taza
Forum Member
Most people who have Naturally Aspirated Subaru's are generally chasing more power or response from their engine.
While some models are more under powered than others, power upgrades are achievable. The majority of people say you can't get more power from an N/A EJ motor. I have to disagree but it is not as simple as forced induction engines.
Subaru's EJ 4 cylinder series ranges from a 1.6l motor to a 2.5l motor. The series was released in 1989 and is still available today. This has given Subaru over 20 years to perfect an already solid, reliable engine.
Increasing power and engine efficiency is about increasing airflow and removing flow restrictions. Their are both minor and major modifications possible to increase power.
This complication of methods is both tested and theory.
Small Stuff
Light Weight Pulleys
These come in both standard drive and under drive versions. They are made from aluminum and are used on your main crank pulley, alternator and powersteering. The benefit of light weight (under drive) crank pulleys is they reduce drag/load on the engine from the accessories.
This can free upto 15% load on the engine.
Can be had for $90-350
Phenolic Manifold Spacer
Grimmspeed make these and work by lifting the manifold from the hot engine block. The material they are created from works as an insulation/heat soak between the block and the manifold. The cooler the manifold, the more dense the air and the more efficient the engine will run.
Grimmspeed;
Throttle Body Spacer
Again works by spacing the throttle body from the manifold. This allows more air in the manifold and when you stomp on the accelerator it reduces the time between the air takes to be drawn into the engine. This or the manifold spacer benefits by increasing throttle response and increasing fuel economy.
Both can benefit by upto 3l per 100km.
Grounding Kits
Replaces the earth leads from the negative terminal on the battery. Allows for a better connection of the electrical system.
More response can be benefitted.
~$50
High Octane Fuel
Higher octane fuel allows the engines computer to further advance ignition timing. Here in Australia our regular fuel is RON 91, we also have 95, 98 and 100(15% ethanol)
I personally am not a fan of the ethanol but I know many people who run it in their vehicles.
I recently ran a unknown mix of diesel and RON91 fuel in my Brumby. Ran alright, pinged under decent load. However it left me strandard 100km from home as the oil in the diesel clogged the fuel filter...
Major Stuff
Exhaust
A CatBack exhaust is a good performance upgrade. Allows more flow (and most of the time noise) from the restrictive stock system. Generally if the engine ranges between 2.0l to a 2.5l a 2" 1/4' is a good upgrade. It allows good flow with some back pressure. If too much back pressure is lost (2.5", larger or no exhaust) the valves can burn.
Since Cat/s(Catalic Converter) are required in Australia and Europe for emissions and legality a Cat-Back is legal.
I have personally found the the system with 1 resonator and a free flowing muffler has a good boxer note without being too loud. However if you want a quiet vehicle 2 resonators can be installed.
$200-600
Extractors/Headers
To get that boxer note unequal length headers must be installed in comparison to the standard headers. Again most aftermarket headers have increased flow and combined with a high flow cat and 2" 1/4' cat back fairly high gains can be achieved.
$150-450
Aftermarket engine management or Tune
Depending on your modifications a tune may or may not be necessary. With a modified engine to get the most gains out of the engine is to have it dyno-tuned to your particular requirements.
However standard Subaru computers have upto 40% adjustment in both directions of air/fuel mixture from standard.. This is good to know for engine upgrades... :iconwink:
The US guys on Nasioc have heaps of experience with this. There are huge amounts of them running EJ25's on EJ18 computers with modifications.
Cams(Camshafts)
Cams aren't very common in Subies here in Aus. In the US it is fairly common. There are a number of companies such as Delta Cams and Rallitek that do cam grinds for all Subarus(EA, EJ and FB series engines).
I personally am going for Delta Cams 1000 torque grind. This works between 1000rpm-3500rpm, where I spend most of my time. It has little to no effect on power up higher in the rev range. There have been cases where this torque grind has increased fuel economy in EJ22's and EJ25's.
Other performance grinds are also available. These can have other significant effects on your engine and it's drivablity. The 2000 grind offered by delta is not recommended for a DD(daily driver).
A cam grind involves sending your existing cams to Delta in the US, they select the profile your after and regrind your cam to spec.
NOTE: Camshaft grinds are not available for the EJ20 N/A as that engine was never released in the US.
Power gains are huge, upto 15% can be had. Yes cams can be done to
$350+
If your due to do your headgaskets it makes for an easy upgrade while the engine is out.
Port and Polishing
Porting involves increasing the diameter of the ports that flow into and out of the heads.
Polishing involves making these ports smooth.'
All in all it increases airflow and as we know the more airflow we have the more power we have.
