Flex Fuel technology is all about using fuels that combine regular gasoline with ethanol or sometimes methanol, allowing vehicles to run on any combination of the two and anything in between. Though you can’t physically modify your vehicle, a change in the fuel can make a difference in performance and fuel consumption depending on the blend and vehicle setup.
What Exactly is Flex Fuel?
It’s like a cooking recipe Diesel and Ethanol are mixed together in engines. The most common versions you'll hear about are E10 and E85. E10 is pretty common and is regular gasoline mixed with up to 10% ethanol. You might already be using it without realizing it But E85 has a much higher concentration because it is generally 51% to 83% ethanol. The amount that goes into E85 can change based on the season and the location. Why? To ensure that your car starts and runs smoothly year-round, blending is adjusted as ethanol reacts differently in cold weather.
Using ethanol in fuel isn't a brand-new idea in the past, it was occasionally mixed to improve the octane rating of gasoline – which helps engine knock – and lessen reliance on imported oil. Today, the push for renewable energy and less environmental change has reinstated the importance of Flex Fuel technology. The ethanol in fuel generally comes from corn, sugarcane and other renewable plants.
But you really shouldn’t just pour any Flex Fuel blend, especially E85, into your Whip. Only vehicles labeled as Flexible Fuel (FFV) are made to handle these fuels. Unlike gasoline vehicles, these cars have special modifications. The people designing motor vehicles who work for car makers are engineers. The engineers design FFVs with changes to the fuel system (like the fuel tank, lines, pump and injectors) and the engine’s computer brain (the Engine Control Unit or ECU). These changes are really important because ethanol, particularly in high amounts like E85, is more corrosive than gasoline and burns differently. If you don’t have those modifications that come from the factory, it could damage your fuel system, and engine, over time. Car manufacturers don’t create flex-fuel vehicles (FFVs) for fun. The fact they do suggests that running on different fuel mixes needs careful engineering, and there’s scope to fine-tune how the engine uses these different fuels.
How Does a Flex Fuel Vehicle (FFV) Actually Work?
What makes a Flexible Fuel Vehicle different under the hood? Basically, they have the right parts and they have got good programming that adapts to whatever mix of gasoline and ethanol is in the tank. FFVs can easily make transitions between different blends without you even noticing.
One of the star players is the fuel composition sensor. Imagine a little nose inside the fuel line, always smelling the fuel to determine what fraction of ethanol is headed up to the engine. The sensor sends this information straight to the ECU or Engine Control Unit of the car.
To stop ethanol, being more challenging on materials than gasoline, from hurting your car, FFVs use extra strong materials in their fuel systems. The fuel tank, the lines that carry fuel to the engine, the pump that pushes fuel to the engine, and the injectors that spray it into the cylinders are usually made from special materials like stainless steel or special plastics that can withstand the damage that ethanol can do. This stops rust and guarantees the gas system works for a long time even when using high-ethanol mixes like E85.
The real magic happens in the ECU's software. With all of this data provided by the fuel composition sensor, the ECU acts like a conductor of an orchestra. It has already been equipped with maps or programs that tell it what engine settings to expect at a certain ethanol percentage. These tweaks take place on the fly, always adjusting things for the best burn.
What kind of adjustments are we talking about?
Ethanol has less energy per gallon than gasoline, so the engine receives more fuel for the same power with flexible fuel injection. When the sensor picks up more ethanol, the ECU tells the injectors to stay open longer, letting in more fuel to each fire. It adjusts the diesel-fuel ratio for low-pressure turbo engines.
The timing when the spark plug fires to ignite the fuel-air mixture is called ignition timing. Ethanol has a higher octane rating than regular gasoline. When the fuel is high octane it resists knocking or premature detonation. This resistance allows the chip to safely advance the ignition timing (fire the spark plug slightly earlier). If you advance the timing the fuel burns more completely leading to more power and efficiency.
The perfect combustion ratio of air to fuel required according to the stoichiometric ratio is different for ethanol than it is for gasoline. The ECU routinely changes the amount of fuel being delivered at any moment to keep the most optimal ratio for the blend in use.
