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Subaru BRZ & Toyota Supra
FeaturesSaturday Morning Car Tune!

Here is how a flex fuel kit works and why it’d be super cool if you get one

This is a psyop. Go buy flex fuel.

But wait, how does this crap even work? Isn’t this just alcoholic corn juice? Isn’t a high alcohol content bad for engines? Well, I have the answers: Works well enough. Yes, it’s just corn. And kinda-sorta-maybe, but not really.

Frankly, I’ve been a skeptic about high-ethanol-blended gas after hearing debates about its usefulness and possible detriments throughout high school auto shop classes. But more and more over the years, I see people preach its gospel, highlighting a niche where high-ethanol fuels shine: high performance. Or, more specifically, high horsepower! 

I recently purchased a track-built Subaru BRZ (more on the car itself below!) from an old work friend with the intent of “finishing” the build and attending more HPDE events. Friends, colleagues, and YouTubers alike have all incessantly hammered on the benefits of ethanol, like sleeper agent brainwashing. And now that I actually have a popular candidate for such a modification, why not give it a try? So, I am. Starting with installing the hardware itself. 

But first! Some nerdery to help folks better understand what any of these doohickeys even are.

Flex fuel and E85 explained

E85 is basically a higher-ethanol-blended variant of regular gasoline. E stands for ethanol, while the numeric value after it represents the percentage mix of ethanol, typically made by fermenting and distilling starchy crops. While barley and wheat can be used, the most common ingredient in the U.S. is corn. Yes, like the kind best served on the COBB. See what I did there? The blend can vary, but the most commonly used blend in performance applications is E85 or 85% ethanol and 15% gasoline.

Flex fuel simply refers to a fuel system that runs on both standard gasoline and high-ethanol fuels, capable of adjusting its tune on the fly and adapting to the ethanol percentage. Nowadays, swathes of vehicles feature flex fuel from the factory, known as flexible fuel vehicles (FFV), from rugged work trucks to million-dollar hypercars. My dad’s old F-150 with the Triton V8 was flex fuel, as do many GM pickups and SUVs. Perhaps most prominently are Koenigsegg hypercars, who advertise their very best power and performance figures on E85.

Subaru BRZ
Image credit: Jeric Jaleco

How flex fuel and E85 work

The physical form of flex fuel in modern cars is nothing more than a sensor system attached to the car’s fuel system. In the case of my BRZ, it’s a mere sensor half the size of a credit card that mounts to the strut tower, plus some fuel lines to redirect fuel into the sensor and a Bluetooth module for feeding ethanol readings to a companion phone app. Generally speaking, for all kits, the sensor reads the ethanol content of the car’s fuel and adjusts the ECU’s tuning to compensate for more or less ethanol. It typically does so on the fly, meaning you fill the car up and go without the need to bust out ye ol’ laptop or Accessport to change tune files like some troglodyte (i.e. me, I have no Bluetooth tuner or phone app).

E85 has become favorable among tuners and weekend warriors for its ability to yield higher horsepower ratings without forcing you to shell out big time on normal race gas. In fact, the E85 actually has a higher octane rating, equal to anywhere between 100 and 105, and features a faster, more efficient burn and flame propagation. E85’s traits carry a whole heap of performance buffs, such as burning cooler, reducing engine temperatures to mitigate knock (premature detonation), allowing compression ratios to be increased thanks to the lessened likelihood of knock, and allowing turbocharged cars to spool marginally faster due to faster burns creating exhaust gases sooner.

All that jargon sounds like a win, win, win! And it should, theoretically, be a win for those running E85. Or at least on dyno days, like the videos embedded at the end.

Debunking flex fuel myths and explaining real cons

Yes, it was very much a concern that E85 was bad for fuel systems, and it’s very much the truth that it’s not the most practical fuel out there for a number of reasons. So, let’s take a quick dive into what’s actually wrong with E85 and what old-timey myths we can dispel to irrelevancy.

