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BMW B58 · Full E85

BMW B58 E85 Tune

M140i · M240i · 340i · 440i · 540i · 740i and 7 more

A full-E85 B58 tune is a calibration written for near-neat ethanol. It offers the largest knock margin of any pump-available fuel, which is why big-turbo B58 builds live on it — but it also demands roughly 30 to 40 percent more fuel mass than gasoline for the same air. On a direct-injection-only B58, that demand, not the turbocharger, is normally what decides how much of E85 you can actually use.

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Platform
B58 Gen 1 · B58 Gen 2
Sold as
B58 calibration, stock turbo through big single
Base calibration
$400–$500
Revisions
Log-based, included

B58 Full E85, by generation.

Gen 1 (B58B30M0) and Gen 2 (B58TU) run different DME software, with different boost, fuelling and torque structures. A Gen 2 file does not belong in a Gen 1 car, and the 540i, M240i and Supra span both generations by model year. Each row is the catalogue calibration this full e85 build is sold as, at its live price, with the add-ons that apply to it. What the car needs first is listed further down.

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B58 Full E85 calibration

Choose your generation to carry it into Find Your Tune. Not sure which you have? Find Your Tune identifies it from the car.

Find Your Tune

Which cars it applies to.

B58 Gen 1 and Gen 2 cars intending to run E70-E85 as their primary fuel. Worth doing on upgraded-turbo and fuel-system-supported cars; on a completely stock car an E30 blend usually delivers more of the benefit for far less complication.

  • B58 Gen 12016-2021M140i, M240i, 340i, 440i, 540i, 740i, X3 M40i, X4 M40i, Toyota GR Supra 3.0Chassis and years
  • B58 Gen 22019+M340i, M440i, M240i, 540i, 840i, Z4 M40i, Toyota GR Supra 3.0Chassis and years

What the calibration changes.

  1. 01

    Fuel system assessed before any target is set

    We start from what your car can deliver. Rail pressure under sustained load on your existing hardware sets the ceiling, and boost and load targets are written underneath it. A calibration that asks for fuel the pump cannot supply is the fastest way to lean out an engine on the fuel that was supposed to make it safer.

  2. 02

    Ignition and boost re-optimised for the knock margin

    Ethanol's charge cooling and effective octane move the knock limit a long way. Timing and boost are re-optimised around the new limit, verified against your knock-correction channels rather than assumed from the fuel type.

  3. 03

    Cold-start and drivability behaviour

    Near-neat ethanol is harder to light when it is cold. Cold-start enrichment, idle fuelling and warm-up behaviour are addressed so the car is still usable on a winter morning rather than only sorted at operating temperature.

  4. 04

    Content tolerance and map switching

    Pump E85 varies. The calibration carries margin for content below target, and where the hardware supports it we build a companion pump-fuel map so a tank of the wrong fuel is a map switch rather than an incident.

What your car needs first.

  • Honest information about your high-pressure fuel pump and injectors — this is the first question, not the last
  • Supplementary port injection or an upgraded HPFP on higher-output builds
  • An ethanol content tester, because pump E85 content moves with the season
  • Fuel lines, filter and pump in known-good condition; ethanol finds tired fuel systems
  • A pump-fuel map as a fallback if E85 is not reliably available near you

What to log.

  • RPM and vehicle speed, so every other channel can be read against load
  • Boost target vs actual boost (or absolute manifold pressure), full pull
  • Wastegate duty cycle, and actual wastegate position where the platform exposes it
  • Ignition timing per cylinder and any knock / ignition-correction channel
  • Intake air temperature and coolant temperature
  • High-pressure fuel rail pressure, target vs actual — the single most important channel on E85
  • Injector duty / pulse width and, where fitted, port-injection duty
  • Measured ethanol content for the tank logged, and the ambient temperature
  • Low-pressure fuel pressure where the platform exposes it

Reading what comes back: the BMW data logging guide goes channel by channel, and the wastegate duty cycle guide covers boost control.

Flash, log, review, revise.

The first file is conservative. Your logs decide every revision after it, and log-based revisions are included in the calibration price.

The process
  1. 01

    Submit your build

    Chassis, engine, full mod list and target fuel. This defines a safe calibration starting point before any file is touched.

  2. 02

    Receive a base map

    A conservative calibration matched to your hardware and fuel, flashed with your own software at home.

  3. 03

    Log and send back

    Full-throttle pulls and part-throttle data captured on our channel list, then sent over for review.

  4. 04

    Review and revise

    We read the logs, adjust the calibration and repeat until the car is running clean and on target.

B58 Full E85 questions.

More answers
Can a stock B58 fuel system run full E85?
At low output, briefly, and with no margin — which is not a recommendation. The B58 is direct-injection only, and neat ethanol needs roughly a third more fuel mass than gasoline for the same air. On a stock high-pressure pump the rail falls behind before the turbo does. If E85 is the goal, plan the fuel system first and treat the calibration as the last step.
Do I need port injection for a B58 E85 tune?
It depends on the output you are after. Supplementary port injection is the usual answer once direct injection alone cannot hold rail pressure at your target load. Send logs on your current setup and the rail-pressure trace will tell us whether you need it or whether an upgraded high-pressure pump is enough.
How is an E85 tune different from an E30 tune?
Same principle, very different demands. E30 gets you most of the knock resistance while staying inside a stock fuel system; E85 goes further on knock margin but roughly doubles the extra fuel demand and brings cold-start and availability problems with it. Our E30 vs E85 guide walks through where the crossover sits.
Will E85 damage my fuel system?
Modern BMW fuel systems are ethanol-compatible in the sense that they tolerate it, but ethanol is a solvent and it will find an ageing filter, a marginal pump or a tired line. It also holds water, so a car that sits needs the tank managed. Age the hardware honestly before committing.

Where this sits in the B58 range.

All tunes

Built around your B58.

Chassis, model year, hardware and the fuel you actually run is all we need. If you already have logs, include them: it usually saves a revision round.

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