Optimize Your Engine’s Performance With Our E85 Fuel Injector Calculator

E85 fuel is an alternative fuel blend that contains 85% ethanol and 15% gasoline. E85 can provide performance and efficiency benefits for flex-fuel vehicles designed to run on gasoline, ethanol blends, or any combination of the two fuels. However, using E85 requires proper E85 fuel system components and ECU tuning to unlock its full potential while avoiding common issues.

Key TakeawayDescription
E85 BenefitsE85 enables more power and timing advance due to its high 100+ octane rating. It requires upgraded fuel system components and custom tuning.
Calculate Injector SizeProperly sizing larger fuel injectors is critical when switching to E85 to supply enough volume. Use HP or fuel flow equations.
Ethanol Fuel SystemFuel pumps, lines, rails, regulators must be robust enough to handle 30% more E85 flow and resistant to corrosion.
Tuning for E85Custom ECU calibration optimizes ignition timing, fuel trims, air fuel ratio, and cylinder pressures to maximize power safely.
Blend RatiosHigher ethanol content unlocks more performance potential up to E85 concentrations. Diminishing returns exist over 50%.

This article will provide an in-depth overview of E85 fuel, how to calculate the correct fuel injector size for E85 setups, and other critical details for safely and reliably running ethanol blends in your vehicle. With the right knowledge, you can properly outfit your vehicle to reap the rewards of E85 without compromising drivability or durability.

 Overview of E85 FuelEthanol fuel injectors

What is E85 Fuel?

E85 refers to an ethanol fuel blend that contains between 51% to 83% ethanol, with the remaining portion being gasoline or other hydrocarbon components. The “85” in E85 signifies that this fuel blend contains approximately 85% ethanol by volume.

The exact ratio of ethanol to gasoline can vary by geography and season based on standardization and availability of source materials. E85 is considered an alternative fuel and is primarily used in flex-fuel vehicles (FFVs) capable of running on gasoline, E85, or any mixture.

E85 Fuel Blend Composition
Ethanol: 75% – 85%
Gasoline: 15% – 25%

Benefits of E85 Over Pump Gasoline

E85 offers several advantages in performance applications due to its higher ethanol content and high octane rating:

  • 📈 Higher octane rating – E85 has an octane rating between 100 – 105 AKI, enabling more aggressive ignition timing for increased horsepower.
  • ⬆️ Increased horsepower/torque – The cooling effect and faster burn rate of ethanol results in 5-15% more power.
  • 💧 Increased fuel flow – More dense ethanol molecules allow running larger fuel injectors safely.
  • 💰 Lower cost – As a domestically-produced crop-based fuel, E85 is often priced lower per gallon than premium gasoline.

These benefits make E85 an excellent choice for heavily modified turbocharged, supercharged, or high-compression engines designed with upgraded fuel system components.

Considerations for Using E85 Fuel

While using heavy ethanol fuels like E85 can unlock great power gains, you need to address some important usage considerations:

  • ⛽️ Decreased fuel economy – E85 has less energy per gallon so your miles-per-gallon (MPG) will drop around 25-30%.
  • 🤔 Flex-fuel sensor required – A flex-fuel sensor is required for the ECU to adjust for different ethanol content.
  • 🔧 FFV fuel system – Fuel lines, injectors, pumps etc must be ethanol-compatible and robust enough to supply more fuel.
  • 🧮 ECU tuning – Custom tuning is required to optimize ignition timing, fuel trim, and boost for E85.

We’ll cover ethanol fuel system components and proper ECU calibration for E85 in more detail throughout this guide. First, let’s look at fuel injector sizing.Fuel System Components for E85 Setups

Running higher ethanol blends like E85 requires upgrading some fuel delivery components to withstand corrosion and safely deliver more fuel volume. Here are the key hardware considerations:

E85 Fuel Lines and Hoses

The first requirement is ensuring all fuel system plumbing and hoses are compatible with ethanol concentrations over 50%. Many components designed for gasoline will degrade over time, resulting in leaks and failures.

PTFE-lined rubber fuel hose or aluminum -AN fuel lines are excellent ethanol-compatible options for lines connecting the fuel tank, pump, rails, and regulators.