An FFV can run smoothly on anything between gasoline to E85 due to constant automatic adjustment done by the ECU. The system is designed to adapt But, the ECU settings from the factory are often a compromise that is designed to work reasonably well across the entire range of fuel blends possible. The fact that the system is adaptable, using sensors and changing ECU settings, creates a great opportunity. If a specific blend is used all the time, for example, full E85 or full E10 all the time, then the engine settings can be improved, specifically for this fuel, beyond what the factory settings choose as a jack-of-all-trades compromise for the entire possible range of fuels with careful ECU re-tuning, often referred to as chiptuning.
What are the Real Advantages of Using Flex Fuel?
Using or switching to Flex Fuel, especially the higher ethanol blends like E85 offers some attractive benefits for the driver and their vehicle.
One advantage that seems to be the most discussed is the possible lower fuel prices. You’ll often find ethanol, especially E85, sold for less per gallon than gasoline at the pump. The difference in price of E85 compared to gasoline could come from the government incentives for biofuels or the low costs of production based on agricultural market impacts. If you drive a lot and have easy access to E85 filling stations, then you can notice a spike in the savings on your fuel bills. It’s kind of like finding a less-costly source for something you do every day. On the other hand, don’t forget about fuel economy. We will go over that in limitations, but you need to consider the price per gallon with how many miles you get with that gallon.
From an environmental view, Flex Fuel is often touted as a better alternative. Ethanol is usually made from renewable corn or sugarcane that we all use. The concept is that burning the ethanol releases carbon dioxide (CO2) that’s generally offset by the carbon dioxide (CO2) the plants absorbed during their growth. Because of this “carbon cycle,” ethanol can produce lower net greenhouse gas emissions over its full life cycle than gasoline refined from fossil fuel. “Using a fuel containing plant material feels like a step towards better driving.
E85 and flex fuel start getting interesting in performance, let’s talk about that. Ethanol has a much higher octane rating than regular pump gasoline. Regular gasoline is 87-93 octane and E85 is 100-105 octane. Why does this matter? High-octane fuel is less likely to make your engine knock (detonate or ping). This resistance allows a tuner to be more aggressive with other settings, such as ignition timing. If we make the spark plug spark earlier, we get more pressure in the cylinder before combustion, which allows for a stronger push back on the piston. The result? Increased horsepower and torque Anyone can join the poker game if they want, but you should first understand how it plays before you place your bets. Poker is a game of luck and skills. That's why it's said that those odds are already in your favor if you understand how poker plays. If you’re looking for greater performance, then E85 will definitely attract you thanks to its high octane rating; getting the engine calibrated to take advantage of it will set the potential free.
How is engine performance and tuning related to flex fuel?
This is where things get fun for those wanting to maximize the advantage of their vehicle.
Flex fuel—especially high-ethanol blends like E85—has characteristics that directly alter engine performance and present major opportunities for tuning (chiptuning).
Ethanol has an octane rating that is significantly higher than gasoline. To clarify, the term ‘octane’ refers to the resistance of fuels to uncontrolled combustion, otherwise known as ‘knock’. Regular gasoline will be 87 to 93 octane and E85 will typically be around the 100-104 octane mark. Because of this higher knock resistance, the ECU has more room to adjust the mixture. It allows for more aggressive ignition timing. The timing can be advanced (the spark plug can be kicked off earlier with respect to the position of the piston) to give the fuel-air mixture extra time to burn, as the piston is pushed down. You could squeeze out more energy from the fuel which directly leads to more hp-torque. Stock FFVs make some use of this, but factory tunes are safe. Custom tuning can tune the ignition timing to take maximum safe advantage of E85’s high-octane. These timing changes will set off gains that normal gasoline isn’t able to take without knocking.
