BMW M88

The BMW M88 engine series is one of the German car manufacturer BMW.

It is a DOHC in-line six -cylinder petrol engine in four-valve technology with fuel injection. The dual overhead camshafts are driven by a duplex chain. The mixture is supplied for each cylinder separately through its own intake manifold and throttle valve (single throttle system).

2.1 Short Description
2.2 M88: Rear mid-engine for handmade small series of the BMW M1
2.3 M88 / 3: Front engine for series production

3.1 nomenclature
3.2 M88
M88 3.3 / 1
3.4 M88 / 2
3.5 M88 / 3
3.6 S38B35
3.7 Overview of variants

History

The approvable road version of the M1 should serve as Homologationsfahrzeug for racing. For this purpose, the standard drive had many opportunities to improve performance keep ready, because the rules of the targeted groups 4 and 5 already then allowed by FIA regulations no profound changes to the engine for racing. The original also included in the considerations, large-volume and prestigious V8 or V10 engine with 144 ° cylinder angle, however, was not realized, as this engine with the designation M81 which arose from preliminary studies for a Formula 1 engine, from scratch would have had to be constructed. On the other hand, we arrived at BMW finally convinced to be able to exist with the already known from the CSL racing touring car M49 six-cylinder engines against the competition.

The development of the unit began after 4/ 76, the first variant M88 was built 1978-1981 in the BMW M1. Served as a basis the already mentioned, perpendicular four-valve racing engine M49 / 3 with 465 hp ( 1976), which was a developed by Schnitzer development stage of the 1974 featured, and still inclined built, 430 hp factory Vierventilers M49 / 2. The later renamed M88 test engine for the M1 was originally called M49 / 5

The inserted into Group 4 version M88 / 1 produced as required 345-361 kW, the engines used in the vehicles for the Procar series of this type also corresponded to Group 4 regulations, however, were uniformly 345 kW/470 hp.

In contrast to group 4, regulations permitted for those in group 5 ( "Special Production Car " ) used vehicles relatively diverse changes to the engine, transmission and chassis: the variant M88 / 2 reached for use in Group 5 vehicles with 3.2 l displacement by means of two turbochargers power up to 625 kW.

The version of the M88 / 3 with 210 kW came in the models BMW M 635 CSi (M6 ) and BMW M5 ( E28 ) were used. The engine builds on the standard engine M30B35. The cylinder head, the intake and exhaust side, however, are based on the original M88 engine.

For export to North America originally katlose M88/3-Motor 1986 had to be fitted with a catalytic converter. Among other things, the compression was reduced to 9.8:1, making the engine power dropped to 191 kW. This version was given the designation S38B35 engine.

The predecessor

Already in the 1960s, worked at BMW of four-valve racing engines. The 1957 BMW Come engineer Ludwig apple Beck developed in 1967 for the entry of BMW in Formula racing a two-liter engine with their preferred and refined for high specific power radial diametral four-valve technology, which had been in 1935 an account of his patent. Here, the combustion chamber has a hemispherical shape, the valves do not hang parallel as in modern four-valve engines, but radially in the cylinder head, also the valves the same function ( one- or exhaust valve) are not next to each other, but each crosswise opposite ( diametrically ) arranged. The angle to each other hanging valves were either activated directly via conically sharpened cams or indirectly through a system of roller rocker and intermediate levers. The valve opening cross-sections that can be achieved, up to 45% higher than those of commonly used today four-valve combustion chambers with a roof shape. As a two-liter engine of the apple Beck four-valve engine 315 hp, 1.6 liter displacement reached 225 hp.

The theoretical advantages of this cylinder head design, namely, very good gas exchange by maximum valve openings and thermal insensitivity by the non-adjacent exhaust valves were realized in multi-cylinder in-line engines by the then extremely complex valve train only at great expense. Due to the large volume of the hemispherical combustion chamber also an elevation of the piston crown to achieve the compaction was necessary, this increases the weight of the piston, and the milled into the piston crown valve pockets were the focal area as a whole appear to be very rugged. Also, the imaginary charge-exchange advantage inverted at low speeds the opposite, because then the gas velocities when flowing into the cylinders were too low by the large valves and there was no sufficient fresh gas charge.

