COBB Flex Fuel Kit

Who is COBB? 

COBB Tuning is an automotive engineering company based out of Rockwall, TX. Founded in 199, they are dedicated to developing solutions that improve vehicles performance and driving experience. COBB makes this possible by taking the entire vehicle-platform into account as a complete system. 

COBB Tuning offers a variety of products to enhance your vehicles performance and driving experience. Some of those products include Intake systemsMotor MountsFuel InjectorsDownpipesBlow off ValvesShift KnobsTurbochargers and more!

In this article we will be covering their COBB Flex Fuel Kit.

What is Flex Fuel System?

A FlexFuel system informs the ECU (engine control unit) through an ethanol content sensor and electronics, that measure the actual content of Ethanol in the fuel system. … This systems allows the vehicle to be “flexible” in terms of what fuel it can run, either pump gas 91-93 octane to E85 or any percentage in between.

COBB Flex Fuel Kit

If you’re looking for a complete plug and play solution to convert your Subaru to a Flex Fuel configuration then the COBB Flex Fuel Kit is for you. You can now upgrade your vehicle without losing factory compensations. This is the easiest to use and most sophisticated Flex Fuel kit on the market. Utilizing OEM fuel and electronic connectors, the Ethanol Sensor Kit measures the ethanol content of fuel being fed to the motor. That data is then converted into a signal that the ECU can use for adjusting calibrations and to be displayed on a custom Accessport monitor.

COBB 324600 Flex Fuel Ethanol Sensor Kit
COBB 324600 Flex Fuel Ethanol Sensor Kit

Utilizing OEM fuel and electronic connectors, the Ethanol Sensor Kit measures the ethanol content of fuel being fed to the motor. That data is then converted into a signal that the ECU can use for adjusting calibrations and to be displayed on a custom Accessport monitor. Fuel System Considerations.

The flex fuel sensor measures the fuel alcohol content, and sends an electrical signal to the engine control module (ECM) to indicate ethanol percentage. The flex fuel sensor has a three-wire electrical harness connector. The three wires provide a ground circuit, a power source, and a signal output to the ECM.

COBB 315600 Flex Fuel Ethanol Sensor Kit
COBB 315600 Flex Fuel Ethanol Sensor Kit

For these reasons, everyone running E85 should have a wideband air/fuel sensor and ethanol content sensor they can monitor. When tuning a non flex fuel vehicle, I generally make customers engine calibrations for E10 gas, E15, E30, E60, E75, E85 or thereabouts depending on the situation.

Fuel System Considerations

Subaru DIT vehicles are not designed for ethanol use beyond 10-15%. That said, ethanol levels between 15-30% are generally well tolerated. Those comfortable with mild risk can run ~E30 and enjoy improved knock resistance, charge air cooling, and a mild improvement in engine power potential. While you can’t get E30 at the pump, pumping a combination of E0/E10 gas and E85 in an appropriate ratio will allow blending of a near E30 mixture in your tank.

COBB 312550 Flex Fuel Ethanol Sensor Kit 3-Pin
COBB 312550 Flex Fuel Ethanol Sensor Kit 3-Pin

On DIT platforms not set up for flex fuel from the factory, at greater than 30% concentration, ethanol has caused oscillating fuel pressure first, progressing to loss of fuel pressure, high pressure fuel pump damage, even making the vehicle inoperable in some cases. Sudden loss of fuel pressure can cause sudden loss of acceleration, stalling, which can reduce braking performance and steering control. Long story short, while the power potential is very attractive, use of high ethanol content fuel is at your own risk. We suggest speaking to your local shop before making any deciscions to help prevent any vehicle damage. 

COBB has performed internal testing in multiple geographic locations with different fuel sources in addition to compiling data from COBB retail shops, our Protuner network, and customers. Results varied significantly. Some users ran several tanks of E85 in a row without issue while some experienced serious loss of fuel pressure in as little as 1-2 tanks of fuel.

Futhermore, COBB suggest monitoring fuel pressure for oscillations. After having fuel pressure issues, some users were able to flush the HPFP (high pressure fuel pump) out with low ethanol gasoline and get it to operate normally again, while others had to replace the whole pump assembly before they could safely drive the car again. After replacing the pump some users experienced repeat failures if they continued to run E85 fuel.

Popular Applications
cobb324600Cobb 15-16 Subaru WRX Flex Fuel Ethanol Sensor Kit
cobb315600Cobb Subaru 08-16 STI / 08-14 WRX Flex Fuel Sensor Kit
cobb312550Cobb 04-06 Subaru STi / 06-07 WRX MT 3-Pin Flex Fuel Ethanol Sensor Kit

In Conclusion

COBB is a trustworthy, reliable brand in the automotive community. If you’re looking to take your Subaru’s fueling system to the next level and convert to Flex Fuel then their kits are the way to go. To begin browsing the COBB flex fuel kit catalog, click here