Oil Catch Can on daily driven GDI new car...is it necessary?

I have the new 2017 Elantra 1.6T "Sport". Reading about oil catch cans at various corners of the interwebz. Is this a necessity because of the nature of GDI (valves are not washed with a fuel mixture), or is this largely hype? I know the early FSI VW engines, among others, had issues. My understanding is that much of that has been mitigated by way of ECM tuning/timing. I don't want to do anything that will lead to warranty concerns down the line (even though, in theory, it would benifit the motor).

My exposure to this scenario has been those engines that are boosted(turbo/SC'd)benefit from an air/oil separator....not so sure of GDI...

I am confused. Elantra 1.6T sport and FSI VW engine? Are VW engines in Elantra's ??

Installed correctly, it probably couldn't hurt. It's something I've been meaning to look into since we bought our CX-5 new. It just clicked over 100k and it's still running just fine.

The issue really depends on the engine. Some engines will end up having a lot of intake deposits, and some wont.

Oddly enough, PFI is the same answer- just different sources of where the buildup comes from.

No harm if you want to spend the money putting one on, but I would not think it's required. For the most part, emissions rules have put the oil consumption in engines down to less than 1qt/10k miles (oil reduces the life span of catalysts). So there should not be much loss.

I'll let you know soon. I put one on my SHO a few months back, I'll check it at the next oil change to see what's in it.

I put them on every car now. After seeing first hand how much they catch. I just put one on the Mazda 3 this past weekend when I had the intake manifold off to remove the tumble valves, and since you have to have the manifold off to get to the pcv valve and it is not a quick or fun task. My intake manifold was a horror show! I had 4mm of carbon on the back of the throttle plate, from the oil being turned to carbon there because that is where the egr valve is. So much carbon that it was flat across the back of the plate as in you could not tell where the pivot on the throttle plate was! The rest of the intake manifold was thick with oil residue. The pcv was gooked up and was not working as well so that probably was contributing to the amount. I use Bob's auto sport air oil separators exclusively. They work fantastic, are made in the USA and they have free shipping. I expect that this will be a non issue now that I've cleaned out the manifold, added a new pcv valve and the separator, I'll check it in about a week to see how well it is catching oil. I usually get about between a teaspoon to a tablespoon of oil out them every two weeks depending on vehicle, temp and how much the vehicle has been driven.

In reply to Rumnhammer:

So you know, the buildup you see on the back of the throttle plate may be there from the factory. For many years, that was put on so that they would not change over time. Some have stopped doing it, some have kept it in the production process.

I would seeing how much was got on my Coyote engine Mustang and my BRZ.....not even taking them to the track.

Just normal commuting with the occasional run through the gears up an onramp.

NO!

alfadriver wrote: In reply to Rumnhammer: So you know, the buildup you see on the back of the throttle plate may be there from the factory. For many years, that was put on so that they would not change over time. Some have stopped doing it, some have kept it in the production process.

Ah, no this was not a coating, this was a thick layer of carbon befitting the flue on a woodstove after ten years of neglect. I'll post pics later this evening. As a side note, the carbon was also apparently blocking the normal gap at the top and bottom of the throttle plate so bad that, it was the cause of my fluctuating idle, now that is clean the idle on the car is rock solid and about 200 rpm higher (normal) then it was before I cleaned it.

In reply to FSP_ZX2:

In the most technical sense it's a modification of the vehicles emissions system which, in it's strictest reading, is illegal.

I'll defer to Alfadriver as he is the expert, however I run one with a check valve on the MS3 because it has a known problem with build-up. The catch can has removed the general nastiness of oil from my intake tract which I appreciate a great deal.

I'll echo that it really does vary on a case by case basis. I really do need to add PI though.

Rumnhammer wrote:

alfadriver wrote: In reply to Rumnhammer: So you know, the buildup you see on the back of the throttle plate may be there from the factory. For many years, that was put on so that they would not change over time. Some have stopped doing it, some have kept it in the production process.

