Nissan MA12S engine

The Nissan MA12S 1.2 L (1,235 cc) engine which was launched in 1987 in Japan.

The Nissan MA12S is a displacement-enhanced version of the MA10S. It came to 1987 with the facelift of Micras on the market. It largely corresponds to the data of the MA10. Changed the stroke (crankshaft), the bore (piston, cylinder), the connecting rod in its length and the cylinder head (bore diameter).

Often Nissan's MA12 engines are characterized by blown cylinder head gaskets . However, this is due to a initially set too low tightening torque for the cylinder head bolts. In a newsletter to the Nissan workshops, Nissan has raised the moment to 65 Nm to 69 Nm. If a new seal must be installed, this must be observed, otherwise the damage will recur. Tightening the screws even more strongly is not recommended as the screws are turned directly into threads in the aluminum block, which tend to rupture at even higher forces, resulting in a very costly repair.

The following MA engines were built by Nissan:

• MA09ERT
• MA10ET
• MA10E
• MA10S
• MA12S

The engines were built in the following, all based on the K10 platform Nissan models:

• Nissan Micra ( HK10 )
• Nissan Micra Turbo (EK10FR)
• Nissan Micra Super Turbo
• Nissan Pao ( PK10 )
• Nissan Figaro ( FK10 )
• Nissan Be-1 ( BK10 )

The breakdown of the engine code:

MA = motor series MA

09/10/12 = [cubic capacity in cm³] / 100

S = carburetor

E = multipoint injection (also known as Nissan ECCS)

R = Roots compressor

T = turbocharger

Mixture preparation 

• For versions without KAT, a downdraft carburetor with electronic shut-off valve to prevent overrun
• for versions with KAT, a downdraft carburettor with mixture control valve and shut-off valve

• This carburetor version is also called single-point injection, it being noted that the mixture control valve does not inject fuel, but adds additional air, thereby achieving a rudimentary mixture regulation.

Performance data 

• Power without CAT: 44KW / 60PS
• Torque without EGR / KAT: 98 Nm at 3000 rpm

• Power with CAT: 40KW / 55PS
• Torque without EGR / KAT: 92 Nm at 3000 rpm

Motor data 

• Bore: 71 mm
• Stroke: 78 mm
• Bore-to-stroke ratio: 1.099
• Compression 9: 1
• 2 valves per cylinder (mounted at an angle, not vertical)
• Inlet valve: 35 mm diameter
• Exhaust valve: 30 mm diameter
• central camshaft driven by toothed belt 
• hemispheric combustion chamber
• hemispherical piston crown
• Cross-flow cylinder head
• Centrally located spark plug

Materials 

• All-aluminum engine block
• All-aluminum cylinder head
• dry cylinder liners made of steel

Crankshaft 

• 5-way mounted crankshaft
• Main bearing diameter 45mm
• Main bearing width 17,1mm
• Connecting rod diameter 40mm
• Connecting rod width 15.1mm
• Crankshaft with holes through the connecting rods for weight reduction

Lubrication system

• Oil content: 2.8 liters (viscosity 10W-40, 15W-40, 20W-50, depending on the application)
• Oil pump in the oil sump, driven by a shaft-gear combination of the camshaft

Cooling system 

• Coolant content 4 liters
• Cooling system without expansion tank (overpressure cooling system)

Ignition on all versions 

• electronically adjusted transistor ignition, driven by camshaft
• Ignition order: 1-3-4-2
• Ignition timing: 10 ° before TDC at 750 / min to 850 / min (for manual transmission)
• Spark plug: NGK BPR4ES-11, NGK BPR5ES-11, NGK BPR6ES-11 (depending on the application)

Motor control

• Control unit without KAT: for shut-off valve and ignition setting
• Control unit with KAT: for shut-off valve, ignition setting and mixture regulation

• Built-in CPU is a Motorola 68000 series processor . The EPROM is not socketed!