About 45% of the vehicles that will be sold in the U.S. this year will come with turbochargers, at least 7 million overall. And they’re a great way to balance performance and fuel economy. But turbos do have their drawbacks.
Stomp on the throttle from a dead stop and you may find yourself waiting for a moment before power fully kicks in. This unwelcome “turbo lag” is a result of the way turbochargers work. They depend on a build-up of exhaust gases to spin their turbines. In turn, that compresses the air going into the engine. But, when starting up from a stop when there isn’t much exhaust pressure, it takes time to “spool up” those turbos.
Automakers have tried a variety of different approaches, and achieved varying – if not entirely satisfactory – results. But SRT, the performance arm of Stellantis, thinks it may have a perfect solution. Its prototype eBoost Air system adds an electrically driven compressor that all but instantly delivers a powerful boost to the automaker’s six-cylinder Hurricane engine even as the powertrain’s twin turbos begin spooling up.
From concept to prototype
SRT – which is short for Street and Racing Technology, is the division designed to boost performance for North American Stellantis brands Chrysler, Dodge, Jeep and Ram. It last year got its own team of engineers who broke off from the rest of the Euro-American automaker’s product development operations.
The eBoost Air system is one of their newest projects – and it reveals just how quickly this skunkworks team can operate. The technology was little more than a vague idea seven weeks ago, said Joel Baker, SRT’s vice president of product engineering. This week, the technology is being demonstrated in a running Jeep Grand Cherokee prototype.
What happens next depends upon how well the eBoost system works in real-world testing. But, considering that, of the 16.2 million vehicles sold in the U.S. last year, 45% were turbocharged, a solution to turbo lag could prove to be a popular feature – especially among performance drivers. “Enthusiasts aren’t interested in technology for the sake of technology,” said Tim Kuniskis, head of Stellantis’s American brands. “But when technology improves performance with no downside, they’re all in.”
How does eBoost Air work
With a conventional turbocharged engine, air is sucked into the powertrain and then directed into turbos – of which there can be one or more. In the case of the Stellantis Hurricane engine there are two. Turbochargers are, at their most basic, compressors that spin up to increase the amount of air forced into an engine’s cylinders. The problem is that they’re normally powered by the gases coming out of the engine’s exhaust. And, at low speeds, like when the vehicle is starting out from a stoplight, there’s not much flowing out of the exhaust. So the turbos need time to build up speed and increase compression.
With eBoost a butterfly valve redirects the flow of intake air to a newly installed compressor positioned upstream of the turbos. Since it’s electrically powered it doesn’t depend upon exhaust gases and can add as much as 10 psi of boost in as little as 650 milliseconds. That’s enough to deliver 90% of a Hurricane engine’s torque, said Baker, calling it “a very simple, elegant solution.”
Once the engine’s turbos are spooled up and delivering full boost, the butterfly valve closes and the eBoost compressor goes into idle mode. But it can fire up again, all but instantly, whenever another quick shot of air is needed. That can happen whenever a driver slams the throttle, whether at a stoplight or when cruising down a highway.
What now?
SRT engineers were able to take the eBoost Air system from concept to prototype by using the latest in manufacturing technology, primarily 3D, or additive, prototyping. This allowed them to rapidly transform digital renderings of key parts – such as the exterior box and the compressor fan blades – into hard parts. Rapid prototyping can work with a variety of composites and metals.
The question is what happens next? In the coming months, Baker explained, SRT will test out the eBoost Air system both in the lab and on street and track courses to see not only how well it performs but whether it can hold up in aggressive driving conditions. Another challenge: determining how to provide power to the electric boost system. The initial prototype draws current from its own small battery connected to the Jeep’s alternator.
“We’re (also) studying the customer,” he added, to see if the benefits would justify the potential cost were it to go into production.
Production plans
“There’s no plans…for production,” he added. “Not yet.” But Baker’s boss, SRT chief Tom Sacoman, said there are clear opportunities for a solution like eBoost Air in the automotive performance market.
The good news, he said, is that the technology could be used on essentially any turbocharged powertrain, including the six-cylinder Hurricane engine used in a variety of Stellantis products, as well as the smaller Hurricane four-cylinder package.
Among the approaches SRT and the Stellantis brands will consider is the possibility of offering eBoost Air as a production option or as an aftermarket feature that could be sold through the automaker’s Direct Connect arm. Any final production decision would depend not only on whether the technology proves as effective as imagined but whether it is durable enough to last the life of an engine. There are also questions about the system’s impact on emissions and fuel economy to be considered.
As for cost? No one at SRT is ready to discuss that topic but Sam Abuelsamid, lead analyst with Telemetry Research and a former auto engineer, said it won’t come cheap. That could mean as much as $10,000 in a package that would include even larger and more powerful turbochargers.
