2009.03.06 It Rains, It Pours
One of the embarrassing issues with Richthofen was that the air-oil separator(s) had a ruptured diaphragm.
One of my co-engineers wondered, "when the hell is the air and oil ever together in a way that needs to be separated?" Yeah, usually they aren't - in most engines. In most engines, the pistons are mostly vertical, with the explody bits at the top, the lubricating oil in the middle, and a large sump at the bottom for it to pool in. Not so with a Porsche 911.
In a 911, they cleverly put the pistons sideways (a "boxer" six configuration), and they have a dry sump. The idea is that the engine is much flatter, and can be lower to the ground for better weight distribution. It also means that the oil tank can be arbitrarily large, which is more desirable for reliability in racing conditions. Unfortunately, this means that there is no big bowl under the crank to catch the oil, which forms a fog in the crank and condenses after the engine stops and the scavenger pumps stop moving the oil to the remote tank. And, since the pistons are sideways, the pooling oil can ooze sideways into the combustion chambers. To compensate, Porsche has air-oil separators to clear out the fog while the engine runs so that this doesn't happen.
Except, of course, when the air-oil separators fail. And so, sometimes, when I started Richthofen up, big billowing clouds of white smoke would pour out of the exhaust. "Oooh, look at the fancy, expensive sports car burning oil!" Embarrassing. Not really a major issue otherwise, but embarrassing.
So, last week, I finally blew the money required to get the air-oil separators fixed. They're tiny little cheap parts, but they're in the middle of the engine. That meant the entire engine had to be disassembled. Scary. It was such a relief to get that fixed, even though I agreed to do it before I found out that my finances had shrunk by about the size of my maintenance budget. It's my vice, I admit.
A relief that evaporated in a choking cloud of white smoke when I started up Richthofen after work.
GAH!
Addendum
Usually, in the past, when the smoke emerged it would do so for several starts thereafter in gradually reducing severity. This time this event was one spectacular moment, but almost immediately went into remission. This gives me a glimmer of hope that this was merely a result of the oil level being a smidgen too high, and that the -ahem- enthusiastic driving style and failure to let the car cool down that morning meant that excess oil was left in the crank. If this is the case, then all is well, and we can live happily ever after.
The most obvious alternative is that I've actually got some dynamic in the engine that eats air-oil separators, and that all I got for my money was a 4-day remission in the symptom. This was the shitty conclusion I jumped to on Friday, and I really hope that it's not so.
Regardless, the wizards at Stuttgart Autotech are going to find out for me on Monday.
Addendum Addendum
The consultation revealed that the smoke is most likely a by-product of how long I left the air-oil separators not functioning. There are going to be drips of oil present throughout my exhaust system, and they're going to burn off a bit at a time at irregular intervals - whenever they ooze from a cooler corner of a manifold to something flashpoint-hot. Like header, which will smoke on startup, or a catalytic converter, which will produce a billow of smoke at any random moment during full-temperature operation.
It's mostly reassuring. I mean, I'm not keen to have any more burning oil smoke puff out of Richthofen at all. But it does look like the fundamental issue has been addressed, and that the symptoms will abate.
In the mean time, I get to focus on enjoying my driving. Which is worth a lot to me. Obviously.