Once the seals and rails are...
Once the seals and rails are ready, they are fitted to the specific block for which the pan is being made. Once everything is fitted properly (including bolt holes), the pieces are tack-welded and then moved to a jig.
The Pump Many of the key benefits of a dry-sump system stem directly from moving the oil pump out of the oil pan and making it a separate unit driven by a belt off the crank. Because the pump is now outside the crankcase, it is actually capable of pulling the oil out of the engine, but also the air. By creating a vacuum inside the engine, oil is pulled off engine parts more easily instead of clinging, rings seat in the pistons better, and the resistance seen by the crank as its counterweights swing through the air is basically removed.
Even a small amount of vacuum inside the crankcase can be helpful, but the engine builder must be careful to properly seal the engine from leaks using proper seals and extra care. Still, Nextel Cup engine builders are using external oil pumps to pull a vacuum as strong as 26 inches of mercury. For comparison, a perfect vacuum is 29 inches of mercury.
Here's our partially completed...
Here's our partially completed pan on a jig. The wrapper is in place, and now the rest of the pieces must be hand cut and fitted.
External oil pumps are broken into stages. Typical dry-sump systems use pumps that are between three and five stages. One stage is always used as a pressure pump. In other words, it pulls oil from the external tank and pushes it into the engine oil galleries. One stage is strong enough to provide all the pressure necessary. For racing, where excess pressure means lost horsepower, the pressure bypass is often engaged. The other stages are all used to pull oil from the engine after the oil has done its job, and also create a vacuum in the crankcase. A single suction stage can adequately pull enough oil for proper lubrication, but multiple suction stages means a smart engine builder can pull oil from different areas of the engine as well as pull greater amounts of vacuum.
For example, Fast Times Fabrication teamed with KT Engine Development to produce a dry-sump motor for a Super Late Model racer. For this engine, Fast Times built a four-stage pump, which means three stages are available to pull oil and air from the engine. Engine builder Ken Troutman used two stages to pull oil from the pan, but the third was plumbed to the lifter valley. The goal is to pull the oil used to lubricate the valvetrain directly from the lifter valley before it can drip onto the cam and crank, a major source of windage. The cam and crank are lubricated by their own oil galleries, and the "splash oiling" from the valley is unnecessary.
Because a pan can include...
Because a pan can include many welds that all must be airtight, it can take a good welder a couple of working days to finish a pan. At Fast Times, the pan remains bolted to its jig the entire time to make sure nothing moves out of position during the fabrication process.
The Oil Tank Instead of storing excess oil in the pan, a dry-sump system continually circulates oil through a large, remote tank usually installed behind the driver's seat. The tank keeps oil away from the crankshaft and provides a good method for cooling. The tank can also hold much more oil than the typical pan, which also helps to keep the engine oil cooler longer.
Valve Covers Although these aren't typically a part of the oiling system, a dry-sump with an external oil pump makes it easy to add oil squirters to the valve covers. Squirters provide a direct cooling spray of oil to the valvesprings that is much more beneficial than any splash oiling they would get otherwise. The greatest benefit from this spray of oil is it helps keep the spring cooler, which is vital because of the heat buildup endemic with the long-term high revs seen in circle track race engines. Because of the oil pump, it becomes quite simple to plumb a pair of valve covers equipped with squirters: Simply tap a line off the fitting that provides oil under pressure to the engine.
To see how all of these components come together in a race engine, check back next month for the second chapter in this series when engine builder Ken Troutman builds and dynos a Super Late Model race engine.