About B58 fueling & e85
For off-road / competition use only. Not legal for use on public roads in the United States, including California.
Fuel is what limits a tuned B58 once you move past Stage 2. If you want to run ethanol blends like E30 to E50, or add a bigger turbo, the stock pumps eventually cannot keep fuel pressure up. When pressure drops, the tune pulls power to protect the engine.
There are four parts to a B58 fuel upgrade. Most owners do them in this order:
- Flex fuel kit. Reads the ethanol content in your tank so the tune can adjust on its own. This lets you mix pump gas and E85 without reflashing.
- Low pressure fuel pump (LPFP). The in-tank pump. It feeds the high pressure pump and any port injectors.
- High pressure fuel pump (HPFP). The engine-mounted pump that feeds the direct injectors. This is the main limit on ethanol content. Dorch, Spool, Precision Raceworks and Fuel-It all make upgrades.
- Port injection. A second set of injectors in the intake for big-turbo or full E85 builds. It needs a controller such as the MOTIV ReFlex.
Every part here needs a tune that supports it. An HPFP needs an HPFP-enabled or custom tune. Port injection needs a custom tune and a controller.
Gen 1 and Gen 2 B58 fuel parts are different. The Gen 2 engine (G-series and Supra) uses a different, higher-pressure factory fuel system. Buy the part for your engine, and send us your VIN if you are unsure.
How to choose
- Good: flex fuel kit. The cheapest step into ethanol. Pair it with a flex-capable tune and run a mild blend.
- Better: flex kit plus LPFP and HPFP. This is our Stage 2+ setup, built for E30 to E50 blends.
- Best: add port injection and a controller. For big-turbo or full E85 builds that need more fuel than the direct injection system can supply.
FAQ
Do I need an HPFP upgrade for my B58?
Only if you want to run more ethanol or more power than the stock pump can support. On Stage 1 or Stage 2 with pump gas, most cars do not need one. If your logs show fuel pressure dropping on ethanol, it is time.
What does a flex fuel kit do?
It reads the ethanol content of your fuel and sends it to the tune. The tune then adjusts timing and fueling on its own. You can fill with any mix of pump gas and E85 without reflashing. It needs a flex-capable tune.
Do I need to upgrade the low pressure pump too?
Usually yes, once you run higher ethanol blends or port injection. The LPFP feeds the HPFP. If it cannot keep up, the high pressure side will not hold pressure either.
Will a Gen 1 HPFP fit my Gen 2 car or Supra?
No. Gen 1 and Gen 2 B58 engines use different fuel systems. The Gen 2 pumps listed here fit both G-series BMW and the A90/A91 Supra.
Do I need port injection?
Only for big-turbo builds or full E85 at high power. It adds a second set of injectors and needs a controller, an upgraded LPFP and a custom tune. Most owners do the HPFP and LPFP first.
