This is a five-stage pump....
This is a five-stage pump. The pressure pump uses a more common gear-type pump, while the scavenge side uses a Roots type. There are all kinds of ideas for accomplishing the same goal.
From the simplest of perspectives, you will need a multistage pump, a tank, a different oil pan, a pump drive, various hoses, and mounting brackets. Costs will vary by application, but plan on spending several thousand dollars. What does this buy you? Total oil control and horsepower gains. Let's talk about that. With a dry sump you gain a more complete control over the oil system. There are still risks, but they are different from those with a wet sump system. One risk occurs when you mount the pump external to the engine and use a beltdrive. The drivebelt could become a liability if it is damaged or the belt jumps off. But this is a problem you can work to mitigate.
There are some non-oil-related advantages to utilizing a dry sump system on your engine. The first thing is that the oil pan is anywhere from 2 to 5 inches shorter than a wet sump's oil pan, and this allows you more choices when mounting the engine in the chassis. You can lower the engine in the chassis to improve the handling of the car, not to mention lowering the nose to get it out of the air stream. Both of these are positives for improved performance on the racetrack.
With a dry sump system you can control the speed of the oil pump by varying the size of the drive pulleys if you have the pump mounted outside the engine. Many applications still utilize a cam-driven pump, but you have options that aren't available with a wet sump system. In a traditional wet sump system, the oil pump speed is half the engine speed. There are no options.
This is a three-stage dry...
This is a three-stage dry sump pump. This pump uses a gear-type high-pressure pump and two gear-type scavenge pumps. This is the type of pump you may see at the track in a high-horsepower application.
The oil pump itself on a dry sump pump is also very different from a wet sump pump. A wet sump pump has one set of gears or impellers that pulls the oil out of the sump and then pressurizes the oil and pushes it through the engine. A dry sump has stages of individual pumps ganged together with separate functions but on a common shaft. Each of the individual pumps has a specific job. There are at least two scavenge pumps that remove oil from the engine and one pressure pump that supplies the engine. This configuration is called a three-stage pump. It's quite possible to have a three-, four-, or five-stage pump. The scavenge pumps pull oil out of the engine and route it to the oil tank. The single pressure stage of the pump pulls oil out of the tank and sends pressurized oil into the oil filter and then into the engine.
Many Advantages
The tank in a modern dry sump system is a very high-tech part. It's designed to remove any air suspended in the oil, which ensures that the pressure pump is fed. The tank is a two-part assembly that can be disassembled for cleaning if necessary. Some applications have heater elements in the oil tank so that the oil reaches operating temperature prior to the race. That's why you see generators being moved along with Nextel Cup cars as they're pushed to the starting line. The generators are powering the oil heater in the dry sump tank.
The scavenge pumps remove oil from the engine and push it into the oil tank. The advantage of having multiple scavenge pumps is that you can remove oil from various locations in the engine. The dry sump pan has several locations from which to remove oil and route it to the oil tank. This means that the oil is scavenged more quickly in a dry sump than a wet sump. It also means that the racer or engine builder can remove oil from the engine in multiple locations, not just the pan. The racer can always maintain a steady flow of pressurized oil to the engine.
This gives you an idea of...
This gives you an idea of the gear and the housing size differentials as we move down the pump, from the high-pressure pump to the scavenge pumps. Each pump can be made with different-sized gears for each scavenge pump. It's something each engine builder can adjust to suit the needs they may have for a specific application. This type of adjustability is not found in wet sump applications.
There are other advantages to using a dry sump oiling system in your race car (if they are allowed in your series). The scavenge pumps also remove air from the crankcase and can actually pull a vacuum in the crankcase. While this is an interesting bit of mechanical trivia, it really has a positive effect on the engine. The low pressure in the crankcase actually helps the ring to seal. The increased differential pressure across the piston rings causes them to expand, and that helps improve ring seal. Engine builders realized this phenomenon and have developed special low-tension ring packages that have less drag in the bores and consequently have a lower friction level. This can help unleash as much as 19 to 22 hp in race engines.
If you race long enough, you are going to lose an engine. When that happens, some hard particles are pulled through the pump. This is not a problem because the pump is capable of being rebuilt. We spoke with some of the manufacturers of dry sump pumps, and all of them sell parts to rebuild the pumps. If you damage a gear, housing, or any part of the pump, you can get replacement parts. It's not uncommon for dry sump pumps to get many years of service. Speaking with Terry Palmer of Razor Pumps, we learned that the company offers the service of rebuilding the customer's pump or selling him the parts to accomplish the job himself. The same service is offered to racers using Johnson's High Tech Performance pumps.
Dry sumps can actually save the racer money over the long term. They offer levels of tuning that are not even options with a wet sump system. A dry sump system is not an economical modification, but the short-term cost is replaced with long-term savings, increased power, durability, and an elevated level of performance that isn't limited to horsepower gains. Stand tall at the podium!