Nissan VQ25DD

The Nissan VQ25DD NEO-Di is a 2.5 l (2,495 cc, 152.24 cu.in.) natural aspirated V6 60° 4-stroke gasoline engine from Nissan VQ-family. The VQ25DD NEO-Di engine debuted in 1998 on the Nissan Cefiro A33.

The Nissan VQ25DD motor features a lightweight aluminum block with a fully balanced four-bearings crankshaft and two aluminum heads with two camshafts (DOHC) and four valves per cylinder. The Nissan VQ25DD engine is equipped with direct fuel injection system, eVTC (Electromagnetic Continuous Variable Valve Timing Control), NDIS (Nissan Direct Ignition System) with individual coils on each spark plug and variable-length intake manifold.

Cylinder bore and piston stroke are the same with the VQ25DE, it is 85.0 mm (3.35 in) and 73.3 mm (2.886 in), respectively. Compression ratio rating is increased to 11:1 or 11.3:1. The Nissan VQ25DD engine produced from 209 PS (154 kW, 206 HP) to 215 PS (158 kW, 212 HP) of output power and from 265 Nm (27.0 kg⋅m, 195 lb⋅ft) to 270 Nm (27.5 kg⋅m, 199 lb⋅ft) at 4,400 rpm of torque.

The breakdown of the engine code is as follows:

• VQ – Engine Family
• 25 – 2.5 Liter Displacement
• D – DOHC (Dual Overhead Camshafts)
• D – Direct fuel injection

General information

Cylinder block

The VQ25DD has an aluminum cylinder block with a four-bearings crankshaft supported system, forged steel connecting rods, a micro-finished one-piece forged crankshaft. The crankshaft journal diameter is 60 mm (2.36 in), the crankpin diameter was increased from 45 mm (1.78 in) on VQ25DE to 50 mm (1.96 in).

The cylinder bore is 85.0 mm (3.346 in), piston stroke is 73.3 mm (2.886 in) and compression ratio rating is 11:1 or 11.3:1. The Nissan VQ25DD motor has two compression and one oil control rings. The connecting rod’s length are 147.7 mm (5.81 in)

Main bearing cap bolts tightening procedure and torque specs:

• Step 1: 32-38 Nm; 3.3-3.9 kg·m; 24-28 ft·lb
• Step 2: Turn all bolts 90-95°

After securing bearing cap bolts, make sure crankshaft turns smoothly by hand.

Connecting rod bearing nut

• Step 1: 19-21 Nm; 1.9-2.1 kg·m; 14-15 ft·lb
• Step 2: Turn nuts 90-95°

Crankshaft pulley bolt

• Step 1: 39-49 Nm; 4.0-5.0 kg·m; 29-36 ft·lb
• Step 2: Put a paint mark on the crankshaft pulley
• Step 3: Again tighten by turning 60-65°, about the angle from one hexagon bolt head corner to another.

Drive plate fixing bolts

• 83-93 Nm; 8.5-9.5 kg·m; 61-69 ft·lb

Cylinder head

The cylinder head is made of strong, light aluminum alloy which gives it good cooling efficiency. The camshafts are driven by single primary and two secondary chains. The primary timing chain transmits the rotational movement from the crankshaft to the intake camshafts, the secondary chains connects intake and exhaust sprocket on each head respectively.

The intake valve diameter is 33.0 mm (1.40 in) and the exhaust valve diameter is 29.0 mm (1.14 in). The VQ25DD motor does not have hydraulic lifters, so special valve lifters are used to adjust the valve clearance.

Head tightening procedure and torque specs:

• Step 1: 98 Nm; 10.0 kg·m; 72 ft·lb
• Step 2: Loosen all bolts completely
• Step 3: 34-44 kg·m; 3.5-4.5 kg·m; 25-33 ft·lb
• Step 4: Turn all bolts 90-95°
• Step 5: Turn all bolts another 90-95°

Camshaft sprocket bolts

• 103-113 Nm; 10.5-11.5 kg·m; 76-83 ft·lb

Problems and malfunctions

The Nissan VQ25DD is reliable and durable.

Some problems that can happen:

• MAF (Mass Air Flow) sensor malfunction
• Pressure reduction in high pressure fuel pump
• Ignition coils malfunction
• Loss of power due to catalyst failure
• High fuel consumption and detonation due to carbon deposits on the valves.
• Engine does not start. Error code is P0335: Crankshaft Position Sensor Circuit. Often the problem is in the starter fault.

The engine has three timing chains, 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 Nissan VQ25DD life expectancy is 200,000 miles of mileage (300,000 km).

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 – 0.34 mm (0.013 in)]

Valve lifters are available in 25 sizes from 7.88 mm (0.3102 in) to 8.36 mm (0.3291 in), in steps of 0.02 mm (0.0008 in).

Example (exhaust valve):
R = 7.90 mm
M = 0.52 mm
N = 7.90 + (0.52 – 0.34) = 8.08 mm, so we need a valve lifter with identification mark 808.

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.