Is that what those are called. I love those.
On the subject of grounding the car and losing an engine, I've been trying to determine how to rig an oil level switch in the pan of my new 7M. Setting it to the height specified by the dipstick isn't too big an issue, it's figuring out that that might mean while the engine is running that I don't know what to do about. How much oil is going to be circulating around the engine while it's running? Since I think I'd need to take the pan off in order to readjust it, it'd be nice to know before hand.
I can think of a few ways to do this.
One would be to use a "fuel level" type sender in the pan. See how things go, and use a Schmitt trigger to set off a low oil light when the level goes below what I log as a low while I know that I have a reasonable amount of oil in the pan, then keep the light on until it goes above a known good point. This is the most complex solution, but has some cool features. I could probably adjust the high and low trigger points for when the engine is not running, and the dipstick levels should be active. Or I could just run a bar graph off the output as an oil level gauge.
Another would be to use the dipstick as a guide. Allow for the level to go to say, 1L below the "add" mark to allow for about that much to be circulating through the engine, and not in the pan. Might trigger false positives at high RPM or at high G manoevering (Though whether or not they're "false" at that point could be up for debate) but if it's a momentary flash of the light, it could just be good information to have as well. Less consistent, but good enough to catch most low oil level situations. This is what I'd LIKE to do, since the switches for these are relatively inexpensive and simple to find. For this though it would be best to know about how much oil to expect to be circulating through the engine within normal range of operations and temperatures.
Finally would be the "Oh shit" idiot light. Set the level just above the oil pickup, so if it goes off, shut the engine off NOW and hope that you haven't lost a bearing YET. Should only ever go off if you're changing the oil and left the ignition on for some reason, or if you've bottomed out the car and holed the oil pan. Minimal usefulness, but just barely better than the "low oil pressure" light that my old V8s used to have that let you know "you've probably already spun a bearing, but you probably haven't put a rod through the block yet."
