Three years after its introduction in Europe, the "hot" Abarth version of Fiat's 500 is launching in North America. And with it comes a MultiAir cylinder head, a unique exhaust system, and engine changes aimed at increasing durability and efficiency.
"North America is the first application for the MultiAir turbocharged engine in a Fiat 500 Abarth," Michael Vincent, Platform Manager for Chrysler Group's FIRE (Fully Integrated Robotized Engine) engine family, said in an interview with AEI during the car's recent U.S. media introduction.
Abarth is Fiat's in-house performance tuning group. Its engineers first applied their powertrain and chassis magic to the new-generation Cinquecento (500) for the 2009 model year. (See http://www.sae.org/mags/aei/4603.) Although the earlier Abarth 500 also used a FIRE-based turbocharged 1.4-L engine with dual intercoolers, it did not employ the MultiAir head.
The 2012 version produces a claimed 160 hp (119 kW) at 5500 rpm and 170 lb·ft (230 N·m) between 2600 to 4100 rpm. The ratings, which are certified in accordance with SAE J1349, represent a 59% increase in power and 70% increase in torque over the 500's naturally aspirated MultiAir base engine.
Fiat's proprietary MultiAir cylinder head features continuously variable intake valve timing and lift control using an electro-hydraulic solenoid, rather than fixed camshaft lobes. The system improves torque and efficiency by significantly reducing pumping losses, using the intake valves to throttle the engine, Vincent explained.
The ability to control individual cylinders gives MultiAir greater flexibility than some competitor systems. (See also http://www.sae.org/mags/aei/8703.)
Creating a "wicked" exhaust note
Beyond the addition of MultiAir technology, the "changes to the engine were regulatory-driven—such as meeting U.S. requirements for onboard diagnostics (OBD II)—and market-driven," said Vincent.
Synthetic 5W-40 oil is recommended for the turbocharged engine, but engineers anticipate that not all vehicle owners will adhere to the suggested guidelines.
"We changed the specification of the piston design by going with an anodized piston top-land and ring groove to make the piston more robust against various types of oils," he noted.
Drivers of other vehicles who end up behind a North American-market 500 Abarth on the open road will hear a unique exhaust signature that is different from that of the European-spec model.
"Sound is very important to the DNA of the car, as [brand founder] Karl Abarth got his start doing custom exhausts," Daniel Fry, Vehicle Development Lead, told AEI. He said the goal was to make the North American version "a little more wicked," so engineers used analytical modeling to help select the appropriate acoustic profile for the exhaust system.
Prototype exhaust parts were built and sound-tested. And, technical specialists evaluated various exhaust tones, including those of the Dodge Viper and Neon SRT.
"We probably tried 12 to 14 configurations for the muffler on the car, but what we went with is no muffler at all. It's an enlarged pipe diameter, even in comparison to Europe's Fiat 500 Abarth," said Fry. Over the length of the car, the cold-end exhaust system bends 10 times and changes its diameter five times, according to Fry.
The North American-sold Fiat 500 Abarth uses the same muffler housing as its European counterpart. "We retained the muffler housing under the rear fascia," Fry said. "It has a useful purpose because it guides the underbody air up and into the rear diffuser portion of the rear fascia, thereby helping to reduce vehicle drag and rear lift."
North America's winter thermal extremes prompted Abarth product planners to offer an engine block heater in the car's cold weather package, as well as specific engine modifications.
"It's not uncommon to see temperatures as low as -40º F in Yellowknife and other far-northern towns in Canada," Vincent noted. "Since the engine uses electro-hydraulic solenoid controls, we had to make the electronic solenoids and the correlating hardware more robust in order for the system to operate in very extreme temperatures."
The Abarth 500 is assembled at Chrysler's Toluca, Mexico, plant, so a majority of the more than 150 individual engine components were re-sourced to suppliers in Mexico, the U.S., and Canada, based on design specifications from Fiat Powertrain in Italy. Component re-sourcing enables Chrysler to meet the North American Free Trade Agreement (NAFTA) content requirements for vehicles built and sold in the region.
Because supplier production processes can vary, modifications are granted if the change does not alter the original specification's intentions.
"One of our goals is to have an interchangeable supply base," Vincent explained. "We want compatibility between NAFTA and European suppliers. So if there's a disaster like the 2011 tsunami and ensuing nuclear plant crisis in Japan, or other problems that knock out supplier production, we have a strategy in place.
"That's why we're maintaining component commonality as much as possible," he said.