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2006 Subaru Fuel System

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There are a number of tried and tested ways for measuring fuel mixtures in your Subaru WRX fuel system that I will cover below and the actuality is that other methods such as cheap DIY meters, reading tea leaves or consulting a psychic and these have no place in Subaru performance tuning.

One of the keys to getting a Subaru WRX with more power is the proper proportion of fuel for a given quantity of air. Either too much or too little fuel leads to an engine that's down on power, delivers poor economy and has a real question mark against its long-term sturdiness. The first job of the ecu tuner is to ensure that the Subaru engine management system has been programmed to supply fuel in the correct quantities at every point.

Fuel mixture is measured in units of either Lambda or air fuel proportion ( AFR ). Also referred in tune-speak as either lean ( small amounts of fuel to air ) or rich ( giant amount of fuel to air ). What is the correct mixture of fuel and air? While there's no such thing as an absolute everywhere setting, the often agreed'golden rules' of fuel mixtures are :

1. At low power outputs (no boost) catalytic converter equipped cars require a fuel mixture of Lambda 0.99 (AFR 14.64) for best emissions, and is the target fuel mixture when the OE ECU is operating in closed loop. Improvements in fuel economy can be made by leaning fuel mixtures off to Lambda 1.05 (AFR 15.4 to 1), but this is done at the expense of cat converter operation and will increase exhaust temperatures when cruising.

2. Medium power outputs (the transition between on and off boost) sees best power achieved at around Lambda 0.89 (AFR 13.1 to 1).

3. At high power outputs things get interesting, as this is the area where the greatest potential for engine damage exists. Version I to VI engines with stock internals running around 1.2 bar boost typically make good power reliability at Lambda 0.78 (AFR 11.5 to 1). At the same boost pressure and with stock internals, Subaru WRX Version VII and later models have redesigned cylinder head combustion chambers for a very different set of burn characteristics and fuel distribution compared to the previous model, dictating significantly richer fuel mixtures of around Lambda 0.75 (AFR 11.0 to 1) or lower to achieve best power safely.

Typically , air fuel proportions in your Subaru WRX fuel system can be leaned barely for a little increase in power on engines equipped with forged pistons, due to their strength and greater heat resistance in comparison to OE cast pistons.

Measuring Fuel Mixtures In Your Subaru WRX Fuel System

There are only 2 paths to check fuel mixtures precisely ; the preferred technique is to use a top of the range Subaru aftermarket wide band air fuel meter in conjunction with a 5 wire Bosch LSU type lambda sensor. This kind of sensor and meter can precisely measure fuel mixtures from Lambda 0.69 ( AFR 10.1 to one ) to Lambda 1.30 ( AFR 19.1 to 1 ) and beyond. Hence the name wide band sensor.

An alternative strategy for cars with flash compatible ECUs such as the Subaru Impreza WRX, fuel mixtures can be read right from the ECU data stream using Delta Dash, with some exceptions. The OE lambda sensor can'see' lean mixtures well, but cannot measure fuel mixtures richer than Lambda 0.76 ( AFR 11.2 ). In addition, at power outputs higher than stock, sensor placement is an issue , as exhaust back pressure between the engine and turbocharger causes a significant decrease in sensor accuracy.

Learn how to select and fit the best Subaru performance parts for the Subaru Impreza, Impreza WRX STi and the Subaru Forester to name a few.

Finding and fitting suitable Subaru aftermarket performance parts doesn't have to be a challenge whether you are working on used Subarus or want to modify a new Subaru.

Get a valuable insight into Subaru models from just about any country in this top selling Subaru book.

Cli ck Here to get Free Instant Access to the First 6 Chapters that will answer many of your Subaru questions.

Additional Information:

2003 Subaru Service
Understanding The 2003 Subaru Air Mass Sensors
Fuel Systems Subaru WRX
Subaru WRX Fuel Systems

2004 Subaru Fuel System

---

There are a number of established ways for measuring fuel mixtures in your Subaru WRX fuel system that I'm going to cover below and the reality is that other methods like cheap DIY meters, reading tea leaves or consulting a psychic and these have no place in Subaru performance tuning.

One of the keys to getting a Subaru WRX with more power is the correct ratio of fuel for a given quantity of air. Either too much or too little fuel results in an engine that is down on power, delivers poor economy and has a real question mark against its long term durability. The first job of the ecu tuner is to make sure that the Subaru engine management system has been programmed to supply fuel in the correct quantities at every point.

