User:Kumboloi/sandbox/Porsche Type 547 engine

Overview
Manufacturer	Porsche
Designer	Ernst Fuhrmann
Also called	Fuhrmann engine Carrera engine Vertical shaft engine Drawer engine
Layout
Configuration	F4 Boxer
Combustion
Oil system	Dry sump
Cooling system	Air-cooled

The Porsche Type 547 engine is a four cylinder boxer automobile engine.

Text excerpt

Porsche: The Engineering Story Jeff Daniels 2007 Haynes Publishing ISBN: 978 1 84425 204 6

Carrera: something else

The Carrera engine was developed, as the Type 547, by a team led by Ernst Fuhrmann. Initially, the chosen dimensions were 85 x 66mm for a capacity of 1,498cc. The completely new aluminium crankcase had 122mm bore centres (instead of 102mm for the standard Volkswagen component, and with 40mm instead of 37mm bank-to-bank offset). Thus the crankshaft - a built-up Hirth type crank, more economical to manufacture in view of the small production volume envisaged - had to be completely new. The 547 engine was longer, but (because of its shorter stroke) little wider than the standard engine - which meant it would fit the 356 body without too much trouble. The combustion chambers were typical high-performance hemispherical, vee-opposed valves angled 39 degrees above and below the horizontal.

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The valves were, naturally, much bigger than in the OHV engine: 48mm inlet, 41mm exhaust. The cylinder heads were also notable for dual ignition, one spark plug positioned - without any apparent regard for service accessibility - 'at each side' between the valves, with dual distributors drivern from the ends of the inlet camshafts. The cylinders were chrome-faced alloy and the downdraught twin-choke carburettors were new instruments from Solex. In recognition of the increasing problem Porsche was experiencing with keeping oil from surging into the wrong places in its horizontal pair of cylinders, Fuhrmann had wisely gone for a dry sump.

However, the read interest of Fuhrmann's engine was its valve gear - the drive to its four camshafts. Today, we would expect to find a chain drive or possibly a toothed belt, running in a single stage or in two stages, over a drive sprocket on the crankshaft nose, and four larger sprockets driving the camshafts at half engine speed. But Fuhrmann took a geared drive from (page 45) the flywheel end of the crankshaft and from there, ran a jackshaft aft to the geometric centre of the flat-4 engine. Here was a second bevel gear, double-faced and 40mm wide to match the cylinder bank offset, from which further shafts and gears drove the exhaust camshafts between the two cylinders of each bank. From here in turn, mini-shafts and gears ran upwards to drive the inlet camshafts. It was a truly astonishing and extremely expensive arrangement, but it added nothing to the overall length of the engine - and it worked. Initially installed in the tubular ladder-framed Type 550 sorts-racing car, it delivered 100bhp at 7,000rpm. For the 356 Carrera, first shown at Frankfurt in 1955 alongside the 356A, this was unwound to 100bhp at 6,200rpm, in which state of tune the Carrera could be driven on the road without difficulty.

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The following year, 1958, saw the 4-cam engine bore-out to 82.5mm for a capacity of 1,587cc. Along with this, the built-up crankshaft gave way to a forged crank running in conventional bearings. The Carrera 1600 engine, carrying the Type 692 designation, delivered 105bhp at 6,500rpm as the 692/2, or 115bhp at 6,500rpm for the 1600GT with a higher compression (9.8 instead of 9.5) and larger-throated Weber carburettors. Two years later, the 692/3 engine became the 692/3a with strengthened crankshaft and connecting rods.

The final iteration in the Carrera development strand was also the most radical. The Carrera 2 appeared in 1962, with an engine designated Type 587, indicating that it had been a long time 'in the works'. In fact, studies for a 2-litre engine had begun very shortly after the original Type 547 4-cam had been laid down. It was bored right out to 92mm, and the crankshaft stroke increased to 74mm, the same as in the standard 356 engine - but this was not, of course, the same crank since the engine's bore centres and offsets were different. The resulting capacity was 1,966cc. Interesting, no changes were made to the cylinder heads: the combustion chambers, valve sizes and angles remained unchanged. One significant change, and a bit of a give-away as to where the engine was most highly stressed in an overall sense, was that an even bigger oil pump was fitted: more than any previous 356-series power unit, the 587 was crucially dependent on a high oil flow rate for the cooling of some areas.