Ethanol has a large evaporative cooling effect apart from its octane benefits. When fuel vaporizes in the intake manifold or in a cylinder, the phase change in liquid fuel (particularly ethanol), absorbs heat from gas and metal. When rubbing alcohol evaporates on your skin, it feels cool. Same way here. Cool air that goes into engines is more dense, which means more oxygen can be packed in – that gives more power. The denser air allows for the burning of more fuel and contributes to power. On top of that, this cooling effect will help to further suppress knock, particularly when the load is high or when driving hard. This cooling effect teams up with high octane to help enable a more performance-oriented tune.
Ethanol needs a different air-fuel ratio for perfect combustion compared to gasoline. The ideal “stoichiometric” ratio of air to fuel for gasoline is about 14.7:1. That’s 14.7 parts air to 1 part fuel. For pure ethanol, the ratio is much richer, around 9.0:1. For E85 it’s in between or about 9.8:1. The engine control unit (ECU) of a flexible-fuel vehicle (FFV) employs a sensor that measures fuel composition, allowing it to adjust the volume of fuel injected automatically.
But with tuning, we can have much finer control over this ratio at different engine speeds and loads. Changing the tune can allow adjusting the air and fuel mixture for specific power (often slightly richer than stoich) or for efficiency, based on the characteristics of E85 and the driver’s goals beyond stock compromises.
What Should Be Considered When Tuning a Flex Fuel Vehicle?
Chiptuning a Flexible Fuel Vehicle (FFV): A professional must carefully consider it in order to realize performance gains without compromising safety or reliability. It’s not about just turning everything up but smart optimization.
Most important of all, consider the ethanol blends you most plan to use. Are you someone who will mainly run E85 whenever possible to maximize performance? Are you just going to use the regular E10 for your every day driving and occasionally E85 to save money? Perhaps you live somewhere E50 or E30 is common. The ideal tune should reflect your actual fuel usage. A tune that benefits solely from E85 may not run smoothly or efficiently on E10, and the other way around. Let the tuner know what you usually put in your car and you should get a tune that suits you best.
One excellent feature that’s often available when tuning FFVs is the tune map switch. Since the vehicle already has a sensor to read ethanol content, it's often possible to program the ECU with different sets of instructions according to the fuel detected. For example, you could have:
· Tuned to give excellent smooth driving and economy on E10/regular gasoline.
· The torque and power performance map designed for E85 takes full advantage of this high octane fuel.
· Maybe even maps for middle blends if needed.
The ecu might switch between these maps on sensor reading or let the driver choose a map manually. It gives you the ability to have it both ways, to run on the most efficient map possible for good economy or the power map to wring out more torque as you wish. The ECU would choose the most efficient map or the one best suited to the fuel in the tank.
It's a good idea to apply dyno testing and custom tuning to it, especially for FFVs due to the variation in fuel composition. A dynamometer (or "dyno") is basically an engine treadmill which lets the tuner measure the actual horsepower and torque output of the engine under controlled conditions while running various fuel mixtures. An expert tuner can tweak your ECU software and immediately observe the effects on the dyno. This permits them to repeatedly alter engine parameters (ignition timing, fuel delivery, boost pressure on turbo engines, etc.) in the quest for the best performance and efficiency with your vehicle and the fuel being tested. This ensures the tune is custom fitted rather than a generic run-of-the-mill estimate.
Safety margins are paramount A tuner who knows what they are doing, will never compromise on your engine’s longevity while tuning you for performance. This means paying close attention to critical engine parameters during tuning – such as the air-fuel ratio (to ensure it’s not running lean), exhaust gas temperatures (EGTs) and listening for engine knock. We’re looking to get performance closer to the safe thresholds, but not crossing the line. It’s important to create safety margins which will allow the engine to sustain the increased stress without any risk.
Finally, consider the limitations of stock hardware. It is possible the factory fuel pump or fuel injectors do not have the capacity to make any power upgrades, especially with the use of E85 needing more fuel. E85 requires about thirty percent more fuel than gasoline to achieve the same power level. If the stock pump can't deliver enough fuel or the injectors can't supply enough quickly enough, the engine could go too lean under high load. That's not good! Sometimes, modifying the fuel system parts is required to safely run E85 and a performance tune at the desired power levels. A decent tuner will check your hardware and inform you if you need to upgrade or not.
