OT-Inverted V12 engine...

[Chuck Wintle]

Going back a few years to the Me-109 airplane. These planes ran with an inverted V12 and my question is this...How did they manage not to foul the combustion chambers with oil if they were inverted? :D

[Tom Veatch]

Going back a few years to the Me-109 airplane. These planes ran with an inverted V12 and my question is this...How did they manage not to foul the combustion chambers with oil if they were inverted? :D

Dry sump engine?


http://en.wikipedia.org/wiki/Daimler-Benz_DB_601

[Jim O'Dell]

I was watching a show the other day at work while at lunch, and it showed an old WW1 plane with a radial engine where the cylinders rotated, not the crank shaft. You'd think that would throw oil into the combustion chamber too! Jim.

[Dave Johnson29]

You'd think that would throw oil into the combustion chamber too! Jim.

It does but they have a scavenger pump to pick it up and send it back to the oil tank.

In a conventional wet-sump engine the oil is just let run out of the last bearing in the line and then make it's way back to the sump which acts as a reservoir.

On a dry-sump engine the oil system is pretty much a closed loop and the last bearings on the runs will have a return line passing the oil back to the oil tank. Any oil that escapes and little always does, is picked up by the scavenger pump and sent back to the tank. The sum area is always pretty much empty or dry.

There are many advantages to the dry sump, it can run in any position and is well suited for aircraft because of that. It also prevents cornering surge in race cars and boats. Some race cars can pull several Gs in a corner and that sends the wet-sump oil up the inside walls of the engine. The engine can run dry for a second or two whereas a dry sump will not do that.

On the subject of the turning cylinder engines, they were called Rotary and they added a huge flywheel effect. Propellor aircraft engines are all about constant speed and mucho torque. Cost and complexity to build saw them pretty much die out after about WW1.

[Horton Brasses]

Mazda RX-7 cars traditional had rotary engines-along with the late great Mazda Millenia S (S for Sleeper). Kind of odd-about the only common current usage of that type of motor. Made for a pretty entertaining drive by all accounts.

[Jim O'Dell]

Yeah, I had a '73 RX-3 with the rotary. It was fun to drive. No torque though. And poor gas mileage. In Jr. college automotive class, we put it on a dyno. Driver (me) had a button that controlled the brake that put resistance on the rollers. The rotary would go to a point, then die. In about 15-20 minutes on the dyno, we thought something was wrong with the machine, I used over 1/2 tank of gas. You could literally watch the gas gauge drop! Twin rotor engine, 2 spark plugs per chamber, 2 distributors, one dual point, one single point, and a 4 barrell carb. Red line was 7000. At 6500, you set off a horn burried in the dash!! I thought I blew the engine up the first time I reached that RPM.:eek:
I could romp on it, let off and it would dump fuel into the exhaust, hit the gas just right, and it would explode causing everyone close to jump. Used it when guys in muscle cars would mess with me when I was in college.:D Hard to tell it wasn't a shotgun blast.
But this is a totally different type of rotary engine, actually a Wankel (Wankle?). The one in the airplane was a radial engine that the cylinders turned with the prop instead of the crankshaft. Jim.

[Dave Johnson29]

Mazda RX-7 cars traditional had rotary engines-along with the late great Mazda Millenia S (S for Sleeper).

They were a different type of rotary. They used the Wankle engine which consisted of a roughly triangular rotating unit inside a roughly figure-eight chamber.

Because there was no stopping and starting of pistons at the top and bottom of the stroke it provided smoother power and higher efficiency. The biggest problem that Wankel had in the late 50s was sealing between the rotor and the chamber. Mazda raised that to new heights with more modern materials and technology but around 50K was a good life before performance began to drop off as the seals began leaking.

They were very successful in racing but those engines were rebuilt with new seals after only a few thousand race miles. Sometimes after only a few hundred.

The latest round of Mazda rotaries (Renisis RX8) are getting much better times between rebuilds thanks to even better seal materials, but they require very diligent and regular maintenance. Mazda recommend checking the oil at every second gas-fill and changing it every 3 months or 3000 miles. The area swept by the rotor and seals has pressure injected oil to aid seal life and the engine is designed to use oil, so clean and plentiful oil is a must. Great little engines though.