Let's talk oil catch cans

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ChrisHolmes
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Re: Let's talk oil catch cans

Post by ChrisHolmes » Wed Nov 21, 2018 7:01 pm

Thanks Dave, so the physics of oil burps is still a bit of a mystery then. If it is indeed oil being sucked / blown through the breather system on earlier cars then have the very low down pipe on the later modified system would make oil burps more likely as has also been posted above!
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Re: Let's talk oil catch cans

Post by mi60o0 » Fri Nov 23, 2018 10:41 am

Thinking of ordering this one
What’s is your toughs ?
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Re: Let's talk oil catch cans

Post by V8 Power » Fri Nov 23, 2018 11:09 am

It's bloody expensive that's my thoughts!
I'm not sure you need to spend that much to get a decent one that does the job.
I am sure someone in the know will comment.
I only paid £15(from memory) for mine second hand. It is a none branded one off by the look of it but seems to do the job.
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Re: Let's talk oil catch cans

Post by ChrisHolmes » Fri Nov 23, 2018 6:08 pm

You don't need an oil catch can unless you have an engine problem IMHO
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Re: Let's talk oil catch cans

Post by SeeJay » Fri Nov 23, 2018 6:09 pm

My understanding is that later S1's had a revised breather system,but the R3 system is completely altered,and so far as I know,R3's aren't known to burp..
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Re: Let's talk oil catch cans

Post by mi60o0 » Fri Nov 23, 2018 11:24 pm

ChrisHolmes wrote:
Fri Nov 23, 2018 6:08 pm
You don't need an oil catch can unless you have an engine problem IMHO
I never had Ava’s oil burp
But I have some trace of oil on the rubber hose before the box box is dry and filter is dry
But after last oil change I’m just on max few mil less than max
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Re: Let's talk oil catch cans

Post by V8 Power » Fri Nov 23, 2018 11:42 pm

Crank cases used to vent to air but in the 60’s the recirc system was introduced so oil vaper etc was drawn back into the intake.
This has the downside of oiling up the throttle body, intake tract etc.
Hence the use of catch cans to capture oil vapour before it reaches the intake.
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ChrisHolmes (Sat Nov 24, 2018 12:10 am)
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Re: Let's talk oil catch cans

Post by JamieM » Wed Nov 28, 2018 12:38 am

Just some potentially interesting data to add to the discussion - I'm one of the people who has always battled against huge oil burps. My engine is from an early-ish model S1 ('54 plate) so no breather mods, and having had many many burps over the last several years, on and off track, both with and without a catch can fitted, and 2 rebuilds, I've tried to look for some patterns. Might be useful for anyone trying to come up with an explanation? Or perhaps just add to the confusion :P :lol:

Firstly, I'm convinced that for me, they only seem to happen just after rapidly letting off the throttle from very high revs. I'm talking above the point where you would hear the beep (so over 8500 minimum, though obviously I don't know the exact conditions as the burps usually catch you off guard!). Basically when you're really pushing it and suddenly let off to decelerate. Rather than when still on the throttle, as most people seem to have described so far (well, no one has explicitly said)?

Secondly, for me at least, it never made a difference whether I was going in a straight line or in a high-G corner. In fact, I think more of my burps have happened going in a straight line, because that's when you usually let off the throttle - before going into a corner. I'm not saying it hasn't happened while cornering hard, but I don't think that's the root cause (though it probably doesn't help).

Thirdly, when it does happen, if I have my 500ml can fitted it usually completely fills the can, and sometimes there's even enough to overflow and still make its way into the intake and create a small blip of smoke out the exhaust (though less than there would be without the can, where it leaves a massive smoke trail). This can be after just having emptied the can on one or two occasions (e.g. track days), meaning the engine somehow threw out over 500ml of oil IN ONE GO. So I don't believe the burp itself it is a gradual build up of oil (though it may be caused by a gradual buildup of crankcase pressure, maybe).

Finally, it was a long time ago now so I'm not 100% sure about this, but I don't seem to remember having as much of a problem before the engine was first rebuilt. It might have happened (I don't remember), but the engine had low compression anyway when I got it, which only got worse until I had it rebuilt (always the plan), so perhaps it never really pushed out enough performance to trigger it, being an old tired engine. I first noticed it once rebuilt and street ported, which is what prompted me to buy a catch can, and since then I've always kept the oil between 1/2 to 3/4 on the dipstick. This helped, but I still got the occasional burp anyway when pushing it. That engine ultimately failed a year later with a leaky water jacket seal, and was rebuilt again under warranty, this time upgraded to a bridgeport. It is still going strong today in a new chassis, and I seem to get less burps now but I'm not sure if that's just because I'm more careful / aware. I also installed an AEM intake, so maybe that has affected it, though I suspect that's just coincidence.

