Subaru has been known as the utilizers of boxer engines and is really good in it. They created a wide range of machines that powered famous vehicles that we see today, such as Impreza, WRX, and many more. But as we can notice, the content of displacements is hovering around a maximum of 2.5 liters. Subaru also made a larger, relatively largest engine in the flat category, hence the EZ30 and EZ36 engines.
Today we will talk about the latest EZ36D engine.
Join me as we talk about the engine’s design, abilities, potential, issues, applications, reliability, and many more.
Let’s get right to it!
What are Subaru EZ36 Engines?
The Subaru EZ36 engine is supposed to be the next-in-line successor of the EZ30R engine, which was partly true, but not that fast as you think. Let’s have some retrospectives. EZ30 engines were introduced in November 2000 for the 2001 model year Outback. Subaru also made a twin-turbo variant released in the following years for the Subaru B11S concept car, unveiled at Geneva in 2003. But the EZ30 was refreshed in 2003, and the second-generation EZ30 was placed under the hood of the newly-introduced Tribeca in 2006.
And from that, the EZ36 was introduced on the restyled version of Tribeca for its 2008 model year. Eventually, it entirely replaced the 3.0 Liter EZ30 engine in the Outback and Legacy starting in 2009 for the 2010 model year.
However, starting with the 2020 model year for the Outback and Legacy, the six-cylinder engine EZ36 was replaced by the premium turbocharged four-cylinder FA24F as an option for automobiles mentioned above. FA24F was previously introduced as the mainstay engine for the Subaru Ascent, the successor to the Tribeca.
Compared to its predecessor, EZ30, the changes that the EZ36 are far more rigid cylinder block. Subaru omitted the Variable Valve Lift System; asymmetrical connecting rods for a more compact packaging; integration of Subaru’s Dual Active Valve Control System (AVCS) for variable intake and exhaust timing; a new cooling system, and a new timing chain design.
Engine Specifications and Design:
- Production Run: 2007 – Present
- Cylinder Head Material: Aluminum
- Cylinder Block Material: Aluminum
- Configuration: Flat-6 (Boxer type)
- Bore: 92 mm
- Stroke: 91 mm
- Valvetrain: DOHC four valves per cylinder
- Displacement: 3.6 L (3629 cc)
- Compression Ratio(s): 10.5
- Weight: 401 lbs.
- Maximum HP: 260 HP at 6,000 RPM
- Maximum Torque: 247 lb-ft at 4,400 RPM
The Subaru EZ36 was the largest displacement flat-six engine available for any Subaru-made vehicle. It has a 3.6 Liter capacity, horizontally-opposed six-cylinder gasoline engine. It debuted in the B9 Tribeca in 2007 and was later offered in the BR/BM Liberty, BN Liberty, BR Outback, and BS Outback.
The Subaru EZ36 or EZ36D uses a strengthened cylinder block made from a die-cast aluminum cylinder block with a 92 mm cylinder bore, a 91 mm piston stroke, and a 10.5 compression rating. Within the cylinder block are sintered iron pieces that control the thermal expansion of journal clearances during warm-up; as reported by Subaru, these iron pieces also alleviate shocks to the crankshaft journals and reduce overall engine vibrations. The 36D block also has cast-iron cylinder liners thinner compared to the EZ30R – 1.5 mm for EZ36D and 2.0 mm for the EZ30R.
Again, in relation to the EZ30R, the distance between bores for the EZ36D engine was decreased by 6.4 mm, but the length of the crankcase remains the same. To add, shorter and asymmetrically inclined connecting rods were used to maintain the same width.
The EZ36D’s crankshaft was supported by seven main bearings same for the EZ30 engine.
The cylinder head was made from aluminum with chain-driven double overhead camshafts per cylinder bank. The EZ36D have three timing chain that operates through a 10-mm chain which drives the idler from the crankshaft’s sprocket; and, from the idler, two 8-mm chains drive the left and right bank camshafts.
For the EZ36D engine, the inside timing chain cover was incorporated on the front surface of the block and heads, while the outside timing chain cover was securely placed to the engine with 39 bolts and sealed three-way.
The engine was equipped with Subaru’s variable valve timing Dual AVCS which controls the intake and exhaust camshafts. Adjustments in the intake and exhaust valve timing, especially in varying driving conditions. It enables the effectivity of the AVCS better for scavenging in the cylinder. It also increases exhaust gas recirculation and reduces pumping losses.
