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"dalek" writes:

As recently as less than a year ago, NASCAR stated it planned to implement hybrid engines in 2024 [forbes.com]. Although rumors indicate that this timeline may have changed, IndyCar has successfully tested the hybrid engines it will begin using in 2024 [indycar.com], and NASCAR probably won't be too far behind. A hybrid engine simply means that it's powered from more than one source of energy, usually a combination of gasoline and electricity.

Formula 1 began using hybrid power units in 2014, which are powered both with gasoline and electric power, and use fuel more efficiently than cars without hybrid components. F1's experiences with hybrid power units and their mistakes could provide some guidance for how other racing series might switch to hybrid engines. Chain Bear provides an excellent discussion of how F1 power units work [youtube.com]. They still contain an internal combustion engine, but the efficiency is increased and energy is recovered in a few ways.

F1 engines are turbocharged, meaning that energy from exhaust getting expelled is used for forced induction. This means that the air in the intake is compressed, and the combustion is more efficient than in a naturally aspirated engine. However, the turbo requires a high exhaust pressure, meaning that there is a lag between when the car accelerates and when the turbo can operate efficiently, which is known as turbo lag. One of the hybrid components is the MGU-K (K for kinetic energy), which captures energy through regenerative braking. Instead of energy being lost as heat during braking, the energy is used to charge the energy store, which is usually a capacitor or a battery. Another component is the MGU-H (H is for heat), which captures energy from the exhaust as it goes through the turbo, and can charge the energy store. The MGU-H can also put energy into the turbo during acceleration to avoid turbo lag.

The last time F1 ran a points race on a true oval track was the 1960 Indianapolis 500 [wikipedia.org], only going to street circuits and road courses since then. These tracks usually have hard braking zones, providing frequent opportunities to capture energy during braking. Even without the MGU-H, F1 cars have many opportunities to capture energy during a lap.

NASCAR runs a few races each year on road courses, and some short ovals like Martinsville [wikipedia.org] and Gateway [wikipedia.org] also have hard braking zones. This is a combination of high speeds on relatively long straights and much slower speeds through corners with small radii and low banking. Regenerative braking would work well at these tracks. However, most other oval tracks do not require nearly as hard of braking, limiting the opportunity to capture energy through regenerative braking. For hybrid engines to have an effect without hard braking zones, energy will need to be captured in other ways these tracks. Despite the lack of a turbo, the obvious solution would seem to be capturing energy from exhaust heat while on throttle.

The problem with capturing energy from exhaust heat is that the MGU-H component of F1 power units is prohibitively expensive and complex [youtube.com], leading to them being removed in rules for 2026. This will result in decreased thermal efficiency [youtube.com], though F1 is planning to use fully sustainable fuels. NASCAR has also sought to cut costs for teams, meaning that adding a component like an MGU-H to capture energy while on throttle seems unlikely.

At least in the short term, racing series that have long races are likely to use hybrid engines instead of going fully electric. If nothing else, this will attract more OEMs to the sport. NASCAR currently has only three OEMs, which are Ford, Chevrolet, and Toyota. Despite frequent rumors of Dodge returning, this has yet to occur, and NASCAR has also failed to attract other new OEMs. It is also likely that hybrid engines would allow for increased overall power despite the internal combustion engine currently being limited to 670 horsepower, and more power may well improve the quality of racing on some tracks. Switching to hybrid engines is likely to benefit both NASCAR teams and fans, and would be a step closer to once again racing true stock cars. However, it's much less obvious how to go about capturing energy on oval tracks where there is little braking, meaning that hybrid engines might not make a meaningful impact at a large percentage of NASCAR tracks.

Given the cost and technical limitations, how can NASCAR actually make hybrid engines work and have a meaningful impact on most of their tracks? It might not be practical to boost power through hybrid engines on NASCAR's fastest superspeedways, where engine power is greatly restricted to keep speeds down and improve safety. But how can NASCAR make hybrid engines work for the other 30-32 races each year?

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