When you’re building a boosted engine combination there are multiple things you need to take into consideration. The type of fuel and the fuel system you plan on running should be at the top of that list. You don’t want to build a fuel system that can’t service your boosted engine’s needs.
Since you can find E85 at the pump, and it has a higher octane than pump gas, it has become a popular fuel for those who use boost as a power-adder. While this seems like a win-win, there is a caveat to using E85, your fuel system must be E85 compatible. We’re here to make it easier for you to build an E85 fuel system for your vehicle. We sat down with Doug Flynn from Holley and Nic Santarpia from Fuel Injector Clinic to get some tips about how to build an E85 fuel system for a boosted high-performance street car.
Most OEM fuel systems aren’t designed to move enough fuel to feed a boosted E85 engine package.
Five General E85 Fuel System Tips
We’re going to consider the fuel pump, fittings, filters, and hoses as parts of the general fuel system. These are the parts that move the fuel from the tank to the injectors. When you’re building a fuel system, all of these items need to be E85 compatible. E85 is ethanol-based, so it will corrode any damage anything that isn’t resistant to alcohols.
Tip 1: Selecting The Proper Fuel Pump For The Application
You know that you need a fuel pump that can handle E85, but there’s more to selecting the correct fuel pump. The pump needs to be able to move enough fuel to support how much horsepower the boosted engine package can generate. The engine is going to burn more E85 than gasoline for the same power output; this is why the fuel pump’s volume capabilities are so important.
“Let’s say you’re going to make 750 horsepower at the flywheel. You need to calculate how many liters per hour that is going to require. There are a lot of different ways of getting there, but perhaps the most common method is to take the brake-specific fuel consumption of the engine, and multiply that by the horsepower. With gasoline, I usually use .5 for the brake-specific fuel consumption figure, or .7 for ethanol,” Flynn states.
Depending on the application, you might have to double up on E85-friendly fuel pumps to meet the engine's needs. 
So how does that math work out in the real world? “So, in this case, you’d multiply 750 by .7, and that calculates out to 525 pounds per hour of fuel that you would need. And 525 lbs/hr equates to about 330 liters per hour. You can find calculators online that will do this conversion for you. I also add a minimum of 20-percent extra capacity to that for safety, so here you’d end up with a pump that outputs 400 liters per hour — and that’s if you never plan to upgrade the motor. You also might want to build in a little more headroom than that if you’re making crazy-high horsepower numbers to keep the engine cool and that sort of thing,” Flynn explains.
Tip 2: Pressure And Voltage Will Affect Fuel Pump Flow
Every fuel pump on the market is going to have flow ratings based on how much voltage is being fed to the pump. This is something you’re going to need to keep in mind when shopping for an E85-compatible fuel pump. You need to make sure your battery voltage and the fuel pump’s output match up. The pump’s output is going to be very different at 12 volts versus 16 volts.
Here’s an example of how the voltage, flow, and pressure are all related.
“You need to keep in mind that the higher the pressure that you run an electric fuel pump at, the lower the flow of the pump is. You should have a chart from the pump manufacturer that shows you how that flow changes as the pressures go up. You can compare that amount on the chart to the pumping target we established earlier by doing that calculation. This will allow you to select the right fuel pump for your specific application,” Flynn states.
Make sure your regulator will be up to keep up with your engine’s fueling needs.
Tip 3: The Fuel Regulator Needs to be Matched To The Fuel Pump
Fuel pump manufacturers are going to have certain regulators they recommend you use with a fuel pump. You want to pay close attention to how that regulator functions when the engine is at idle. What the regulator does when the engine is at idle is important, because that’s when it’s sending the greatest amount of fuel back to the fuel tank. With the additional volume of E85, this becomes doubly important.
“If the orifice in the return passage in the seat of the regulator isn’t big enough, the regulator won’t bypass enough fuel back to the tank, and the pressure will rise significantly at idle. Then, when you go wide open throttle, the fuel pressure will drop. People in that situation often think that they’ve got a bad fuel pump, when they’ve actually just got the wrong regulator. You need a regulator that has enough bypass capacity to keep up with the fuel pump based on the fuel pump’s flow capacity, and the fuel pump manufacturer will be able to determine that,” Flynn says.
Fuel filter size is important to keep your fuel system healthy. 
Tip 4: Size Matters When It Comes To Filter Choice
Any fuel has the potential to contain contaminants that will harm parts of your fuel system. Your E85 fuel filter needs to be large enough so it doesn’t impede the flow of fuel, plus, it needs to have the correct filter mesh size to keep junk out of your injectors without overly restricting flow.
“As with the regulator, the bigger the fuel pump is, the bigger the filter should be. You don’t want to pair a huge pump with a tiny filter, because the filter will end up choking the flow. And if you’re using E85, you should also verify that the filter you’re planning to use is compatible with that fuel. If you have an in-line pump that’s not in the tank, you’re going to want a 100-micron pre-filter before the pump and a 10-micron filter after the pump, no matter what. If you have an in-tank pump, the filter sock on the pump functions as the pre-filter,” Flynn states.
