BMW’s i8 supercar may have been the most innovative plug-in in the industry.
Plug-in hybrids are becoming increasingly popular, and full-electric, self-driving vehicles may take over the world one day. And within all of this phenomenal innovation that is unfolding before the word’s eyes, there is something special that catches your eye as it rolls past, and you lose yourself in the Bavarian beauty known as the BMW i8. It’s a sporty, powerful vehicle with a powertrain and structure that Top Gear calls “just as unorthodox and brave as the styling.”
BMW unveiled the i8 at the 2013 Frankfurt Motor Show, and U.S. car. buyers were able to get behind the wheel of their own i8 the following year. BMW released an i8 roadster in 2018 before announcing two years later that production on the vehicle would end in June 2020.
Manufacturing a BMW i8 is in itself a feat of modern automotive construction, owing to the vehicle concept, drive technology, and unique mix of carbon-fiber-reinforced plastic, and aluminum.
“Yet again, we have proved our ability to meet the highly discerning standards and personal specifications of our customers with unique solutions and unparalleled skill,” said BMW Plant Director Hans-Peter Kemser at the 2020 send-off of the company’s final 18 BMW i8 Roadsters at BMW’s Leipzig plant. “For BMW i8 production to end with a finale like this is something we can all be very proud of.”
Here, we review the fascinating history of this innovative but short-lived supercar and dive into its interesting hybrid powertrain.
BMW i8 Engine: A Brief History
First and foremost, the flash of the BMW i8 isn’t all talk. It’s powered by a 1.5L 3-cylinder turbo engine that’s good for 228 horsepower and is paired with a six-speed automatic AWTF-80 SC transmission made by Aisin Seiki.
Then, paired with the gasoline engine over the front axle is a hybrid synchronous motor that spins the front wheels for an additional 129 horsepower. With a combined 357 horsepower, the i8 can accelerate from 0-60 in just over four seconds. It is a sportscar –– there’s no denying that.
BMW focused on the importance of aluminum panels and lower drag coefficients to make the i8 a success. In all-electric mode, the i8 can travel about 15 miles depending on your driving habits, maxing out at a top speed of 75 mph. With the two drivetrains working together, the top speed is limited to 155 mph electronically. This all adds up to an impressive 76 MPGe (an EPA equivalent to mpg).
Where Did it Come From?
So, you have performance, luxury (it is a BMW after all), futuristic design, and economic fuel consumption, but where did the i8 engine come from? While the two parts of the powertrain described above work well together, perfecting the design took time and perseverance. German engineers at BMW have developed a list of inline engines, including 3, 4, and 6 cylinders, including the 3-cylinder engine first used in the BMW i8.
These engines, dubbed “B38,” were based on 500 cc per cylinder –– hence 1.5L or 1500 cc. The B38K15T0 engine is transversely mounted right behind the driver and intended to focus on fuel consumption and performance.
For five consecutive years, BMW won the International Engine of the Year award for its hybrid technology in the i8, and by 2018, had won a total of 69 class awards. The pedigree that BMW draws from is nothing short of prestigious, and this engine is no exception.
How Does it Work?
BMW is no stranger to innovative engine technology. It’s a common practice for manufacturers to steadily improve how their vehicles function. With the B38 engine platform, BMW maintained a greener approach. With any direct injection engine, a common problem is black exhaust soot that can eventually cake up around the rear exhaust pipe. This, largely, has to do with the positioning of the fuel injectors in the engine.
With a lot of BMW direct injection engines, you’ll find the injectors in different places for different reasons. The 2007 BMW 335i, for example, has its injectors installed near the spark plugs in a performance-optimum place in the combustion chamber.
However, the more current N20 engine (a four-cylinder twin-scroll turbo) has its injectors placed horizontally between the outside edges of the intake valves, adding a bit of performance and economy. The B38 engine in the i8 has high-pressure vertically placed injectors in the center, which, is intended for something completely different.
BMW’s powertrain integration manager, Heidelinde Holzer, points out that “vertical injectors better mix fuel and air, leading to reduced soot formation.” Reducing soot at the inception of spark not only reduces soot in the exhaust but also provides a more efficient combustion cycle.
Additionally, the B38K15T0 in the i8 (and all of the B38 series) uses an aluminum block and head that’s 20 pounds lighter than the current N20 engine, increasing both efficiency and performance. This, coupled with other focused weight savings on the i8, meant that less could truly be more.
What’s more, BMW’s aluminum blocks are much cleaner to dispose of than earlier magnesium blocks. In the end, the luxury automaker’s ultimate goal was to produce a cross-platform engine line that was both cost-effective, reliable, and quick to manufacture.
In the B38 engine’s case, both the gasoline and diesel variants share 40% of their components. The three-cylinder in the i8 has the same valves and pistons as its two older siblings, but performance versions will have more performance-focused internals.
BMW i8 Engine’s Lithium-ion Battery
While BMW has developed and produced this new set of engines, it’s important to remember the other portion of this incredible workhorse. Mated with the B38 3 cylinder is a 98-kilowatt electric motor powered by a 7.1 kWh lithium-ion battery. With a maximum range of 15 miles in all-electric and 330 miles for the whole system, it certainly is a green sports car.
What’s more, when driving at cruising speeds, the regenerative braking will recharge the battery for later use. If you run out of juice, simply plug it into a regular 120V wall socket. You can also purchase BMW’s “Wallbox” home charging system for around $1,250. Another bonus for going green is that electric power is not only immediate but maximum, producing high amounts of torque.
Even the best gasoline engines have difficulty matching the ability of an electric motor. It doesn’t need multiple gears or a smooth shift –– it just needs your foot mashing the accelerator for full power. With the battery mounted in the center of the vehicle (where a drive shaft channel would normally be), it replaces spinning metal bits with a low, weighted center of gravity. Making the i8 even more dynamic when driving.
This is why the electric motor makes such a good team with BMW’s new B38 engine. While the gasoline engine is turning the back wheels, your electric motor is turning the front wheels, giving you standard all-wheel-drive (AWD). These components work together to methodically and effectively put power to the wheels and deliver a great driving experience.
Final Thoughts
BMW has done a lot of things right since it built airplane engines for the Germain army during World War I. Their M-Series of vehicles is synonymous with speed and aggressive power. But what they’ve done with the i8 is something considerably more elegant. They’ve packed a lot of technology into a small space, required respectable power from a small engine, and crammed the future of renewable energy.
All of this into a vehicle straight from a fictional story about the extreme future. Only they’ve done it in a time where we can see it with our own eyes.
The BMW i8 engine shouldn’t surprise anyone, but rather stir up the wonder about what’s possible and what we likely will see more of as technology progresses. We love the direction BMW went with the i8 engine, and we’d be hard-pressed to find a more cohesive green sports car.
Photos: BMW