Ah, no this was not a coating, this was a thick layer of carbon befitting the flue on a woodstove after ten years of neglect. I'll post pics later this evening. As a side note, the carbon was also apparently blocking the normal gap at the top and bottom of the throttle plate so bad that, it was the cause of my fluctuating idle, now that is clean the idle on the car is rock solid and about 200 rpm higher (normal) then it was before I cleaned it.

And that's what it looks like. Really- it looks like thick regular deposits.

That's my point. It may be that it's not supposed to be there, but just so you know, for many throttles, it was intentionally put in.

I remember seeing that in our throttles for many, many years.

edit- one thing to note- if you are talking a regular, non boosted 3, the one really has to ask where the oil is coming from to coat the throttle that badly- the PCV and purge inlets to the intake manifold will be downstream of the throttle. If you are getting oil back flow up the fresh air line to the crank- that's a totally different problem- and not the PCV line that would have a catch can on it.

The0retical wrote: In reply to FSP_ZX2: In the most technical sense it's a modification of the vehicles emissions system which, in it's strictest reading, is illegal. I'll defer to Alfadriver as he is the expert, however I run one with a check valve on the MS3 because it has a known problem with build-up. The catch can has removed the general nastiness of oil from my intake tract which I appreciate a great deal. I'll echo that it really does vary on a case by case basis. I really do need to add PI though.

As long as it's not vented to atmosphere, I'm not sure I would consider the modification illegal.

The valving of boosted engines is odd, though, that I'm totally on board with. Have to have the right check valves plus the right aspirators to make it flow correctly.

The0retical wrote: In reply to FSP_ZX2: In the most technical sense it's a modification of the vehicles emissions system which, in it's strictest reading, is illegal.

I suppose in the strictest interpretation it could be seen as illegal, but since you just intercepting oil vapor that would be burned in the intake charge lowering the octane rating of the gas vapor in the charge and causing the cat to work harder and causing build up of carbon etc making the engine run more poorly and very probably increasing emissions. I hardly think this would be something that would be considered something that anyone is going to hold your feet to fire over. If anything, this should reduce the amount of emissions by not burning all that oil etc. Now just a catch can that vents to the atmosphere would be a different story, but what this does is just takes out the nasty stuff and lets the rest go through to be burned sans the oil vapor.

alfadriver wrote:

Rumnhammer wrote:

alfadriver wrote: In reply to Rumnhammer: So you know, the buildup you see on the back of the throttle plate may be there from the factory. For many years, that was put on so that they would not change over time. Some have stopped doing it, some have kept it in the production process.

Ah, no this was not a coating, this was a thick layer of carbon befitting the flue on a woodstove after ten years of neglect. I'll post pics later this evening. As a side note, the carbon was also apparently blocking the normal gap at the top and bottom of the throttle plate so bad that, it was the cause of my fluctuating idle, now that is clean the idle on the car is rock solid and about 200 rpm higher (normal) then it was before I cleaned it.

edit- one thing to note- if you are talking a regular, non boosted 3, the one really has to ask where the oil is coming from to coat the throttle that badly- the PCV and purge inlets to the intake manifold will be downstream of the throttle. If you are getting oil back flow up the fresh air line to the crank- that's a totally different problem- and not the PCV line that would have a catch can on it.

Yes I replaced the pcv as it was stuck halfway open and was where the oil was coming from. This stuff was definitely not from factory. This will be more clear after I put some pics up. There was so much crud coming through the pcv valve that the fitting where the hose connects to the intake manifold was about 1/4 of the way covered in residue.

Browse around the mk6 gti forums - it's been proven time and time again that catch cans do NOTHING for carbon build up. Run top tier fuel and good oil and don't worry about it. Give it the good old Italian tune up often too

FWIW, my 2011 GTI had to have the intake valves cleaned at 50k miles, due to cold start misfire issue (known indicator of buildup on this engine series). No catch can installed, though. Asked independent / enthusiast shop of their opinion of putting one on at that time. Answer back was it win't hurt anything as long as you keep up with emptying it, but tgey had not seen any real benefit either. On the other hand, our 2014 Accord is still just fine at 80k miles ... it also has DI and no catch can.

BTW, fuel quality used has no effect on this issue, as it never crosses over the intake valve heads where the builup occurs on a DI engine. Benefits on Top Tier are useful elsewhere in the fuel system, but not here. Snd yes, I use it whenever I can.

