Oil trap for PCV: emissions-lowering modification, Volvo 240/244/245

[ademonrower]

This one is mainly for the Europeans with early-model volvo 200s or any car with an early PCV system. It won't save noticeable amounts of fuel, but it will significantly improve exhaust emissions.

Background: Till the early 1980s, Volvo didn't fit oil traps in its PCV (positive crankcase ventilation) system. This leads to two problems: 1. quite large amounts of condensed oil build up in all of the piping, the intake air duct, the throttle body and even the air filter right at the front of the engine compartment. If unchecked, it can even start to wet the air filter, thus reducing air intake and engine efficiency => worse emissions and lower mpg or l/100 km. 2. unnecessary quantities of oil being burned, because essentially oil-vapour-laden crankcase gas gets fed into the combustion cycle. I really didn't like this, because I often notice the smell of burned oil around my car: not gross, but still, it gives internal combustion engines a bad reputation, and it can easily be avoided here's how:

I made an oil trap from a container with a steel-wool scouring pad as the "condenser". This acts as a very large surface area on which the oil droplets can condense, grow in size and trickel off to the bottom of the container, which I can periodically unscrew and tip the oil back into the engine (saves oil too :-) . The inlet to the container is directly connected to the outlet of the PCV system (see pictures), and consists of a copper tube with holes drilled in the BOTTOM end (important!). This pushes down through the steel wool to the bottom of the container. The outlet is simply an attachment next to the inlet in the screw cap of the container, and it takes air from the top of the container (i.e. it doesn't go down into the steel wool), which is now, after condensation of oil on the steel wool, free from oil. This air then goes straight into the standard hoses for feeding it into the throttle body (very little) and into the air intake just behind the air filter). Thus, much cleaner air enters the combustion cycle, and you get much, much less "oiling" and gumming-up of the hoses, air filter, and all components of the throttle body/carburettor and intake manifold. This will also reduce maintenance! I hope it's quite obvious from my pictures how I made this. An additional note: by adapting hose diameters with other hoses of smaller diameter together with appropriate hose clips, you can easily still use the flame-trap joint with the two outlet ports. However, you can now discard the metal flame-trap insert, because in your oil trap you basically have a flame-trap as well :-) I made absolutely sure that, where I secured the jar in position (with a cable tie) it didn't touch any parts of the vibrating engine, particularly not metal parts. You definitely don't want that!

BTW I used a small glass conserve jar as the container, and heat-fixed and glued the thread of a sturdy plastic bottle with convenient cap to the top of it. Otherwise, as long as you have a good thread and sturdy cap, you could use the original jar lid. IMPORTANT: the jar lid must make a good seal, must not come loose, and the entry/exit tubes must make a good seal. Rubber O-rings and simply making the holes in the plastic cap a very tight fit did the job for me. The gas going through this system by this point is not particularly hot: in my experience it's well below 80 degree C because after a long drive, I can hold the container in my hand no problem. So, the plastic components of my system aren't subjected to great temperature, and the plastics I used are all mineral-oil-resistant. That's the last important point! BTW, using a piece of COPPER pipe as the inlet for the oil trap is great, because it conducts heat away from the vapour very quickly, and already starts the condensation process. My exhaust smell has almost disappeared :-) When I service the cylinder head and replace the exhaust valve stem seals (rubber), it will probably decline to unnoticeable. I'm very happy with this modification. If anyone want's more details, please write: thanks!

BTW, and interesting related point: on all early European Volvo 200s with OHC engines, you will see a steel plate covering an opening in the engine block (redblock) immediately beneath the intake manifold. Why? Well, because the oil trap that SHOULD be there was only there in cars exported to the US, where emissions regulations have always been stricter than in Europe!!! Bit embarrassing for us in Europe :-( Anyway, if you have an early V200 without the engine-block-mounted oil trap, you can't simply fit one, because the circuitry of the later PCV systems was different from the early ones, which have the outlet right on the camshaft cover instead of lower down. It's more convenient simply to continue using that outlet and mount the oil trap as a separate component where you can easily access it high up in the engine compartment :-)

[oil pan 4]

I vent mine to the ground.

