Subaru EJ20: Everything You Need To Know

After Subaru EJ20’s success for three decades as a mainstay machine that powered iconic vehicles such as the WRX STI, it is one of the more notable variants of the EJ family of engines.

It eventually meets its end, concluding its three-decade tenure after the successful release of the ‘Final’ edition in 2020, unveiled at the Tokyo Motor Show, a Japan-exclusive limited to just 555 cars that featured the last out of the EJ20.

But what makes EJ20 such a charismatic and powerful engine? Let’s find out everything we must know about this engine’s design, reliability, issues, tuning potential, and many more.

Let’s get right to it!

What are EJ20 Engines?

Subaru EJ20 is a flat-four gasoline engine with SOHC and DOHC releases; there are also turbocharged versions and corresponding upgrades that were modified to cope with the rising technologies of the automotive industry.

The Subaru EJ engines launched in 1989 in the Legacy vehicle and have multiple variants in displacement over the years. Here in the United States, we are more used to the larger 2.5 liter EJ25 that are currently installed in the WRX STI as well as in WRX way back in 2006. However, present WRX vehicles use the latest 2.0 liter FA engine.

Anyway, even not as famous as it should be, EJ20 still managed to be a popular swapping engine, especially JDM enthusiasts.

This 2.0 Liter engine replaced the smaller 1.8 Liter EA82 and was the first representative of the EJ series and became the basis for the EJ line for so many years.

Engine Specifications and Design:

• Production Run: 1989 – 2020
• Cylinder Head Material: Aluminum
• Cylinder Block Material: Aluminum
• Configuration: Flat-4 (Boxer type)
• Bore: 92 mm
• Stroke: 75 mm
• Valvetrain: SOHC with two valves cylinder and DOHC four valves per cylinder
• Displacement: 2.0 L (1994 cc)
• Compression Ratio(s): 8.0, 8.5, 9.0, 9.5, 9.7, 10.0, 10.1, and 10.2
• Weight: 500 lbs.
• Maximum HP: 320 HP at 7,200 RPM
• Maximum Torque: 413 lb-ft at 2,000 – 5,000 RPM

The Subaru EJ20 cylinder block is made from aluminum with cast-iron dry sleeves and a block height of 201 mm. The cylinder bore diameter is 92 mm, piston stroke of 75 mm, 130.5 mm connecting rod length, and a compression height of 32.7 mm.

The engine block is then installed with two aluminum heads, one camshaft on both intake and exhaust with two valves per cylinder, on the initial release, and followed with dual cams on some production with four valves per cylinder.

These camshafts are belt-driven and. The intake valve diameter is 36 mm, and the exhaust valve diameter registers at 32 mm. The spark plugs are placed centrally for better combustion in the chamber.

The most common EJ20 variant is the SOHC-designed EJ20E which was installed in the Subaru Legacy and produced in four installments or generations. Each generation has designated power specifications – 125 HP, 133HP, 153 HP, and 140 HP.

Subaru also released a naturally aspirated DOHC head, EJ20D, that powered the 1989 – 1999 Legacy, producing 150 HP at 6,800 RPM. The power of Subaru Legacy 2 and Impreza first generations are increased to 135 HP. 2003 – 2009 are 140 HP.

Applications of EJ20E Engine:

• 1989 – 1994 BC – BF Series Legacy JDM
• 1993 – 1999 BD – BG Series Legacy JDM
• 1998 – 2004 BE – BH Series Legacy JDM
• 2003 – 2009 BL – BP Series Legacy JDM
• 1991 – 1999 BC, BD, BF Series
• 1993 – 1999 GC – GF Series Impreza JDM
• 2008 – Present GH – GE Series IMpreza JDM
• 1994 – 1999 GC and GF Series Impreza JDM
• 1990 – 1993 Isuzu Aska

Subaru started their SOHC engines with open-deck block design with naming them EJ20Ns, N being the number of modifications or updates. These engines have new cylinder heads, lighter pistons, and intake manifolds great at low RPMs.

In 1998, Subaru started to produce EJ201 and EJ202. These two are Phase 2 engines with new SOHC heads, open deck block, and lighter pistons. EJ201 and EJ202 has 125 HP at 5,6000 RPM.

Later, EJ202 was improved and used a more lightweight cylinder block as well as the sleeves, 4-2-1 headers, MAF sensor, and a modified intake manifold. These upgrades allowed the engine to increased its power to 138 HP at 5,600 RPM and 65 lb-ft of torque available at 4,400 RPM.

EJ203 is characterized by the use of a MAF sensor and has an electronic throttle body.

The EJ204 is a phase two engine also that features DOHC cylinder block heads. It used an AVCS variable valve timing system on the intake camshaft and a 50-degree adjustment range. The EJ204 has a power of 155 HP, and there are 180 HPs available too.