Since the contemporary Cosworth four-valve engine with the simpler, roof shaped combustion chamber with parallel overhead valves and the flat piston head showed that it is better in practice, then a similar construction was pursued under the direction of Paul Rosche, 1968 First, however, still as M12 with diametrically (crosswise) opposite intake and exhaust valves, due to the formula 2 regulations with 1.6 liters of displacement. To further improve performance, this engine was later fitted with three spark plugs per cylinder, the Lucas injection of the formula 2- apple Beck- M10 was replaced by a ball Fischer- injection. Its successor, the M12 / 2, first used in the course of the 1970 Formula 2 season, then today's conventional valve scheme had with adjacent parallel overhead valves same function.

The resulting formed in 1973, a very successful four-cylinder four -valve engine with the designation M12 / 6 for the formula 2 with later up to 330 hp (after regulations change ) now two liter engine was the basis for both the large four-valve six -cylinder racing engines of type M49, as well as for the supercharged 1.5-liter four-cylinder engine for the Formula 1 the two-liter four-valve engine used in the BMW 2002 racing touring and rally cars, however, were of Schnitzer Motorsport, as intake and exhaust tract of the work - valve engine on the ' wrong ' side were ( exhaust left instead of right, intake manifolds right instead of left).

This branch: S14 four-cylinder ( 1986-1992 )

Since the used in touring car racing since Angang 1980s 635 CSi offered no potential for competitive developments, a four -cylinder four- valve engine was developed for an upcoming sports model of the compact and lightweight 3-series E30. This engine was based on the already proven in motorsport M10 cylinder block, which endured until about 1000 hp as "Formula 1" - turbo engine and the Nelson Piquet, 1983, the first Formula 1 World Champion of the turbo era was. On this cylinder block tentatively a shortened two combustion chambers cylinder head of the M88 / 3 was set. The later series cylinder heads were based on the design, especially from the experiments to the previous racing engines of the type M49 and M88 many results and experiences templates.

As a series motor the S14 had the E30 M3 engine displacements of 2.3 ( S14B23 ) and 2.5 ( S14B25 ) there were liters with outputs ranging from 143 kW/195 hp to 175 kW/238 hp, for the export market to Italy because of local luxury tax vehicles with more than 2 liters capacity reduced to just these S14B20 engine capacity with 141 kW/192 hp yet after all.

In racing the S14 developed in the first stage as a 2.3 liter 220 kW/300 hp, which even reached as of 1990 employed 2.5 liter up to 264 kW/360 hp.

The successor: S38- six in the E34 M5 ( 1988-1995 )

Since the emission purified variant of the M88 / 3, the S38B35, both in power and torque as well as respect to the potential for future stringent emission regulations the requirements for not enough E28 larger and heavier E34 sedan in comparison to the M5 series, was in 1988 in a first stage of the displacement of the original 3.4 l increases to just over 3.5 liters. The now -called S38B36 engine also got a higher compression ratio of 10:1, a header similar to the earlier M88 / 3, a variable intake manifold and larger throttle (now 48 mm diameter ), other camshafts and a Motronic M1.2 of the then latest generation with air flow meter. Thus, the power output increased to 232 kW/315 hp and torque increased to 360 Nm.

However, in 1991 this was no longer enough, because now the Mercedes 500E made with a 240 kW/326 hp V8 engine for competition, and for the S38B38 engine capacity was again increased to now 3.8 liters, as the compression ratio to 10, 5:1. The motor controller took over a Bosch Motronic 3.3. By switching to static ignition distribution, larger valves ( 38.5 mm to 32.5 mm outlet ) and throttle (now 50 mm diameter ) and lighter crankshaft and pistons, the power was raised to 250 kW/340 hp and the torque 400 Nm, an additional switching point of Schaltsaugrohrs at 2480 min-1 caused a significantly better torque at low engine speeds. On the exhaust side, a new, larger manifolds and a double-flow catalyst system with a total of 6 metal monoliths was installed for reduced exhaust back pressure for low exhaust emissions after a cold start was provided by a secondary air injection.