While some models are more under powered than others, power upgrades are achievable. The majority of people say you can't get more power from an N/A EJ motor. I have to disagree but it is not as simple as forced induction engines.
Subaru's EJ 4 cylinder series ranges from a 1.6l motor to a 2.5l motor. The series was released in 1989 and is still available today. This has given Subaru over 20 years to perfect an already solid, reliable engine.
Increasing power and engine efficiency is about increasing airflow and removing flow restrictions. Their are both minor and major modifications possible to increase power.
This complication of methods is both tested and theory.
Small Stuff
Light Weight Pulleys
These come in both standard drive and under drive versions. They are made from aluminum and are used on your main crank pulley, alternator and powersteering. The benefit of light weight (under drive) crank pulleys is they reduce drag/load on the engine from the accessories.
This can free upto 15% load on the engine.
Can be had for $90-350
Phenolic Manifold Spacer
Grimmspeed make these and work by lifting the manifold from the hot engine block. The material they are created from works as an insulation/heat soak between the block and the manifold. The cooler the manifold, the more dense the air and the more efficient the engine will run.
Grimmspeed;
~$160
Throttle Body Spacer
Again works by spacing the throttle body from the manifold. This allows more air in the manifold and when you stomp on the accelerator it reduces the time between the air takes to be drawn into the engine. This or the manifold spacer benefits by increasing throttle response and increasing fuel economy.
Both can benefit by upto 3l per 100km.
Grounding Kits
Replaces the earth leads from the negative terminal on the battery. Allows for a better connection of the electrical system.
More response can be benefitted.
~$50
High Octane Fuel
Higher octane fuel allows the engines computer to further advance ignition timing. Here in Australia our regular fuel is RON 91, we also have 95, 98 and 100(15% ethanol)
I personally am not a fan of the ethanol but I know many people who run it in their vehicles.
I recently ran a unknown mix of diesel and RON91 fuel in my Brumby. Ran alright, pinged under decent load. However it left me strandard 100km from home as the oil in the diesel clogged the fuel filter...
Major Stuff
Exhaust
A CatBack exhaust is a good performance upgrade. Allows more flow (and most of the time noise) from the restrictive stock system. Generally if the engine ranges between 2.0l to a 2.5l a 2" 1/4' is a good upgrade. It allows good flow with some back pressure. If too much back pressure is lost (2.5", larger or no exhaust) the valves can burn.
Since Cat/s(Catalic Converter) are required in Australia and Europe for emissions and legality a Cat-Back is legal.
I have personally found the the system with 1 resonator and a free flowing muffler has a good boxer note without being too loud. However if you want a quiet vehicle 2 resonators can be installed.
$200-600
Extractors/Headers
To get that boxer note unequal length headers must be installed in comparison to the standard headers. Again most aftermarket headers have increased flow and combined with a high flow cat and 2" 1/4' cat back fairly high gains can be achieved.
$150-450
Aftermarket engine management or Tune
Depending on your modifications a tune may or may not be necessary. With a modified engine to get the most gains out of the engine is to have it dyno-tuned to your particular requirements.
However standard Subaru computers have upto 40% adjustment in both directions of air/fuel mixture from standard.. This is good to know for engine upgrades... :iconwink:
The US guys on Nasioc have heaps of experience with this. There are huge amounts of them running EJ25's on EJ18 computers with modifications.
Cams(Camshafts)
Cams aren't very common in Subies here in Aus. In the US it is fairly common. There are a number of companies such as Delta Cams and Rallitek that do cam grinds for all Subarus(EA, EJ and FB series engines).
I personally am going for Delta Cams 1000 torque grind. This works between 1000rpm-3500rpm, where I spend most of my time. It has little to no effect on power up higher in the rev range. There have been cases where this torque grind has increased fuel economy in EJ22's and EJ25's.
Other performance grinds are also available. These can have other significant effects on your engine and it's drivablity. The 2000 grind offered by delta is not recommended for a DD(daily driver).
A cam grind involves sending your existing cams to Delta in the US, they select the profile your after and regrind your cam to spec.
NOTE: Camshaft grinds are not available for the EJ20 N/A as that engine was never released in the US.
Power gains are huge, upto 15% can be had. Yes cams can be done to
$350+
If your due to do your headgaskets it makes for an easy upgrade while the engine is out.
Port and Polishing
Porting involves increasing the diameter of the ports that flow into and out of the heads.
Polishing involves making these ports smooth.'
All in all it increases airflow and as we know the more airflow we have the more power we have.
Last edited:
, but still :lol:.