Factory oil catch cans - why not?

[RomanV]

Ive always been curious as to what oil catch cans are for, so I had a dredge through some old threads on the subject.
(a quick search on the net turned up SFA, apart from ads, and people making a web page about how 'bling' their greddy catch cans are. )

From what I can gather, the benefits of using a catch can are:

Removing the oil from the intake charge, effectively raising the octane rating of the fuel/air mixture.

It stops filthy (and potentially harmful) oily crap re-entering your engine, and coating your intake manifold, throttle(s), etc...

And the downsides....
You have to empty the can out every now and then....
Is that it?

Generally every 'mod' you can do to a car has a tradeoff. Emptying a can every now and then doesnt seem like much of a burden, (to me at least) compared to the potential benefits.

Is that the only reason that catch cans are not used on factory engines? The inconvenience of having to empty the can?
I can understand why Joe Public would not want to have to do this.

But... Is there something I am missing? Any hidden downsides?

My new motor runs relatively high compression, (11:1), so anything I can do to help prevent detonation has got to be good.

So, any thoughts on the matter?

Cheers.
Dave.

[Fraud]

I would be interested to know also, as it would be a possible mod for my car as well.
Brett

[Adamal]

I think its purely for what you've stated. Joe Blogs can't be bothered adding the excess back into the engine.

[pervert]

I got one that came with a webber carb and manifold I bought, it has a drain on it so you don't even need to empty it.

One downside (well a downside if you actually clean your engine bay) is that it has a breather filter on top, and everything under the bonnet gets coated in a fine coating of oil...

[blackie]

why would they bother...?
it would just cost them extra money and 90% of people dont even know what they do.

and engines still last 200 000+ without them.

[mr pad]

and engines still last 200 000+ without them.

less its a mitsi...

[RomanV]

Yeah, you raise good points.

I suppose the public would perceive a 'catch canned' engine as wasteful, seeing as you have to dispose of the oil. Whereas an engine that burns it into the atmosphere appears cleaner.

[Adamal]

Who's to say that you'd HAVE to dispose of it though? I mean, it would otherwise go back into your engine, so why not just put it back while the engine is off and it has become a liquid again?

[RedMist]

Adamal, Firstly the engine oil out of the breathers does not go back into the sump. Its directed into the intake to be burnt.
Secondly the oil turning to vapour generally isnt all that much oil. It contains fuel and water. Both things you dont want in your fuel to begin with, so emptying the contents back into the sump isnt wise.

[Adamal]

Thank you for the enlightenment, RedMist

[wde_bdy]

Car manufacturers have emissions requirements, so all the fumes and crap have to be burnt. The main benefit of a catch can is you don't get all that crap going into your engine, and generally vent the fumes as well. You will also find that unless you are using high RPM you get bugger all actual oil and rubbish anyway, the factory oil drains are sufficient to keep the oil where it should be and most of the rest is vented. In places like Oz the emissions requirements get you a nice fine if you vent your catch tank to atmosphere, so a non vented catch tank is fairly common where NZers normally vent them.

Callum

[Mr Revhead]

re redmists point.

iv got a can on my 20v, i was going to add a drain to the sump, but the first time i emptyed it, it wasnt full of oil, id had 1/2 a cup of water in it.....

[Santa'sBoostinSleigh]

what i cant believe is why people pay/charge around $100 for one!

[Alex B]

From what i saw at levles the kathmandu alloy drink bottles work well, blus they are bling

[fuel]

Some mitsis in the 80s had them factory, like the 1.8L ECI Turbo Cordia, Sigma GSR FWD 2L turbo, think some Starions had them too.

And yeah it's an emissions thing.

[MrBob]

pfft, catchcan. Just vent it back to mothernature.

[TygerTung]

Yeah turbo cordia's have factory ones, but they drain back into the sump anyway.

It's just an emisions thing, the oil vapor is bad for the environment!

[RedMist]

pfft, catchcan. Just vent it back to mothernature.

Yes and what happens on starting? or a misfire?

Can anyone say "vacuum"?
How about "suck the shit that you have gathered in the vent pipe back into your engine"?. Ever noticed how much grit oil attracts in an engine bay... mmmm.... Hence I hate those bling catch cans that arent filtered.

[Fraud]

Hence I hate those bling catch cans that arent filtered.

But we ALL know bling is more important than practicality

[Jebus]

In some applications, such as carbys the extra oil flowing around the inlet through the carbs side of things isnt always a bad thing.