The EZ36D engine runs on a sequential, multi-point fuel injection system; it has a higher injector flow rate than the EZ30R. Conversely, the EZ36D machine has its individual ignition coil for each cylinder, commonly known as coil-on-plug, with high energy discharge spark plugs for a better ignition performance.
Though the EZ36D was modeled a new and revised combustion chamber design for more efficient fuel combustion, its compression rating was lowered to 10.5 in comparison to the larger 10.7 for the EZ30. Two knock sensors enable the ECU to adjust the ignition timing in response to the feedback provided by the combustion noise.
The cooling system of the EZ36 engine uses a parallel-flow design that utilizes a water separation chamber in the engine block that allows the coolant to flow to and across the cylinders individually – rather than traversing from cylinder to cylinder – and to wade through the cylinder heads simultaneously.
In addition, the parallel-flow cooling system is an excellent cooling system since it achieved more engine coolant temperature and reduces combustion temperatures by 187 – 252 F for a 34 Fahrenheit increase in the knock limit. This improves the low to mid torque range and enables a safer operation even on a lower RON (Research Octane Number) fuel. Moreover, ignition timing could be advanced because the temperatures are cooler and do not promote engine knock.
The exhaust design of the EZ36D is a ‘‘U-turn’’ type, which aims at the exhaust to minimize vibration. The EZ36D machine was also equipped with EGR (Exhaust Gas Recirculation). An exhaust port positioned on the rear left cylinder head supplies exhausts gas via a metal pipe to an electronically-controlled EGR valve.
Engine Tuning, Upgrades, and Modifications
The Subaru EZ36D is almost the same as the EZ30 engine and does not have diverse differences. So tuning, bolting a turbo, and supercharger are your choices to increase the power of your EZ36D engine. But it would be best if you build a turbo for the EZ36D and some performance parts.
It is pretty expensive to build such a setup, but if you want, you have to replace your stock pistons with forged ones, those types that can make a compression ratio of 8.5. Also, you need to buy Pauter rods, retainer kits, new valves, valve springs, ARP studs, and if you want to achieve more than 400 HP, you should be buying a sleeve for the block.
Next, you should buy a turbocharger – Garrett GT3582 and do not forget about the oil return line and oil feed line. For the turbocharger, you need a turbo manifold, K&N cold air intake system, piping, FMIC, GTR injectors, or any injector of your choice that has the same power. You will also need a powerful fuel pump, fuel pressure regulator, blow-off valve, 3-inch performance exhaust system, wastegate, VEMS ECU, or the likes of it.
With such a setup, your EZ36 can gain 500 HP and 15 psi maximal boost pressure. If you choose to retain the stock internals and install a supercharger kit, then you can reach 400 or more HP since the stocks can absorb this power increase.
Problems Surrounding the EZ36D Engine:
The Subaru EZ36 engine is a far more reliable engine than its predecessor, the EZ30. But we cannot avoid the unnecessary occurrence of any troubles or issues when using our machine. Even having the advantages of a flat boxer engine, some weaknesses or problems can affect the EZ36.
The first issue is the timing chain noise. The timing chain tensioner primarily causes this issue; maybe it has failed or is slowly going in that direction. Though it is unusual to replace the chains since they are more superior in material and make than the belt ones, in this case, you need to replace the chain tensioner and the timing chain.
The second issue is the engine overheating of the EZ36D. There are three main reasons for this problem, the radiator, the water pump, and the head gasket. Check your radiator; it might be faulty; if the issue cannot be rooted there, try checking the engine’s water pump as well as its thermostat and the air in the cooling system. If it is still not there, your head gasket might have leaks; leaks are the primary drivers of overheating since engine oil goes out without any restrictions beyond that.
To add, you need high-quality engine oil and fuel for this engine to maximize its potential and valuable life. It would be best if you also serviced it regularly to solve other problems that you cannot notice.
Subaru EZ36D as a successor of the EZ30 engine, really proved that it carries the legacy that EZ30 brought when it was first released. This engine was a product of development to offer the consumers a large, powerful but steady, grounded, and stable boxer engine. Being a large boxer have its own advantages, and one of them is the cornering abilities of such machines compared to the conventional inlines out there. It also has efficient fuel consumption and cooling system that are reliable for such high demanding engine. Though it is somehow pricey and shares some problems, I still consider the EZ36D as a solid and reliable engine capable of lasting 250,000 to 300,000 miles and even more.
I hope that this brief and straightforward discussion helped you understand the pieces of information regarding Subaru’s EZ36 engine design, issues, reliability, applications, and overall impact on the automotive industry.