Proper engine oiling is one of the single most important ingredients to any internal combustion engine. Especially in the racing and high performance world, where every engine builder is greedy about their parasitic horsepower losses, oiling takes on added significance. When speaking in terms of race engine oiling, two distinct methods exist for supplying internal components with the vital lubrication they demand: a wet sump or a dry sump. In this tech feature, we’ll take a look at the differences between a dry sump and wet sump, overview the components utilized in both systems, and answer the question “when and why should I opt for a dry sump”?
To accomplish this, we’ve reached out to some of the biggest and most recognized names in the aftermarket and racing industries, including Moroso Performance Products, Canton Racing Products, and Peterson Fluid Systems.
- Moroso, in business since 1968, is one of the worlds most respected aftermarket brands and today manufactures more than 4,000 different products, including some of the most popular and complete oiling components in the industry.
- Canton Racing Products, based in Connecticut, produces a wide range of oil system components, from their leading oil pans to oil coolers, hoses and fittings, oil system adapters, accumulators, and much more.
- Peterson Fluid Systems, likewise, offers a complete line of parts for your oiling needs, led by their renowned dry and wet sump oil pumps, as well as tanks, drives, filters, cooling, and more. Both Canton and Peterson have been in operation for more than 25 years.
Dry sump oiling systems are the safest, most dependable, oiling systems available, and they’re popular in forms of racing that the rules allow them. – Thor Schroeder
In an internal combustion engine, everything from the camshaft(s) to the pushrods to the cylinders and the crank require an appropriate form of lubrication in order to operate and continue a long life of operation. How you get the oil to those important components and where it comes from does play a role in the loss or gain of horsepower, however. A conventional wet sump oil system is used in virtually every vehicle on the road and in the majority of all drag racing vehicles. In racing terms, a wet sump system is more of the “entry level” setup, if you will.
In a wet sump oil system, the oil resides in a large oil pan containing a sump at the front or rear of the engine, depending on the location of the cross member and how the engine builder has set it up. A pickup tube mounted to the oil pump collects the oil and sends it back through the oil cavities in the block. That hot oil then trickles back down through the engine during its operation to the oil pan and repeated. There are also external wet sump systems, that utilize an externally-mounted pump that operates off the crankshaft and scavenges oil from the sump in the oil pan.
In a dry sump oil system, meanwhile, the oil is contained in an external reservoir rather than in a large, deep oil pan, and is pumped into and out of the engine back through the reservoir via an external oil pump.
As you can imagine, a dry sump system is more complex, requires more space in the engine compartment, and is of course more expensive, but it does offer a number of exceptional benefits to those that can afford it and wish to gain every ounce of horsepower they possibly can. This is why Pro Stock, Pro Modified, and racers in nearly every form of heads-up racing where they’re permitted by the rules opt for nothing less.
What are the benefits you ask?
- Because a dry sump system typically uses a very shallow pan to collect the oil, the engine can be placed much lower in the chassis, thereby lowering the overall center of gravity of the vehicle
- The use of the external reservoir provides the ability to run a larger capacity of oil
- The larger oil capacity that a dry sump offers allows the oil to cool and released gasses from ring blow by and the movement of the crankshaft
- Having the oil pump mounted outside of the engine/oil pan allows for easier maintenance or replacement of the pump
- Although of less importance in a straight-line drag racing application, dry sumps are less susceptible to oil pressure loss in racing environments where high-g loads from high speed cornering slosh the oil out of reach of the pickup tube
“Dry sump oiling systems are the safest, most dependable, oiling systems available, and they’re popular in forms of racing that the rules allow them, especially where low chassis height is important for good handling,” said Moroso’s Thor Schroeder. “Horsepower gain is maximized because there is virtually no oil in the pan and no internal pump, allowing the windage tray or screen to run the full length of the pan.”
As described above, there are significant differences between a wet sump and a dry sump oil pan. While a wet sump is the primary containment device and thus carries the size and weight of such, the dry sump pans are much shallower and, depending on the level of vacuum, may have little to no oil contained within them at any time.
Whether you’re in the market for a wet or dry sump pan for drag racing, circle track, marine, trucks, or road racing, Canton Racing Products has a pan for it.
Canton manufactures dry sump pans for Chevrolet and Ford engines – both the big and small block variety – that measure just five to seven inches deep and feature a number of different options.
Canton’s dry sump pans are made both in cast form and of aluminum with a billet rail, but as Canton’s Jeff Behuniak tells us, “The oil pan is a basic thing, so as long as it controls the oil, the performance is really the same other than a slight weight difference.”
The oil pumps that are used in a dry sump system are mounted and operated externally to the engine and oil pan, and are typically run off a belt drive from the crankshaft. In simple terms, these pumps have a pressure stage and a scavenge stage, although in reality most pumps – especially those for high performance use – feature one pressure stage and at least two stages of scavenge, with many sporting three or four stages of scavenge depending upon the application.
For those unfamiliar, scavenging is the pulling of the oil and air that’s inside the crankcase of the engine back to the oil reservoir. In some configurations, the oil will run through an oil cooler on it’s trip from the oil pan back to the reservoir.
What Are Stages?
A dry sump oil pump generally has three or more stages, with one operating as the pressure side that pulls oil from the external reservoir and delivering it to the engine. Pumps generally will have three or more stages, where the remaining stages will act to place a vacuum in the crankcase and pull the used oil from the engine. Like the single-stage pressure side, a single scavange stage has enough pressure to pull the oil, but additional stages allow for greater levels of oil suction.
