Subaru EZ30 Engine

1. Specifications
2. Overview, problems
3. Performance tuning

Subaru EZ30 engine specs

Subaru EZ30 engine reliability, problems and repair

This engine was put into production in 1999 and it is a successor of EG33. At that time it was flagman Subaru motor, its displacement was 3.0L, therefore they installed it only on the largest cars.
EZ30 engine was created completely from scratch, and it used aluminum Flat-6 cylinder block with cast-iron sleeves, 2 mm thick, cylinder block deck height is 202 mm. Inside there was crankshaft with a piston stroke 80 mm, connecting rods length is 131.5 mm, pistons diameter is 89.2 mm, piston compression height is 30.3 mm, and compression ratio is 10.7. Due to all this, they received 3 liter capacity.
This cylinder block was covered with aluminum DOHC heads with two camshafts, 4 valves on the cylinder. Specs of EZ30 camshafts are the following: duration is 254/226 deg, lift is 10.0/9.5 mm. These camshafts are put in action by means of two timing chains.
EZ30 applies aluminum variable-length intake manifold. Its switching happens at 3,600 rpm.
This motor showed 220 horsepower at 6,000 rpm, and torque 289 Nm at 4,400 rpm.
In 2003 it was modified and received the name EZ30D which is still known as EZ30R.
The EZ30R engine differs from EZ30 in the modified heads with the improved ports, and also variable valve timing AVCS and variable valve lift system AVLS on the intake side was added (adjustment range is 50°). The valve lift depends on turns and has 3 positions: to 2,000 rpm, 2,000-4,000 rpm, over 4,000 rpm.
Also EZ30R uses electronic throttle body with diameter 76 mm, a plastic intake manifold, MAF sensor is used instead of MAP sensor and the new exhaust manifold is applied.
All these modifications allowed to receive 245 horsepower at 6,600 rpm, and the torque increased up to 297 Nm at 4,200 rpm.
Firing order of EZ30 is 1-6-3-2-5-4.
Production of EZ30 engine continued till 2009, but since 2007 it was gradually substituted with newer EZ36 .

Subaru EZ30 engine problems and malfunctions

1. EZ30 timing chain noise. Check timing chain tensioner, most likely it has failed. Usually it needs to be replaced together with timing chains.
2. EZ30 overheating. There are two main reasons: first check the radiator if it is necessary, buy an aluminum radiator, it will help. The second reason is blown head gasket.
If it didn’t help, then check water pump, the thermostat or perhaps there is air in the cooling system.
Another problem with EZ30 is fuel consumption, you should spend money on gasoline more often than usually.
But you shouldn’t be afraid, you won’t face these problems often (except high fuel consumption).
In general, EZ30 is reliable engine for daily use. You need to serve it regularly and to use high quality engine oil. If your country has a problem with qualitative gasoline, then just use more or less normal gasoline. All this will increase EZ30 engine lifespan to 200,000 miles of mileage and even more.

Subaru EZ30 engine tuning

EZ30 Turbo

To increase EZ30 power without turbocharger, you need to buy aftermarket exhaust system. It will give a little additional power and will improve the sound considerably. Stock headers and exhaust system of this engine don’t allow to receive all possible power. You don’t need to go further and to build powerful n/a engine, it is better to build EZ30 turbo.
Good turbo project will be pretty expensive, but if you want, we will tell how to make it. You have to replace stock pistons with forged (CR ~ 8.5), also to buy Pauter rods, valves, valve springs, retainer kits, ARP studs and if you want to receive power more than 400 horsepower, then we recommend to buy sleeves. But all this doesn’t make sense if we don’t install turbocharger. You will need Garrett GT3582 turbocharger and don’t forget about oil feed line, oil return line. For this turbocharger you need turbo manifold, you can make it yourself or find where to buy it. Also buy K&N cold air intake system, FMIC, piping, GTR injectors or injectors for powerful STI. You will also need more powerful fuel pump, Bosch 044 will be the good choice. You should also buy fuel pressure regulator, BOV valve, wastegate, 3″ exhaust system, VEMS ECU or something similar.
Such EZ30 turbo, with boost pressure 15 psi (~1 bar), will be able to show about 500 horsepower.
You can build EZ30 turbo using stock internals and even receive 400+ horsepower. But it is risky, in this case use water/methanol injection system.
Simpler option it to build supercharged EZ30. You will need only supercharger kit, for example Raptor which has boost pressure 7 psi (0.5 bar). It is normal for stock internals and you will receive 350+ horsepower. 

<<<<<