We love to geek out on new engine technology, no doubt about it. But, is an inline-six worthy of our attention? What if it’s a V8 killing, 500-hp twin-turbo inline-six? Stellantis’ all-new Hurricane I6 may sound like it was built in the 1950s. However, the 3.0L twin-turbo, inline six-cylinder engine was just announced last week to meet its broader mission of reaching net-zero carbon emissions by 2038 (part of its Dare Forward 2030 strategic plan).
We have to give kudos to Stellantis for even developing an internal combustion engine in this environment where most OEMs are focused on EVs. The company is hedging that the U.S. market is not done with ICE yet (although Europe is another story). The OEM notes that it is committed to electrifying its lineup – to at least 50-percent by 2030 – that leaves the other half for those who still want internal combustion.
According to Micky Bly, Stellantis’ head of propulsion systems, the Hurricane will play a key role in its portfolio for years to come. “The Hurricane twin-turbo is a no-compromise engine that delivers better fuel economy and an important reduction in greenhouse gases without asking our customers to give up performance.”
The I6 engine configuration has been immortalized in the performance arena through such legendary platforms as the Toyota 2JZ, Nissan RB26DETT, and BMW N55/S55. And who can forget Chrysler’s long history with straight-six, from the Chrysler slant six to the AMC-based 4.0L used in Jeeps for decades?
There are some advantages to an inline-six over V configurations. First off, it is naturally a smooth runner due to the balanced cylinders and firing order. It is essentially two 3-cylinder engines mirroring each other. The inherent balance allows for a crankshaft free of counterweights. And they are torque monsters (many are oversquare) with good low to mid-range power, where 90 percent of street driving is performed. The Jeep 4.0L put out more torque than some larger-displacement counterparts.
The downfall of the I6 configuration was mainly due to packaging. They are tall and long and not easy to fit into compact applications. However, this won’t be an issue for the Hurricane since it looks like it will be used in larger SUVs and trucks.
The Hurricane is based on the current 2.0L turbocharged 4-cylinder with the same bore, stroke, and cylinder spacing. It delivers better fuel economy and fewer emissions than larger engines and makes more horsepower and torque than many naturally aspirated V8s and boosted sixes today. The engine will be offered in standard and performance variants. A third variant, dubbed the Tornado, is believed to be making its debut later this year.
The standard output (SO) version is tuned for fuel economy and uses a cooled exhaust gas circulation (EGR) system. It makes more than 400-hp and 450-lb.ft. of torque, even being the “standard output” model. In contrast, the high output (HO) version makes more than 500-hp and 475 lb.-ft. and will have increased fuel economy over a V8 during heavy usage such as towing.
The twin-turbo Hurricane has some bonafide muscle, but will it overtake the Hemi? So far, there’s been no word about dropping the V8s, but Stellantis says the Hurricane is the future, for whatever that’s worth.
The Hurricane has a broad, flat torque band and maintains more than 90-percent of its peak torque from 2,350 rpm to the redline. There are rumors that the Grand Cherokee will be the first to feature the engine, albeit at a $2,000 premium over the Hemi. The TTI6 will debut in dealerships sometime later this year.
A cast-aluminum block with deep skirts and a structural aluminum alloy oil pan encase a forged crankshaft and forged connecting rods secured with cross-bolted main caps. The blocks are pretty stout from the factory as they are deck-plate honed for optimum cylinder bores (straight and round), which also helps improve fuel efficiency.
There’s some pretty cool technology employed on the Hurricane that we haven’t seen before in a mass-production engine, including low-inertia, high-flow turbochargers that feed three cylinders each for faster throttle response.
Then there’s the low friction Plasma Transfer Wire Arc (PTWA) cylinder coating in the bores to improve heat transfer by allowing more aluminum around the cylinders than traditional iron liners. The PTWA coating is ultra-thin compared to a cast iron liner and has ten times the wear resistance.
Fuel is fed to the cylinders via high-pressure (5,075 psi/350 bar) direct fuel injectors with pumps actuated by a chain-driven shaft. The exhaust manifolds are integrated into the cylinder head and are water-cooled. The oil pump has variable displacement output and can adjust scavenging based on demand. In other words, there’s some cool s**t in these engines.
The engine-mounted water-to-air charge air cooler reduces the air temperature before entering the intake manifold. This allows more performance via advanced ignition timing and helps manage in-cylinder temperatures. It also uses an electric pump to circulate coolant after the engine is shut down for increased durability.
The Hurricane employs different boost strategies, depending on the version. The SO delivers a peak boost of 22 psi, while the HO turbos pump 26 psi of peak boost. The HO uses oil-jet cooled, forged aluminum pistons with an anodized top ring land and a diamond-like coating (DLC) on the pins to reduce friction. The compression ratio is 9.5:1 on the HO with 91 octane fuel.
The PTWA coating adopted from the aerospace industry basically melts a steel alloy wire at 4,150 degrees Fahrenheit, producing microscopic particles that are sprayed onto the cylinder walls at high velocity. These fine particles “splat-cool,” forming a physical bond to the aluminum bore. This coating process leaves more aluminum between the cylinders, enabling better heat transfer and engine cooling. This allows for more air-fuel mixture adjustment and the ignition timing advance over a wide operating range.
The bottom line is there’s some cool tech found in these engines, but it is a pity that we are likely seeing an early death knell of the Hemi as Stellantis adjusts their lineup to current emission and fuel-saving standards. But time will tell if there’s a new lifeline for V8s down the road.