As always, increased capacity translated into greater torque output, the 2-litre Type 587 delivering 162Nm instead of the 120Nm of the 1.6-litre Type 692 - and what is more, the torque peak came at 4,600rpm instead of an eye-watering 5,000rpm. Power output rose to 130bhp at 6,200rpm. For the final higher-performance versions, Carrera GS and GT, the power was 140bhp and 155bhp respectively. Today, we would not regard 155bhp from a 2-litre engine as anything special, even without taking exhaust emissions into account, but that is a measure of how far engine design has advanced in the interim. At the time, the 4-cam Carrera engine represented one of the peaks of production engine technology, even if that production was in small volume. It could hardly be said to have laid the foundation for what was to come, because Porsche's future lay with six cylinders rather than four, yet in many ways it prepared the enthusiasts for the future.

History

Work on a new high performance engine began in the summer of 1952. Project 547 was assigned to Ernst Fuhrmann, who had done work on the Grand Prix Cisitalia, and new camshaft profiles for competition Porsches. Fuhrmann had the backing of von Hanstein.

Unusually oversquare for the time. Bore centre spacing increased to 122 mm from the 102 of the original VW engine. Hemispherical combustion chambers. Valves vertical, inclined at 39° from the centreline. 48 mm inlet and 41 mm exhaust.

Valvegear design inspired by flat-twelve of the Cisitalia car. Drive was taken to one cam in each bank, then to the other cam.

Drive to the cams was taken from a gear at the flywheel or output end of the crankshaft. A pair of helical gears drove a half-speed shaft in the sump, directly below the crankshaft. At the other end of the crank, below the engine's centre main bearing, the half-speed shaft (called the countershaft by Porsche) carried back-to-back spiral bevel gears. These in turn rotated smaller gears on hollow shafts which extended straight out to the left and right. At its respective side of the engine, each shaft turned a gear at the centre of the lower exhaust camshaft; from that point another shaft rose vertically to turn spiral bevel gears at the centre of the inlet camshaft.

The shafts into and inside the heads rotated at crankshaft speeds. Shafts were hollow, carried oil to the cylinder heads.

Cam lobes were not integral with the camshaft. Lobes were made separately and keyed to the shaft. Making changing profiles and materials easier.

Pistons were domed, and cast by Mahle out of 127 aluminum allow. Piston had one oil ring and three compression rings above it. Wrist pins were free floating in the piston and the small end. Crankshaft was a built-up Hirth model with roller bearings. Main bearings were roller bearings in three main fournals and fo rthe rod bearings.

Crankshaft assembled by Hirth, made of ten main pieces, four being rod bearing hournals.

Each throw of the cranksahft was heavily counterwieghted. Slugs of heavier metal were inserted into the cheeks of the four counterweights.

Lbracant was SAE 30 oil. Pumped to the three main bearings through brass metering jets.

Two-sided oil pump driven by a gear at the tip of the half-speed countershaft. Pump housed in a cylindrical casting fitted into a cavity formed by the two halves of the crankcase.

External oil reservoir, dry-sump. Crankcase was two halves split vertically down the middle. Aluminum aloy crankcase. Four long studs around each cylinder clamped the cylinder head (one to each pair of cylinders) down agains tthe finned cylinder.

Individual cylinders were made of aluminum with chrome-plated bores by Mahle.

Cooling air would pick up heat from the inlet side before flowing down to cool the hotter exhaust side. Finning was expensive, total area of finning increased by 1000 cc to 3600 cc compared to earlier Porsche engines. Design of the engine's blower handled by Franz Xaver Reimspiess. Had gone to Steyr after 1945, then back to Porsche in 1951. Fan was a radial-outflow with reverse-curved blades. Designed and patented the dual-fan flower used on the Type 547. Fan drew air from both front and back of the engine. Generator in the middle acted at the fan drive shaft and support. Front and back sections of the fan fed completely separate cooling ducts to the front and rear opposing cylinder pairs.. Flow divided internally by a lateral bulkhead. At 7300 rpm the fan required 8.8 hp to run and delivered 2750 cubic feet of air per minute. The fan was driven by a vee-belt.

The engine used two spark plugs per cylinder. Two Bosch distributors, one for the inner pair of plugs and the other for the outer pair. The distributors were driven from the ends of the inlet camshafts and could be mounted on either the front or back of the engine.

By the autumn of the year 1952 the engine was built and being tested. First unit, 547-01, assembled on March 1953. First unit run on 2 April 1953. Engine also used new carburetors; Solex 40 PII (aka 40 PJJ). Two 40 MM downdraft bores with a single central float bowl and single accelerator pump. 34 mm venturis fitted.

Second series 547 prepared for a 550 entered in the 1954 Millie Miglia. This version had a revised cylinder head design. The exhaust cam coveres were finned to cool the oil in the head and to strengthen the cover. The inlet cam covers carried the Porsche name in raised letters between raised horizontal strips. Weber 40 DCM carburetors replaced the Solex units of the series one. The throttle bores were closer together on the Weber equipped engines and the carburetors were mounted on revised inlet manifolds.