Applications of EJ204 DOHC naturally aspirated AVCS:

• 1999 – 2001 Legacy B4 TSR JDM BE – BH series
• 2003 – 2009 Legacy JDM BL – BP series
• 2003 – 2007 Legacy Europe BL – BP Series
• 1993 – 1999 Impreza JDM GC – GF series
• 2007 – 2011 Impreza GE – GH series
• 2005 – 2007 Europe Forester SG series
• 2008 – 2011 Forester JDM SH series
• 2008 – 2012 Exiga JDM YA series
• 2009 – 2014 Legacy Europe and South Africa BM and BR series

EJ20 engines became more renowned due to their turbocharged versions. 

And the first of such engines is the EJ20G. It is among the first to use turbocharger and oil nozzles, low compression pistons, and a closed decked block. The capacity of the stock fuel injector is 380 cc.

There are three categories for the EJ20G engines:

First is the rocker-style HLA EJ20G:

This engine produces 195 HP at 6,000 RPM and 215 HP for the GT at 6,400 RPM. These engines can be identified through the coil on plug, with 2 M6 bolts per coil and valve covers with quad-cam 16-valve.

All of these engine have an air-to-water intercooler setup.

Second is the Bucket-style HLA EJ20G:

Subaru has used this updated version across all WRX models since early 1992. The engine cylinder head is installed with hydraulic lifters instead of the rockers arms used in the previous EJ20G models.

Pistons are modified using a cast aluminum material and have oil squirters. It is followed by an open-deck block equipped with piston oil squirters until the EJ20K WRX engines release.

These EJ20Gs can be identified through a tab on the right surface of the block half and a smoother surface. The EJ20G continued to be the primary engine in the WRX wagon with an automatic transmission from 1996 until 1998; then, it was replaced by the EJ205.

And the third is Shim-under-bucket style EJ20G:

The power ranges from 217 HP to 271 HP at 6,000 and 6,500, respectively. These EJ20G variants can be identified by coil on plug with one M8 bolt per coil and valve covers with four-cam 16-valves and horizontal lines on top the plug holes and has slanted intercooler.

The STI RAs that used these engines received the upgraded Shim-under-bucket style lifters, unlike the standard HLA buckets that WRX and WRX STI had.

These engines feature lighter valves, STI factory 8.5 compression rating, INKO marked intake valves, and EXKO marked exhaust valves.

The installments are then followed with the EJ20K with two categories almost identical to the EJ20G. 

The first is the shim over bucket style and shim under bucket style. The power output varies from 286 HP and 300 HP. These engines can be identified by plug leads, smooth valve covers, and a wasted spark coil on the intake manifold center.

To add, the intake manifold is red for all STI models. It utilizes an IHI ball-bearing turbo, VF23, or VF24 on the STI. These EJ20K have die-cast pistons for all WRX models; STI typeRA and STI models share the exact factory forged pistons.

EJ205 engines are used for the WRX models outside Japan as of 1999. The Japan-exclusive WRX use EJ207 from 199 – 2001. After 2001, all WRX vehicles use EJ205 until 2006, when USDM WRX models changed their engines to EJ255.

Next is the EJ207, which was produced for the GC8 in UK, Japan, and Australia.

The EJ207 has an 8.0 compression ratio, idle air integrated into the throttle body, wasted spark coil off-center of manifold, red or bare aluminum intake manifold, open deck block, inlet under the manifold, AVCS variable valve timing, and higher rev limit than EJ205.

Version 7 has a single-scroll turbocharger, top-feed injectors, throttle by cable, and omitted the TGV. Versions 8 and 9 are both twin-scroll, throttle by cable, AVCS, top feed injector engines. There are no TGVs also.

The intake manifold is one piece, the spark plugs are one step colder compared to other STIs. The exhaust is different with the USDM WRX down to the headers. There is no immobilizer for these versions.

The engine speed is limited to 8,000 RPM.

EJ20X and EJ20Y Engines:

These engines are based on the same engine platform; the X is designated to indicate an automatic, and the Y indicates a manual one. The EJ20X was launched in the 2003 Legacy GT matched to a five-speed automatic transmission.

The EJ20Y engine was introduced in the following year in 2004 Legacy GT, with a five-speed manual transmission.

The EJ20X and EJ20Y engines are open deck types where the cylinder walls were supported at the three and nine o’clock positions. It has an aluminum block with 92 mm bores – with cast iron cylinder liners – and a 75 mm piston stroke for a capacity of 500 cc per cylinder, with thicker cylinder walls.

The crankcase of these engines has five main journals, and the flywheel housing was cast with the crankcase for increased rigidity. Th EJ20X has a forged crankshaft and connecting rods with cast aluminum pistons with forged crowns.

Both of them have aluminum cylinder heads with cross-flow cooling, DOHC design per cylinder bank, and four valves per cylinder – both two for intake and exhaust v, that were actuated by roller rocker arms.

