Some people will tell you that ethanol is the devil’s nectar that Obama slips into your gasoline to implode your gas-guzzling V-8. Others will act like it is the greatest thing to ever happen to hot rods. Clearly the truth is somewhere in between. Since Day One I’ve been fascinated with the prospect of cheap race fuel you can buy at your local pump, which has nearly the same chemical properties as methanol to cool your intake charge. However, it comes with some obvious and undesirable side effects.
In my adopted state of Florida, E10 is the cocktail of choice for any vehicle powered by unleaded gasoline. This 10% ethanol blend is typically fairly consistent since the seasons don’t change like other states. Now I, personally, have never had an issue with E10 in any of my late model hot rods, including my ’94 Firebird that sat for months at a time. However, the 10% ethanol content is known to break down fuel system components in older vehicles. And let’s face it; some of these cars have some pretty brittle fuel lines and connections to start. So if you want to keep your classic mostly stock, it would certainly be frustrating. At that point, your only option is to seek out one of the few stations that offer ethanol free gas or to purchase fuel by the barrel from VP Racing, Rockett Brand, etc. In fact, VP Vintage was formulated with this type of customer in mind. It is a leaded, ethanol-free gas with 98-octane and a shelf life of up to 2 years.
Though it has taken some time, manufacturers have adjusted to modern fuel cocktails such as E10. In fact, I just purchased a lawnmower that is even E10 compatible. Aftermarket manufacturers have become hip to it as well. Most likely that had something to do with my Firebird’s trouble-free performance, using a Racetronix fuel pump. At present, the only inherent issue with running E10 is that the formulation changes by season. For normal driving, the O2 sensors in an electronic fuel injected vehicle will adjust the fueling accordingly. However, for a high performance or race car with precision tuning this can be problematic. The stoichiometric point will vary per fuel formulation, which is not variable in a normal ECM and calibration. It is a preset value that is often incorrectly set from the factory for ethanol-free test fuel. This is where Flex Fuel comes in.
Flex Fuel systems, whether factory or aftermarket, have a sensor that measures the ethanol content of the fuel. Typically they are mounted between the fuel pressure regulator and the fuel tank. The beauty of this is that it automatically adjusts the timing and fueling for the ethanol content – from 0 to 100%. So not only does it adjust for varying blends of E10, but also E85, which is much less consistent in its formulation. And in a high-powered streetcar, a Flex Fuel system allows you to run E85 on the street and E98 at the track. But when neither is available, you can dump in some 93-octane without listening to your engine knock the whole way home. The rub with running ethanol in any vehicle, though, is that you will need enough fuel injector and pump to account for the added volume needed. The lower energy content of ethanol means you will use 35% more fuel.
The beauty of ethanol, though, is that it has very high octane. E85 out of the pump is typically 99 to 105-octane, and it’s cheaper than premium unleaded (let alone race gas). As you may know, octane measures how much fuel can be compressed before detonation. So the higher the number, the more resistant to harmful knock (aka pre-ignition) it will be, and the more ignition timing, [engine] compression or boost you can utilize to increase power. The chemical composition to E85 has other benefits as well that help prevent knock. Like methanol, which is sometimes used to cool the intake charge, E85 has a higher heat of vaporization than gasoline. More energy is needed to evaporate the fuel, so less is left over to heat the intake air. And higher air density means more power as well as lower heat losses (lower combustion temperature). Like methanol, ethanol has some inherent issues with cold start-up, which is why a 15% (or more) blend of gasoline is used.
With so much going on inside the combustion chamber, it is no wonder why the aftermarket and OEMs are only beginning to scratch the surface of E85’s potential. What is surprising to me is that E85’s application has moved beyond the typical junkyard turbo 5.3L LSx combo, and is finding a home in high compression and mostly stock vehicles. Since many performance cars use the same ECM architecture as some of their more pedestrian counterparts, converting many late-model cars to Flex Fuel isn’t all that complicated for a quality shop. In one example, I saw a naturally aspirated ‘14 Camaro Z/28 pick up 20hp and 25 lb-ft of torque with tuning and stock compression. And with a mostly stock C7 Corvette, the same shop went from 427-rwhp and 449 lb-ft to over 450hp and 471 lb-ft of torque. Now imagine what a tank full of E85 and custom tuning could do for the new Hellcat Challenger or ’15 Corvette Z06.
At the end of the day, ethanol is horsepower to hot rodders. It is not just some harmful filler that gets dumped into gasoline to make our cars more environmentally friendly. It is an octane additive, and when used in a higher concentration can be an extremely potent means of increasing power. Yes, this comes at a cost, but it is very rare that horsepower doesn’t these days.