Category Archives: Turbo

Ej20, ej20G, EJ257, gc8, Intake, Intercooler, STi, Subaru, TMIC, Tuning, Turbo, WRX

Overboost and Underboost Subaru common causes:

Overboost and Underboost Subaru common causes:

The common causes for overboost or underboost: This is a basic guide on the possible causes and some solutions to those causes of a overboost or a underboost situation in a turbocharged subaru.

Overboost and Underboost Subaru common causes: This is the layout of the stock turbo subaru boost control system.
Overboost and Underboost Subaru common causes: Turbo Subarus: Common Overboost and Underboost issues with Turbo Subarus.

Overboost:

1.) Decat + High flow induction –  Cure: Reduction of the solenoid duty cycle or alteration of restrictor size will help return boost output to its normal level.

2.) Split, poor fitting, or disconnected pipes – Cure: Replace or refit pipes, the pipes that will cause this issue are between the wastegate actuator, solenoid, and the turbo. Including up to the restrictor on the return pipe of the 3 port solenoid.

3.) Manual Boost Controller – Electronic Boost Controller set too high – Cure: Don’t be so greedy and back the boost duty/adjuster off to a safe level.

4.) Restrictor Pill not fitted / size incorrect – Cure:  Ensure restrictor pill is fitted (3 port) if so on a 3 port reduce the restrictor size and on the 2 port increase the restrictor size to reduce the boost to a safe level.

5.) Clogged 3-port solenoid: It is possible that the flow of air through the 3-port solenoid could be restricted between the turbo outlet port and the wastegate actuator port if the solenoid is very dirty (usually oil vapor from the intake system), this allows the wastegate to remain clamped shut longer than it should be causing a potential overboost situation. Cure: Clean with carb or clutch/brake cleaner.

6.)Loss of solenoid funcation: Although this is not bverboost it shows itself with very simmilar symptoms, its an interesting scenario. It is possible for the solenoid to fail or even stick shut while under boost. This will result in a rapid reduction of boost pressure to wastegate pressure approx 0.5 BAR. So if you were running at full boost 1.0 BAR for example and the solenoid was to fail shut it would feel just like overboost as the wastegate rapidly opens due to the solenoid blocking off the spill from the wastegate. Cure: Either clean the solenoid with carb or clutch+brake cleaner or replace the solenoid.

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Ej20, ej20G, EJ257, exhaust, gc8, Intake, Intercooler, JDM, STi, Subaru, TMIC, Tuning, Turbo, UK, USDM, WRX

Wastegate and Boost Creep FAQ

Wastegate and Boost Creep FAQ

What is Boost Creep?

Boost creep is a situation where your wastegate port is not large enough to allow the exhaust gas to bypass the turbo. What happens is the exhaust gas will choke the wastegate port preventing further gas flow through the port. Then, the exhaust gas has to take the path of least resistance which is through the turbine of the turbo. This will spool the turbo ‘uncontrolled’ beyond your normal controlled max boost level.

Wastegate and Boost Creep FAQ: A stock Subaru turbo with the internal wastegate and stock actuator.
Wastegate and Boost Creep FAQ: A stock Subaru turbo.

The turbo will be spooling past wastegate spring rate pressure even though the wastegate is fully open thus it is uncontrolled. The best way to check for boost creep is to connect the turbo outlet port directly to the wastegate actuator port and go for a drive. In 4th gear you should normally get a stable boost level of about 0.5 BAR, if you have boost creep the boost will hit 0.5 BAR and will continue to rise with rpm until you either back off or hit overboost fuel cut.

Boost creep should only be present on a turbo that has very little restriction. For example a fully de-catted and high flow induction. It’s been found that the fast spooling IHI VF35 is very prone to boost creep. The cure is to remove the turbo and enlarge the wastegate port. Then, fit a stronger actuator 0.75 BAR the reason for this is because you have made the wastegate port larger. The effective size of the wastegate plate acting against the exhaust gas flow is larger which allows the exhaust gas excert more force on the wastegate plate.

This in effect weakens the effectiveness of the actuator. Before the increase in size of your wastegate port the actuator would open at 0.5 BAR, after the increase the actuator would open earlier at 0.3–0.4 BAR. After these changes are made to the turbo either a boost controller or a remap (to adjust solenoid duty cycle) should be sought to control the boost to a safe level.

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Ej20, ej20G, EJ25, EJ257, gc8, Intake, Intercooler, JDM, STi, Subaru, TMIC, Turbo, UK, USDM, WRX

Boost control systems on a Turbo Subaru:

Boost control system on a Turbo Subaru:

This guide covers most  boost related issues including a short introduction on how your boost systems work. This information is based on the Classic Impreza’s, but will cover the newer WRX/STi cars to a certain extent.

