Miata Fuel Pump Info

Common Facts and info on Miata fuel pumps:

  • Fuel pumps are rated in LPH. LPH as in the 190 or 255 means “Liters Per Hour” and not fuel pressure available. The stock pump supplies enough LPH in most cases until you get into major forced induction mods. The maximum pressure available from the stock fuel pump was between 78 to 85 PSI. That should be sufficient to run the 5-6psi of boost level.

  • The most popular model is a direct replacement of the in-tank OEM fuel pump. But keep in mind an overly large fuel pump is not always the way to go.

  • For the longest time the Walbro 255 lb/h fuel pump had been the accepted pump for all forced induction Miatas. On Miatas with a return line, the 255 flows more fuel at any giving pressure level than is needed. They tend to overload the OEM FPR and cause the system to run rich even in vacuum. Instead of idling at 35psi and reaching 48psi at 0~hg, it will run closer to 40psi at idle and 55psi at 0~hg.

  • If you have an aftermarket ECU, the stock pump more than enough to support 300rwhp with the stock regulator. Changing the fuel pump does nothing but flow enough fuel…it doesn't change any other factors in the fuel entering the combustion chamber.
  • The stock Miata fuel pump can only provide so much fuel (tends to max out around 85 psi). So, you need to upgrade the pump if you plan to fuel past 70-80psi, usually due to running small injectors on an FMU setup. Raising the fuel pressure raises the size of the injectors. Since it requires an aftermarket fueling device to control +20/30% larger injectors, adding more fuel pressure is the logical solution.

  • The ideal pump is the Walbro 190 lb/h HP fuel pump. HP stands for high pressure. It is important you get a HP unit if you plan on raising the fuel pressure levels past 90psi. The HP models can supply fuel up to 130psi. The standard 190 lb/h fuel pump is maxed at 90psi and the standard 255 lb/h pump is maxed at 80psi. The 190 HP unit will not only supply four 700cc injectors with enough flow to maintain 40-50psi in the fuel rail (enough for 400hp), but out flows the 255 HP model after 100psi.

  • It is recommended for most applications to go with the 190LPH, 190HP if using a FMU.

99-05 Miata

  • The 99-00 miata, with no return line, is noted as having fuel pressure drop towards redline from that factory. These miatas fuel at a constant 60psi of fuel regardless of pressure conditions inside the manifold, however it seems with forced induction, and even high powered N/A builds, the stock pump is not enough. The 255 HP model is the only model that has been noted to maintain the pressure at redline.

So what should I get?

  • OEM Replacement or Mild Upgrade:
    • If you're looking to replace your fuel pump and don't want to spend the money on the expensive OEM replacement, the Deatschwerks DW100 Series pumps are designed to be mild upgrades from the OEM pumps, which will satisfy 90% of the owners out there. DW100 Series for Miata
  • Track Racing (such as Spec Miata) or Boosted Applications:
    • The issue with going with higher flow pumps is that they will overpower the stock fuel pressure regulators and create an overly rich air/fuel ratio, robbing power instead of creating it. IF you're running an aftermarket fuel pressure regulator and can control the extra pressure of the Walbro 190-255 or Deatschwerks 200-300 series, then those pumps would be fine. 
      • Walbro 190lph High-Pressure: These are the ideal pump for most applications that need more fuel. They come in two different varieties, standard flow and high-flow. The standard flow is not as common as the high-flow.
      • Deatschwerks 200 Series: This is a good setup and flows 165lph compared to the Walbro 190lph. It's what we use in our Spec Miatas and falls in-between the Walbro 190 and Deatschwerks 100 series, which is a stock replacement/mild-upgrade pump. 
      • Walbro 255lph: This is a strong pump designed for engines that have larger injectors and need the extra fuel. It will overpower the stock fuel pressure regulators, so ensure you have a strong fuel pressure regulator
      • Deatschwerks 300 Series: A step up from the Walbro 255, the 300 series is a 320lph pump and is more than the normal Miata will ever need.