First, the real cons:

  • It’s not as widespread at gas stations. Yes, you’re right. Not every gas station has it, and E85 is more common in some states and cities than others. In some places, it’s as easy as traveling to a nearby pump, whereas in others, it’s probably better to buy what you need and store it as you probably won’t find another E85 pump after that. Speaking of storing it.
  • It’s hard to store long-term, as ethanol can attract water, not only diluting the fuel but posing serious risks of rust and water vapors damaging fuel system components if left to sit. J.D. Power also notes that E85 can sit for anywhere between one to three months due to the fuel being likely to oxidize and lose combustibility over time. Compare that to three to six months for regular gasoline and roughly a year or more for diesel.
  • Old cars don’t really like it. There’s a reason some gas stations, such as Maverick, offer totally pure, ethanol-free gasoline. It’s friendlier to classic rides. Ethanol, being an alcohol, is an anti-lubricant and can dry out and damage materials in older fuel systems. On top of all that, they’re trickier to tune for E85 if the car is carbureted, as the carb has to be rejetted every time you swap fuel types.
  • While it’s a cleaner, cooler burning fuel, it’s actually not as power-dense as gasoline, meaning you need to use more of it to make meaningful gains. Sources range from 10% to 33% loss in power density, meaning your fuel economy dips down just as much to compensate since your ECU will adjust to expend more fuel. Colleagues who ran flex fuel in their tuned Scion FR-Ss and Toyota 86s did indeed see power gains at the expense of 3 to 4 mpg during regular driving. 

Now, the myths: 

Perhaps this is one big overarching myth. The notion that E85 is a dangerously corrosive and volatile fuel is a load of crap. Sort of. The alcohol content can dry out suboptimal materials in older or ill-equipped cars and leave a varnish on metal components, but it’s not going to eat away at your fuel system, cause it to blow up, or suddenly chew a hole in your tank. High-ethanol fuel is frequently confused with ethanol race fuels, which can have corrosive additives in them, relegating them to only short-term uses such as racing, or methanol, which actually is far more corrosive than ethanol.

While ethanol may not have been as safe in older vehicles, it’s widely regarded that most modern cars are more than capable of handling higher-ethanol blends. There’s at least a 10% blend of ethanol in regular pump gas, anyway. The high alcohol content can even function as a fuel cleaner, clearing out deposits from lines and injectors, similar to SeaFoam, which also has a high alcohol content. Now, that doesn’t mean go run E85 in your car right now, as you still need a tune for your computer to know what to do with the higher octane rating.

Make sure your car is tuned. Make sure your vehicle is equipped to handle it with the right sensors and modern, resilient components. And if you’re still concerned, the popular safeguard for peace of mind is typically one or two tanks of regular, top-quality pump gas a month.

Another fun fact. It’s also been noted that OEM flex fuel systems are less than stellar at running on E85. Introducing flex fuel into their mainstream cars was a bit of an afterthought and a way for manufacturers to get federal credits following the passage of the Alternative Motor Fuels Act in 1988. Interestingly, it’s akin to how late 2000s and early 2010s EVs were nothing more than mere “compliance cars” whose sole purpose of existing was to literally just exist for the company’s benefit in the wake of strict regional emissions and fuel economy laws.

Installing the hardware

After a quick stop at a speed shop I used to work at to snag a flex fuel kit for a bargain, I was on my way to meet a friend, who reassuringly performed these installs numerous times before. It was my off day over an extended New Year’s holiday weekend. I was on my merry way to see a friend for a quick garage hangout/install job. What could go wrong?

See, I can say that because it already happened. So there’s nothing to jinx. Right?

Thankfully, the BRZ/GR86 platform is as spacious inside as ever, with a wide-open engine bay allowing for easy access for damn near anything (except spark plugs). As my mechanic friend explained to me, all the work needed for the hardware would take place solely near the driver-side shock tower. So, as for what the installation entails.

I kid you not. It was as quick as letting the fuel system sit so it could depressurize a bit, opening the lines so we could install the new lines from the kit, and feeding those new lines into the flex fuel sensor that sat nice and pretty beneath the base of the strut tower brace.

Subaru BRZ E85 flex fuel install
Image credit: Jeric Jaleco

Bam. Easy. And we only spilled a little bit of fuel after impatiently starting before the system could depressurize further. Oh, and when removing the strut tower brace to install the flex fuel sensor beneath it, we may have dropped a piece of hardware that braces against the master cylinder to keep it from moving under hard braking. It doesn’t thread into anything. It simply sits atop a threaded stud, and the pressure of threading the stud into the strut tower brace pins it against the master cylinder. When you relieve the pressure to remove the brace, it simply falls into the abyss of the engine bay, never to escape because there’s a skid plate underneath from the factory.

