Oil

Oil is needed to ensure the engine's continued function. The oiling system will often make a small or negligible impact on horsepower from the engine, unless the engine blows up from a lack of adequate oil pressure, in which case you will have zero horsepower. Careful design is needed to make sure the engine won't explode in the middle of a corner.

System design

Oil System Differences

The vast majority of FSAE internal combustion cars use motorcycle engines. One of the key differences between motorcycle engines and car engines is how the oil system functions.

Wet Sump

Wet Sump Schematic

In a stock motorcycle engine, the oil is stored in an internal oil pan. This is called a “wet sump” oil system. On a motorcycle, this design continues to function during hard lateral turns because the motorcycle itself leans into the turn, allowing the oil pickup to remain submerged during the turn. In a four wheeled vehicle, the engine cannot tilt into the turn, and the oil is forced against the side of the pan, sometimes away from the oil pickup. This leads to oil starvation, which leads to low oil pressure. Wet sump systems can be successfully used in FSAE cars, but usually significant alterations to the stock oiling system are needed, especially if the team also wants to shorten the oil pan to lower the CG of the engine or for packaging reasons. Redesigning the oil pan from scratch is common. Baffles can be added to decrease starvation in corners. To significantly shorten the height of the oil pan, the oil pickup will likely also need to be shortened. Filling the engine past the level expected by the manufacturer is also possible, as long as the crankshaft doesn't hit the oil and whip it into a froth.

Oil Accumulator

One middle ground between a wet sump and a dry sump is a wet sump system with an oil accumulator (often known by the proprietary brand name Accusump). The accusump is an external oil reservoir system that sends oil to the engine when oil pressure goes below a certain threshold. When the driver leaves the corner, the oil returns to the reservoir. This way, the engine is guaranteed a certain oil pressure, until the oil reservoir runs empty, which can happen in long sweeping corners. Accusumps are more common on road racing cars, where corners can be much longer than on autocross tracks.

Dry Sump

Dry Sump Schematic

In a dry sump oil system, the oil for the engine is stored in an external reservoir. The oil that collects at the bottom of the engine is quickly removed by a scavenging pump, and routed into the external reservoir from which the supplies for the engine and the turbocharger are drawn. A common industry solution, a dry sump is often used in very high performance engines for a variety of reasons, including reducing the load on the engine by pumping the oil electrically, or reducing the frictional work the engine has to overcome by reducing windage. An advantage of a dry sump for FSAE is that the pan height can be reduced due to the external reservoir replacing the wet sump. This eliminates the oil starvation problem during cornering and brings the engine closer to the ground, lowering the center of gravity. A dry sump is common in FSAE for forced induction applications, as high lateral accelerations reached in the FSAE competition greatly increase the chances of temporary oil starvation of the turbocharger.

The main downside to a dry sump is the large oil tank needed to ensure adequate oiling performance (and to meet the rules), which adds weight and can be hard to package.

Oiling for Turbochargers

The engine has a robust internal oil management and supply system, so a brief or inconsistent oil supply will have limited consequences for the engine itself. However, the turbocharger is spinning at well over 200,000 rpm, meaning even a small perturbation in oil supply will spell disaster for the bearing system. [citation needed, our source this in our senior proj was alumni communications]