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Discussion Starter · #1 ·
Okay have l got this right? The equinox has two pcv systems? One that functioning when the manifold vacuum is high and the other when you have very little or no vacuum like wot? The reason I'm curious is that wouldn't the PVC system that uses the fresh air intake only works when you have very little vacuum like wot? I want to install a oil catch can but some guys say no use putting it on the fresh air intake system but that would be when the engine is producing the most blow by and likelyhood of pulling oil vapors into the intake because that's when the rpms are high like wot?
 

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The real question is why you want to install a catch can at all. The PCV system is designed to remove fuel and water vapor (unavoidable byproducts of ICE operation) and not allow pressure to build up in the crankcase. Some oil vapor comes along as well. Designed properly, this system works fine with normal maintenance. Obviously a recent design wasn't done properly and as a result has generated some hypersensitivity to the issue.

If you could go back in time and install a catch can on every vehicle you ever owned you would be draining water from it at regular intervals. Nature of the beast.

The problem I have with catch cans is they defeat a portion of the EVAP emissions control system. You find water in the catch can, but the fuel vapor has already left to join the rest of the greenhouse gases.
 

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It gets installed between the valve cover and the intake tube, I personally don't like the catch can because it would fail emissions and with the increased amount of tubing the likelihood of one of those lines freezing up increases, also you have to drain it often. There is a little catch on the intake tube from factory , even that should be checked and drained once a year or so.
 

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The main reason for installing a catch can is to reduce the amount of oil vapour that would otherwise end up as deposits on the backside of the intake valves. Unlike port fuel injection with GDI there is no fuel sprayed into the intake ports. With port injection that spray of gasoline would wash away oil vapour and keep the backside of the intakes clean, but with GDI deposits on the backside of the intake valves are quite common. So a catch can with a GDI engine means less oil vapour going into the intake system and less deposits forming on the backside of the intake valves.
 

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Discussion Starter · #5 ·
The real question is why you want to install a catch can at all. The PCV system is designed to remove fuel and water vapor (unavoidable byproducts of ICE operation) and not allow pressure to build up in the crankcase. Some oil vapor comes along as well. Designed properly, this system works fine with normal maintenance. Obviously a recent design wasn't done properly and as a result has generated some hypersensitivity to the issue.

If you could go back in time and install a catch can on every vehicle you ever owned you would be draining water from it at regular intervals. Nature of the beast.

The problem I have with catch cans is they defeat a portion of the EVAP emissions control system. You find water in the catch can, but the fuel vapor has already left to join the rest of the greenhouse gases.
Can you explain how it defeats the PVC evac system? I would only put it on the PVC system that functions when the engine is using the pvc valve from the top of the valve cover because it is the one that functions when l have it at high rpms, this l think, would be the system were most blow by is being produced and being transferred to intake. the catch can lm thinking of using is sealed?. The other is internal so a complete bypass set up would be required. when the engine is idling there is not very much crankcase vapors being produced at idle thus very little flow. Apparently the internal pcv (in the intake manifold usually plugs from carbon buildup not from freezing, the concept is to prevent carbon buildup on the valve's because the oil vapors stick to the intake valves and dry out and harden. Like what stopwatch mentioned. I check my fluids often so the hassle to empty is okay with me, my warranty is finished being a 2015
 

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Is there clear evidence, not guilt by association with the early GDI 2.4L assumptions, that properly maintained, non-oil burning engines plug their PCV systems and develop massive carbon buildup on the back of intake valves?

If there is, where the hell is all the carbon coming from?
 

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I put a catch can on my '16 3.6 . It catches about 2 oz. of oil between changes via the OLM.
Carbon on intakes can also come from intake valve being open on shutdown and vapors going backwards up intake. With DI there is no valve washdown like port injection.
Yes shut down stops fuel but also ignition so residual vapors are present to ''move'' around back up intake with valves being open randomly on stopped engine.
 