Safe boost levels:

When modding your car without mapping (full de-cat and high flow induction etc) you increase the efficiency of your turbo which could result in engine damage due to lean running at high rpm / max boost. To prevent damage always try and keep your boost level as close to standard as possible until your car is mapped for the increase in boost pressure.

TLDR: Don’t screw with your boost levels until you get the car tuned by someone who knows what they are doing. Otherwise you’ll probably end up with a blown up Subaru.

Boost Issues:

Is the boost control system connected correctly:

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AWD, Old School Subaru, Subaru, Turbo, USDM

Buy this now: 1989 Subaru XT6

Buy this now: 1989 Subaru XT6

A Subaru XT6.
Subaru XT6.

If you want to own a really cool and really rare piece of Subaru history you should take a look at this XT6:

I have a 1989 Subaru XT6 5 speed with full time all-wheel drive and low miles. It is a 2.7 liter flat six cylinder engine and functioning air ride suspension. I’ve had the car for two and a half years now and it looks completely different from when I bought it. I’ve spent more hours working on it than I would probably like to admit. It has a new water pump, new timing belts, new fuel pump, new radiator, new plugs, new tranny and rear diff fluid, and four new tires, new exhaust. Over this previous summer the whole car was sanded, cleaned up, dents removed and straightened the whole body. It has a fresh coat of factory Subaru red and it looks awesome, you need to see it in person to really appreciate it. Countless hours put into it. I really don’t want to sell this awesome car but it is a historic subaru that deserves to be kept clean and taken on the occasional cruise. I’d accept trade offers preferably a subaru or truck but shoot me an offer.

Subaru XT6 for sale.
Subaru XT6 for sale.

Craigstlist

Is this 1989 Subatu XT6 a good deal or something that should be skipped? It’s from Wisconsin so I would be weary of rust, but it looks pretty rust free to me. I would inspect underneath the car however to be sure. What does everyone else think? Comment below!

EJ257, Intercooler, JDM, STi, Subaru, TMIC, Turbo, USDM

JDM Automatic Intercooler STi Switch Install:

JDM Automatic Intercooler STi Switch Install:

Here is the step by step guide to installing the JDM Automatic Intercooler STi switch. For those of you wondering the advantage of upgrading to the JDM automatic intercooler switch is that it essentially works as a on/off switch for the STi intercooler sprayer. So there is no more constant pushing of the sprayer button. Push the button once to turn it on, and again to turn it off. However, it will empty out your intercooler sprayer tank very quickly if you keep it on.

Here is the switch we are going to be installed:

JDM Automatic Intercooler Switch: The JDM intercooler switch that you will be installing.
JDM Automatic Intercooler Switch: The JDM intercooler switch that you will be installing.

1.) Pop out the fuse box panel. The fuse box panel is located underneath and to the left of the steering wheel.

2.) Use your fingers to depress the tab on the button of the button to pop it out.

JDM Automatic Intercooler Switch: The USDM stock STi switch that you will be removing.
JDM Automatic Intercooler Switch: The USDM stock STi switch that you will be removing.

3.) Pull the switch out of the dash.

4.) Depress the tab on the back of the plug to remove the switch.

JDM Automatic Intercooler Switch: USDM STi intercooler switch removed. Get ready to install the JDM switch now.
JDM Automatic Intercooler Switch: USDM STi intercooler switch removed. Get ready to install the JDM switch now.
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Ej20, EJ25, EJ257, forester, Impreza, Legacy, Ringland, STi, Subaru, Turbo, USDM, WRX

Oil Additives: What Subaru Says

Oil Additives: What Subaru Says

Subaru of America does not recommend the use of any engine oil additives in any Subaru engine crankcase. Subaru engines are designed to be lubricated with normal petroleum or synthetic-based engine oils in the viscosity and grade indicated in the Owner’s Manual for each specific engine and usage condition. Subaru has not tested the effectiveness or compatibility of any engine oil additives.

Oil Additive: Avoid adding any oil additives to your Subaru boxer engine.
Oil Additive: Avoid adding any oil additives to your Subaru boxer engine.

However, the use of such oil additives does not void warranty coverage. Usage of any additive is at the owner’s discretion. Since Subaru has not tested the compatibility or effectiveness of any such additives, should an engine failure occur that is determined to be caused by the incompatibility or performance of such an additive, the vehicle owner would be be referred to the additive manufacturer to request reimbursement of the cost of the repair.

If you are using oil additives to try to save a leaking headgasket it’s better to just suck it up and just either install new headgaskets yourself or have the work done by a trusted mechanic.

