Nissan MR18DE

The Nissan MR18DE is a 1.8 l (1,797 cc, 109.65 cu.in.) straight-four 4-stroke natural aspirated gasoline engine from Nissan MR-family.

The MR18DE engine features a lightweight aluminum block with a fully balanced five-bearings crankshaft and aluminum head with two camshafts (DOHC) and four valves per cylinder.

The cylinder bore is 84.0 mm (3.3 in) and the piston stroke is 81.1 mm (3.19 in). Compression ratio rating is 9.9:1. The Nissan MR18DE motor has an electronic throttle, continuous variable valve timing system CVTC on the intake camshaft, EGR system and NDIS (Nissan Direct Ignition System) with individual coils on each spark plug.

It produces from 124 to 128 PS (91 to 94 kW; 122 to 126 HP) of horsepower and 173-176 Nm (17.6-17.9 kg·m, 127-130 lb·ft) of torque.

The breakdown of the engine code is as follows:

• MR – Engine Family
• 18 – 1.8 Liter Displacement
• D – DOHC (Dual Overhead Camshafts)
• E – Multi Point Fuel Injection

General information

Cylinder block

The MR-family engines use the same technology as in the HR-series. The MR18DE has an aluminum cylinder block with a five-bearings crankshaft supported system. Cylinders in the Nissan MR18DE engines are fitted at an offset to minimize friction arising from the angle of the connecting rod as a piston descends into the cylinder. The resulting smoother reciprocating motion of the pistons contributes to high power output and high torque as well as fuel economy. Also, the structure is designed so that the piston remains in the upper part of the cylinder longer than in a conventional engine (piston velocity slows down). This permits more efficient use of combustion energy and effectively improves thermal efficiency.

The crankshaft and camshaft journals are finished with a polishing tape to produce a mirror-like finish. The result is a thorough reduction in friction on these bearing surfaces of key engine components. The cylinder bore is 84.0 mm (3.3 in) and the piston stroke is 81.1 mm (3.19 in) and compression ratio rating is 9.9:1. The Nissan MR18DE motor has two compression and one oil control rings.

Cylinder head

The cylinder head is made of strong, light aluminum alloy which gives it good cooling efficiency. Each camshaft is supported by five bearings. The MR18DE has continuous variable valve timing system (C-VTC) on the intake camshaft. C-VTC enables variable valve timing in response to engine rpm and throttle opening. Enhanced control and reduced system friction improve response and optimize torque characteristics.

Intake valves are 34 mm in diameter, intake duration is 224°, and the exhaust valves are 27.6 mm, exhaust duration is 212°. The MR18DE motor does not have hydraulic lifters, so special valve lifters are used to adjust the valve clearance.

The engine has a plastic intake manifold with an integrated tumble control valve. The MR18DE is equipped with EGR (Exhaust Gas Recirculation) system. This system returns a portion of the exhaust gas to the intake side to reduce fuel consumption and minimize emission.

Head tightening procedure and torque specs:

• Step 1: 40 Nm; 4.1 kg·m; 30 ft·lb
• Step 2: Turn all bolts 100°
• Step 3: Loosen all bolts completely
• Step 4: 40 Nm; 4.1 kg·m; 30 ft·lb
• Step 5: Turn all bolts 100°
• Step 6: Turn all bolts another 100°

Problems and malfunctions

The Nissan MR18 is reliable and durable. This engine sometimes has a problem with alternator belt (whistle noise). It needs to tighten or replace the old belt by a new one.

The engine has a timing chain, their service life is about 150,000 miles of mileage (200,000-250,000 km). The valve clearance needs to be adjusted every 60,000 miles of mileage (90,000 km). The MR18DE motor life expectancy is 200,000 miles of mileage (300,000 km) or more.

Maintenance data

Valve clearance adjustment data

Calculate the thickness of new adjusting valve lifter so valve clearance comes within specified values.

R = Thickness of removed valve lifter
N = Thickness of new valve lifter
M = Measured valve clearance

Intake:
N = R + [M – 0.30 mm (0.012 in)]
Exhaust:
N = R + [M – 0.33 mm (0.013 in)]

Valve lifters are available in 26 sizes range from 3.00 mm (0.1181 in) to 3.50 mm (0.1378 in), in steps of 0.02 mm (0.0008 in).

Example (intake valve):
R = 3.10 mm
M = 0.52 mm
N = 3.10 + (0.52 – 0.30) = 3.32 mm, so we need a valve lifter with identification mark 332.

Vehicle applications

Author: Sergei Wers
About: Co-founder and CEO of a multi-brand auto repair shop (engine repair, chassis repair, body repair and painting) for over 15 years. I have been developing internet sites with technical specifications for more than seven years.