The number of stages of vacuum you run on the pump will determine the pan layout, as well. In general, a four-stage oil pump for example, will have three oil scavenge ports on the pan.
According to Morten, many high horsepower drag racing applications use six-stage pumps in order to scavenge as much oil as possible, with as much as 19-inches of vacuum in effect in some examples. However, 13-inches of vacuum is generally deemed the “safe” zone for bracket racing-style engines before you start pulling oil from the wrist pins and cylinder walls.
Many of the pumps on the market, including those from Peterson, are a positive displacement design, meaning if you turn the pump slower it pumps less volume, and vice versa if you turn the pump faster. Cam-driven pumps will generally spin at 50% of engine speed while the standard belt drive pumps operate around 57% of the engine speed.
Peterson offers pulleys of different tooth counts to increase or decrease the pump speed for a given engine, depending on the engine builders specifications. Ideally, you want the pump to turn quick enough to provide the engine with the oil that it needs and maintain oil pressure but not so quick that you’re bypassing oil. Smaller engines that require less volume of oil may operate in the area of 45% of engine speed.
Peterson offers their line of R4 dry sump pumps, featuring a patent pending four lobe twisted rotor design in both the pressure and scavenge bodies, in variants from three to six stages. These pumps flow in excess of 30 GPM for some of the most demanding racing engines and with incredible vacuum abilities.
Moroso also offers a line of oil pumps – both wet and dry sump. Explains Schroeder, “The Moroso Billet Aluminum wet sump oil pumps for small and big block Chevrolets have three times larger mounting area to prevent breaking and weigh one pound less than stock oil pumps and pickups. The inlet areas are increased to prevent cavitation, and thrust bearing assemblies that increase housing and gear life due to drive shaft axial forces on the drive gear.”
A vital part of a dry sump system, the external oil tanks separate the air from the oil, preventing foaming while delivering a continuous supply of oil to the pump regardless of the racing conditions.
Both Moroso and Peterson offer a number of dry sump oil tanks in a variety of sizes, shapes, and capacities for different drag racing applications – be they for a doorslammer, dragster, sport compact, or a nostalgia car.
In the Moroso catalog, you’ll find several dry sump tanks, including their standard drag race tanks in 13- and 15-inch sizes holding 5 or 6 quarts and with or without breathers. These are all engineered with carefully placed inlet locations using -AN fittings, large diameter screw-on filler caps and drain plugs. The
Dragster tank, meanwhile, measures 20-inches in height and 6-inches in diameter to fit the cozy confines of a dragster chassis. Adding to the ease of use, this tank in particular is a two-piece design so it can be taken apart and cleaned.
Peterson Fluid Systems, likewise one of the leading manufacturers of racing oil tanks, produces a standard 7-inch Drag Race tank with an integrated NHRA legal tank with -AN fittings and a catch can among other optional elements. This tank is both used by and certified by the championship duo of Kurt and Warren Johnson in the NHRA Pro Stock ranks.
Also in the Petersen lineup is a short 1-1/2 gallon “Flowerpot” tank, which sports a slow profile design for nostalgia cars and similar where height is a concern. Peterson can also work with you to custom design an oil tank for your specific needs.
Should You Dry Sump?
This brings us to the question that many of you new to or on the fence about dry sump oiling may be asking: should you upgrade to a dry sump system, and what determines whether you NEED to or not?
As pointed out above with the benefits of a dry sump, much of the decision is based upon your budget and your needs. If you’re a heads-up racer that demands every drop of power and torque regardless of cost, or you’re hellbent on delivering optimum oiling to your internal combustion investment, then a dry sump is your answer. Unlike many other components, there is no elapsed time or horsepower figure at which point you have to make the switch. As the experts we spoke with pointed out, it’s really personal preference of how much vacuum you want to pull from the engine, because only you or your engine builder can determine what’s suitable for your combination.
Said Schroeder, “Can a wet sump work as well as dry sump system? Yes and No. Even though Moroso sells three different series of dry sump pumps, production and custom dry sump oil pans and production and custom dry sump tanks, certain applications are better suited to a wet sump oiling system than a dry sump oiling system. On street applications, all but the most exotic and high performance street cars are better suited to a wet sump system. This is because a dry sump system adds complexity, cost, and the user has to be more mindful of what the system is doing, along with added maintenance. ”
“A dry sump is always going to be better if your class allows it,” says Morten. “Unlike a wet sump with an internal oil pump, you can set the speed of the pump to the engine to adjust pressure.”
Continued Morten, “Cost would be a limiting factor in the decision. If a racer is trying to build a car on a budget, a wet sump setup is going to be a bit cheaper because you don’t have all of the added components. But if a racer were to opt for a wet sump with a external pump, it does allow them to upgrade to a dry sump system down the road and they’ll already have some of the parts that they need.”
As you’ve learned here, stepping up to a dry sump oiling system isn’t exactly a cut-and-dry, black and white issue. There is no determining factor in regards to horsepower or elapsed time goals, although an adequate dry sump system will obtain you more of both. What it boils down to is efficiency and your own particular needs, and the choice is often best laid in the hands of an experienced engine builder. Like any other luxury in the automotive world, it largely has to do with how much you’ve got to spend. But chances are, if you’re in deep enough to consider going with a dry sump, you’re already in that upper expense category anyway.