High-Flow Fuel Pumps

In addition to ethanol-safe materials, running E85 requires a high-flow fuel pump capable of delivering at least 30% more volume to feed larger injectors. An in-tank pump upgrade like a Walbro GSS342 can support 500+ horsepower E85 configurations.

Higher horsepower setups, big turbo builds making over 800 wheel HP, or engines over 6 cylinders may need multiple external pumps. Use our fuel pump calculator to determine required flow rates and psi for your setup.

Large and High-Flow Fuel Injectors

Larger, high-impedance fuel injectors capable of delivering more fuel volume are necessary for E85’s increased fuel demand. Popular injector upgrades include Bosch EV14 and Deatschwerks DW65c flow-matched sets with flow rates from 1200 cc/min and up.

We’ll cover E85 injector sizing formulas and calculations in detail next.

Flex Fuel Sensor

A flex fuel content sensor is crucial for allowing your engine computer (ECU) to adjust fuel trim across different ethanol concentrations from E10 when filling up at any pump to E85. This flexibility ensures optimal performance, driveability, and safety.

Flex sensors provide a widely-variable resistance signal to the ECU based on the ethanol content. Common examples are AEM’s 30-1200 flexible fuel ratio sensor or Delphi’s Flex Fuel Sensor.

Now let’s jump into calculating the optimal size injectors to meet your engine’s fueling demands when running high ethanol E85.

How to Calculate Fuel Injector Size for E85

Properly sizing fuel injectors is a critical step when switching to E85 to ensure you can feed enough fuel volume safely while avoiding excessive heat or impedance issues from oversized injectors.

There are two common methods to calculate the required fuel injector size for E85:

  • 1. By engine horsepower – Simplest method when you know your current or expected horsepower.
  • 2. By fuel flow requirements – More advanced method factoring in fuel pressure, desired air/fuel ratio, etc.

Let’s walk through both fuel injector sizing calculation formulas:

MethodDescription
1. Engine Horsepower MethodQuick estimate based on HP target
2. Fuel System Flow CalculationsFactors in AFR, fuel pressure

E85 Injector Size by Engine Horsepower Method

The simplest E85 injector sizing formula estimates required fuel flow rate based on your engine’s current or expected maximum horsepower.

  • General Rule of Thumb: Plan for 1 lb/hr of fuel flow per 1 HP
  • So a 500 HP engine would need 500 lb/hr of total fuel flow

Then divide your needed fuel flow by your number of injectors to get the flow rate per injector.

  • For a 4-cylinder engine, divide total flow by 4 injectors
  • For a 6-cylinder, divide by 6 injectors

And so on.

Here is the E85 injector size formula based on horsepower:

maximum-horsepower-output x (1 lb/hr of fuel per 1 HP) = total-fuel-flow

total-fuel-flow / number-of-injectors = minimum-E85-injector-flow-rate

Example:

  • 500 WHP engine
  • 4 cylinder engine so 4 injectors
  • Targeting 11:1 air/fuel ratio
500 HP x 1 lb/hr per 1 HP = 500 lb/hr total fuel flow needed500 lb/hr / 4 injectors = 125 lb/hr per injector required==> Choose 1300 cc/min E85 fuel injectors

So for a 500 HP 4-cylinder engine, the math shows needing E85 injectors flowing around 125 lb/hr each to supply enough fuel. Injectors in the 1200 – 1300 cc/min range would work well here.

The lb/hr method gives you a general idea of required fuel flow rate for ethanol based on horsepower targets. To narrow things down, we can use a more advanced formula involving desired air/fuel ratios and fuel system pressures.

