EJ25 Engine

Subaru EJ25 engine

The largest member of the EJ family was released in 1995 and carried the designation EJ25, and this engine is widely used in all major car models. The EJ25 Subaru engine used the same aluminum cylinder block with cast iron liners dry, which is applied in EJ20, but the diameter of the cylinder was raised from 92 mm to 99.5 mm, height remains the same (201 mm). The crankshaft was installed with 79 mm piston stroke, instead of 75 mm per 2 liter counterparts. The length of the rods remained the same 130.5 mm and the piston compression height was reduced to 30.7 mm (32.7 mm was). All this has made it possible to obtain a working volume of 2.5 liters.

In the first variation EJ25D used twin-shaft cylinder head (DOHC) with 4 valves per cylinder. Drive timing belt and timing belt replacement is necessary every 100 thousand. Km. EJ25D Power is 155 hp at 5600 rev / min, 1997 changed the pistons and power climbed to 10 hp

This motor was raised until 1998, and later was replaced by a more modern engine EJ251. It relates to a power plant and Phase II equipped with a new cylinder head, one on each camshaft (SOHC), as well as new molybdenum-coated pistons, the compression ratio increased to 10.1. Produced and EJ252 engines meet the high environmental standards of the State of California and the different intake throttle valve position of idling and DBP.

In 1999 it appeared the form of the 25th – EJ253 engine, with DMRV instead of DBP, in the intake manifold of the engine there appeared flap Tumble Generator Valves, which helps to improve environmental performance. Since 2006, I began to be used i-AVLS system changes the lift height of the intake valves. In 2009, the number of motor finalized, after which he received the lightweight pistons, modified intake ports, a plastic intake manifold, the other spark plugs, refined system i-AVLS, facilitated by the exhaust system.

In 1998 it was released with twin-shaft EJ254 with DOHC cylinder head, which is the heir EJ25D and related to Phase II. The Motor is using AVCS system on the intake camshafts.

EJ255 engine has become established on the Forester, Impreza WRX and Legacy from 2004-2005 and was a turbocharged engine with a semi-closed unit, DOHC cylinder heads and variable valve timing on the intake camshafts AVCS. Compression ratio in the EJ255 reduced to 8.4 units used turbine TD04L, boost pressure is 0.8 bar. This makes it possible to remove 210 hp at 5600 rev / min. In another version of the engine, boost was increased to 0.93 bar, set a larger intercooler and removed 230 hp at 5600 rev / min. Also on the EJ255, Japanese Forester STI, the turbine was VF41. On WRX III the turbine was  VF52, inflating 0.92 bar. On the Legacy GT VF46 turbines (pressure of 0.95 bar) were set up in 2009, which provided 250 hp at 6000 rev / min. After 2009 on the Legacy GT turbine installed VF45 (pressure 0.87 bar), it has added another 15 hp

On WRX STI versions used EJ257 engine with a semi-closed cylinder block, other pistons compression ratio under 8.0, modified cylinder head with the other combustion chambers, with AVCS system. This engine is a turbine IHI VF48 (boost pressure of 1 bar), it is sufficient to remove the power of 280 hp at 5600 rev / min. The EJ257 for the WRX STI III with compression ratio of 8.2, was added AVCS system on the intake and exhaust camshafts, power increased to 300 hp at 6000 rev / min, 407 Nm of torque at 4000 rev / min. In the US STI turbine used IHI VF39, the boost pressure of 1 bar.

In addition to the EJ20 and EJ25, a series of EJ included EJ15, EJ16, EJ18 and EJ22.

Since 2011, the atmospheric 2.5-liter EJ were replaced by FB25, and the turbo FA20.

