Miami V8 Engine

“It took three years and $36 million but we believe the result is a new benchmark for a high-performance V8.” That is how Bryan Mears, Managing Director of Prodrive’s Asia Pacific Division, describes the 5.0-L supercharged power unit of the latest Australian-built Ford Falcon GT.

Prodrive had the task of creating what Mears regards as “essentially a new engine” although using the block, crankshaft, and some ancillaries of Ford’s Coyote V8, which powers the 300-kW (402-hp) North American Mustang. The result is the supercharged Miami, which he describes as an affordable, world-class engine, designed and built to rigorous Ford standards.

Though naturally aspirated, the Coyote had been design-protected for a supercharged variant, but there was a great deal more to creating the Miami than simply bolting on a supercharger.

As with all new engines, regardless of capacity and power, it had to have environmentally responsible credentials and be capable of meeting future global emissions standards.

“The old 5.4-L ‘Boss’ unit used by Ford Performance Vehicles (FPV) was a tough act to follow, but it had reached the limit of its emissions development and mechanical strength,” explains Mears.

The Prodrive-developed Miami is 47 kg (103.6 lb) lighter. It also returns more power—335 kW (449 hp) at 5750 rpm, compared to 315 kW (422 hp) at 6500 rpm for the Boss unit. And as is required for the brand, there is more torque at lower engine speeds, with a claimed 570 N·m (420 lb·ft) available from 2200-5500 rpm instead of a peak 550 N·m (406 lb·ft) at 4750 rpm.

Straight-line performance figures for the Australian-built Falcon GT include a claimed standing start quarter-mile time of less than 13 s with 0-100 km/h (0-62 mph) in less than five seconds.

Prodrive is a British company that already runs the Ford Performance Racing team in the Australian V8 Supercar Championship. Its Asia-Pacific Technical Center, which incorporates its powertrain engineering group and led the Miami project, is close to FPV’s Melbourne facility.

The Miami program brought plenty of challenges. For a start, the engine had to meet the “One Ford” global standards for engineering and durability, yet be affordable at relatively modest volumes. Despite the company’s global philosophy, some 40% of the engine is manufactured in Australia and all engines are hand-built at FPV on the only V8 assembly line in the country. For the Falcon GS and GT models, this means around 1500 engines per annum.

The engine also had to embody the headroom to meet future emissions and performance targets, said Prodrive Australia’s Head of Programs Paul Cook.

The naturally aspirated Boss V8 uses aggressive valve timing to reach the required power output while satisfying EU3 emissions standards. This approach was felt to be incompatible with the need to meet EU4 requirements with improved low-speed torque. After investigating several design options, it was concluded that the most easily implemented path would be a supercharged engine running modest levels of boost.

The Coyote’s cylinder block design already included six-bolt, cross-bolted main bearing caps to provide stable crank location under the high load conditions. Its crankshaft had the necessary reserves of strength, and the front accessory drive was capable of accepting the increased loads of a supercharger drive, explained Cook.

But the Miami is a very different engine to the Coyote, he stated. So different that he regards it as “essentially new.”

The Harrop-built supercharger is the result of intense design and optimization. It uses Eaton TVS (Twin Vortices Series) rotors, to a specification developed by Jaguar in the U.K. (Harrop is the Eaton distributor in Australia.) It is housed in a casing designed specifically for FPV.

Computer simulation techniques allowed Prodrive engineers to achieve required supercharger installation criteria, especially the drive ratio and intake runners. The simulations proved it possible to reach the targets without an intercooler—quite a challenge when Australian summer ambient air temperatures in some areas can reach 45°C.

A complete new intake system positions the supercharger between the cylinder banks, providing an integral high-efficiency plenum and runners. The exhaust system uses a stainless steel manifold and a close-coupled catalyst for each bank. The new, four-tailpipe exhaust system includes an active flap to achieve regulatory compliance with what is deemed an appropriate sound.

“We put a lot of time into ensuring that the car will deliver a sound that our customers will enjoy,” says Cook.

Lightweight, low-friction pistons provide a compression ratio of 9.25:1 to suit the increased charge density and temperature. Stronger connecting rods, powder forged with precision-fractured caps, carry the increased firing loads and support a rev limit of 6250 rpm. The piston skirts are cooled by oil spray jets added to the block and ride on fully floating, nitrided wrist pins. Inconel exhaust valves are fitted.

Supercharging simplified the creation of different power options. As well as the 335-kW (449-hp) specification for the Falcon GT, GT-E, and GT-P, all running at 0.4-bar maximum boost, there is a 315-kW version, peaking at 0.34-bar (5.8-psi) boost, for the Falcon GS. Cook explains that this leaves untapped potential for future upgrades using higher boost levels, possibly using an intercooler.

Parts retained from the Coyote unit have been optimized for the Miami. The work includes rebalancing the crankshaft to suit the new piston and rod weights. The fuel injectors were found capable of the required flow, having been rated originally to be compatible with ethanol fuel blends. They were reset to suit the combustion characteristics of a supercharged engine.

Prodrive ran the Miami program as a “turnkey” project within the framework of Ford’s recently introduced Global Product Development System (GPDS), described by the company as a comprehensive and rigorous approach distilled from the best practices of Ford, Volvo, and Mazda. This saw Prodrive Australia becoming the nerve center for complex communications and logistics, coordinating input from Dearborn, MI; Canada; Germany; and the U.K.

Development and validation processes included accelerated engine endurance tests, simulating 250,000-km (155,342-mi) use in 14 weeks, and a vehicle durability program of 170,000 km (105,633 mi). The program used three levels of hardware: handmade prototypes for early evaluation, preproduction samples for development, and production parts for final validation.

Eight preproduction vehicles were taken through typical Australian drive cycles, with ultralong distance drives including the Outback. One crew drove from Melbourne to Darwin, 3752 km (2331 mi) across the Outback.

Mears believes that Prodrive saved FPV about a year compared to typical GPDS timing. “Because we’re not part of a large company, our decision-making process can be quicker and less influenced by factors outside the project,” he explained.

A central facet of this was extensive use of simulation and computer analysis, using computational fluid dynamics (CFD), one-dimensional simulation, and finite-element and nonlinear thermal-stress analysis. By applying nonlinear analysis, the Miami’s cast stainless manifolds passed their cracking test at the first attempt.

“All over the world, vehicle manufacturers struggle to make niche model programs financially viable in the face of substantial engineering costs,” says Mears. “The customer expects the same or better quality and durability from a limited-volume car as a mainstream model, yet the development overhead incurred must be recovered from a much smaller production run.

“We have produced an affordable, world-class engine to rigorous Ford standards through simulation for ‘right-first-time’ design and by the intelligent use of key existing parts. And there’s even the potential to sell finished engines back into the USA.”

*Article from SAE International January 2011