Note: In 1990, the regulation DIN 70020 was replaced for the determination of engine power through the regulation ECE R85. This results in comparison with slightly different performance figures for vehicles registered after 1990 series production: the S38B38 (1991 ) reached in accordance with DIN 70020, the power of 255 kW/347 hp, the S38B36 (1988 ) according to ECE R85 230 kW/312 hp.

The E34 M5 with the S38B38 was only available in the EU, North America and Switzerland, the M5 was only sold with the S38B36 engine with a slightly modified catalyst system, the power thus fell to 229 kW/310 hp.

Design features

Short Description

Water -cooled six- cylinder in-line engine with pressure lubrication
Engine block made of cast iron with spheroidal graphite
Lightweight aluminum piston with recesses around the piston pin boss; in the piston crown incorporated combustion chamber cavity with valve pockets; three piston rings: compression ring square ring, intermediate ring minute ring, oil ring Dachfasenring with garter spring

Forged connecting rods made of steel, connecting rod distance 144 mm
Seven -bearing crankshaft forged from steel with 12 counterweights and torsional vibration dampers ( Massetilger ) at the front tailshaft
Aluminum cylinder head, cross flow cooling
Two overhead camshafts, timing chain with mechanical- hydraulic chain tensioner
Four valves per cylinder operated directly by bucket tappets; Valves the same function in parallel next to each other hanging, cross-flow flushing; double, one within the valve springs
Summarized manifold injection with rod - actuated throttle valves, diameter of 46 mm throttle valves, intake manifolds in pairs to form double - stub

Inlet valve Ø 37 mm, valve angle 18 ° to the axis of the cylinder, exhaust valve Ø 32 mm, valve angle 20 °
Central, slightly off-center by the larger compared to the exhaust intake valves spark plug location, Bosch spark plug X4CS or X5DC, candles thread M12 × 1.5
Fan exhaust manifolds, pipes up to merge the same length and cross-section

M88: Rear mid-engine for handmade small series of the BMW M1

In order to achieve an optimal center of gravity position in the race, the engine heaviest item ( M88: 238 kg ) of the vehicle in a central position, located in center of the vehicle ahead of the rear axle. For the lowest possible center of gravity this provides the dry-sump lubrication, as the engine oil is not in the oil pan underneath the engine, but in a separate oil tank. Thus the very flat oil pan is for the collection of the oil which is then pumped by a vacuum pump to the tank. Also at the low height of the engine contributes to the dual dry clutch used, which requires only a smaller diameter compared to the single disc for the transmission of the same torque. All this provides for a location of the vehicle center of gravity of only 460 mm above the road surface. Unlike all other series engines in BMW road vehicles, the motor is not tilted, but vertically instead installed.

The cylinder head of aluminum casting is divided in two horizontally. The head lower part contains the combustion chambers and exhaust ports, the valve guides and the holes for the cylinder head bolts. The control housing or cylinder head top part includes the camshaft including storage, valve springs and tappets. This division simplifies manufacturing, especially the manufacture of the castings by the avoidance of complex molds, and maintenance. The valve clearance is adjusted by replacing the tappets, this is indeed complex, but even at very high speeds reliable. The cross-flow cooling of the cylinder head with a separate inlet for each of the cylinders results in a uniform temperature distribution over the entire length of the engine, in the normally available cooling water inlet at the front side of the motor of the last cylinder would be significantly hotter than the first.

In contrast to the BMW 2002 TII and 2002 turbo - motors, which also inserting the ball Fischer- injection, the injection pump is attached to the front side of the motor, but to the output side (coupling side), and is driven via a toothed belt of the intake camshaft. The purely mechanically operating ball Fischer PL06 operates with a relatively high pressure system, it includes a cold-start enrichment and an overrun cut-off. The injectors are not energized, but opened by the pressure which is supplied to the valve from the mechanical injection pump to the desired injection timing; the opening pressure is about 35 to 38 bar. This high pressure results in a very good atomization of the injected fuel. The injection works sequentially, that is, each cylinder gets its fuel when the intake valves open.

