Subaru Flex Fuel Update!

As promised, we have a TON of updates regarding our forthcoming release of Subaru Flex Fuel. Buckle up, this is a long one!

If you frequent the COBB Blog you’re someone that could always use some more horsepower. You also have or at least consider modifying your car with different bolt-on parts. That, along with proper tuning, can yield some nice power gains. But, there are even easier ways to gain power than bolting on a new part. Easier gains can be achieved through the use of different fuels. The potential for more power exists through simply increasing the octane content of the fuel feeding your car’s engine. Many take advantage of high octane race gas. While this is good option, it can be very expensive and is often impractical when it comes to refueling. That’s where ethanol comes in.

What the heck is Ethanol?

Ethanol is an alcohol based fuel that is distilled from plants like corn and sugar cane. It is often touted as green and renewable but I’ll leave the eco-consciousness verdict up to you. One thing it certainly is is a fuel that delivers a higher octane content than pump gas. Technically the octane rating of alcohol cannot be measured. However, with some solid math and good estimations, pure ethanol is concluded to be over 100 octane.

Most ethanol can be easily obtained in the US in the form of E85. E85 is a mixture of up to 85% ethanol and 15% [insert hydrocarbon here]. The 85 doesn’t refer to pure ethanol but instead denatured fuel ethanol. Since ethanol is made using the same process as adult beverages, a mix of 2% hydrocarbons must be added to make denatured fuel ethanol. This makes it “unsuitable for beverage use under a formula approved by a regulatory agency to prevent the imposition of beverage alcohol tax.” So essentially, we’re looking at a maximum of 83% ethanol. The remaining 15 non-ethanol part can be “Unleaded gasoline, gasoline blendstocks for oxygenate blending (BOB), natural gasoline, or other hydrocarbons in the gasoline boiling range.” It’s also important to note the ethanol content will not always be 83%. In fact, it can be as low as 51% and still be sold as E85. Since the ethanol content varies, and the “gas” part can’t be identified, it’s difficult to estimate the actual octane rating. This discrepancy can be disregarded when using race grade E85 or E98 which have more strict content grades but buying fuel by the drum defeats our purpose. Even with those huge discrepancies in mind, with a few modifications, pump E85 can still provide a cheap and reliable fuel alternative and increase power.

What parts do I need?

Since E85 has less energy by volume compared to gasoline, your fuel system must be capable of additional flow requirements. Upgraded fuel pumps and injectors can be expected on traditional port injection vehicles. It’s important these upgrades are specifically cordial with ethanol based fuels. Fuel pumps rely heavily on fuel to keep themselves lubricated. Unlike gasoline, ethanol is not petroleum based. Not only does it not lubricate, it actively cleans lubrication. Aside from the cleaning trait of alcohol, it’s also hygroscopic. This means it pulls moisture from the surrounding air. If E85 sits in the injectors for long periods it can cause them to rust. Rust in injectors when you’re dealing with tolerances of a few thousandths of an inch results in drastic changes in flow rates. Even with stainless internal injectors it’s a good idea to start the car at least weekly if ethanol is in the system to prevent this from happening. Long story short, make sure your fuel system upgrades comply with E85 or you’re gonna have a bad time.

Since there is such a disparity in E85 from station to station and from season to season an ethanol content sensor is necessary. This can be used on certain platforms in conjunction with Accesstuner to account for necessary tuning changes caused by differences in fuel content. As an added bonus, especially if you travel through places where E85 is not available, this sensor will allow you to accommodate any fuel from regular pump gas all the way to E85 and anywhere in between.

COBB Flex Fuel Parts and Packages

The key to our Flex Fuel system is the COBB Ethanol Sensor Kit. This kit consists of an ethanol sensor along with a converter that translates the signal from the sensor into something your vehicle’s ECU can use. We will also be including a harness and replacement fuel lines that make this a true plug-and-play solution.

COBB has also developed a Fuel Pressure Sensor Kit. This will allow users to monitor fuel pressure at the fuel rail on the Accessport V3. In our testing, the Fuel Pressure sensor kit is very important to verify a Flex Fuel car (or any car really!) is running safely. It will be a requirement for our Flex Fuel Off The Shelf maps.

Beyond that, we will be offering a host of Flex Fuel Packages that make it very easy to configure any car to utilize our Flex Fuel implementation. From completely stock vehicles to those already utilizing a Stage 2 or Stage 3 setup, we’ll have you covered! Some examples are listed below.

Awesome, now what cars will this be compatible with?

Our initial release will be compatible with the 2008-2016 STI and 2008-2014 WRX. Additional vehicle support will be added in the following months. 2015-2016 WRX support will be the second release, followed afterwards by Pre-2008 WRX/STi. We are still investigating support for select Legacy GTs and Forester XTs.

Shut up and take my money! When can I have it?!

The above listed hard-parts will be in stock at COBB Dealers, COBB Shops, as well as www.cobbtuning.com in the coming weeks. Subaru Flex Fuel compatible software along with these hard-parts will be available everywhere at the beginning of January 2016.