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Is there clear evidence, not guilt by association with the early GDI 2.4L assumptions, that properly maintained, non-oil burning engines plug their PCV systems and develop massive carbon buildup on the back of intake valves?
This is really two issues. First the 2.4l engine really does not have a true PCV valve, it has an orifice. This orifice is quite small ( about 1/16" ) and yes over time it does partially or fully blocked up with deposits. ( some people call it called carbon ) These deposits come from the blowby gases that get past the piston rings into the crankcase. ( all engines have some blowby ) But the PCV orifice blocking is not the direct cause of buildup on the back of intake valves. This is a GDI issue where the back side of the intake valve is not being "washed" by the incoming spray of gasoline. The idea of adding a catch can is to reduce the amount of oil / blowby gunk going into the intake manifold there by reducing the build up on the back side of the intake valves.
 

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I put a catch can on my '16 3.6 . It catches about 2 oz. of oil between changes via the OLM.
Carbon on intakes can also come from intake valve being open on shutdown and vapors going backwards up intake. With DI there is no valve washdown like port injection.
Yes shut down stops fuel but also ignition so residual vapors are present to ''move'' around back up intake with valves being open randomly on stopped engine.
2 oz. of oil(1/16th of a quart) over what? 4, 5 thousand miles? Want to try a rough calculation of how that works out to per valve opening event? It's a really small number and most of it goes into the chamber and burned.

I don't know where you're going with the fuel vapor thing, however, PFI engines aren't immune to valve deposits.
 
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This is really two issues. First the 2.4l engine really does not have a true PCV valve, it has an orifice. This orifice is quite small ( about 1/16" ) and yes over time it does partially or fully blocked up with deposits. ( some people call it called carbon ) These deposits come from the blowby gases that get past the piston rings into the crankcase. ( all engines have some blowby ) But the PCV orifice blocking is not the direct cause of buildup on the back of intake valves. This is a GDI issue where the back side of the intake valve is not being "washed" by the incoming spray of gasoline. The idea of adding a catch can is to reduce the amount of oil / blowby gunk going into the intake manifold there by reducing the build up on the back side of the intake valves.
And I maintain that, without excessive oil consumption, where is all the carbon coming from to cause all the deposits?

I can accept excessive oil consumption potentially plugging a restricted PCV system. And PFI is going to help "wash" away excess carbon deposits on the back of the valves.

But as long as my engine isn't using any measurable amount of oil between changes I'm not going to worry. Engines that don't burn oil and don't leak coolant internally are generally happy engines if maintained well.

Time to stop beating this poor horse. I doubt if anyone's mind has been changed.
 
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And I maintain that, without excessive oil consumption, where is all the carbon coming from to cause all the deposits?
Ok, so lets go out to your car and remove a sparkplug. Look down the sparkplug hole into the cylinder. Does the top of the piston look like shiny metal or are there combustion deposits on it? I'm quite sure that you would be looking at some amount of deposits on that piston. And even in the very best engine a small amount of the same deposited material ( along with air, fuel, water vapour, exhaust etc. ) will make its way past the piston rings into the crankcase. This is blow by and this is where it comes from...
Time to stop beating this poor horse. I doubt if anyone's mind has been changed.
You certainly haven't changed mine!
 

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Just add one final fly to your direct injection is the work of the devil theory ointment, can you explain how diesel engines survive it?
 

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Diesel and gas motors, Apples and oranges. Case closed.
 

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Diesels are internal combustion engines, direct injection engines that have PCV systems just like gasoline direct injection engines.

For this specific topic, which I believe is the claim that the lack of upstream fuel delivery to "wash" combustion byproducts (delivered through the PCV system) from the intake valves, diesels are no different than GDI engines.

Case reopened.
 
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To what extent do diesel engine intake valves suffer from the same carbon build up as gasoline Direct Engines?





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Richard Neal

, former Fleet Mechanic -Explosive Ordnance Tech -Machinist at Lockheed Martin (1986-2016)
Answered May 5, 2019

Gasoline Direct Injection (GDI) engines are MORE susceptible than Diesel engines to carbon deposits forming on the backs and stems of intake valves. The reason for this is that gasoline engines run with the intakes system under vacuum most of the time, where Diesel engines do not. This is inclined to draw traces of oil through the valve guide where it burns on the stem and back of the hot valve. Since, with GDI, there is no wet fuel in the intake port, fuel detergents aren’t present to dissolve the build-up. Intake valve deposits haven’t, historically, been problematic for Diesel engines.
 

