Understanding the EFI Process


fuel pressure regulator cut away

Fuel Pressure Regulator (FPR) – Mechanical device that maintains fuel pressure on Return Fuel Systems (fuel system that returns unused fuel back to the fuel tank). Most OEM FPRs operate at a 1:1 ratio and they work up to a given relative pressure (boost) at which point the FPR can no longer raise the fuel pressure. The failure point of a stock FPR is usually around 18-24psi. This is usually due to a mechanical limitation that has been engineered into the system to keep the cost of the production FPRs down. If you are going to continuously run more relative pressure (boost) than this then you may want to upgrade your FPR to an adjustable unit that is capable of working at higher pressure levels.

MBT – Minimum spark advance for Best Torque output. This is a state where you have calibrated the ECM to the maximum power available, or the maximum power that engine can produce under the given conditions. Running less ignition advance than MBT will usually lose power; Running more ignition advance than MBT will usually lose power as well and bring the motor close to the detonation threshold.

Millisecond (ms) – One thousandth of one second.

Open Loop System – An EMS sub-system which does not have a dynamic  ability to trim (or modify) its performance. An open loop system will simply do what it was programmed to do without any sensory feedback.

Overrev or Overrun – A condition where the RPM exceeds the engine’s ability to mechanically hold together.

aeromotive fuel pressure regulator

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