Fuel mixture is measured in units of either Lambda or air fuel ratio ( AFR ). Also referred in tune-speak as either lean ( small amounts of fuel to air ) or rich ( big amount of fuel to air ). What's the correct mix of fuel and air? While there is no such thing as an absolute everywhere setting, the often agreed'golden rules' of fuel mixtures are :

1. At low power outputs (no boost) catalytic converter equipped cars require a fuel mixture of Lambda 0.99 (AFR 14.64) for best emissions, and is the target fuel mixture when the OE ECU is operating in closed loop. Improvements in fuel economy can be made by leaning fuel mixtures off to Lambda 1.05 (AFR 15.4 to 1), but this is done at the expense of cat converter operation and will increase exhaust temperatures when cruising.

2. Medium power outputs (the transition between on and off boost) sees best power achieved at around Lambda 0.89 (AFR 13.1 to 1).

3. At high power outputs things get interesting, as this is the area where the greatest potential for engine damage exists. Version I to VI engines with stock internals running around 1.2 bar boost typically make good power reliability at Lambda 0.78 (AFR 11.5 to 1). At the same boost pressure and with stock internals, Subaru WRX Version VII and later models have redesigned cylinder head combustion chambers for a very different set of burn characteristics and fuel distribution compared to the previous model, dictating significantly richer fuel mixtures of around Lambda 0.75 (AFR 11.0 to 1) or lower to achieve best power safely.

Generally air fuel ratios in your Subaru WRX fuel system can be leaned a little for a small increase in power on engines provided with forged pistons, due to their strength and bigger heat resistance when put next to OE cast pistons.

Measuring Fuel Mixtures In Your Subaru WRX Fuel System

There are only 2 ways to check fuel mixtures exactingly ; the preferred method is to use a top quality Subaru aftermarket wide band air fuel meter in conjunction with a 5 wire Bosch LSU type lambda sensor. This kind of sensor and meter can accurately measure fuel mixtures from Lambda 0.69 ( AFR 10.1 to 1 ) to Lambda 1.30 ( AFR 19.1 to 1 ) and beyond. Hence the name wide band sensor.

An alternative strategy for cars with flash compatible ECUs such as the Subaru Impreza WRX, fuel mixtures can be read right from the ECU data stream using Delta Dash, with a few exceptions. The OE lambda sensor can'see' lean mixtures well, but cannot measure fuel mixtures richer than Lambda 0.76 ( AFR 11.2 ). Additionally, at power outputs higher than stock, sensor placement is an issue , as exhaust back pressure between the engine and turbocharger causes a significant decrease in sensor accuracy.

Learn how to select and fit the best Subaru performance parts for the Subaru Impreza, Impreza WRX STi and the Subaru Forester to name a few.

Finding and fitting suitable Subaru aftermarket performance parts doesn't have to be a challenge whether you are working on used Subarus or want to modify a new Subaru.

Get a valuable insight into Subaru models from just about any country in this top selling Subaru book.

Cli ck Here to get Free Instant Access to the First 6 Chapters that will answer many of your Subaru questions.

Additional Information:

Avoiding 2008 Subaru WRX Fuel Leaks
2006 Subaru Service
Fuel Systems Subaru WRX
Subaru WRX Fuel Systems

2001 Subaru WRX Fuel System

---

There are a number of proven methods for measuring fuel mixtures in your Subaru WRX fuel system that I will cover below and the reality is that other methods such as cheap DIY meters, reading tea leaves or consulting a psychic and these have no place in Subaru performance tuning.

One of the keys to getting a Subaru WRX with more power is the correct ratio of fuel for a given quantity of air. Either too much or too little fuel results in an engine that is down on power, delivers poor economy and has a big question mark against its long term durability. The primary job of the ecu tuner is to ensure that the Subaru engine management system has been programmed to deliver fuel in the correct quantities at all times.

Date Published: Dec 05, 2009 - 5:27 pm

2007 Subaru WRX Fuel System

---

There are a number of proven methods for measuring fuel mixtures in your Subaru WRX fuel system that I will cover below and the reality is that other methods such as cheap DIY meters, reading tea leaves or consulting a psychic and these have no place in Subaru performance tuning.

One of the keys to getting a Subaru WRX with more power is the correct ratio of fuel for a given quantity of air. Either too much or too little fuel results in an engine that is down on power, delivers poor economy and has a big question mark against its long term durability. The primary job of the ecu tuner is to ensure that the Subaru engine management system has been programmed to deliver fuel in the correct quantities at all times.

Date Published: Dec 05, 2009 - 3:51 pm