Either use Subaru’s OEM synthetic motor oil or use Rotella T6 motor oil. If your Subaru is still under warranty by Subaru it’s best to get your oil changed by a Subaru dealership and avoid introducing oil additives into your boxer engine. Even if it’s Subaru’s official stance that they won’t void warranties if oil additives are involved it doesn’t mean that they won’t if there is more evidence of engine “tampering”. Avoid anything that could potentially cause a dealership to refuse service to your car in the future.

Otherwise you might have a expensive repair bill if your Subaru boxer engine spins a bearing or has a ringland failure. Of course adding aftermarket parts like an exhaust or intake along with a tune will greatly increase the justification of a Subaru dealership to void a warranty more than adding oil additives.

Not adding oil additives can be another step in avoiding a void warranty from Subaru of America. On a final note remember that Subaru can scan your ECU for previous tunes even if you went back to a stock tune and will void a warranty for that.

2.5RS, AWD, Drivetrain, Ej20, EJ25, EJ257, forester, gc8, Legacy, STi, Subaru, Turbo, WRX

Maintenance:Subaru Periodic Maintenance Part 1:

Maintenance: Subaru Periodic Vehicle Maintenance Services:

Vehicle maintenance is an important factor for proper vehicle operation. It’s the vehicle owner’s responsibility to ensure that fluid levels (engine oil, coolant, etc.) are checked frequently, in accordance with the instructions in the Subaru owner’s manual. However, many ‘gas and go’ vehicle owners may not take the time to fulfill these basic responsibilities. This places added importance on the performance of periodic maintenance services. If the Subaru owner isn’t looking after his vehicle, it falls to the automotive service professional to ensure that proper maintenance procedures are performed.

Maintenance: Subaru Periodic Vehicle Maintenance: It's always important to periodically check your Subaru's timing belt for wear and tear.
Maintenance: Subaru Periodic Vehicle Maintenance: It’s always important to periodically check your Subaru’s timing belt for wear and tear.

The frequency of scheduled inspection and maintenance services required by late model Subaru vehicles is minimal when compared with vehicles of the past. For example, even the very commonly used term ‘tune-up’ has lost most of its original meaning. In the old days, a ‘tune-up’ meant fresh spark plugs, points and condenser, and basic engine adjustments such as timing, idle mixture and idle speed. Modern technology has eliminated the need for many of these adjustments and replacement parts. However, the tune-up is alive and well— only its definition has changed.

While the number of vehicle items requiring regular replacement has decreased, the number of items needing periodic inspection has not. Whether you call it a tune-up or something else, this service offers an excellent opportunity for all engine belts, hoses and ignition wires to be checked for wear and tension. Old tune-up standbys like spark plugs, fuel and air filters are still on every Subaru vehicle and still require periodic inspection and replacement as necessary.

The same applies to all other items on the Subaru maintenance schedule. The important thing is to carefully inspect each item. If additional corrective action is required, now is the time to find out.

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AWD, Ej20, EJ25, EJ257, forester, Impreza, Legacy, STi, Subaru, Turbo, USDM, WRX

Subaru OBD-2 Diagnostic Trouble Codes:

Subaru OBD-2 Diagnostic Trouble Codes:

This is a list of the OBD-2 diagnostic trouble codes for Subaru Impreza, WRX, STi, Forester, and Legacy.

Subaru OBD2 Diagnostic port
Subaru OBD2 Diagnostic port

P0031 Front oxygen (A/F) sensor heater circuit low input
P0032 Front oxygen (A/F) sensor heater circult high input
P0037 Rear oxygen sensor heater circuit malfunction
P0038 Rear oxygen sensor heater circuit high input
P0065 Air assist injector solenoid valve malfunction
P0066 Air assist injector solenoid valve circuit low input
P0067 Air assist injector solenoid valve circuit high input
P0100 Mass or Volume Air Flow Circuit Malfunction
P0101 Mass or Volume Air Flow Circuit Range/Performance Problem
P0102 Mass or Volume Air Flow Circuit Low Input
P0103 Mass or Volume Air Flow Circuit High Input
P0104 Mass or Volume Air Flow Circuit Intermittent
P0105 Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction
P0106 Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem
P0107 Manifold Absolute Pressure/Barometric Pressure Circuit Low Input
P0108 Manifold Absolute Pressure/Barometric Pressure Circuit High Input
P0109 Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent
P0109 Intake Air Temperature Circuit Malfunction
P0111 Intake Air Temperature Circuit Range/Performance Problem
P0112 Intake Air Temperature Circuit Low Input
P0113 Intake Air Temperature Circuit High Input
P0114 Intake Air Temperature Circuit Intermittent
P0115 Engine Coolant Temperature Circuit Malfunction
P0116 Engine Coolant Temperature Circuit Range/Performance Problem
P0117 Engine Coolant Temperature Circuit Low Input
P0118 Engine Coolant Temperature Circuit High Input
P0119 Engine Coolant Temperature Circuit Intermittent
P0120 Throttle/Petal Position Sensor/Switch A Circuit Malfunction
P0121 Throttle/Petal Position Sensor/Switch A Circuit Range/Performance Problem
P0122 Throttle/Petal Position Sensor/Switch A Circuit Low Input
P0123 Throttle/Petal Position Sensor/Switch A Circuit High Input
P0124 Throttle/Petal Position Sensor/Switch A Circuit Intermittent
P0125 Insufficient Coolant Temperature for Closed Loop Fuel Control
P0126 Insufficient Coolant Temperature for Stable Operation
P0128 Thermostat malfunction
P0130 O2 Sensor Circuit Malfunction (Bank 1 Sensor 1)
P0131 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)
P0132 O2 Sensor Circuit High Voltage (Bank 1 Sensor 1)