The indirect injection has a single throttle system, as in the early 1970s by the Alpina Alpina A4 engine ( BMW 2002 tii basis ), was also with ball Fischer- injection, used for the first time.

The ignition of Magneti Marelli is an electronic, contactless ignition, the ignition TDC is determined with Hall sensor on the crankshaft and a manifold to the exhaust camshaft.

Particularly striking are the outside air intake and exhaust system. Suction side, a single throttle system is used, ie for each cylinder its own suction tube ( for all cylinders of course the same length ) with throttle valve with a diameter of 46 mm and is located very close to the intake port of the cylinder head. This can be ascribed to an exact mixture uniformity, and on the other hand a very good response ( response to movements of the accelerator ) to make sure. For racing engines, the throttle, even fully open yet represent a flow resistance are replaced by flat slide that can completely release the pipe cross-section. On the exhaust side, a header is installed, ensure its long and up to merge exactly the same length tubes for optimal exhaustion of the exhaust from the cylinders.

M88 / 3: Front engine for series production

In contrast to M88, M635 CSi and BMW M5 is the M88 / 3 in the BMW built in traditional location, namely the front - mostly because, of course, that these were as a front-engine rear wheel drive cars already in series production.

In order to save costs on the one hand and on the other hand, simplify maintenance, fell back in the construction of many already proven series parts. So corresponds to the crankshaft with a long stroke which until 1982 built 3.5 lM 30, the engine block with oil supply and water pump and the crankshaft, flywheel and belt drive, along with the ancillary units were taken from built after 1982 3.4 liter six- cylinder engine. The torsional vibration damper on the front tailshaft, however, had to be re-tuned for the higher speeds of the M88 / 3.

Unlike the M88, the valve clearance is now adjusted by balancing plates ( "shims " ), which lie on the tappets. So now have the camshafts for the adjustments no longer be expanded. Otherwise, the cylinder head of the M88 / 3 with respect to constructive characteristics does not differ from its predecessor.

The control of fuel injection and ignition are taken together by a Bosch Motronic. Next significant cost savings through the elimination of expensive as well as high-precision mechanics the ball Fischer- injection This also now further possibilities for efficient tuning of ignition timing and injection quantity on the current operating status of the engine. For the detection of the load state of a storage flap air flow meter is used; the ball Fischer injection moved into its information about the load state of the throttle valve position, however, since no information on the actual intake air flow was present, it is to be understood, in practice, rather than reference load state ( possible deviations of the intake air mass flow, for example, by clogged air filter are not detected can see above).

The fuel pressure before the injectors is 3 bar; actually is the pressure differential to manifold vacuum for all engine operating conditions 3 bar, therefore the injected fuel quantity is directly proportional to the activation time of the injectors. The injectors are electrically actuated by the Motronic control unit.

For the S38B35 with catalytic emission control, the compression was lowered to 9.8:1, the engine therefore requires unleaded fuel with an octane rating of 95 RON. It was also increased with a reduction of the camshaft opening times the internal exhaust gas recirculation, this reduces the HC engine-out emissions (emissions before catalytic converter). The engine is now equipped with an area controlled by the Motronic idle control valve, with a person sitting in a connecting piece of the otherwise double-flow exhaust system the oxygen sensor, the fuel- air mixture is held exactly at lambda = 1.

Variants

Nomenclature

From 1963, new rules for naming new vehicle and engine projects were introduced at BMW; Vehicle projects received a Exx and engine projects a Mxx, where the letter was in each case followed by a number starting at 01. This has not yet been applied for the first four-cylinder engines of the New Class, as the original M113 engine has been developed in the late 1950s, this was then further developed to M115, debuted in the BMW 1500 in 1961; until the turn further developed two-liter engine of the BMW 2000 then was named M05 in 1965. The numbering system followed none but was purely chronological.