Advanced E85 Fuel Injector Size by Fuel Flow Calculations

Let’s look at a more precise method of calculating injector size for E85 applications involving some fuel system parameters:

  • Target air/fuel ratio – Like 11:1 to 12.5:1 for high power
  • Fuel pressure – Typically 43.5 psi for most TBI and MPI systems up to 75 psi
  • BSFC – Brake specific fuel consumption based on engine efficiency

We’ll use the following version of an advanced fuel flow equation:

(Target air/fuel ratio x BSFC x Engine displacement x RPM) / (Number of injectors x Duty cycle % of injector) = Injector flow rate

This calculates the minimum fuel flow rate needed per injector based on the parameters above. Let’s break it down:

  • Target AFR – 11:1 is common for peak E85 power
  • BSFC – .50 is standard for turbo engines, up to .65 for NA engines
  • Engine Displacement – Your engine size in liters
  • RPM – Max RPM (like 6500-7000 rpm peak)
  • Number of injectors – 4, 6, 8 injectors etc
  • Duty Cycle % – Typically 80% max for headroom

Plug your numbers into this fuel injector size equation:

(Target AFR x 0.50 BSFC x Displacement x Max RPM) / (Number of injectors x 80% injector duty cycle) = Min. E85 injector size

Let’s run through an example scenario:

  • 🏎 500 WHP Evo X 4G63 turbo build
  • 💨 Shooting for 11 AFR at peak power
  • 🛢️ Stock 2.0L displacement
  • ⚙️ Capable of 7000 rpm
  • 💉 4 fuel injectors
  • 🚰 Moderate 43.5 psi rail pressure

Step 1) Plug the details into the fuel flow rate equation:

(11 AFR x 0.50 BSFC x 2.0L displacement x 7000 RPM max) / (4 injectors x 0.80 duty cycle)

Step 2) Solve:

(11 x 0.50 x 2.0 x 7000) / (4 x 0.80) = 1303 cc/min

Result: 1303 cc/min injectors should support ~500 WHP on this 2.0L 4G63 at 7000 RPM and 43 psi rail pressure, running 11:1 AFR on E85 fuel.

I’d spec a set of four 1300 cc/min E85 injectors. This flow rate matches what the simplified horsepower estimation method showed earlier.

You can manipulate the variables like AFR, displacement (if you build the motor bigger), expected boost pressure and max RPM to determine exactly what size E85 injectors you need. Inputting precise details gives you the best results.

Now let’s look at properly calibrating the ECU and tuning the engine to handle high ethanol concentrations for maximum performance and safety.

ECU Tuning and Calibration for E85 Setups

Adding E85 ethanol fuel requires custom tuning adjustments to avoid issues and unlock its performance potential by:

  • Optimizing ignition timing for the higher octane
  • Adding the right fuel for oxygenated properties
  • Adjusting target air/fuel ratios
  • Alleviating increased cylinder pressure from extra boost or compression
  • Managing ethanol’s aggressive solvency Cleaning carbon deposits

An ECU reflash or aftermarket programmable ECU provides the calibration flexibility to handle wide ethanol variance.

Adjusting Ignition Timing

Taking advantage of E85’s extremely high 100+ octane for aggressive, maximum-power ignition timing is the main key to making power.

  • More advanced spark timing translates directly into higher combustion pressures and temperatures, unlocking torque and horsepower exponential to degrees of timing added
  • Must be balanced with engine strength limits like cylinder pressures to avoid detonation or hardware failure
  • +10-15 degrees more timing over pump gas is common for high-compression NA engines
  • Turbo builds see +5-15 degrees timing gains depending on octane limits and cylinder pressures

Tuning Fuel Trims

Adjusting short and long-term fuel trim correction tables for ethanol’s low energy density compared to gasoline is critical.

  • ECU uses oxygen sensor feedback to compensate lower air/fuel ratio
  • Adds equivalent of 25-30% more fuel to match gasoline energy output
  • Prevents dangerously lean conditions under load risking detonation

Setting Target Air Fuel Ratios

Bumping up peak cylinder air/fuel ratio targets takes advantage of ethanol’s superior detonation resistance for more power safely.

  • 11:1 – 12.0:1 AFR range common for high output turbo builds
  • 12.5:1 possible with high octane ethanol, maximizes power
  • Creates cylinder cooling effect and slows boost heat spike
  • Careful AFR tuning avoids dangerously lean conditions

Managing Higher Cylinder Pressures

The combination of extra timing advance and boost magnification from ethanol’s cooling properties can dangerously increase cylinder pressures.

Proper tuning strategies include:

  • Reduce boost set point maximums
  • Lower boost PSI tapering over safe limits
  • Add EGT limits to taper timing if temperatures rise
  • Bleed off additional intake charge air

These tactics prevent peak cylinder pressures from growing unsafe for stock components.

