While the fancy boys may run a dry-sump system on high-end race engines (along with some factory models), the vast majority of engines in the world use wet-sump oiling. Understanding how wet-sump oiling works allows you to optimize the system for peak pressure and performance. This knowledge is critical for high-performance racing applications.

Michael Zeranski, president of Canton Racing, recently sat down with EPARTRADE’s Brad Gilly to discuss wet sump oiling in high-performance applications, specifically production vehicle racing. Epartrade’s weekly webinar on YouTube is a great resource for deep diving the science and theory of high-performance engineering.

What Is A Wet-Sump Oiling System?

Nearly every engine ever made uses a wet-sump oil pan, meaning that all of the engine’s oil is located inside the oil pan on the bottom of the engine, with a large sump that ensures the oil pickup is always covered with oil. Unlike a dry-sump, which uses a much smaller oil pan that relies on a separate, external oil tank to store the engine oil, wet sump systems are inherently sloppy. The oil splashes all over as you drive; in fact, some early engines relied on splash oiling for lubrication. All that oil movement can lead to oil starvation in hard cornering and acceleration situations.

Tuning your wet-sump system stabilizes the oil pressure, limits parasitic loss from windage, and eliminates oil scavenging issues. This process involves fine-tuning your overall fluid volume, pan design, baffles and windage trays, oil pump, and the pickup. “When you address these issues, you can prevent those low-pressure situations,” says Zeranksi.

A T-sump pan like this Canton sheet metal pan for an LS engine can provide the capacity you need without putting the pan below the chassis where it is at risk.

Starting with capacity, this is the first area to consider. Most older V8s hold five to six quarts of oil, while a Honda four-cylinder holds only four quarts. This is fine for the street, but in high-performance applications, increasing the capacity is where you start. “Increasing the pool of oil naturally reduces the chances of oil running scarce,” Zeranski says. Overhead cam engines tend to hold more oil at the top end, reducing how much oil is in the pan. Increasing the oil pan capacity can immediately rectify some of those issues.

Increased capacity also helps reduce and stabilize the oil temperature, as there is more mass of oil to spread out the heat. With more oil in the pan, you get more oil-to-pan contact, which helps dissipate more heat as well. In turn, the lower temps stabilize the viscosity of the oil. The evidence that this works is obvious by looking at modern OEM engine capacities, with some V8s holding eight quarts. Of course, you can’t just overfill the pan, which would cause extreme windage issues.

Baffles, like this 3-door unit, trap oil around the pickup to ensure that the engine doesn’t starve for oil in high-g situations.

Wet-Sump Pan Design and Oil Capacity

How the pan is designed is critical to gaining capacity. If the oil is too high, the oil develops windage, where the crank whips up the oil. Even though it may be a slight amount of oil splashing over the crank, it generates significant drag, killing power and efficiency. The right pan can increase engine performance, but a poorly designed pan has the opposite effect.

Wet-sump systems must balance capacity, windage, and sloshing. Adding a 10-inch-deep sump will certainly get the oil away from the crank, but that puts the pan at risk from external damage, especially in lowered vehicles. This is where you get into T-sumps. T-sumps are popular for chassis cars, as they can provide more oil capacity without creating depth and the associated clearance issues. Their design depends on the specific chassis configuration and ground clearance requirements of the vehicle.

This is a stock LS louvered windage tray. These help control the oil return and stop crank windage from whipping up the oil.

Baffling and Windage Trays

Next up are baffles and windage trays. Modern engines have full-length windage trays from the factory, but go back just to the ‘90s, and there was nary a windage tray to be found from the OEMs, just crankshafts frothing up the oil. Thankfully, the aftermarket picked up the slack, though.

Windage trays help to direct the oil away from the crank and down to the sump, where it can be collected by the pickup and baffling system. They also provide a physical barrier between the oil in the sump and the spinning crankshaft. Preventing the oil from being whipped up by the rotation of the crank, the oil remains in the sump and does not create turbulence around the crank, thereby reducing drag. The bigger the crank and stroke, the bigger a deal windage becomes.

The right size pickup tube is just as critical. If you have a high-volume pump, but too small of a tube, flow is reduced, which can induce cavitation at high RPM.

Baffles prevent oil from moving away from the pickup by way of trap doors or static walls. Baffling is determined by the intended use; road racing baffles are different from drag racing due to the different inertial forces they see. For example, in drag racing, the sudden launch force pulls the oil to the rear of the pan. A baffled sump may have stationary walls around the rear of the sump, stopping oil from draining away from it, while a trap door flap folds in to allow oil from the front of the sump to flow towards the pickup. Road race and circle track baffles are similar, but the walls and trap doors are on the sides to prevent pressure drop in hard corners. Circle track baffles are biased to one side, whereas road course systems typically have four trap doors for every inertial situation.

