| kc1337 | 01-19-2009 11:25 AM |
Quote:
Engine
History
The McLaren F1's engine compartment contains the mid-mounted BMW S70/2 engine and uses gold foil as a heat shield in the exhaust compartment.Gordon Murray insisted that the engine for this car be naturally aspirated to increase reliability and driver control. Turbochargers and superchargers increase power but they increase complexity and can decrease reliability as well as introducing an additional aspect of latency and loss of feedback, the ability of the driver to maintain maximum control of the engine is thus decreased. Murray initially approached Honda for an NA powerplant with 550 bhp (410 kW; 560 PS), 600 mm (23.6 in) block length and a total weight of 250 kg (551 lb), it should be derived from the Formula 1 powerplant in the then-dominating McLaren/Honda cars.
When Honda refused, Isuzu, then planning an entry into Formula 1, had a 3.5 V12 engine being tested in a Lotus chassis. The company was very interested in having the engine fitted into the F1. However, the designers wanted an engine with a proven design and a racing pedigree.
In the end BMW took an interest, and the motorsport division BMW M headed by engine expert Paul Rosche[5] designed and built Murray a custom-designed 6.1 L (6064 cc) 60-degree V12 engine, which was 14% more powerful than specified and 16 kg (35 lb) heavier – despite being based on the original specifications of 550 bhp (410 kW; 560 PS), 600 mm (23.6 in) block length and total weight of 250 kilograms (550 lb).
Specifications
The final result is a custom-built 6.1 L (6064 cc) 60-degree V12 with an aluminium alloy block and head, 86 mm (3.4 in) x 87 mm (3.4 in) bore/stroke, quad overhead camshafts for maximum flexibility of control over the four valves per cylinder and a chain drive for the camshafts for maximum reliability, the engine is dry sump. At 266 kg (586 lb), the resulting engine was slightly heavier than Murray's original maximum specification weight of 250 kg (551 lb) but was also considerably more powerful than he had specified. The bespoke engineered engine for the F1 is called the BMW S70/2.[6]
The carbon fibre body panels and monocoque required significant heat insulation in the engine compartment, so Murray's solution was to line the engine bay with a highly efficient heat-reflector: gold foil. Approximately 25 g (0.8 ounce) of gold was used in each car.[7]
The road version used a compression ratio of 10.5:1 to produce 627 brake horsepower (467 kW)[6] at 7400 rpm—considerably more than Murray's specification of 550 horsepower (404 kW). Torque output of 480 ft·lb (651 N·m) at 5600 rpm.[8] The engine has a red line and rev limiter set at 7500 rpm. Other, more highly tuned, incarnations of the F1 produced up to 691 bhp (515 kW; 701 PS) at 7500 rpm and 735 N·m (542 lb·ft) of torque (updated LM engine), making a significant performance improvement. There is only one other McLaren F1 roadcar with this engine.[citation needed]
In contrast to raw engine power, a car's power-to-weight ratio is a better method of quantifying performance than the peak output of the vehicle's powerplant. The standard F1 achieves 550 hp/ton (403 kW/tonne), or just 3.6 lb/hp. Compare with the Enzo Ferrari at 434 hp/ton (314 kW/tonne) (4.6 lb/hp), the SSC Ultimate Aero TT with 1003 hp/ton (747.9 kW/tonne) (2 lb/hp), and the Bugatti Veyron at 530.2 hp/ton (395 kW/tonne) (4.1 lb/hp).
The cam carriers, covers, oil sump, dry sump, and housings for the camshaft control are made of magnesium castings. The intake control features twelve individual butterfly valves and the exhaust system has four Inconel catalysts with individual Lambda-Sound controls. The camshafts are continuously variable for increased performance, using a system very closely based on BMW's VANOS variable timing system for the BMW M3;[9] it is a hydraulically-actuated phasing mechanism which retards the inlet cam relative to the exhaust cam at low revs, which reduces the valve overlap and provides for increased idle stability and increased low-speed torque. At higher RPM the valve overlap is increased by computer control to 42 degrees (compare 25 degrees on the M3)[9] for increased airflow into the cylinders and thus increased performance.
To allow the fuel to atomise fully the engine uses two Lucas injectors per cylinder, with the first injector located close to the inlet valve – operating at low engine RPM – while the second is located higher up the inlet tract – operating at higher RPM. The dynamic transition between the two devices is controlled by the engine computer.[9]
Each cylinder has its own miniature ignition coil. The closed-loop fuel injection is sequential. The engine has no knock sensor as the predicted combustion conditions would not cause this to be a problem. The pistons are forged in aluminium.
From 1998 to 2000, the Le Mans–winning BMW V12 LMR sports car used a similar S70/2 engine.
The engine was given a short development time, causing the BMW design team to use only trusted technology from prior design and implementation experience. The engine does not use titanium valves or connecting rods. Variable intake geometry was considered but rejected on grounds of unnecessary complication.[9]
| So Honda could have potentially have powered the Mclaren F1. |
