Ford Miami V8 Engine: Boss 315, 335 and 351

Introduction

The Miami V8 was a 5.0-litre supercharged petrol engine that was first offered by Ford Performance Vehicles (FPV) in October 2010 with 335 kW and 315 kW outputs (internal codes V2G and V2X, respectively).

Based on Ford’s Coyote V8 engine which was introduced in the Ford Mustang in late 2010, the Miami V8 was developed by Prodrive in a $36 million program that ran simultaneously with the development of the Coyote V8 from 2007 to 2010. For the Miami V8, all components for supercharging – such as the supercharger, crankshaft damper, accessory drive, sump, exhaust manifold and intake manifold – were locally sourced and the Miami V8 was assembled by hand at FPV’s plant in Campbellfield, Victoria; annual production capability for the Campellfield facility was around 1500 engines.

The Miami V8 was developed to comply with Euro IV and beyond emissions standards. The 5.4-litre Boss V8 engines which preceded the Miami used aggressive valve timing and detuning would have been necessary for Euro IV compliance. Key features of the Miami V8 included:

• An aluminium alloy block and cylinder head;
• Double overhead camshafts and four valves per cylinder;
• Variable intake camshaft timing;
• HVT 1900 supercharger;
• 9.25:1 compression ratio; and,
• 6250 rpm rev limit.

As a result of its aluminium alloy construction, the Miami V8 engine was 47 kg lighter than its Boss 315 predecessor.

Block

Like the Coyote V8 engine, the Miami V8 had a deep skirt aluminium block with 92.2 mm bores and a 92.7 mm stroke for a capacity of 4951 cc. Furthermore, the bores were spaced at 100 mm intervals and had pressed-in iron cylinder liners. The Miami V8 engine block had six-bolt, cross-bolted main bearing caps to provide stable crank location under high load conditions and, for rigidity,

• The casting for the aluminium block had reinforcing webbing;
• The main bearing bulkhead widths were increased (relative to its predecessor); and,
• Nodular iron cross-bolted main bearing caps with 12 mm head bolts were used.

Crankshaft, connecting rods and pistons

The Miami V8 had a forged steel crankshaft that, relative to the Coyote V8, was rebalanced to suit the different connecting rods and pistons. Produced by Metaldyne, the high-strength powder forged connecting rods had precision-fractured caps and were 150.7 mm long.

The higher strength, cast aluminium pistons – produced by Mahle – had a hard anodised top ring groove and fully floating, nitride wrist pins. Like the Coyote V8, cooling jets were fitted in the cylinder block’s main webs to spray the underside of the piston (at the piston boss and the bottom of the crown).

Cylinder head and camshafts

Like the Coyote V8 engine, the Miami V8 had an aluminium alloy cylinder head which was designed to support high pressures and provide cross-flow cooling. With cross-flow cooling, coolant would rise from the block on the exhaust side of the head, pass around the exhaust valves, then flow past the spark plugs, to the intake side of the cylinder head and then into a manifold (effectively a galley that was cast into the intake side of the cylinder head). From the manifold, coolant would exit at the front of the head to a cross-over passage that was cast into the block.

The Miami V8 engine had hollow, double overhead camshafts per cylinder bank that were individually chain-driven, with a hydraulic timing tensioner on each chain. Furthermore, the camshafts were synchronised through a secondary timing chain.

Whereas the Coyote V8 engine had Ford’s ‘Twin Independent Variable Cam Timing’ for variable intake and exhaust camshaft timing, the Miami V8 only had variable intake camshaft timing.

Valves

The Miami V8 engine had four valves per cylinder were actuated by roller finger followers, while zero valve clearance was mainted by direct-acting hydraulic lash adjusters. Due to its higher temperatures, the intake valves for the Miami V8 were chrome plated, while the exhaust valves were coated with Inconel (a nickel alloy containing chromium and iron). Valve dimensions and lift for the Miami V8 were the same as the Mustang GT Coyote V8 from 2010 to 2014:

• Intake valve diameter was 37 mm;
• Exhaust valve diameter was 31 mm;
• Intake valve lift was 12 mm; and,
• Exhaust valve lift was 11 mm.

Intake

For the Miami V8 engine, the air intake system included a high-flow cold air intake system, a sealed cold air box and a high-flow conical filter. The Miami V8 had a specially developed two-piece, cast aluminium intake manifold that was produced by New Metric (based in South Australia) and had tuned runners. Furthermore, the intake manifold had a supercharger outlet air diffuser which controlled air charge motion out of the supercharger and provided cylinder-to-cylinder flow balance.