Since the late 1970s, this system was nearly arrived at the numbers below 100, a new grading system from 1980 imposed retrospectively, after the four-cylinder for the M10 family, the little six-cylinder ( 2.0 to 2.7 liters, the cylinder center distance 91 mm) for M20 and the six-cylinder ( 2.5 to 3.8 liters, the cylinder center distance 100 mm ) belong to the M30 family. The motor sports and racing engines got the letter S preceded by the subsequent number is based on the first digit in the base family; So the S14 is based on the M10 and S38 on the M30. This system is used by BMW until today.

In 1978, presented M88 engine of the BMW M1 follows of course the old numbering scheme, with the later, introduced in 1984 M88 / 3 only for nostalgic reasons - for the public should ensure that the direct sequence of the M635 CSi engine are represented by M1 - yet these number retained and has been called internally S38.

M88

Use:

From 11 /78 BMW M1
Cubic capacity: 3453 cm3 (after tax formula: 3400 cm3)
Bore: 93.4 mm
Stroke: 84 mm
Compression ratio: 9.0:1
Piston speed at rated speed: 17.4 m / s
Camshaft opening time 267 ° KW ( both camshafts are identical)
Power: 204 kW ( 277 hp) at 6500 min-1
Torque: 330 Nm at 5000 min-1
Miscellaneous: mechanical ball Fischer PL06 high-pressure injection pump with injectors DLO 20D ( opening pressure 35 to 38 bar), SAE 701 A Ignition Magneti Marelli with electronic adjustment of the ignition timing, dry-sump lubrication, exhaust manifold, hydraulically actuated two-disc dry clutch, engine longitudinally in front of the installed rear upright

M88 / 1

Use:

Group 4 Procar
Cubic capacity: 3498 cm3
Bore: 94 mm
Stroke: 84 mm
Compression 11.5:1
Piston speed at rated speed: 25.2 m / s
Power: 345-361 kW ( 470-490 hp) at 9000 min-1
Performance of the Procar engines: uniform 345 kW ( 470 hp) at 9000 min-1
Torque: 390 Nm at 7000 min-1
Deviations from the M88: Capacity up to the limit of 3.5 liters increased throttle replaced by flat slide, valves and channel cross-sections increased, sharper camshafts with extended timing, forged pistons, gear oil cooling for switching and rear

M88 / 2

Use:

M88 / 3

Use:

From 4 /84 BMW M635 CSi model, from 1985, the BMW M5 ( E28 )
Cubic capacity: 3453 cm3
Bore: 93.4 mm
Stroke: 84 mm
Compression 10.5:1
Piston speed at rated speed: 18.2 m / s
Camshaft opening time 264 degree crank angle ( both camshafts are identical), camshafts driven by single-row roller chain
Power: 210 kW ( 286 hp ) at 6500 min-1
Torque: 340 Nm at 4500 min-1
Other: electronic fuel injection and ignition (Bosch Motronic M1.1 ) fitted with storage flap air flow meter, wet-sump lubrication, exhaust manifold, single-plate dry clutch, engine by 30 ° inclined to the right

BMW 745i E23, national version South Africa: since it could not installed in South Africa because of the link traffic of the exhaust - turbocharged engine of the 745i ( the steering gear of the right arm claimed the space of the turbocharger ), was for this country in the M88 / 3 in the top model of the 7 Series combined optionally with an automatic transmission installed.

S38B35

Use:

From 1986 model BMW M 635 CSi Cat ( Europe) / M6 ( USA, Japan)
Cubic capacity: 3453 cm3
Camshaft opening time 248 ° KW ( both camshafts are identical), camshafts driven by double row roller chain
Power: 191 kW (260 hp) at 6500 min-1
Torque: 330 Nm at 4500 min-1
9.8:1 compression
Deviations from the M88 / 3: Motronic with idle controller, 6-in -2- cast manifold, twin-scroll ceramic catalyst with a lambda probe, controlled tank venting with charcoal filter. Externally, the S38B35 to the differently shaped cylinder head cover can be seen: the inscription is BMW M Power ( M88 / 3: M Power only ), and the oil filler cap is not on the intake camshaft, but on the timing chain case.

Variations

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