P0133 O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)

P0134 O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)
P0135 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
P0136 O2 Sensor Circuit Malfunction (Bank 1 Sensor 2)
P0137 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
P0138 O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)
P0139 O2 Sensor Circuit Slow Response (Bank 1 Sensor 2)
P0140 O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)
P0141 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)
P0142 O2 Sensor Circuit Malfunction (Bank 1 Sensor 3)
P0143 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 3)
P0144 O2 Sensor Circuit High Voltage (Bank 1 Sensor 3)
P0145 O2 Sensor Circuit Slow Response (Bank 1 Sensor 3)
P0146 O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 3)
P0147 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 3)
P0150 O2 Sensor Circuit Malfunction (Bank 2 Sensor 1)
P0151 O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)
P0152 O2 Sensor Circuit High Voltage (Bank 2 Sensor 1)
P0153 O2 Sensor Circuit Slow Response (Bank 2 Sensor 1)
P0154 O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 1)
P0155 O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)
P0156 O2 Sensor Circuit Malfunction (Bank 2 Sensor 2)
P0157 O2 Sensor Circuit Low Voltage (Bank 2 Sensor 2)
P0158 O2 Sensor Circuit High Voltage (Bank 2 Sensor 2)
P0159 O2 Sensor Circuit Slow Response (Bank 2 Sensor 2)
P0160 O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 2)
P0161 O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)
P0162 O2 Sensor Circuit Malfunction (Bank 2 Sensor 3)
P0163 O2 Sensor Circuit Low Voltage (Bank 2 Sensor 3)
P0164 O2 Sensor Circuit High Voltage (Bank 2 Sensor 3)

P0165 O2 Sensor Circuit Slow Response (Bank 2 Sensor 3)
P0166 O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 3)
P0167 O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 3)
P0170 Fuel Trim Malfunction (Bank 1)
P0171 System too Lean (Bank 1)
P0172 System too Rich (Bank 1)
P0173 Fuel Trim Malfunction (Bank 2)
P0174 System too Lean (Bank 2)
P0175 System too Rich (Bank 2)
P0176 Fuel Composition Sensor Circuit Malfunction
P0177 Fuel Composition Sensor Circuit Range/Performance
P0178 Fuel Composition Sensor Circuit Low Input
P0179 Fuel Composition Sensor Circuit High Input
P0180 Fuel Temperature Sensor A Circuit Malfunction
P0181 Fuel Temperature Sensor A Circuit Range/Performance

P0182 Fuel Temperature Sensor A Circuit Low Input
P0183 Fuel Temperature Sensor A Circuit High Input
P0184 Fuel Temperature Sensor A Circuit Intermittent
P0185 Fuel Temperature Sensor B Circuit Malfunction
P0186 Fuel Temperature Sensor B Circuit Range/Performance
P0187 Fuel Temperature Sensor B Circuit Low Input
P0188 Fuel Temperature Sensor B Circuit High Input
P0189 Fuel Temperature Sensor B Circuit Intermittent
P0190 Fuel Rail Pressure Sensor Circuit Malfunction
P0191 Fuel Rail Pressure Sensor Circuit Range/Performance
P0192 Fuel Rail Pressure Sensor Circuit Low Input
P0193 Fuel Rail Pressure Sensor Circuit High Input
P0194 Fuel Rail Pressure Sensor Circuit Intermittent
P0195 Engine Oil Temperature Sensor Malfunction
P0196 Engine Oil Temperature Sensor Range/Performance
P0197 Engine Oil Temperature Sensor Low
P0198 Engine Oil Temperature Sensor High
P0199 Engine Oil Temperature Sensor Intermittent

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