Tuesday, July 11, 2006

Oil vapour recovery system

After installing the oil vapour recovery filters (also known as crankcase breather filters) I did a bit of research on the internet, since I was initially concerned at observing "mist" coming from the filters when I opened up the bonnet. You can see the two breather filters in the picture below, the two small cone filters that protude forward from the top of either crankcase cover, attached to black hoses that run to the back of the crankcase cover.

Now that I've disconnected the hose to the inlet system, the fuel and oil is vented to the atmosphere. Not good for the environment since oil particles cause smog (amongst other things). Before, this oil and fuel was sent to the inlet system and burnt in the combustion cycle. Good for the environment, but not so good for the car, since oil reduces the efficiency of the cumbustion cycle, plus the vapour is a bit warm, heating the charge air slightly (this is probably negligible though). I also suspect that the oil from this oil vapour system was falling onto the air filters in the air boxes and clogging them up, since when I opened up the air boxes I noticed a reasonable amount of oil staining on the top (engine side) of the filters. This will have been robbing the engine of some power since it will have reduced the efficieny of the air filters considerably.

After looking on the EurospareS site, it would be possible to retro-fit a PCV (positive crankcase ventilation) system onto my pre-MY94 Ghibli by ordering the parts pictured below (click on picture to enlarge):

This system has an oil knock out tank, which collects the oil vapour and re-cycles it back into the oil system via a conneciton to the sump tank. This means that only warm air with a bit of fuel vapour is sent to the inlet system for combustion and means that oil system is closed loop rather than open loop as I have it and how it was installed on the pre-MY94 Ghiblis.

This is good for the environment, since the unburnt fuel gets burnt and the oil stays in the engine. I'm not convinced that it's good for the car though, since the oil that collects in the knock out tank is undoubtedly contaminated and will degrade the quality of the oil in the engine. This means that regular oil changes are very important! On the old system, the oil vapour simply gets burnt and the volume of oil in the engine decreases. This means that checking the oil level on the pre-MY94 cars is more critical than on the MY94 cars (mental note to check the oil level more frequently on my car!).

If I put my environmentalist hat on, I'd go for the option that was already installed on my car, with the oil and fuel vapour being burnt in the engine. With my tuning enthusiasts hat on, I prefer the option as it is now, venting straight to atmosphere (I like the smell). I think the solution that is installed on the MY94 cars is driven by anti-smog legislation. I think it's only environmentally sound if the used oil is recycled or disposed of in a controlled manner that is environmentally sound, but as a driver I can't gaurantee this, since it's the responsibility of the garage who does the maintenance work or of the disposal company where I drop the used oil off at after making the oil change myself.

Since I don't drive my Ghibli frequently, I don't think I'm a big contributor to environmental damage with this car. If I used the car daily then I'd probably retrofit the PCV system. But for occassional driving, I'd rather know that the oil quality is good and that there's the highest quality mixture going through the cylinders. So for now I'll stick to the newly modified system.

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