A third series 547 engine first appeared in the 550/RS1500s prepared for the 12th and 13th of June 1954 at Le Mans. These engines had longer fins on the exhaust cam covers. The decorative lines were deleted from the inlet cam cover. The crankcase breather was modified. Three of the Le Mans cars had 1498 CC engines developong 114 net bhp at 6800 rpm. A fourth engines had its bore reduced to 72.5 mm, dropping displacement down to 1089 cc. This engine was built for Auguste Veuillet, and driven by Gustave Oliviere and Zora Arkus-Duntov.This car won the 1100 cc class when the OSCAs retired. All three 1498 cc engine cars retired with holed pistons. Additional cooling to the rear cylinders was added by modifying the internal baffling. Internal cooling was improved by enlarging the carburetor jets on that side. And ignition advance was strictly limited.

Swiss racing driver, engineer and fuel injection specialist Michael May transferred from Mercedes Benz to Porsche to work on the 753 engine, but wound up developing improvements for the 547/3 engine instead. May's changes included reducing the oil pressure, removing two of the engines five piston rings, using a new hardening process on the built-up Hirth crankshaft, narrowing the inlet ports, modifying the piston crowns and valve depth, using direct fuel injection, and adding a second non-drive fan impeller below the driven one. The cam profiles were unchanged. The modified engine, dubbed 547/3B, managed to produced a reliable 182–186 hp (135.7–138.7 kW) at a time when May estimated that the 753 was producing just 140 hp (104.4 kW), the Ferrari 156 V6 engine 150–152 hp (112–113 kW) and the Coventry-Climax and BRM V8s about 158 hp (117.8 kW). May felt that the 547/3B could win Formula One races, and showed Porsche's engineers that the 804 chassis could be modified to take the four-cylinder. He then struck an agreement with Ferry Porsche to have a 547/3B installed n a 718/2 that May would personally drive in practice at the 1962 Pau Grand Prix. When the car failed to arrive at Pau, May left Porsche for Ferrari. Only three 547/3B engines were ever built.

Specifications

Porsche Type 547 engine, as used in the later 550 cars

Engine

Configuration	4 cylinder air cooled horizontal opposed 4 overhead camshafts
Power	Approximately 110 PS (81 kW; 110 hp) at 6200rpm
Bore	85 mm (3.35 in)
Stroke	66 mm (2.60 in)
Piston displacement	1,498 cc (91.4 cu in)
Compression ratio	9.5:1
Crankcase	Aluminum
Cylinders	Aluminum hard chromed walls
Cylinder head	Aluminum
Valves per cylinder	An intake and an exhaust
Valve operation	2 camshafts per head driven by vertical shafts
Crankshaft	Built-up Hirth full roller bearing
Pistons	Aluminum
Air blower drive	V-belt and crankshaft to generator shaft
Crankshaft to blower ratio	1:1
Air volume	1,100 L/s (2,330.8 cu ft/min) at 6200 rpm
Lubrication	Dry sump with oil cooler and filter in main current
Firing order	1-4-3-2
Distribution drive	Camshaft
Spark plugs	Temperature valve 260-80
Carburetors	Solex 40 PJJ or Weber 40 DCM
Muffler	2 of them leading to an exhaust pipe
Clutch	Fichtel & Sachs K12 Porsche Special

Variations and derivatives

Type 547/3B

Swiss racing driver, engineer and fuel injection specialist Michael May transferred from Mercedes Benz to Porsche to work on the 753 engine, but wound up developing improvements for the 547/3 engine instead. May's changes included reducing the oil pressure, removing two of the engines five piston rings, using a new hardening process on the built-up Hirth crankshaft, narrowing the inlet ports, modifying the piston crowns and valve depth, using direct fuel injection, and adding a second non-drive fan impeller below the driven one. The cam profiles were unchanged. The modified engine, dubbed 547/3B, managed to produced a reliable 182–186 hp (135.7–138.7 kW) at a time when May estimated that the 753 was producing just 140 hp (104.4 kW), the Ferrari 156 V6 engine 150–152 hp (112–113 kW) and the Coventry-Climax and BRM V8s about 158 hp (117.8 kW). May felt that the 547/3B could win Formula One races, and showed Porsche's engineers that the 804 chassis could be modified to take the four-cylinder. He then struck an agreement with Ferry Porsche to have a 547/3B installed in a 718/2 that May would personally drive in practice at the 1962 Pau Grand Prix. When the car failed to arrive at Pau, May left Porsche for Ferrari. Only three 547/3B engines were ever built.

Desmodromic

Desmodromic experiments based on technology initially from Mercedes Benz, later Porsche developments.