How AFD Cracked the Code for Extracting 30 HP More from E85

by Jeff Smith (Hot Rod Network) By now, everybody knows about ethanol and E85. If you don’t, it’s time you caught up with the rest of the world. ... Today, the U.S. Department of Energy defines E85 as actually any blend of 51 to 83 percent ethanol with gasoline. This is required because winter blends of E85 generally contain greater percentages of gasoline to allow easier starting in cold weather. All of this is important because ethanol blends do change day to day at the pump as well as throughout the seasons. So several years ago, GM created an ethanol sensor installed in all flex fuel vehicles that measures the percentage of ethanol in the fuel and constantly reports this percentage to the ECU.

Advanced Fuel Dynamics (AFD) is a relatively new company that addresses variable E85 blends and offers some interesting performance advantages that deal with this issue of constantly changing blends. The AFD system uses this sensor as the basis for a very interesting plug-in system called ProFlex that can be quickly and easily installed on many late-model, electronically fuel injected vehicles. The system measures the percentage of ethanol and then employs a simple plug-in harness and stand-alone controller that reads the existing commands from the stock ECU and re-calculates these signals into re-tuned versions as calculated using their infinitely variable ethanol tuning map. Users are able to run any blend of gasoline and ethanol seamlessly.

Here’s how this works. Straight ethanol as a fuel produces roughly 25 percent less heat (in BTUs) than gasoline. So with a given percentage of ethanol mixed with gasoline, the Advanced Fuel Dynamics fuel sensor measures the ethanol percentage, calculates a new command based on this percentage and increases the amount of fuel delivered to produce an effective air-fuel ratio.

The biggest issue comes down to the size of injectors used in the engine. This is important because with a greater ethanol load such as 70 to 85 percent ethanol, this will require a significantly greater fuel flow capability to match the demanded air-fuel ratio. Many performance cars out there have large enough injectors to be able to handle this additional fuel flow.

Tuning for all blends of ethanol can be tricky, so AFD tests every vehicle on a dyno while running E85 to make sure the onboard injectors have enough capacity and the AFR stays at acceptable levels throughout the rev range. When vehicles require an injector upgrade, AFD can supply the right injectors for the job.

In one particular case study, Advanced Fuel Dynamics added its ProFlex Commander package to a C5 Corvette. This particular car was powered by an LS1 and based on AFD’s testing on a chassis dyno, this particular car improved from 299 to 329 rwhp with a matching gain in torque to a 345 lb-ft peak.

Some enthusiasts may want to monitor the actual ethanol percentage in the tank. AFD thought of this as well and provides their free ProFlex Connect App that can be quickly loaded into your smart phone and displays the percentage of ethanol in the system at any time via a bluetooth connection.

Another feature of ethanol that is not commonly appreciated is that the octane rating of ethanol is not based on a straight blend percentage. For example, a mix of just 30 percent ethanol with gasoline (E30) can bump the octane rating of 93 gasoline up to almost 100 octane. Mix ratios above 50 percent realize increasingly smaller improvements in the octane rating. So it’s possible that a mix ratio of 50 percent or below will allow engines to perform better with the inherent higher octane rating while still allowing the use of the stock or near-stock size injectors. This also minimizes the decrease in fuel mileage that occurs with larger percentages of ethanol. High ethanol race blends available by the barrel and at some tracks can carry as much as a 116 octane equivalency rating.

There are actually multi-tiered reasons why an engine will gain additional power when using ethanol-mixed fuel. The main advantage is not just the additional octane, but ethanol also enjoys a high latent heat of vaporization. What this means is that ethanol tends to absorb heat out of the air when the fuel is mixed with incoming air. A cooler intake charge is denser which will make more power but it also reduces the engine’s sensitivity to detonation. This means that an engine with even a mildly aggressive timing curve will allow the engine to generate the most power it is capable of producing.

Where this system could really show some benefits is with pro touring and Drag Week style cars that could use the added octane of an E50 or E70 to minimize triggering detonation sensors and pulling back timing. Plus, pump E85 is far less expensive than race fuel. READ MORE