Removing Fuel System Deposits

Heavy ethanol concentrations act as an aggressive fuel system cleaner dissolving carbon, which takes some adaptation.

  • ECU adjusts for extra fuel needed as injectors flow more freely
  • Temporary fuel trim swing rich then back to baseline
  • Cleans intake valves, combustion chambers enhancing airflow

Now that we’ve covered proper ECU tuning let’s examine how different ethanol blend levels affect performance.

Fuel Blends – E10, E30, E50, E85 Performance

E85 race fuel

There are 4 common ethanol blend ratios used in performance applications:

Fuel TypeEthanol Content
E1010% ethanol mix
E3030% ethanol mix
E5050% ethanol mix
E85Up to 85% ethanol mix

Higher ethanol concentrations enable more aggressive tuning and greater power gains thanks to ethanol’s superior octane over gasoline.

However, heavily modded engines see diminishing returns over 50-60% ethanol content as the extra oxygen and cooling effects plateau. Fuel system capabilities also limit realistic concentrations.

Let’s examine the performance impact moving from basic E10 pump gas to hardcore E85 racing fuel mixes.

10% Ethanol Blend (E10)

E10 refers to everyday pump gas containing up to 10% ethanol. Running basic 10% corn fuel has minimal impact in stock vehicles but poses limitations for big turbo builds:

  • 93 AKI limits timing to avoid knock 🤐
  • Stock fuel system handles only minor power mods before needing upgraded injectors, pumps etc
  • No advantage over pump gas without flex fuel sensor

Heavily tuned engines quickly outpace pump gas octane limits and stock fuel system capabilities. E10 offers no advantage for big turbo builds without also upgrading the fuel components.

30% Ethanol Blend (E30)

E30 provides a nice compromise for moderately tuned street cars looking for a bit of a power bump and improved economics without needing a full flex fuel setup.

Benefits of E30 include:

  • 🎛️ Decent mid-grade ethanol mix for basic bolt-ons
  • ⛽️ Only need 91+ octane fuel as base for 30% ethanol
  • 🚗 Mostly stock vehicles can take advantage of E30
  • 💰 E30 is cost effective alternative to premium gasoline
  • 🏎️ Good for tuned NA engines making up to 350 WHP

Compared to hardcore E85, E30 is easier on fuel system components and doesn’t require expensive upgrades to injectors, pumps and lines for most street cars.

You can utilize E30’s 100-102 octane and extra oxygen to spike timing 2-3 degrees and lean out the air/fuel ratio for cleaner combustion. This adds 5-7% more mid-range torque and top end power over plain 91 octane.

To run E30 properly in otherwise stock vehicles, an E30-compatible ECU tune is recommended to adjust for the oxygenated fuel properties.

While E30 gives you 93+ octane levels allowing moderately aggressive timing, the max potential ethanol cooling and detonation resistance benefits have diminishing returns under 50% ethanol concentrations.

FAQs:

  1. What is E85 Fuel?
    E85 fuel is an ethanol blend containing 51% to 83% ethanol and the remainder gasoline. It’s used in flex-fuel vehicles and is known for its high octane rating and performance benefits.
  2. How Do I Calculate the Correct Fuel Injector Size for E85?
    Injector size for E85 can be calculated using the engine horsepower method or the more advanced fuel flow requirements method, considering factors like air/fuel ratio and fuel pressure.
  3. What are the Benefits of Using E85 Over Regular Gasoline?
    E85 offers a higher octane rating (100 – 105 AKI), increased horsepower/torque, denser fuel flow for larger injectors, and often lower cost per gallon compared to premium gasoline.
  4. What Considerations Should I Keep in Mind When Using E85?
    Be aware of decreased fuel economy, the need for a flex-fuel sensor, compatibility of fuel system components with ethanol, and the requirement for custom ECU tuning.
  5. How Does E85 Affect Engine Tuning and Performance?
    E85 requires adjustments in ignition timing, fuel trims, and air/fuel ratios. Its high octane rating allows for more aggressive timing, leading to increased horsepower and torque, but also requires careful management of cylinder pressures and fuel system cleaning.

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