In reply to einy :

My 2016 KIA Forte5 EX GDI has manual instructions to use only "TopTier" gas and use a fuel additive very 3750 miles... but neither of those will do much to keep the intake valves in a GDI engine clean. The local dealer pitches their "fuel system service" (they probably run a can of SeaFoam though the throttle body) for like $179, and they tell you to have it done every 15K miles. Mine has about 28.5K miles on it now, and I finally decided to to that myself for the first time (using the CRC "GDI Intake Valve and Turbo Cleaner" instead of SeaFoam). My cost was $13 and a bit of my time... the results were noticeable, but not dramatic. I could go the OCC route, but I think I'll just do the intake valve cleaning process maybe every 15K miles (maybe every 7.5K) and see if things don't stay happy.

placebo...  won't hurt anything, but won't really do anything other than giving you a good feeling inside every time you empty the thing..  

dean1484 said:

I am confused. Elantra 1.6T sport and FSI VW engine? Are VW engines in Elantra's ??

No but the fuel injection systems are similar and the VWs have well documented issues in the area.

pointofdeparture said:

dean1484 said:

I am confused. Elantra 1.6T sport and FSI VW engine? Are VW engines in Elantra's ??

No but the fuel injection systems are similar and the VWs have well documented issues in the area.

But just because the fuel system is the same does not mean the deposits will be the same.  Or the benefit of running with a better oil separator.

Motive just did a decently in depth video on catch cans / air oil seperators, may be worth a view.

More empirical data from my personal experience, approximately three years after my post above, as this thread looks to be alive again:

1) My GTI initially had its intake valves cleaned via walnut blasting at 50k miles due to cold start misfires (which is the leading indicator for the VW TSI engine design that buildup is now a problem) becoming an every day event.  After cleaning, cold engine misfires were completely eliminated.

2) The GTI, right before its recent sale at 93k miles, was starting to have cold start misfires again.  I would say based on past experience that another round of intake valve cleaning was needed, if I had decided to keep the car.

3)  I didn't baby the GTI, lug the engine, or anything else that would seem to possibly increase the build up rate of carbon on the intake valves.  That said, I didn't kick the crap out of it either.

4) I have a co-worker has a GTI of the same year and mileage as mine (~ 93k) and has never had a problem with cold engine misfires.  He does not run a catch can, and has never done an intake cleaning with Seafoam, etc., etc. If anything, his driving style is more sympathetic than mine, so ???

5) Our '14 Accord with 2.4 liter / CVT combo - also a DI engine - has 140k miles on it.  It does not have a catch can, I have never done an intake cleaning with Seafoam, etc., etc.  (Side note:  It did just recently require a cleaning of the throttle body interior, as it was causing the throttle plate to hang up and trigger an engine shut down as a result.  Over-current to the throttle position stepper motor?  Not sure.  Either way, clean throttle body, reteach idle, all good.)  Runs great with no cleaning service to the intake valves at all, so far.  Meaning that, at 140k miles, good to go.  (Hope I didn't jinx myself.)

What do I make out of this body of experience?  Not sure.  On the VW TSI front, from a sample size of two, it seems as though there is variability in how that engine design works in practice.  That said, nobody at either the VW dealer service department or the VW independent that I used was surprised in the least by the need for an intake valve cleaning at 50k mile intervals.  Would a catch can help?  Maybe, maybe not.  It makes sense that it would keep some level of oil from passing though the intake system, and assuming oil being carbonized is what is building up on the back side of the intake valves, should at least stretch out the interval between required cleanings.  Then again, ???  Finally, Honda seems to have a better design vs. VW, from my sample size of one.  Make of that what you will.

The only engine that I own that has DI is my 2013 F-150 with the 3.5 V6 Eco-boost engine.  On the F-150 forums installing a catch can is a popular discussion topic.  I purchased my truck with high miles and while I haven't checked the intake I have not experienced any of the issues that would indicate coked up intake valves or gummed up throttle body.  I think as someone posted earlier a particular engine may or may experience this problem. It depends on how the vehicle is used/abused as much as any other cause.