Subaru BRZ E85 flex fuel install
Image credit: Jeric Jaleco

Thank you, Cusco, and thank you, Subaru. Very cool. So now what would’ve been a 20-minute install extended to nearly 45 as we busted out ye ol’ jack and a magnet tool to fish for this piece of the Cusco master cylinder brace from under and on top of the car. It was a humorously stupid and frustrating endeavor that finally ended in success after shaking a car a bunch, then jacking up one side with the wheel cranked to full lock so we could reach from inside the wheel well. 

Hey, we did it, didn’t we? And in the end, we installed the kit. Er, actually, my friend did. Thanks, Kaleb. A Bluetooth module included with the kit mounts near the firewall and lets me read the current ethanol level via a phone app, which, on pump gas, was a whopping, dyno-breaking, tire-shredding…

7%. I’ll take it!

Tune coming soon!

No. There’s no tune at the time of writing. But there will be! And you bet I’ll be back to report on my findings once I get this sucker all pumped up with corn juice. Most tuners expect gains of anywhere between 20 to 30 horsepower on this FA24 flat-four engine with E85 alone, and there are plenty of dyno videos that can back those claims. Will I count myself lucky? We shall see.

Knowing my luck, I wouldn’t be surprised if a piano falls on this car a day after the tune file comes in my email inbox. But fingers crossed. May the Car Gods, please, for the love of all that’s internally combustible, bless me with the same power gains these lucky lads below have experienced.

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EVs ExplainedFeatures

EVs Explained: What is a kilowatt-hour, and while we’re on the subject, what is a kilowatt?

“Now presenting our brand-new (insert new EV here), with a 50-kWh battery pack and 300 kW motors,” exclaims some extravagant press release from yet another startup. While it’s quite nice of you to spill all the beans like that, I’m still left wondering what the heck some of these measurements mean, and I’m sure some of you are too.

Welcome to this blooming age in the automotive landscape, where electrified cars stand on as big a pedestal as traditional dinosaur-powered performance vehicles. So many newfangled machines. So much innovative tech. Yet, interestingly, there’s not much in the way of explanation behind some of the most basic terminology, and what few definitions do exist lie buried under mounds of glitzy press material and spec sheet drag racing.

We’ve all read the brochures and the magazine reviews, diving into the colorful world of fully electric cars and plug-in hybrids. They’ll toss around new terminology like it’s already in the common vernacular, ignoring the fact that this is still relatively fresh tech being drip-fed to the world. Therefore, many terms haven’t fully clicked in people’s minds. But hopefully, this new explainer series should clear the fog around these words that are becoming as household as “horsepower” or “miles per gallon.” 

Our inaugural lessons to kick off this series: what the heck even are “kilowatts,” how do they relate to electric cars, and how do they pair with the equally-tossed “kilowatt-hours?” Well, I’m glad I asked – and hopefully drove enough interest to entrap you here – because it’s time to get schooled in five minutes or less.

Rivian R1T Charging in the desert
Image credit: Rivian

What is a killowatt?

This frequently-spoken term is not exclusive to EVs or electricity and can trace its core components back to pretty much any of our high school science and math classes. Anyone who has ever stumbled across a German auto magazine will likely guess where this is going.

Kilowatts are merely a metric measurement of power output, just like horsepower. Plain and simple.

Renault Mitsubishi Alliance Exposed Motors
Image credit: Renault Group

A kilowatt (kW), which translates to 1,000 watts (W), is the alternate unit of measurement if you’re too cool for horsepower. If you want to click with your new friends from Frankfurt, talk about how many kilowatts the straight-six in their 1995 C36 AMG makes. There’s even a brainless, one-step formula for converting kilowatts into ponies. Simply multiply your kilowatts by 1.341. 

For instance, let’s say you stumble across aforeign auto magazine talking about how the E92 M3 GTS had a power output of 331 kW – again, metric, so 331,000 W if you wanted to break it down. Before you scroll another line down the spec sheet looking for a pre-calculated conversion, you can multiply that 331 by 1.341 to get 443.87, on par with the manufacturer-claimed 444 horsepower. 

Bingo! Easy, right?

Lucid Air Sapphire
Image credit: Lucid Motors

Shift over to electric cars. Just as horsepower has become the ubiquitous unit of power measurement for internal combustion engines, the kilowatt has achieved a similar status for electric motors and may be used to denote output before official horsepower and torque ratings are published. The methodology for translating power measurements remains unchanged from pistons and cylinders to stators and magnets. Imagine some gilded brochure for the Tesla Model S Plaid that states that its motors’ combined output equals 760 kW. Multiply that by 1.341, and bam! 1,019.16, in line with its 1,020 horsepower rating. 