E85 fuel systems require a specific type of fittings and hoses. 
Tip 5: Guidelines For Fuel Lines And Fittings
Just like every other part of the fuel system, your lines need to be sized correctly. An E85 fuel system is also going to require fuel lines that won’t be damaged by the corrosive fuel.
“Because fuel injection lines generally run at higher pressures than carbureted applications, you can typically get away with running a smaller line. When you’re using E85, you need to keep in mind that you’re using 40-percent more fuel than gasoline. For 500 to 1,000 horsepower, a -8AN feed line is going to be fine, and the return line should ideally be the same size as the feed line. You should also use Teflon-lined hoses in this type of application. E85 is corrosive, and it’ll tear up a rubber-based line over time. Teflon won’t have that issue,” Flynn explains.
If the fittings aren’t E85-compatible, they will leak and eventually fail.“With E85, you want to use fittings that are either stainless steel or anodized aluminum to prevent corrosion. Regardless of the fuel type, you should avoid using 90-degree fittings whenever possible. With a hard, 90-degree turn like that, the fuel is basically hitting a wall and changing direction, and that will reduce the pump flow. A better solution here is a swept tube fitting, which provides a gentler radius for the change in direction to help maintain consistent flow,” Flynn says.
Not all fuel injectors are designed to work with E85. Make sure you get the correct injectors to prevent big issues.
Four E85 Fuel Injector Tips
We’ve looked at all of the fuel system parts that move the E85 to the engine, now it’s time to cover what delivers the fuel into the engine. The fuel injectors that are used in an E85 fuel system need to be compatible with the fuel and they need to be sized correctly.
Always make sure your fuel injectors will work with your intake and fuel rails. 
Tip 1: Check Your Fuel Injector Fitment
Not all builds are the same, so there could be some fitment differences between the OEM injectors and what you need. If you’re using an aftermarket intake manifold, fuel rails, or a combination of the two, that will also change the injector fitment.
“Injector fitment is another often overlooked factor when it comes to choosing the right injector for your build. At Fuel Injector Clinic, our part numbers represent fitments that fit a factory vehicle, however, with aftermarket parts being involved, fitment can change with an aftermarket rail or intake manifold. It is important to check if these changes alter your injector fitment requirements. Takes measurements to confirm manifold and rail bore diameters, and distance from manifold to rail. Generally, with this basic information, we can get a set of injectors appropriately set up for these changes,” Santarpia explains.
Tip 2: High Impedance Vs Low Impedance Is Important
Injector impedance is the measurement of the ease that a circuit can process current when direct voltage is running across it. A high-impedance injector is going to have coil resistance that ranges from 8 to 16 ohms. Low-impedance injectors will have a coil resistance of just 4 ohms or less.
According to FIC, if you have the option to select high-impedance injectors over low-impedance injectors for your build, do it.
“Always choose high-impedance injectors if possible. Some older vehicles use low-impedance injectors, which is an outdated technology. Low-impedance injectors don’t match the level of control and stability that comes with modern high-impedance injectors. The swap to high impedance can be as simple as a resistor-pack delete. The difference between high impedance over low impedance is night and day in terms of idle quality, drivability, and ease of tuning. Any tuner that I’ve spoken to that has worked with both low- and high-impedance injectors has conveyed this sentiment,” Santarpia states.
What's inside your fuel injectors is just as important as to home much fuel they can move. 
Tip 3: Make Sure The Injectors Have The Right Internal Parts
What’s inside the fuel injector is very important when it comes to E85 compatibility. You need an injector that’s filled with robust parts that can handle the corrosive fuel, while still delivering enough to keep up with the fueling demands of a boosted engine.
“Fuel consideration is always important with any component of your fuel system, and luckily with most modern injectors having stainless steel internals, they are generally compatible with most fuels. One thing to note here is that when using Methanol, no matter the injector, we always recommend flushing the system with some pump gas after a race or if the car will be down for some time,” Santarpia says.
Don’t use injectors that are lacking data. That data will make tuning your vehicle much easier
Tip 4: Select Injectors That Have Plenty Of Good Data
When it comes time to start tuning a boosted engine that’s feeding on E85, you need to be very precise to keep the mill happy. A good set of aftermarket fuel injectors should come with a sheet that provides what the flow is at different pressure and voltage levels. This information makes it much easier for a tuner to get your boosted combo that runs on E85 figured out.
“Choose an injector that has good data included with the injector, or that can easily be found. Tuners will chase their tails with a slew of issues that all really stem from bad data or no data. The computer needs to know precisely how long to open the injectors to get the desired amount of fuel, and it can’t do that without proper data. It really does make the tuning process much smoother having an injector that comes with good data,” Santarpia explains.
Selecting the right fuel system parts is critical to keeping the engine happy and healthy. These tips should assist you in making the best choices for your build and help it to reach its full potential.