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Discussion Starter · #17 ·
Just add one final fly to your direct injection is the work of the devil theory ointment, can you explain how diesel engines survive it?
Sorry
I'm unfamiliar with the diesel direct injection engines design and if they also suffer from the same carbon buildup issue. Maybe someone in the forum will know?
Diesels are internal combustion engines, direct injection engines that have PCV systems just like gasoline direct injection engines.

For this specific topic, which I believe is the claim that the lack of upstream fuel delivery to "wash" combustion byproducts (delivered through the PCV system) from the intake valves, diesels are no different than GDI engines.

Case reopened.
I would assume that they too would suffer from the carbon buildup on their intake valves, but the carbon buildup is from the PVC system vapors that hit the hot valve losing the vapors and leavening behind the carbon, being both engines use close to the same engine oil they will suffer from this issue, alot of people think the carbon is from the combustion process and the intake valve lets some of the burnt exhaust into the intake but the buildup is from blow by/ oil vapors. Thus the reasoning for a catch can off the upper PVC system. The built in internal pvc system is l believe not responsible for the carbon buildup because it only functions when you have a high vacuum in the intake like idling and deacceleration and engines don't produce any significant blow by when they are decelerating or idling. I believe that a oil catch can is worth installing and a one way vented cap to avoid crankcase pressure and the risk of popping out the rear main seal if one of these two pcv systems do become plugged $25 for a vented cap and $50 for a oil catch can, l believe could make the difference between having issues expensive issues as time goes by, to inspect a catch can when you check the oil level to me no big deal. I just want to make my vehicle reliable, these 2.4 direct injection engines are l believe good engines they are cheap to operate and the power is reasonable for a 4 cylinder engine.
 

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To what extent do diesel engine intake valves suffer from the same carbon build up as gasoline Direct Engines?





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Richard Neal

, former Fleet Mechanic -Explosive Ordnance Tech -Machinist at Lockheed Martin (1986-2016)
Answered May 5, 2019

Gasoline Direct Injection (GDI) engines are MORE susceptible than Diesel engines to carbon deposits forming on the backs and stems of intake valves. The reason for this is that gasoline engines run with the intakes system under vacuum most of the time, where Diesel engines do not. This is inclined to draw traces of oil through the valve guide where it burns on the stem and back of the hot valve. Since, with GDI, there is no wet fuel in the intake port, fuel detergents aren’t present to dissolve the build-up. Intake valve deposits haven’t, historically, been problematic for Diesel engines.
Now we have a new theory. Oil being drawn past the valve stem seals. Worn seals and guides perhaps, but in tolerance guides and seals? No way.

The people advocating these modifications need to decide what the problem is. Is it fuel vapors? Carbon from blowby gases? Oil mist from crankcase vapors? Oil leaking past valve stem seals?

If upstream fuel delivery is the only preventative measure for this problem I have sad news for you. Intake valve deposit issues have been around since before Henry Ford's time. I have seen severe cases caused by internal coolant leaks, high oil consumption, heavily worn valve guides to name some. Fuel "washing" the back of the valves didn't save them.

Significant levels of deposits require a significant source of contamination. Some (and I have no clue what percentage "some" is) 2.4L GDI engines had such a source of contamination apparently.
 

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I gotta say, allot of people say that hole in the back of the intake manifold on the 2.4 is a pcv orifice and they have to clean up dried carbon or drill it out. If it is a pcv orifice then why is the purge valve hooked to the front of it and how the heck is there no oil sludge to be found along with the dried carbon? I still say the only real pcv on the engine is on the valve cover to the intake. The carbon deposits in the "pcv" hole is coming from the intake valves and is directly routed to the middle two intake runners from the purge valve.
 

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The carbon deposits in the "pcv" hole is coming from the intake valves and is directly routed to the middle two intake runners from the purge valve.
Actually the PVC orifice does not connect to the purge valve port at all. There are internal passages going from the PCV orifice, ending in each of the intake runners. Look at the attached photo, I've passed a piece of wire through the holes... Try blowing some compressed air through the purge valve port and you'll see that is is no connection between the purge valve port and the PCV orifice and it's outlets.

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