Harrop HTV 1900 Supercharger

The HTV 1900 front drive, rear entry supercharger for the Miami V8 engine was produced by Harrop Engineering in Victoria using Eaton Twin Vortices Series (TVS) sixth-generation rotors that were originally developed for Jaguar. As Eaton’s Australian distributor, Harrop was responsible for manufacturing the supercharger housing and used rotors supplied by Harrop. The supercharger was positioned under the intake plenum in the engine’s ‘V’, providing an integral high-efficiency plenum and runners.

The HTV 1900 supercharger was so-called because it had a displacement of 1.9-litres (1900 cc) per revolution. The supercharger had an inlet bypass valve that was controlled by the Powertrain Control Module (PCM); when cruising, the bypass valve would operate to improve fuel efficiency and reduce power consumption by the supercharger to 3 kW.

For Miami engines producing 315 kW, maximum boost pressure from the HTV 1900 supercharger was 0.34 bar (4.9 psi); for engines producing 335 kW, however, maximum boost pressure was 0.40 bar (5.8 psi). During development, FPV envisaged that increased performance could be achieved through higher boost pressure and the possible introduction of an intercooler.

The Miami V8 had an electronically-controlled ‘drive by wire’ throttle and a 75 mm throttle body.

Injection and ignition

The Miami V8 had sequential multi-port fuel injection (SFI) via eight solenoid-operated injectors. The injectors were mounted in the fuel injection supply manifold (within the intake manifold) above the cylinder heads. The injectors were positioned so that their tips delivered fuel just ahead of the intake valves. Compared to the Coyote V8, the however, Miami V8 had:

• A higher flow fuel pump;
• A two-piece stainless steel fuel rail assembly;
• A four bar fuel pressure return system; and,
• Higher flow injectors.

The Miami V8 engine had a 1-5-4-8-6-3-7-2 firing order and a compression ratio of 9.25:1.

The Miami V8 had coil-on-plug ignition via iridium-tipped spark plugs. For the Miami V8, the injection and firing order was 1-5-4-8-6-3-7-2; in contrast, previous engines in Ford’s Modular V8 family had a 1-3-7-2-6-5-4-8 order.

Exhaust

The Miami V8 engine had a stainless steel manifold and a close-coupled catalytic converter for each cylinder bank. The metal matrix catalytic converters had a diameter of 140 mm and volume of 2.1 litres per assembly. To reduce exhaust back pressure, the catalytic converters featured thin foil technology.

For FPV sedans, the Miami V8 engine had a bi-modal exhaust system – controlled by the PCM – which reduced exhaust noise in part throttle applications but provided greater exhaust noise under higher throttle inputs.

Lubrication

Like the Coyote V8 engine, the Miami V8 had a positive displacement, internal gear oil pump with top seal rotors (commonly known as a gerotor pump) that was mounted on the front face of the cylinder block. For the Miami V8, however, a new cast aluminium high-volume winged oil pan was introduced with cast-in baffles to maintain oil supply under high g forces.

The Miami V8 engine had a force-feed lubrication system whereby oil was supplied – under full pressure – to the crankshaft main bearings, crankshaft trust main bearing, connecting rod bearings and oil galleries; all other parts were lubricated by oil splash.

Cooling

Compared to the Coyote V8 engine, the Miami V8 had an upgraded cooling system which included:

• A high-efficiency radiator and fan pack assembly;
• A new engine oil cooler;
• A high-efficiency automatic transmission oil cooler; and,
• A new vehicle heater circuit.

Although the Miami V8 engine did not have an intercooler, it did have an open-filter cold air induction system.

FPV FG GT-F: 351 kW

Released in June 2015 with a limited production run of 550 units, the engine for theFPV FG GT Fproduced peak outputs of 351 kW at 6000 rpm and 570 Nm at 2500-5500rpm. Compared to the standard FPV FG GT engine, which produced peak power of 335 kW, the FPV GT-F is understood to have higher maximum boost pressure. Furthermore, the ‘transient overboost function’ could provide peak power in the range of 410-420 kW and peak torque of up to 650 Nm depending on the prevailing atmospheric conditions. In higher ambient temperatures, the overboost function would be limited to fifteen (15) to twenty (20) second bursts.