valve is supposed to close somewhat to keep the vacuum from getting too high. On the EBM, it might be that the PCV valve is closing down too much, causing pressure to build up in the crankcase, forcing oil past seals it's not supposed to get past. When I first heard about someone gutting the PCV valve, I expected that they would get a CEL. That hasn't happened, so it seems that a gutted PCV valve is not allowing too much vacuum to flow, and would seem to be a safe mod. And it has solved the smoking problem for many.

Or when vacuum is low, like with A/C some of the stock PCV are not fully open so are not flowing and then it backs up on turbo inlet side .

Someone with issue would have to test it good so see what exactly is the cause an effect with stock PCV .

 

[UPRSteve]

Do you guys have plans for a catch can setup that will work with aftermarket turbos? My turbo sits right where your catch can is supposed to mount.

Yes we do. Each turbo kit is going to be different but we can 100% build one for you. Best bet is to shoot me a call monday. 561-588-6630

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