BMW i8 Engine: Not All Hybrids Are Created Equal 

Michael Massey
Apr 14, 2021

BMW’s i8 supercar may have been the most innovative plug-in in the industry.

2018 BMW i8 Roadster-Photo by BMW

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.

2014 BMW i8-Photo by BMW

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). 

2016 BMW i8-Photo by BMW

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. 

2018 BMW i8 Roadster-Photo by BMW

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. 

2018 BMW i8 Roadster-Photo by BMW

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

Frequently Asked Questions

Apr 23, 2022

What kind of engine does a BMW i8 have?

The BMW i8 comes with a 1.5L 3 cylinder engine in the car that makes 228 horsepower and 236 pound-feet of torque. This is combined with a hybrid motor that makes 141 horsepower and 184 pound-feet of torque. This leads to a combined output of 369 horsepower and 420 pound-feet of torque. This is a decent amount of power in a car that only weighs 3,394 pounds and allows it to go from 0 to 60m miles per hour in 4.5 seconds.

The engine in the BMW i8 is a bit of a controversial thing. The styling of the i8 is extremely bold and aggressive so many people had hopes that it would have one of the V8 engines that are found across BMW's M lineup. The i8 is more of a vision of the future from BMW of how there can be sporty hybrids on the market.

The i8 has a rated fuel economy of 76 MPGe when you combine the electric and gasoline motor. It may not have the power to match the styling, but it does excel in how economical it is to drive.

Is an i8 a supercar?

Whether or not the BMW i8 is a supercar is something that has been debated since it first came out. The styling of both the coupe and roadster scream supercar with the low lines, the aggressive front and rear, and the doors that lift up like many of the other supercars on the market.

Where the BMW i8 fails to be a supercar is in the engine and performance. When you look at an i8 you expect it to make a lot of noise and be fast. Unfortunately, the i8 really cannot keep up with the modern supercar offerings from the other big brands like Ferrari, Lamborghini, and McLaren in terms of performance. While those brands shoot for 0 to 60 times in less than 3 seconds the i8 does the sprint slower than an M3.

Overall the i8 is not a supercar in my opinion. It is a demonstration by BMW's technical group about how they can make a hybrid car that looks good and is enjoyable to drive.

Is the BMW i8 sound fake?

The noise in a BMW i8 is fake and pumped out via speakers that are in and outside of the car. The i8 does not have a loud engine or a large exhaust on it at all. The 1.5L 3 cylinder engine is as quiet as most of the other hybrid vehicles on the road.

BMW knew that with the aggressive sporty styling of the i8 they needed to improve its sound. So much of the driving experience with a sports car comes from the sound that it makes when you step on the gas. The sound of the engine revving up can lead to an emotional connection with a car, so BMW used engine sounds from some of their other sports cars to make a sound profile to play with the i8 when the engine is revved.

The i8 is a unique take on a sports car, but they never took off well in the supercar community because they were just a little too slow and didn't fit in with the competition.

