DIY: Dual Oil Catch Cans 370Z

wstar

It means your combustion (and whole upper end, really) will be slightly cleaner, because you're not tossing oily vapors back into the intake to be re-burned. Improves octane by 0.00001% or something probably, too.

In a nutshell:

(1) Why is the crankcase ventilated? If the crankcase wasn't ventilated, you'd get oil leaks at the engine seals due to pressure buildup.

(2) Why didn't Nissan just design it to ventilate to open air instead of recycling it into the intake? Emissions reasons, the EPA doesn't like you ventilating oily vapors.

(3) Why doesn't Nissan install a catch can from the factory, thus meeting EPA *and* not putting dirty oil vapors into the intake? Because you usually have to empty a catch can even more often than you change oil, and if you let it go too long and fill up, the liquid oil will get sucked into your intake via vacuum while the car's running, and that's *really* bad. Most people have a hard time even changing their oil on time, there's no way a consumer car can have catch cans from the factory. They'll just fill up and dump into the engine anyways, possibly catastrophically. Keep in mind cornering/braking/accel G-forces will make the fluid in the can crawl up the walls. You have to keep the level low enough to not walk up to the vacuum line and get sucked in as liquid. Good can design can help with those problems.

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