Subaru WRX STI 2003 engine sound

EJ25 engine specs

Manufacturer	Gunma Oizumi Plant Also called	Subaru EJ25 Production	1996-present Cylinder block alloy	Aluminum Configuration	Flat-4 Valvetrain	SOHC 2 valves per cylinder DOHC 4 valves per cylinder Piston stroke, mm (inch)	79 (3.62) Cylinder bore, mm (inch)	99.5 (3.86) Compression ratio	8.2 (EJ257) 8.4 (EJ255) 8.7 (EJ257) 9.5 (EJ25D 1996) 9.7 (EJ25D 1997-1999) 10.1 (EJ251/EJ252/EJ253) 10.7 (EJ254) Displacement	2457 cc (338.8 cu in) Power output	224 kW (155 HP) at 5,600 rpm 239 kW (165 HP) at 5,600 rpm 298 kW (165 HP) at 5,600 rpm 300 kW (173 HP) at 5,600 rpm 224 kW (170 HP) at 6,000 rpm 239 kW (210 HP) at 5,600 rpm 298 kW (230 HP) at 5,600 rpm 300 kW (250 HP) at 6,000 rpm 239 kW (265 HP) at 6,000 rpm 298 kW (280 HP) at 5,600 rpm 300 kW (300 HP) at 6,000 rpm Torque output	190 Nm (385 lb·ft) at 2,800 rpm 220 Nm (393 lb·ft) at 4,000 rpm 226 Nm (413 lb·ft) at 4,400 rpm 225 Nm (406 lb·ft) at 4,000 rpm 238 Nm (385 lb·ft) at 2,800 rpm 320 Nm (393 lb·ft) at 3,600 rpm 320 Nm (413 lb·ft) at 3,600 rpm 339 Nm (406 lb·ft) at 3,600 rpm 347 Nm (393 lb·ft) at 2,800 rpm 392 Nm (413 lb·ft) at 4,000 rpm 407 Nm (406 lb·ft) at 4,000 rpm Redline	– HP per liter	63.1 67.2 67.2 70.4 69.2 85.5 93.6 101.8 107.9 114 122.1 Fuel type	Gasoline Weight, kg (lbs)	120 (500) Fuel consumption, L/100 km (mpg) -City -Highway -Combined	for WRX STI VA 14.0 (11) 8.4 (21) 10.4 (16) Turbocharger	 Naturally aspirated Mitsubishi TD04L (WRX/Forester) IHI VF39 (STI) IHI VF41 (Forester STI) IHI VF45 (Legacy GT) IHI VF46 (Legacy GT) IHI VF48 (STI) IHI VF52 (WRX) Oil consumption , L/1000 km (qt. per miles)	up to 1.0 (1 qt. per 600 miles) Recommended engine oil	0W-30 5W-30 5W-40 10W-30 10W-40 Engine oil capacity, L (qt.)	4.0 (EJ25D, EJ25 2007+) 4.5 (2000-2007) 4.3(WRX/STI 2000+) Oil change interval, km (miles)	5,000-10,000 (3,000-6,000) Normal engine operating temperature, °C (F)	– Engine lifespan, km (miles) -Official information -Real	 – 250,000+ (150,000) Tuning, HP -Max HP -No life span loss	 350+


This engine is also installed in

  • Subaru Impreza (WRX/STI)
  • Subaru Forester
  • Subaru Legacy/Outback
  • Subaru Baja
  • SAAB 9-2X

EJ25 2.5l engine Problems and malfunctions

EJ25 2.5 liter engine has the same problems as 2.0 liter. About them you can read here

Subaru EJ25 engine tuning

Exactly as with the 2-liter EJ20, EJ25 and many other atmo engines there is no sense to tune them. Sell it and buy the EJ255 and EJ257, only they should be further developed in this series.

A typical chip with exhaust you can add about 30-40 hp. For more power to the EJ255 you need some modifications which, in general, are no different from those that have been recommended for the construction of fast EJ205, but it is better to use a turbine from STI – IHI VF48. This config will give about  the 300+ hp.

If you still want to drive faster with EJ257 – the turbine configuration with TD05-18G might help.

How to Rebuild an EJ25 Subaru Engine


1999 Subaru Forester EJ25 Engine Removal


Subaru Timing Belt Replacement (EJ25 SOHC)


  1. https://en.wikipedia.org/wiki/Subaru_EJ_engine#EJ25
  2. http://www.superstreetonline.com/how-to/engine/impp-1103-subaru-ej-series-engine-tech/
  3. http://www.gumtree.com.au/s-engine-engine-parts-transmission/subaru+ej25+engine/k0c18475
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