Owner Reviews

accountCircle GZ on April 28, 2021
Pleasure to drive the 2016 i8
I leased for 2 years 2016 model and it's amazing car to drive everyday, it's efficient for city and regular driving and surprisingly fast for 1.5L 3 cylinder car. Real pleasure to drive, I drove it from LA to NYC in less then 3 days and it was amazing experience. During this 2 years all the maintenance was done and covered by BMW and I didn't have to pay a cent, as for reliability wise I think it's very reliable only problem I experienced was with low coolant error which was fixed by dealer and all it was a bubble in the hose even with that problem car never stopped working and never overheated, drove to the dealer without problem. I would highly recommend this car and I would buy it again for sure!
accountCircle Hung N on June 5, 2021
2016 BMW i8 pros of a fast and beautiful designs
BMW knows a thing or two about building cars that combine good looks and performance. With the plug-in hybrid 2016 BMW i8, stunning eco-friendly technology has been added to the mix. Able to sprint to 60 mph in just 4.5 seconds, the exotic i8 also boasts 15 miles of electric-only range and a total range of 330 miles on combined electric and gasoline power. In other words, the i8 is a great fit for just about any combination of driving demands.
accountCircle Taylor H on May 17, 2021
My 2015 BMW i8 is decent after plenty of maintenance.
I bought it used and it runs well but only after lots of maintenance. Last year a new engine was put in my check engine light is still on to this day but it seems to be running just fine. Sometimes the steering wheel is hard to turn. Inside is pretty spacious which you would not think when you look at it from the outside. I also like my screen it is nice and large for me to see things like directions.
accountCircle Harold G on May 10, 2021
2014 BMW i8 2DR CPE is the best.
The i8 looks amazingly radical. Minimal-drag shape-work for efficiency is artfully combined with flourishes of crowd-pleasing flamboyance. The powertrain and structure are just as unorthodox and brave as the styling. A small mid-mounted 231bhp petrol engine drives the rear wheels through a six-speed automatic gearbox, while a biggish 143bhp electric motor drives the front wheels.
accountCircle Anton C on April 25, 2021
2016 BMW i8 is a very nice luxury sports car.
There are no issues with my vehicle. It performs very well and is very nice. The interior is sleek and is comfortable, as well as modern. The dash is easy to navigate. The car itself drives very well and is very fun to ride as it is sort of seen as a sports car. One downside is that you get a lot of attention which can be annoying.
accountCircle Steven C on April 26, 2021
2017 BMW i8 uses the highest technology in vehicles.
My vehicle is the best purchase that I have made since it has multiple benefits and I have had no problem. It has excellent performance, consumes little gasoline, uses the highest technology in vehicles, is extremely comfortable and spacious for me and my family, has a high security system and adapts to any style.
accountCircle Nora L on June 10, 2021
2017 BMW i8 review. What you want to know.
First off, I love my car! It is my baby. The performance is really good, up to 100 mph. Rarely ever problems, but when there are, it has something to do with the engine giving out. It is very comfortable, I sleep in my car sometimes when I have really long shifts. And the features of the car are very modern.
accountCircle Stacy C on April 22, 2021
2014 BMW i8. A really nice car.
Very reliable. Drives very smoothly. Gets me where I need to go. The vehicle is very great. I like driving around neighborhoods with the windows down the performance is very great. It's very comfortable the seats are very soft. I love the features the mirrors and windshield wipers work great.
accountCircle Zach S on May 4, 2021
Turbocharged hybrid engine. 2016 BMW i8
Fast, sleek and affordable. I drive the car every day and it's my daily. I recommend you buy this vehicle. Is a hybrid and it is turbocharged. It's faster than a good majority of sports cars. If you are looking for a fun weekend cruiser this is definitely the choice you may want to consider.
accountCircle Trey L on May 16, 2021
Review and information for 2019 BMW i8.
The car’s performance is great, it is very comfortable, seats are soft and cushioned, runs very well on the road. It is an amazing car. But the air conditioning sometimes does not work for some reason, it is cuts off and on. I have already got it checked out but still the same problem.
accountCircle Jayla H on April 30, 2021
2019 BMW i8 Coupe. You can customize your BMW i8 online and get a good deal.
My vehicle the BMW i8 EPA fuel economy ratings are impressive. It runs smooth and the seating is very comfortable. It's designed for a two seater. There is barely any storage to fit groceries and stuff in the trunk. It is not the fastest car. My i8 can go up to 60 mph in 4.1 seconds.
accountCircle Jacky B on May 30, 2021
2016 BMW i8, I energy efficient exotic sports car.
Highs: outside-the-box design, comfortable enough for daily use, feels light and quick. Lows: the opposite of practical, not as quick as it looks, too much plastic bits in the interior. Verdict the i8 is a flashy and fuel-efficient alternative to legitimately exotic sports cars.
accountCircle Shane H on May 14, 2021
Excellent Ride With A Couple Setbacks. 2017 BMW i8 Coupe
It's a very smooth ride. Comfortable and spacious seating. LOVE the radio! At the same time though, there's often recalls issued for the vehicle and the occasional engine issues that require it being taken in for repair, but other than that it's a great car!
accountCircle Kristy U on May 24, 2021
Love my 2014 BMW i8! Fun and exciting car!
Excellent performance, smooth ride, fast, comfortable. Have no problems or concerns. I absolutely love my BMW. Great gas mileage! Fun to drive. I would definitely recommend this car to anyone looking to buy one. My next car will be a BMW! Fun, exciting car.
accountCircle Owen T on May 20, 2021
I love the speed of the 2015 BMW i8 and how it feels and looks inside and outside.
My car is a great car. The interior is very nice and comfortable and the exterior looks very smooth and nice. Very nice speed and acceleration. The car drives very smoothly and is a very wonderful car. I highly recommend it if you have the money to buy it!
accountCircle Gabe S on May 27, 2021
What separates the 2017 BMW i8 from other cars.
Cockpit control. Everything a driver desires is within your reach. Ergonomically oriented tactile controls, plus a standard 8.8" touchscreen display and the intuitive BMW idrive system, place you in complete control of your high-performance plug-in hybrid.
accountCircle Pete W on May 24, 2021
Everybody should know that 2015 BMW i8 car goes really fast ad does not take too much gas.
My vehicle gets good mileage and I do not have spend a lot of money on gas. I am a fan of the shape of the car and how it never gets too hot. I have no dislikes about my vehicle
accountCircle Christopher B on June 2, 2021
The 2017 BMW i8 best looking car they made.
It rides smooth and its fast also I love the doors the seats are comfortable. The design is slick. The only problem is the car is low so it makes it hard to get out of it.
accountCircle Seth S on May 12, 2021
2016 BMW i8 is electric and it doesn't need gas.
It is my dream car and it's very nice. It is very fast and comfortable. And it looks awesome. It is the future of all cars and BMW has done a very good job.
accountCircle Quan J on May 19, 2021
2017 BMW i8 is fast.
The car is really fast but it doesn't have a lot of space. The model is really good and it is a really nice car.
accountCircle Ariana K on June 4, 2021
2016 BMW i8 has been dependable and efficient.
I like the feel of my vehicle and the drive is smooth. The AC is really cool and the brakes are smooth.
accountCircle Me B on May 30, 2021
It is great. Love my 2015 BMW i8.
Dislike where the front cupholders are located. Wish the battery held a longer charge for more miles.
accountCircle Edwin C on May 25, 2021
2016 BMW i8 goes super fast. You need to be extra careful when driving.
I love the car. It looks very sporty. It goes really fast too. I don't like the colors though.
accountCircle Christopher L on May 14, 2021
The BMW i8 2017 in one of the best cars ever.
I have a BMW i8, it is an awesome car. It has an awesome engine, it has never let me down.
accountCircle Joe P on April 16, 2021
Fast acceleration in the 2016 i8
It's really a nice car for an affordable price.
avatar Michael Massey
Michael Massey is a Los Angeles-based automotive writer who has been working in the auto industry since 2014. He is a former member of the Content Team of Edmunds, where he got to drive nearly 300 vehicles in one year as a part of his job. Additionally, He was an Auto Damage Adjuster with Geico, which included over two months of intense training that teaches how a car is put together and the specific functions of everything from the suspension to engine components.
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