Nissan VQ25DD

Nissan VQ25DD Neo-DiThe 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

Engine Specifications
Engine codeVQ25DD
LayoutFour stroke, V6
Fuel typeGasoline (petrol)
Production1998-
Displacement2.5 L, 2,495 cm3 (152.24 cu in)
Fuel systemMulti Point Fuel Injection
Power adderNone
Power output 209 PS (154 kW, 206 HP) at 6,400 rpm
215 PS (158 kW, 212 HP) at 6,400 rpm
Torque output 265 Nm (27.0 kg⋅m, 195 lb⋅ft) at 4,400 rpm
270 Nm (27.5 kg⋅m, 199 lb⋅ft) at 4,400 rpm
Firing order1-2-3-4-5-6
Dimensions (L x W x H):
Weight

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)

Cylinder block
Cylinder block alloyAluminium
Compression ratio:11:1 or 11.3:1
Cylinder bore:85.0 mm (3.346 in)
Piston stroke:73.3 mm (2.886 in)
Number of piston rings (compression / oil):2 / 1
Number of main bearings:4
Cylinder inner diameter (standard):85.000-85.010 mm (3.3465-3.3468 in)
Piston skirt diameter (standard):84.980-84.990 mm (3.3457-3.3461 in)
Piston pin outer diameter:21.989-22.001 mm (0.8657-0.8662 in)
Connecting rod bushing inner diameter:22.000-22.012 mm (0.8661-0.8666 in)
Connecting rod big end diameter:53.00 mm (2.0866 in)
Connecting rod center distance:147.60-147.70 mm (5.8110-5.8149 in)
Piston ring side clearance:Top0.045-0.080 mm (0.0018-0.0031 in)
Second0.030-0.070 mm (0.0012-0.0028 in)
Oil0.015-0.125 mm (0.0006-0.0049 in)
Piston ring end gap:Top0.20-0.30 mm (0.0079-0.0118 in)
Second0.31-0.46 mm (0.0122-0.0181 in)
Oil0.20-0.60 mm (0.0079-0.0236 in)
Crankshaft main journal diameter:59.975 mm (2.3612 in)
Crankpin diameter:49.956-49.974 mm (1.9667-1.9674 in)
Crankshaft center distance:36.61-36.69 mm (1.4413-1.4445 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.

Cylinder head
Block head alloyAluminium
Valve Arrangement:DOHC, chain drive
Cylinder head height:126.3-126.5 mm (4.97-4.98 in)
Valves:24 (4 valves per cylinder)
Valve head diameter:INTAKE33.0-33.3 mm (1.299-1.311 in)
EXHAUST29.0-29.3 mm (1.142-1.154 in)
Valve length:INTAKE96.57-96.77 mm (3.8019-3.8098 in)
EXHAUST95.02-95.22 mm (3.7409-3.7502 in)
Valve stem diameter:INTAKE5.965-5.980 mm (0.2348-0.2354 in)
EXHAUST5.955-5.970 mm (0.2344-0.2350 in)
Valve spring free length:INTAKE42.94 mm (1.690 in)
EXHAUST52.28 mm (2.058 in)
Exhaust camshaft journal diameter:№125.935-25.955 mm (1.0211-1.0218 in)
№2, 3, 4, 523.445-23.465 mm (0.9230-0.9238 in)
Camshaft cam height:INTAKE44.96 mm (1.770 in)
EXHAUST43.50 mm (1.712 in)

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 (HOT)
Intake valve0.304-0.416 mm (0.012-0.016 in)
Exhaust valve0.308-0.432 mm (0.012-0.017 in)
Compression pressure
Standard13.0 kg/cm2 (185 psi) / 300 rpm
Minimun10.0 kg/cm2 (142 psi) / 300 rpm
Compression differential limit between cylinders1.0 kg/cm2 (15 psi) / 300 rpm
Oil system
Oil consumption , L/1000 km (qt. per miles)up to 0.5 (1 qt. per 1200 miles)
Recommended engine oil 5W-30
Oil type APISJ
Engine oil capacity (Refill capacity) With filter change 4.7 L
Without filter change 4.4 L
Oil change interval, km (miles)6,000 (3,000)
Oil Pressure, kPa (kg/cm 2, psi) Idle speed: More than 98 (1.0, 14)
2,000 rpm: More than 294 (3.0, 43)
Ignition system
Spark plug Standard: PLFR5A-11 (NGK)
Hot type: PLFR4A-11 (NGK)
Cold type: PLFR6A-11 (NGK)
Spark plug gap1.1 mm (0.043 in)
Spark plug tightening torque20-29 Nm (2.0-3.0 kg⋅m, 14-22 ft⋅lb)

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.

ColdHot
Intake0.26-0.34 mm (0.010-0.013 in)0.304-0.416 mm (0.012-0.016 in)
Exhaust0.29-0.37 mm (0.011-0.015 in)0.308-0.432 mm (0.012-0.017 in)

Vehicle applications

ModelYears Produced
Nissan Cefiro (A33)1999–2002
Nissan Cedric1999–2004
Nissan Gloria1999–2004
Nissan Skyline (V35)2001–2006
Nissan Stagea (M35)2001–2007
Naza Ria2004-
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1 Comment

  1. Hello I was hoping to find the specific fuel specs for the engine but I don’t see it. I wish to know what the fuel pressure in Mpa should be as also how to decarb the valves.

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