Tracking? Heck yeah, you are!

But the way that kilowatts relate to EVs is only half the story. One must also understand their relation to battery packs.

What is a kilowatt-hour?

While electric motors measure power output by kilowatts, battery packs measure energy capacity by kilowatt-hours. If you’ve read this far and decided you can’t stand me, please consult this handy YouTube video below for its breakdown of what a watt hour is and how it’s calculated. However, should you despise video explainers more than my written words, then please bear with me, as there’s a bit more to it than what we’ve discussed so far.

“How battery capacity is measured and what is Wh? (Watt Hour)”

A kilowatt-hour (kWh) determines how much energy can be expended over a unit of time, which, in the context of EVs, directly relates to a vehicle’s maximum power output and range. While the kWh is now a standard unit for measuring EV battery capacity, it’s long been a common unit of measurement for energy consumption in homes and appliances.

Lucid Air Sapphire - Exposed Car Internals - Top View
Image credit: Lucid Motors

Back to the Model S Plaid, let’s say you’re flooring it down the highway at a perfectly legal speed. Your foot’s all the way down on the throttle, extracting every bit of that 760 kW output. Welp. Congrats. You’ve killed it. The car dies within seven to eight minutes or roughly 0.13 hours after starting with a full charge, as the Model S Plaid’s battery has a capacity of 100 kWh, meaning it can expel 100 kW of power over roughly an hour. 

Now, let’s switch things up and say you’re on your way home from doing Tesla owner things, such as hot yoga and overpaying for bread with avocado on it (this is satire, by the way, so relax.) You’re taking it easy and hypermiling every stretch of the way, probably only expending an average of 50 kW during your drive. You’ll likely see about two hours’ worth of use and be able to travel a significantly farther distance with that 100 kWh battery than if you were to demand maximum attack from the electric motors a majority of the time.

Humorously, if you build some Frankenstein bastard child of a project car using the Plaid motors hooked up to a base model Nissan Leaf’s 40 kWh battery and went flat out, the party would be over in less than three minutes. Do with that information as you will, project car YouTubers of the world. 

That’s perhaps the simplest way to explain its relevance to prospective consumers. Smaller battery packs with lower capacities will result in shorter overall ranges and limit how much power an EV can reasonably output, while larger battery packs flip the script, enabling longer distances and more kW of power.

Lucid Air Action Shot
Image credit: Lucid Motors

It’s why you often see the pricier, long-range variants of electric vehicles sport more powerful motor setups and longer overall ranges, thanks to their higher kWh rating. And it’s partly why some performance variants with even more powerful motors wired to the same batteries (or even slightly bigger) may have shorter ranges, as their elevated performance now demands more from the battery, in addition to other factors like stickier tires, thermal challenges, and aero changes.

“Watt do you mean it can’t charge any faster?”

Last tidbit! Before we go too deep down a rabbit hole that’d require another article, let’s discuss how kilowatts and kilowatt hours pertain to charging your EV. Yes, everyone’s least favorite part. 

Just as kilowatts measure the power coming out of your EV, kilowatts can very much be used to measure the power going back into your EV, hence why we also measure chargers’ outputs in kW.

For example, a 50 kW charger will theoretically fully replenish a 50 kWh battery from next to nada in roughly an hour. A 100 kWh “fast charger” should be able to do the deed on the same battery in approximately 30 minutes. Ever wonder how these fast chargers can get monstrous powerhouses like the Model S Plaid, Lucid Air, or Taycan Turbo S up and ready to rock in less than an hour? Because fast chargers can output anywhere between 150 to well over 300 kW.

Rivian R1S closeup
Image credit: Rivian

Note other limitations can hinder how quickly an electric car can charge, including the set kilowatts an EV can accept. For instance, the new Volvo EX30 only has a maximum charge rate of 153 kW, which is more than enough for its 64 kWh battery, but far behind the 350 kW max charge rate of a comparable Hyundai Ioniq 5.

Class dismissed… for now.

Of course, there are so many other smaller factors that feed into the performance, charging, and discharging of an electric vehicle, which we can spin into another piece. But that’s the basic jist of the relationship between the fat K-W and the new wave of electric chariots.

For now, remember that kilowatts measure the power the car uses and produces while kilowatt-hours represent the energy stored in the battery pack, which directly impacts the EV’s range and output. And to any prospective owners out there, I hope this lesson has better equipped you to shop with confidence – or at least read Euro auto mags without scratching your head at the power figures.

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