Here’s How Race Cars Change Fluids Mid-Race Without Spraying Hot Liquids Everywhere

You’re in the pits at a major world-class endurance race. Your team’s car is in the lead with a few hours left to run. Imagine it. You’re focused, but the slightest hint of anticipation and giddiness is lurking at the edge of your pscyhe. Just then, you hear a call over the radio. Instantly, there’s a pit in your stomach, your palms sweaty. Oil pressure just dropped over the last few laps. It seems like there’s a leak. This could ruin everything… but your team came prepared.

In motorsport, planning for negative eventualities often makes the difference between trophies and could-have-beens. Plenty can go wrong with a race car, particularly over the extended length of a hardcore endurance race. For that reason, teams plan the quickest possible fixes for all sorts of problems. When it comes to fluid loss, having some quick-fill ports accessible on the race car can keep it in the fight when it would otherwise be a steaming, broken mess at the side of the racetrack.

In a recent Facebook post, Pratt Miller Motorsports gave us a direct insight into how it fits fill ports on its race cars. Formerly known as Corvette Racing, the team is one of the most successful American outfits in sports car racing. It’s currently campaigning a Chevrolet Corvette Z06 GT3.R in the IMSA SportsCar championship. The post gives us a look at the door sill of the race car. There, we see ports for topping up coolant, engine oil, and gearbox oil. A loss of any one of these fluids could easily see the car retiring from the race, and likely with expensive damage to boot.

This technology isn’t just limited to the Pratt Miller Motorsports cars, though. I spoke to IMSA race mechanic and auto writer Bozi Tatarevic to get the low down on how common these systems are in motorsport, and how they’re used. “I have seen those ports in IMSA, and used them on the Lexus [RCF GT3] to fill oil during a pit stop,” explains Tatarevic. “Typically, these ports are placed around the car or some require the hood to be pulled off to be accessible.”

In the case of the installation on the Corvette, he notes that location can matter, depending on how your race goes.  “The notable thing with the Corvette implementation is that they were all placed in one spot that is easily accessible,” he says. “That can be a benefit from a time perspective but it does come with the drawback of losing access to all of your fluid fill points if the car sustains damage in that section.” In the case of the Lexus RCF GT3, which Tatarevic worked as a crew member, the oil fill port was located at the base of the windshield.

You can see me doing an oil fill in this pit stop POV from 2021. https://t.co/5SJRBFO1mN

— Bozi Tatarevic (@BoziTatarevic) October 20, 2023

In the 2021 pitstop seen above, you can see Tatarevic topping up the race car in seconds during a stop. That’s thanks to the use of the Subek Oilstick. It’s a tank of oil that is pressurized at 87 psi (6 bar). The tank has a total capacity of 2.32 quarts (2.2 liters), but in actual use, it’s designed to be filled up with 1.9 quarts (1.8 liters) of oil, with the rest of the internal space used for air. The device is pressurized for fast delivery of oil into the vehicle’s dry sump oiling system. This is achieved with compressed air via a Schrader valve in the base. It’s the same kind of valve you’d find on a bike tire. The oil itself is delivered to the car via an F2K or LiTec valve, depending on what the team in question wishes to use. These quick disconnect fittings are designed for “dry break”, meaning the tank nor the vehicle squirts oil on disconnect.

Subek also manufacturers systems for refilling cooling systems in a pinch under the name Waterpick. These systems allow topping off coolant without spillage. Often, refilling coolant requires the delivery of a great deal more fluid than with engine or gearbox lubricants; Subek’s systems are designed to deliver anywhere from 7.4 quarts to 13.7 quarts in the Waterpick line. They force water into a hot cooling system under pressure, using CPC or Stäubli couplings to do so without spraying hot coolant or steam everywhere.

As you might imagine, race teams don’t just put these systems on for a laugh. They can make a very real difference in results. Tatarevic notes the recent case of Meyer Shank Racing winning the 2023 24 Hours of Daytona, formally known as the Rolex 24.  The team’s Acura ARX-06 had a gearbox oil leak that came to light mid-race. Thankfully, the team was able to top up the car and keep the gearbox operational, all the way to the finish.

Both Meyer Shank Racing and fellow Acura racers Wayne Taylor Racing also had to flush engine oil during the race, due to biofuel used compromising the engine oil in short order. “Their oil was getting diluted by fuel, if I remember correctly, so they had to top off on almost every pit stop,” says Tatarevic. In the case of Wayne Taylor Racing, they actually lost time when they had to fix an oil filler tube that broke during the race. Usually, though, the systems are just fitted as insurance, Tatarevic explains. Most race cars are designed to ideally run for a full race distance without replacing their main fluids.

Indeed, it’s for similar reasons of insurance that Formula 1 teams have fittings that allow air pressure to be topped up at pitstops. Compressed air is used for the pneumatic valve springs in Formula 1 engines, and occasionally teams can have problems with leaks or pressure loss mid-race. Indeed, in the 2023 Bahrain Grand Prix, McLaren’s Lando Norris had to pit a total of six times to recharge his engine’s air system due to an ongoing leak.

 

These rapid-refill systems are primarily seen on high-dollar racecars and motorbikes. However, amateur racers have found great success pursuing the same idea. MotoIQ writer and long-time hero of the site Dave Coleman credited a garden sprayer with winning two championships all the way back in 2010. It all started with his Nissan Sentra SE-R rally car, which had a head problem. The regular loss of coolant saw engine temperatures spiking. Worse, it was difficult and dangerous to try and refill the cooling system at breaks between stages while it was still hot. Opening it under those conditions would see the coolant boiling over and spraying everywhere. Waiting for it to cool wasn’t an option in the limited time available. He needed a way to refill the cooling system while it was still hot and pressurized.The solution was a humble garden sprayer. Coleman realized the radiator cap on the Sentra was built to handle up to 18.5 psi. At pressures above that, the cap opens and blows coolant into the overflow bottle. All he had to do was put coolant into the garden sprayer, charge it above 18.5 psi, and hook it into the still-pressurized cooling system. He decided on air tool fittings, which are able to handle over 100 psi without breaking a sweat.

A quick-release fitting was welded into a piece of pipe and spliced into the top radiator hose, allowing water to be pumped in before the radiator. This allows water pumped in from the sprayer to heat up with the rest of the coolant before reaching the engine, reducing the risk of thermal shock causing damage. On the garden sprayer, a matching fitting and a ball valve were fitted. The sprayer could then be pumped up by hand to around 30 psi or so, hooked up to the fitting on the car, and the ball valve opened. The fluid in the sprayer would then be forced into the cooling system, topping it up. Coolant will flow into the overflow bottle when the system is full. If the initial charge in the garden sprayer doesn’t fill the system enough, a few extra hand pumps generally got the system to full.

The system later served Coleman well as he attempted to win the 2010 24 Hours of LeMons championship with the Frankenmiata and the Eyesore Racing team. In its final race, the car swallowed a full 3 quarts of coolant at every pitstop on its way to second place at the Buttonwillow event. That podium finish was enough to clinch the championship for Eyesore Racing.

ADVERTISEMENT

Fundamentally, it all comes back to that old racing adage: to finish first, first you must finish. Having gear that lets you keep a car full of fluids with a minimum penalty in time spent in the pits can make a big difference in this regard. It’s always going to be of greatest importance in endurance racing, where the hours are long and there’s so much more scope for things to go wrong. In any case, it’s very much a case of preparedness. You’d rather have it and not need it, then need it and not have it. Such a simple thing as a convenient fill port can make the difference between race victories and championships, or lamenting what could have been.

Image credits: Sobek, Lewin Day, Pratt Miller Racing