Electrical Issues
Electrical issues can be caused by exposed wires, poor connectivity, poor battery ground, or alternator charging issues. OEM engine ground wires are prone to corroding and are missing on a large portion of the vehicles that we work on in the shop. We can replace any loose or missing ground wires and get your engine management system running in tip top shape.
Spark Plugs
One of the most commonly overlooked maintenance items is the spark plug, and these lead to issues in a large portion of the vehicles that we work on at the shop. Incorrect plug gap is one of the most common, as well as damaged or fouled plugs causing misfiring and all sorts of other driveability issues.
For basic bolt on modifications such as a 3” turbo back exhaust, intake, and boost control solenoid upgrades, one step colder heat range spark plugs are suggested. We use one step colder NGK Iridium spark plugs to help with pre-ignition, reducing the risk of creating conditions which could lead to knock. If colder spark plugs are installed, don't start and stop your engine when cold. If the vehicle is not allowed to run until the engine is up to operating temperature, be prepared to change spark plugs more frequently.
Fuel Issues
Fuel Octane
In order to get optimal performance from your Subaru, fuel octane should be 91 whenever possible, or whatever is the highest fuel octane available locally to you. It’s best to tune on the fuel that is available in your area to avoid potential knock conditions after a custom tune has been performed. In Manitoba, the best fuel available is 93 octane at certain Shell stations.
Fuel Delivery System
Fuel system delivery is of paramount importance when it comes to performance, especially for those seeking to create more power. Even one small issue in the fuel delivery system can prevent your vehicle from reaching its desired horsepower level. Common issues in this area can be attributed to an old or poorly installed fuel pump or fuel filter. Fuel lines should also be checked for cracks and secure connections.
Other issues may be attributed to sub-optimal base fuel pressure - it is critical that the correct base fuel pressure is set if you are running an aftermarket fuel pressure regulator. If an aftermarket turbo kit is installed, both fuel injector and fuel pump upgrades will be required. The OEM fuel injectors with an upgraded fuel pump are limited to support around 300~350 whp, more specifically dependent on the year/model of your Subaru. This limitation can cause cylinder misfire issues, resulting in poor idle and reduced driving quality. Depending on the fuel pump modifications, upgrading the fuel pressure regulator or changing to a return-style fuel system may help to achieve the ultimate horsepower goal.
When seeking to increase power over 350 whp, upgrading the fuel pump, fuel rails, lines and fuel pressure regulator are HIGHLY recommended before a custom tune. This recommendation is in place as OEM injectors can easily go static, or reach close to 100% operating duty cycle when normal bolt on modifications (3” turbo back exhaust, intake, EBCS, intercooler, etc.) and the OEM turbo are in place. Static or damaged injectors (stuck open or closed) can result in erratic fuelling, putting engine health at risk. In addition, OEM lines, rails and regulator can cause uneven distribution at high power levels which can lead to a damaged cylinder.
Mechanical Issues
Engine
All cylinders should have good compression. A compression test will be performed in the Pre-Tune Check-up to ensure the variance between cylinders is within acceptable levels. Some compression issues can be resolved by correcting an out of “time” timing belt, but in most cases there is physical damage that leads to the reduction in compression such as damaged pistons, valves, or headgaskets.
Clutch
It is important that the vehicle’s clutch is rated for the desired power levels you hope to achieve after the tune. If a turbo larger than stock size is installed on your Subaru, it is a good idea to upgrade the clutch as well.
The stock clutch is not designed to “hold” the torque a high-powered engine will produce, resulting in a slipping clutch. If an upgraded clutch is needed, keep in mind that some aftermarket clutches require a break-in period to “bed” the material. Most STIs and WRXs with bolt-on stock turbos have no issues with the OEM clutch in place while tuning.
Transmission Torque Capacity
The WRX transmission has a limited torque capacity around the 300-350 ft-lb range, but this varies greatly depending on driving style and whether or not the transmission has been previously damaged. This factor will limit the power potential of the build unless you are ready to upgrade the transmission as well.
Turbocharger Issues
A boost "leak" test will be performed to ensure the correct use and installation of wastegate lines, vacuum lines, the boost solenoid, springs, etc. This test will also serve to verify all the couplers are tight and that there are no leaks on the intake manifold or blow-off valve. Having a well-sealed system is vital for performing a proper tune.
Blow Off Valves
Vent-to-atmosphere blow-off valves can sound super cool - however, they increase the risk of backfiring when lifting the throttle, a sign of running overly rich. With stock turbos or drop-in turbo applications staying below 22-24 psi level the factory blow-off valves can remain as they should not cause any issues. If an aftermarket blow-off valve is desired, recirculating it back into the intake like the OEM set-up is recommended. If you are being tuned in Speed Density (no MAF sensor), an aftermarket vent-to-atmosphere blow-off valve can be used since the MAF sensor is no longer present to monitor any airflow lost in the system when the valve opens.
MAF/MAP Sensors
The MAF sensor on a Subaru with a stock diameter intake tube can support roughly 350~375 whp. If using a drop-in turbo that supports more than 350~375 whp, a Speed Density tune is recommended. This allows the limitations of the MAF sensor to be bypassed, or removed altogether. If the OEM MAF sensor is removed, an aftermarket air temperature sensor will need to be installed. All turbo Subarus also have a MAP sensor. The OEM MAP sensor is good to around 22-23 psi. If pressure levels higher than 21-22 psi are desired, an upgrade of the MAP sensor will be required.
Large Turbos
When running a turbo that is larger than the stock size, a 3-port boost control solenoid is recommended to provide the most boost control range at higher rpms. External wastegate springs may also need to be upgraded to allow the 3-port boost control solenoid to achieve the correct level of boost control.
Intercooler Upgrades
Depending on the vehicle’s modifications and desired power, an upgraded top-mount or a front-mounted intercooler may be necessary. This is typically the case when using a turbo larger than the stock size. The front mount position can increase cooling efficiency as the intercooler is protected from heat soak from the engine bay, a situation which leads to inconsistent power and almost immediate knock conditions. For stock location turbochargers, our recommendation begins with a high quality PWR top-mount intercooler.