The EJ20X and EJ20Y are equipped with Subaru’s Dual Active Valve Control System, which provides the variable intake and exhaust valve timing. The Legacy GT, the EJ20X, was installed with a twin-scroll IHI VF38 turbocharger; the EJ20Y has a larger Mitsubishi TD04 HLA 19T.

Both have a 9.5 compression rating and a fast spooling turbo that yields a torque-full engine performance.

EJ20TT

It can also be referred to as the DOHC Sequential Twin Turbo and inter-cooled engine. This engine was installed in Australian Market Liberty B4 models and Japanese-spec Legacies, both right-hand driving.

The pistons are lighter and have a shorter skirt than the WRX EJ20T to allow a higher engine speed.

Engine Potential

Like we mentioned above, the EJ20 series became prosperous due to its tuning and upgrade potentials. However, I hope it is clear that increasing the power of a naturally aspirated EJ20 is non-sense.

What we will do is to buy an EJ207 or EJ205 and to make a swap.

If you have a turbocharged EJ205, you will need to buy an STI intake system, VF30 turbocharger, blow-off valve, ACL bearings, aluminum 2-row Mishimoto radiator, FMIC, Walbro 255 fuel pump, boost controller, and a 3-inch performance exhaust system.

After installing these parts and configuring the ECU, the EJ205 can reach about 300 HP.

It is possible to increase the engine capacity of your EJ20 to 2.2 Liters, but you will need a stroker that includes an EJ25 crank, Mahle pistons, ARP head studs, and H-beam rods.

To attain more than 350 HP of power on your EJ207 engine. But you need performance parts to upgrade, such as a frontal intercooler, Cusco engine mount set, 3-row Mishimoto radiator, and sump baffle plate.

A new TD05-18G turbocharger, HKS blow-off valve, fuel lines, 800 cc/min fuel injectors, heavy-duty timing belt, cold air intake, oil cooler, 12 mm oil pump, equal length headers, and a 3-inch aftermarket exhaust system.

Adjust the ECU correctly, and you can reach 350HP or more – a very nice ceiling for the EJ207 stock internals.

To reach beyond the 500 HP mark on the EJ207 engine, you need head porting and forged pistons.

Problems Surrounding EJ20 Engines:

I think we all can nod our heads that all engines are not perfect – far from being there. But even with that, we want to keep our machines in good running condition and prolong their useful life.

That is why we avoid encounters that will put our engines in peril. Same with the EJ20, though it has strong internals and reliable block can still be caught off guard of some issues.

First is the engine knocking sound. This is not new to the engines because others experience this too. Anyway, you can hear a knocking noise in EJ20 coming from the fourth cylinder.

The fourth cylinder is the hottest, but the worst cooled among other cylinders; hence the pistons begin to knock. At first, in cold starts, the engine knocks, then all the time after that.

Indeed that is a bad sign for your machine, nothing comes good from that sound, though, so you will need to keep a budget aside and overhaul it.

Another issue that needs to be addressed is the excessive oil consumption of the EJ20, especially the turbocharged ones, and can affect small sizes of naturally aspirated engines.

Maybe the piston rings failed; that is why this happened in the first place. Loose internal components can also cause this. Subaru recommended changing the oil in time and use the recommended oil.

That leads us to the last thing, the oil leak. We can say that this engine consumes a lot of oil but is unaware that there might be leaks in the valve cover gaskets and camshaft seals.

This can confuse you, especially if you are experiencing the issue mentioned above in excessive oil consumption.

Engine oil is essential for all engines so that problems will not pop like crazy. Use high-quality original engine oil. If your country has a hard time finding quality gasoline, use the best option.

Grave concern for high-quality fuels is regarded for this engine.

In terms of reliability, owners of the naturally aspirated should be ecstatic since their engines are more reliable and have a longer life than the turbocharged ones; they can last more than 150,000 miles.

The engines of the Impreza WRX and STI should be overhauled every 60,000 miles.

Summary

This engine has a wide variety to choose from. Multiple engine developments and modifications proved its longevity as well as its flexibility to be installed in different vehicles and driving conditions.E

ver since it arrived in the industry, EJ20 has been regarded as one of the most reliable and powerful engine blocks.

Ideal for low to mid RPM ranges and torque-dominated performance, this engine is deemed to be used in some applications in drifting, race tracks, and even drag racing. It is also a good engine swap for enthusiasts who want to taste the savory crisp of the EJ20 engine.

It shows a lot of potential and aftermarket support. The price is just right, not over the top but still provides an excellent cash-back for the money you spent on. Not that monstrous kind of engine, but it will still be worthy of being put as a sleeper, in my opinion.

With the proper maintenance and care, this engine can last more than 150,000 miles. Don’t forget to use high-quality engine oil and fuel for better engine performance.

I hope that this simple rundown of the EJ20 engine helped you understand the engine’s design, architecture, origins, reliability, issues, potential, and overall impact on the automotive industry.