Oil Catch Can?

[rodester5 0]

Hi all, I'm new to this site, and new to the oil catch can. I have one (about 1ltr) on my 1.9GTI on carbs. It must be emptied after only 5 laps of Castle Coombe, if not, it makes a right mess of the engine bay and windscreen.

My questions are, What is it meant to do, is it ok to empty it back into the engine and do I have a problem.

 

Cheers

Kevin

[Batfink 201]

What size is it? Where is it in the enginebay..low down or high up?

[rodester5 0]

It's about 1ltr, the shape is like a bottle on a racing bike. It is mounted at the left inner arch inline with the strut and the inlet tube is about 1 inch higher than the rocker cover.

[harryskid 193]

Do not put it back in the engine!

[smithy 1]

i would say the problem is from the cam cover breather,mine was initially running from cam cover and i could see oil running through pipe when revs were raised.can is mounted on inner wing by coil

 

I left that one going down to bottom of filler pipe and ran the one from filler cap to the can and then to the inlet,i used a mi16 cap with just the large outlet and blanked off barb on throttle body.

This way it seems to catch any oil but not too much is dragged through,oh and all gauze crap is removed from cap and neck aswell.

[Batfink 201]

Been a while since I looked at an 8v head. Does it have a shield/baffle to stop oil directly going down the cam cover breather? If not then that could be the problem?

[opticaltrigger 52]

My questions are, What is it meant to do, is it ok to empty it back into the engine and do I have a problem.

 

 

Hi Kevin,well starting with the above first.

It's meant to do pretty much what it says on the tin (catch oil).

Personaly I dont agree with putting it back in.

And last of all,yes I think you could well have some issues with the motor.

 

It's hard to say anything more than conjecture here Kevin as we cant see it in person but on the surface of things 1ltr of oil in 5 laps sounds excesive to me.

Have you had a think about your piston rings and bores,if you havent allready done so,just for interest's sake try a quick compresion test and see what you get back.Or even better have a compresion leak down test done,this will reveal much more about the state of the engine.

 

All the best O.T.

[allye 530 3 Cars]

In answer to what does it do and why -

 

with the standard system the oil vapour from the crank case created by the heat of the engine goes through the injection system (or carb) and burnt/out the exhaust. The selling point behind catch tanks being they prevent all the vapour going through your injectors, whether or not they actually do a lot of good is probably quite debateable!!

 

I had trouble with them in the past, I wouldn't use one again.

[GLPoomobile 958]

The selling point behind catch tanks being they prevent all the vapour going through your injectors,

 

And I thought I didn't understand breather systems properly

 

I'm sure it makes sense in your head, but you've worded that quite badly

Edited April 18, 2011 by GLPoomobile

[GLPoomobile 958]

Can anyone explain why it's not good to drain the oil back in to the engine (to the sump)? The only downside I can see is if the oil contains moisture.

 

EDIT: maybe I answered my own question When the oil vapour condenses in the tank does some water content seperate out? Sorry for my pish, non-scientific wording

Edited April 18, 2011 by GLPoomobile

[24seven 104]

From my understanding it can sometimes contain moisture as well, which you don't want being pumped around your engine as a lubricant! Due to a misunderstanding of the regulations the catch tank on our F4 car ended up having a breather to the inlet manifold as well when we last went testing :S. Aside from completely defeating the object of a catch tank a fair bit of fuel was finding itself in there along with the oil and some moisture.

[allye 530 3 Cars]

Well that is what it does, i'm talking about oil catch tanks not the entire breater system as you out of context take it.

[rallyeash 155]

basiclly a catch tank does just that. Its a tank that a breather from the rocker cover goes to. Engines create moisture naturally and rather than returning that moisture back into the engine which we don't want in our oil for obvious reasons you send it to a seperate tank and empty it every now and again.

[GLPoomobile 958]

Well that is what it does, i'm talking about oil catch tanks not the entire breater system as you out of context take it.

 

It wasn't taken out of context. You said that it stops oil vapours "going through the injectors". You probably meant that it stops oil vapours going back into the inlet manifold and fouling the injectors as it is drawn through into the combustion chamber, in which case you just worded it badly as I said before. The vapour cannot go "through" the injectors.

 

I'm not deliberately being a pedantic arsehole, I was just highlighting some possible confusion.

Edited April 19, 2011 by GLPoomobile

[Batfink 201]

Are we arguing semantics here but with bad communication?

The catch tank collects oil vapour as it cools and turns back into a liquid. Instead of sending contaminated oil back to the sump its collected, any other gases are vented to atmosphere rather than into the induction system to burn off in combustion. As oil based products will not burn effectively to produce power its better for racing but not the planet...

It certainly does not go through the fuelling system and out the injectors

[mikeygulley 19 1 Cars]

On the 8V engine I would run the pipe that goes from the oil filler cap to the inlet pipe before the throttle body into the catch tank at a lower level then from higher up on the tank back into the inlet pipe. If that makes sense??

[harryskid 193]

You still would not want to return that crap oil back in to your engine!

[GLPoomobile 958]

So how is it any different to the oil returning to the engine via the original breather system?

 

I'm not being obtuse. I understand why it's of benefit on a high performance track oriented car, but on a road car is it really necessary? I suspect lots of people fit catch tanks on road/fast road cars because they see it as another "must have" on the modifications list. I think the discussion needs some balance because people keep saying you don't want to return the oil to the engine and yet that's exactly what the original manaufacturer system does do, with no significant issues.

[24seven 104]

GLP, The manufacturer returns the oil vapours via the breather system into the inlet manifold to be burnt by the engine because it's a lot easier than having to empty a catch tank twice a week or half way through a long journey. What the OP is asking (and what myself and others meant by not returning it back to the engine) is can he put the crap collected in the catch tank back into the lubrication system, i.e. through the oil filler, to which the answer is no you shouldn't.

[harryskid 193]

GLP, The manufacturer returns the oil vapours via the breather system into the inlet manifold to be burnt by the engine because it's a lot easier than having to empty a catch tank twice a week or half way through a long journey. What the OP is asking (and what myself and others meant by not returning it back to the engine) is can he put the crap collected in the catch tank back into the lubrication system, i.e. through the oil filler, to which the answer is no you shouldn't.

 

Exactly,oil in catch might have dead flys or sand in it and acid moisture, not good for your engine

[Daviewonder 533 3 Cars]

Is it illegal or an mot failure to vent your crank into the atmosphere?

[24seven 104]

Probably both. Plus you'd have to vent it carefully so as not to make a mess of the surrounding area. For a road car there's really no reason not to just keep the standard breather system, and on a track car if you really feel the need to try and eek that extra tiny bit of performance then just use a catch tank.

[smithy 1]

Is it illegal or an mot failure to vent your crank into the atmosphere?

 

i doubt it my old scooby passed mot,s no problem with the breathers going via a catch can and then out to atmosphere,only thing about going to atmos is best to run hose to rear of car under boot or you get fumes inside.

 

as for being illegal i doubt that also as the breathers on train engines are vented to atmosphere,i find it hard to believe this would happen if against the law.

[24seven 104]

I should have clarified my post, without a catch tank I can't see it being road legal. As long as you're not purposely just letting it go on the road (i.e. into a catch tank or back into the intake) it's fine.

[harryskid 193]

I use a catch can on my rally car and it passed its mot. How ever in some forms of motor racing it a req for it to be catch tanks and properly vented.Also they have to be a spec size.