[ademonrower]

Surely that's not legal... Or was it a joke? :-)

[oil pan 4]

Venting the pcv to the ground is perfectly legal here. Why would I want to filter the air, then contaminate it with oil and combustion byproducts and allow the oily, combustion byproduct air it to be sucked up by the aluminum turbocharger compressor?

[ademonrower]

The turbo diesel (or turbo anything) might be a different case, and I admit to not knowing that in certain places venting PCV-gas to the ground is legal. I always believed that PCV re-circulation (well, actually just burning) was introduced as a result of stricter emissions norms. Unfortunately, as many of us know, some emissions norms don't make any sense in their consequences... Anyway, thank you for the explanation as to your case.

[freebeard]

Unfortunately, as many of us know, some emissions norms don't make any sense in their consequences...

Your perspective depends on how big a pile of money you're camped out on.

Different strokes for different folks. It's not the Lawless West, you can't just pour used motor oil on the ground. At least not here in Salmon country.

[hayden55]

Just curious how much are you catching? Vacuum assisted catch can are notoriously inefficient.
I use an open air catch can and its helpful for condensed fuel vapor in the winter on my prius. I doubt I have caught half an ounce of oil total so far in almost 20k miles. But fuel/water vapor wise I've probably caught 8oz/5000mi in the winter.

[ademonrower]

I don't know in quantitative terms yet, because I've only driven around 200 km (120 miles) so far, but I can see a little oil starting to collect. The qualitative test - and I have (my wife tells me) a very good sense of smell :-) - is that I can hardly smell the exhaust anymore. I have tuned my carburettor very finely, so hardly any gasoline smell: it was basically just a little oil getting burned. I suspect that in older cars (mine is from 1979) the combination of slightly more piston blow-by and less efficient PCV in general produces more crankcase gas. That said, the Volvo redblock engines - cast iron block - wear very well (it's not rare to see the diamond honing on the cylinder walls still almost factory-perfect after 500,000 km!). My bottom line is that my particular modification worked well for my particular car. That might be luck, and at the most it's an experiment with n=1 :-)
Thank you also for alerting me to a potential caveat: particularly in winter, you don't want simply to tip the collected liquid back into the engine: it might well contain lots of water and even be an emulsion... hmmm... in general I think it's probably a good idea to check the liquid anyway... and probably just tip it into a used oil container... probably does more harm than good to recycle it... ?

[hayden55]

Originally Posted by ademonrower

I don't know in quantitative terms yet, because I've only driven around 200 km (120 miles) so far, but I can see a little oil starting to collect. The qualitative test - and I have (my wife tells me) a very good sense of smell :-) - is that I can hardly smell the exhaust anymore. I have tuned my carburettor very finely, so hardly any gasoline smell: it was basically just a little oil getting burned. I suspect that in older cars (mine is from 1979) the combination of slightly more piston blow-by and less efficient PCV in general produces more crankcase gas. That said, the Volvo redblock engines - cast iron block - wear very well (it's not rare to see the diamond honing on the cylinder walls still almost factory-perfect after 500,000 km!). My bottom line is that my particular modification worked well for my particular car. That might be luck, and at the most it's an experiment with n=1 :-)
Thank you also for alerting me to a potential caveat: particularly in winter, you don't want simply to tip the collected liquid back into the engine: it might well contain lots of water and even be an emulsion... hmmm... in general I think it's probably a good idea to check the liquid anyway... and probably just tip it into a used oil container... probably does more harm than good to recycle it... ?

Yeah for the most part unless its burn consistently as vapor its probably best to just dump it out.
Big turbo cars can have a lot of blow by and then it really is mostly oil getting pushed in.

[cRiPpLe_rOoStEr]

A catch can is always good, but the oily vapours getting routed to the intake tract might not be much a matter of concern, as long as they don't condensate so easily or don't get mixed with particulate matter from the EGR. But I guess you know, the particulate matter issue is more of a problem with Diesels or direct-injection gassers. In a regular gasser with a carburettor or a more conventional injection, the oily vapour will be dilluted by the air-fuel mixture and burn easily. Oil droplets OTOH may stick to the intake manifold, and any other residues sticking to it will be much of a PITA.