Something else to think about - when at high revs under WOT, although the mass flow rate of air is high, it is free and able to flow (otherwise you wouldn't be making power!). We are at high load, so as anyone who has ever played around with mapping or hooked up a boost/vacuum gauge will know, the pressure in the intake manifold should actually be theoretically pretty close to atmospheric, despite the engine gulping down huge amounts of air. But if suddenly the throttle snaps shut (still at high revs)... then that's a massive pressure change down to maximum vacuum (overrun conditions) - the biggest step change the engine will see in the shortest time period (biggest "differential"). Admittedly the strong vacuum is only present after the throttle, whereas the oil filler breather is connected just before, but I wonder if it being plumbed in so close to the throttle has anything to do with it... probably not but who knows!

TL;DR Basically I personally think the conditions to get it to happen are a buildup in crankcase pressure over time, then once it's high enough the burp is triggered by being at WOT and high revs (more or less redline), and quickly letting off, at which point there is a massive blow back of oil for some reason we're not quite sure of yet (the actual "burp"). But you don't see the effect until you get back on the throttle, at which point all that oil is then sucked from the intake into the engine, and THAT's when you get your smokescreen.

Just some ramblings with no direction in particular. Sorry for the essay :P
Last edited by JamieM on Thu Nov 29, 2018 7:12 pm, edited 1 time in total.
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exiled--viking (Thu Nov 29, 2018 5:59 pm)
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Re: Let's talk oil catch cans

Post by warpc0il » Wed Nov 28, 2018 10:11 am

I think there are 3 stages to the burp event, which may or may not occur in rapid succession...

1. Whatever causes the oil-rich vapour (or liquid oil) to be blown into the intake hose.

2. Sudden/sustained shut-off of the throttle that reverses the flow in the intake hose, such that the MAF and air filter element get contaminated.

3. Sudden/sustained increase in airflow that draws sufficient oil into the engine to create noticeable smoke.

Note that the sequence could be 1, 2,3 or 1,3,3,3,2,3 etc. on different occasions.

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Re: Let's talk oil catch cans

Post by Culdranth » Thu Nov 29, 2018 6:15 am

Holy poop, I kick started this thread again lol. Cheers for all the Info. Need a coffee and an awake mind to digest all the information. car's off the road at the moment so not in huge rush.

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Re: Let's talk oil catch cans

Post by exiled--viking » Thu Nov 29, 2018 6:06 pm

I have one fitted yes the cars different with the SC but have found that now it only needs to empty around every 6 months or so and there is little oil in the can around 100ml or so so I dropped the size to this little 500ml one ;)



cans next to the grotty air filter that's now been changed ;)






thanks for taking the time to look ;)
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Re: Let's talk oil catch cans

Post by jagasee » Mon Mar 11, 2019 11:46 am

Resurrecting this thread again, but haven't shared my experiences for a while...

I've been getting fairly regular oil burps for about 7 years, ever since the engine was rebuilt.
I fit a cheapy toyo catch can but it would still overfill that and end up in the intake anyway.

A couple of years ago I fitted the revised breather system from a newer car to see if this would improve anything, I still get the burps but they are more manageable. Instead of going into the catch can and sometime into the air intake, the burped oil gets routed into the lower intake manifold instead. I still get a smokescreen but my intake, air filter and catch can remain relatively clean. It normally also causes a flashing engine warning light to signal a misfire but I guess that's just because of the amount of oil dumped into the engine. It recovers within a few seconds as if nothing had happened.

I generally feel that it was down to a poorly fitted seal during the rebuild, but I never pushed them to check it under warranty and now it's far too late.

I've just learnt to manage it over the years. I keep my oil level around 1/4 full and since I don't have to regularly clean my air intake I generally just pretend it doesn't happen...
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Re: Let's talk oil catch cans

Post by goodeggbob » Mon Mar 11, 2019 9:20 pm

dont you mean keep oil level at around 3 quarter full?

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Re: Let's talk oil catch cans

Post by mi60o0 » Mon Mar 11, 2019 9:20 pm

I have two cans for sale if some one is after one
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Re: Let's talk oil catch cans

Post by jagasee » Tue Mar 12, 2019 9:03 am

I keep my oil level between one quarter and half full.
I'm not suggesting others do this, but I know my car and this limits the amount of oil ingested by the engine.

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Re: Let's talk oil catch cans

Post by Scartlead » Fri Mar 22, 2019 10:47 pm

Interesting read all. Wondering should I fit one :-k , com'on another shiny addition to the engine bay :shock: :)
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