The mindblowing Toyota Le Mans engine that matched F1 – the TS040

Racing tech

When WEC introduced new engine rules Toyota decided to buck the trend – and created one of the most incredible power units motor sport has ever seen

Toyota Le Mans 2014

Toyota's TS040 brought set new standards for efficiency eked out of a naturally aspirated engine

DPPI

135 years of innovation: making of the internal combustion engine, Part 7

2014 ushered in a new era of racing with both Formula 1 and WEC (World Endurance Championship) introducing fuel flow limiting regulations, reflecting the desires of manufacturers to burnish their sustainability credentials. The result has been a revolution in race engine design, with engineers pushing the bounds of thermal efficiency to unprecedented levels.

In F1, the regulations were and still are very prescriptive, placing limits on most areas of engine architecture and the types of energy recovery systems permitted. This was not the case in the WEC. The rules specified that works LMP1 entries had to run hybrid systems, with up to two permitted, but engine choice was effectively free. The different powertrains were balanced by the EOT (Equivalence of Technology). Put simply (it was far from simple), this allowed for different engine configurations, four, six, eight or even 12-cylinder, with different fuel types and hybrid system outputs, to be competitive against each other through differing fuel flow and fuel load allowances.

F1 and the WEC started a trend towards downsizing; the former went to 1600cc, turbocharged engines and in the WEC, Audi retained redesigned its (already very efficient) diesel V6 while Porsche entered with a compact, V4 gasoline engine, coupled to a thermal energy recovery system. Toyota bucked this trend, at least initially. Its answer to the imposition of fuel flow limits was to refine its existing V8, first introduced with the TS030 in 2012, into what may well be the most efficient naturally aspirated engine ever created.

Toyota TS040 engine

Toyota increased the engine size from 3.4 to 3.7-litres

Lawrence Butcher/Toyota

Bored out to 3.7-litres from 3.4-litres for the 2014 season, the Toyota V8 was the epitome of a traditional race engine; naturally aspirated, 90-degree bank angle, four valves per cylinder, it even relied on traditional port injection. However, under the surface, every aspect of the engine was refined to push its efficiency.

When Toyota decided to enter the WEC for the 2012 season, its main competition was to be Audi, following the departure of Peugeot in 2011. This meant it was up against a highly refined TDI powertrain, coupled with a front hybrid motor and flywheel-based energy store. Though the TDI engines were efficient and powerful, they were heavy and in order to compete, Toyota knew had to bring a race car that could counter the strengths of the then all conquering diesels.

Toyota’s approach was to build the lightest gasoline engine it could, with the greatest power and thermal efficiency possible, a philosophy it continued with the rule changes in 2014. Following the engine’s retirement at the end of 2015, Toyota’s Hisatake Murata, who was in charge of its development outlined: “We still wanted a light weight V8 engine, making high power, with good efficiency, coupled with a powerful hybrid system.”

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But how to get the efficiency needed to match the fuel flow rules?

“The direction has always been to increase compression ratio, while reducing mechanical friction and further reducing weight,” he explained.

The subject of compression ratio is a particularly interesting one. In its quest to drive efficiency, Toyota ended up running in the region of 17:1 compression ratio, an exceptionally high figure for any engine, especially one running spec fuel in an endurance racing environment. As well as pushing the compression ratio ever higher to increase power, Toyota also had to improve the combustion efficiency, allowing it to run the engine increasingly lean. With the latest generation of direct injected, turbocharged engines, this is a somewhat easier (relatively speaking) task than with port injection.

The injection system on the V8 was simple yet elegant in its execution. It used eight solenoid injectors, firing down the individual throttle runners into each inlet port. The injectors were mounted in bosses in the inlet tract, above the throttle valves (rollers, rather than butterflies, minimising flow restriction), with the nozzles angled relative to the inlet path. Very similar in concept to most road car port injection setups.

Toyota 2014 Le Mans car refuelling

Rule changes in WEC on fuel-flow forced a design rethink

DPPI

However, the engine was always running on the edge of knock and to ensure it remained reliable, Toyota needed a solution to keep an eye on the combustion. This came in the form of real-time combustion pressure measurement, something that had never been considered for use beyond the dyno test cell before, let alone in endurance racing.

“We use two systems, so knock control by sensing vibration, plus combustion pressure sensors. We developed a combustion sensor with a manufacturer to use during races,” revealed Murata. “Combustion pressure sensing is very useful for many aspects of the engine, not just knock, but also for tuning the spark timing and other things. However, during the early stages, we had a lot of trouble with combustion sensors, but we can now make a very tough combustions sensor [which can last a Le Mans race distance].”

Of course, the engine cannot be considered in isolation, as it was used in conjunction with a powerful hybrid system. In its initial TS030 guise, this consisted of a rear mounted hybrid motor, and later, with the arrival of the TS040, both rear and front motors, giving a total power output in excess of 400bhp. Coupled with a super capacitor system, the electric motors endowed the Toyota’s with ferocious pace and the combined power of the hybrid and engine was over 1000bhp.

In 2014, the engine proved to be a competitive unit, but by 2015, Porsche was getting into its stride with development of its 919, and Toyota was lagging. Ultimately, it was the drive towards ever higher hybrid system power that killed off the V8. With the regulations forcing a fuel flow cut for each step up the hybrid scale, coupled with the ACO removing a further 10MJ of fuel energy per lap (at Le Mans) for 2016, the use of a traditional port injected engine was no longer a competitive option.

Toyota Le Mans 2014

Despite its impressive efforts with the power unit, third was the best Toyota could manage at La Sarthe in 2014

Toyota

“It is a balance, with every year’s regulation changes, we are forced leaner and leaner,” recalled Murata. Ultimately, it was forced to move to a twin-turbocharged V6 configuration in 2016 with the TS050 (the shift was originally planned for 2017) which would go on to secure its maiden Le Mans win in 2018. However, the V8 was and remains, a truly remarkable racing engine.

Just how far the V8 concept had been pushed only became apparent once it had been retired. When asked what the thermal efficiency of the engine was, Murata stated in 2016. “It was over 40%.” This was a truly spectacular figure, particularly when one considers that the first generation (2014) 1600cc, V6 Formula One engines were working at around 40%, with all of the benefits of forced induction, direct injection, turbocharging and speed control of the turbocharger via the MGU-H. That Toyota was able to match this figure with what was in essence, a traditional engine, not too dissimilar in its basic makeup than the DFV of 40-years earlier, was a staggering achievement.

135 years of innovation: making of the internal combustion engine