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Old 10-15-2023, 06:47 AM   #1 (permalink)
Join Date: Feb 2023
Location: Germany
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Oil trap for PCV: emissions-lowering modification, Volvo 240/244/245

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 :-)

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Ecky (10-19-2023)