Even though the biggest benefits of a windage tray come in around 5,000 rpm, they also help direct the oil that is returning to the pan from the top end into the sump, which is a net benefit at any RPM. A tray may be a simple wire mesh screen or a louvered tray, depending on the engine and intended use. A stock street engine may not “need” a tray, but a stroker crank will generate a lot more windage. If the engine sees much time over 5,000 rpm, you would likely benefit from a windage tray, to the point of freeing up as much as 15 horsepower. Free horsepower and better oil control is certainly worth the effort.

Screens tend to perform a little better on the dyno compared to louvered trays, but the engine is stationary in these tests. The advantage of a solid tray is that they are stronger and do a better job of keeping the oil in the sump away from the crank. “I definitely recommend a louvered tray for aggressive road racers,” Zeranski says. “There might be a percent or two difference in power, but the tray performs better in violent off-road action.”

Oil coolers and their respective lines also affect the pressure and flow. The line size must match all the way through.

Oil Pump and Pickup

The oil pump and pickup combination play a critical role in delivering oil to the engine, and the choice of pump depends on the engine’s characteristics, such as bearing clearances, piston squirters, and valve oilers, all of which require more volume. The choice of pump is also influenced by factors such as oil viscosity, with thinner oil being easier to flow but harder to build pressure with.

Low oil pressure can lead to a loss of hydrodynamic lubrication and result in metal-to-metal contact, while excessive pressure can waste energy. Modern engines with cylinder deactivation create some issues in this realm. For example, a GM Gen V LT-series engine uses the oiling system as a hydraulic pump to control the DOD/AFM system. If you delete this part of the engine, you can end up with 120 psi of oil pressure, which is way too much and can kill seals, cause leaks and failures. If you used the old-school thinking, you might swap the pump out for a high-pressure, high-volume pump, but that would be a bad idea. Relying on the oil pump’s bypass system to constantly bleed off excess pressure leads to wasted energy if the pump is turning just to bypass it.

When choosing an oil pickup, there are many options available for a given block and pump, and the selection will depend on the pump chosen, with considerations including the diameter of the pickup tube, which can be limited by atmospheric pressure, friction, and viscosity. A stock SBC has 5/8-inch-diameter tube, but some high-volume pumps require 3/4-inch diameter to get the flow needed to support the pressure and volume. If you try to run too small a pickup, you get cavitation, which will kill your pump. Especially in high-revving engines.

This graphic shows how the accumulator works. Under good pressure, the Accusump is full of reserve oil. When there is a pressure drop, such as a sudden drop in RPM, the oil is pushed into the engine, ensuring that it is properly fed. The moment the pressure returns, the reserve oil goes back into the accumulator automatically.

Modern engines, such as the LS, Ford Modulars, and Coyote, all have large pickup tubes from the factory. With diameters up to 1-1/8 inches, the OEMs certainly recognize the importance of tube diameter. That said, a one-inch tube on an Gen-I SBC is too much. It has to be part of the overall design of the system. The pickup itself is another key component, made specific to each type of pan. With a baffled pan, the pickup must be located in a precise position to get the most benefit from the baffle. The target gap is about 3/8 inch between the pan and pickup to take advantage of the oil in the sump.

Wet-Sump Accessories and Temperature Control

Controlling temperatures is crucial for a good oiling system. High temperatures can indicate issues from a poorly functioning oil system. Viscosity breakdown is directly related to temperature, so reducing the oil temperature with a cooler can solve these issues.

Canton’s Accusump oil accumulator provides added protection for wet-sump oiling systems. Not only by adding capacity but also providing a surge of oil if the pressure drops. It is essentially a shock absorber for your oil; when the pressure drops, the accumulator pushes more oil into the system. When the oil pressure is back up to the correct level, the accumulator receives extra oil for the next instance. Without that extra oil injection, these momentary interruptions in flow can create hot spots and wear in the engine.

When diagnosing oiling issues, it is important to know when the issues come in — does it start right away or after a few laps? When the issues show up later, that is usually an indication of slow oil return. Adding capacity will help alleviate those issues. Ensuring that the oiling system is as efficient as possible, maintaining a good oil reserve in the sump and minimizing windage is the key to maximizing the performance of the engine as a whole.