What Is an Oil Catch Can, and Why Doesn't Every Car Have One?

[mpower]

Catch can on an LS is a wise investment. Especially with a few kms and if you like to give it a squirt, these things slurp down oodles of oil. It's pretty easy to keep the system sealed and make use of the existing PCV so it's legal.

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really? both of my LS1's barely use any oil between changes. Catch cans feel like snake oil.

 

[monstar]

really? both of my LS1's barely use any oil between changes. Catch cans feel like snake oil.

There is a lot of bull surrounding them for sure, and most stuff is a can with steel wool and mounting clips. As above the issue is Direct Injection mainly, and some cars have ineffective PCV. Both ideal candidates for better air oil separation for proper operation.
But the idea that oil lowers octane is bull, straight up. It is all over the internet but strictly speaking in certain circumstances like cold start detergent fuel can cause uncontrolled combustion. That’s detonation and rare not WOT need more killawasps coz pinging.
So apart from DI coking of valve stems, ineffective PCV causing gumming of TB / plenum, is not a performance enhancer, not for LS, is snake oil.

 

[MACE]

In regards to the effectiveness of a catch can/oil air separator, I guess also comes down to the condition of the engine as well in regards to the amount of blowby it produces.

This aside, oil consumption, does influence carbon build of the runners and chambers, which may be problematic in the medium to long-term (short term if the engine gets a genuine hiding and is not in the best of health), for engine performance. Along with a negatively impacting motor octane number (2 stroke oil, less of an issue).

In regards to the impact of carbon, deposits, came across a nice research paper that covers it well, as shown in the link below.

http://archiwum.inig.pl/INST/nafta-gaz/nafta-gaz/Nafta-Gaz-2014-04-04.pdf

 

[monstar]

In regards to the effectiveness of a catch can/oil air separator, I guess also comes down to the condition of the engine as well in regards to the amount of blowby it produces.

This aside, oil consumption, does influence carbon build of the runners and chambers, which may be problematic in the medium to long-term (short term if the engine gets a genuine hiding and is not in the best of health), for engine performance. Along with a negatively impacting motor octane number (2 stroke oil, less of an issue).

In regards to the impact of carbon, deposits, came across a nice research paper that covers it well, as shown in the link below.

http://archiwum.inig.pl/INST/nafta-gaz/nafta-gaz/Nafta-Gaz-2014-04-04.pdf

I think the octane number is the measure of knock resistance of the fuel, independent of the engine it is used in. No doubt deposits cause combustion problems, but the introduction of oil does not lower the octane rating of the fuel whatsoever. The linked article proposes that deposits in the chamber leads to increased compression (!!) which in turn leads to an increased octane requirement (of the fuel) to be used.
My point is that burning oil doesn't lower the octane of the fuel being used, as is commonly repeated over the internet. Yes indeed the highest specific output engines, 2T and those powering F1 cars are designed to burn oil as fuel.
Latest research suggest low speed pre-ignition issue plaguing downsized DI & DI turbo cars, first thought related to carbonised coking (of the intake valve and chamber) deposits accumulated via PCV, is related to combustion of detergent oils though blow-by under certain temperatures and load conditions. Specifically the oil turns to an emulsion which when mixed with fuel under (DI) pressure ignites prematurely. This relatively rare and uncontrolled emulsion is neither oil or petrol rather a third hydrocarbon product from detergents in the oil.

 

[MACE]

I will see if I can find an old article by a researcher from BP, where they have mentioned the degradation of motor octane rating due to oil consumption. The impact that this has on a healthy stock engine though, is minimal and taken into account in the factory calibration. On a tired engine, from personal experience, it does. Admittedly, that issue was solved by using an atmospheric catch can at the time, which is something that I would strongly recommend against nowadays.

 

[Immortality]

I think the octane number is the measure of knock resistance of the fuel, independent of the engine it is used in. No doubt deposits cause combustion problems, but the introduction of oil does not lower the octane rating of the fuel whatsoever. The linked article proposes that deposits in the chamber leads to increased compression (!!) which in turn leads to an increased octane requirement (of the fuel) to be used.
My point is that burning oil doesn't lower the octane of the fuel being used, as is commonly repeated over the internet. Yes indeed the highest specific output engines, 2T and those powering F1 cars are designed to burn oil as fuel.
Latest research suggest low speed pre-ignition issue plaguing downsized DI & DI turbo cars, first thought related to carbonised coking (of the intake valve and chamber) deposits accumulated via PCV, is related to combustion of detergent oils though blow-by under certain temperatures and load conditions. Specifically the oil turns to an emulsion which when mixed with fuel under (DI) pressure ignites prematurely. This relatively rare and uncontrolled emulsion is neither oil or petrol rather a third hydrocarbon product from detergents in the oil.

The burning of so called "oil" in F1 engines is nothing like the oil the cars we mere mortals drive

 

[monstar]

The burning of so called "oil" in F1 engines is nothing like the oil the cars we mere mortals drive

Depends on oil quality of course, on this forum I think quite a considerable percentage of members with V8s use 100% PAO per our Penrite oils, same synthetic stuff as formula one. Of course they are not SIDI, hence my point that not everyone need rush out get a catch can coz makes poor performance.
Introducing a little oil into the combustion process does help to quell detonation hence turn up the boost and or timing just a little bit. The oil acts as a sort of coolant to the charge, as certain high grade synthetic oils are a great deflector of heat. Use of explains why MB and Ferrari (now) have so much extra power in qualifying, and got busted last year.

 

[Immortality]

Depends on oil quality of course, on this forum I think quite a considerable percentage of members with V8s use 100% PAO per our Penrite oils, same synthetic stuff as formula one. Of course they are not SIDI, hence my point that not everyone need rush out get a catch can coz makes poor performance.
Introducing a little oil into the combustion process does help to quell detonation hence turn up the boost and or timing just a little bit. The oil acts as a sort of coolant to the charge, as certain high grade synthetic oils are a great deflector of heat. Use of explains why MB and Ferrari (now) have so much extra power in qualifying, and got busted last year.

The FIA have limited how much oil an engine can consume during a race by a substantial amount so I'd say that avenue to gain advantage has been mostly negated.

The other consideration on a lot of modern engines is the EGR system. Oil vapour and hot gasses in the intake = baked on crap everywhere. Twice as bad on any direct injection engine.

 

[Pollushon]

really? both of my LS1's barely use any oil between changes. Catch cans feel like snake oil.

That's awesome dude, I like to hear success stories but it's just not true of every LS and every driver. The snake oil is in whether you need one and in your case, no, don't waste your cash.

Like Mace pointed out it all comes down to blowby and blowby comes down to a multitude of factors. The fact a manufacturer puts a PCV system on means it's a real thing.

To make the point simple I live in Canberra where we have racetracks called public roads and no shortage of challengers. My 250k LS gets its legs stretched everyday in every way

The cost of this style of driving is a film of oil through my manifold. About 400mls per 5k oil change. That 400mls gets caught inside a glorified tin can now and only gases get through. It's worth every cent to me

All the more important for when this gets tuned next week

 

[Immortality]

Do I see water/meth injection?