I just wrapped up a tune for a customer vehicle that had a Roush 427R crate motor and a Holley Terminator X Stealth. Dyno tuning found another 60HP AND added reliability and longevity to the engine. Sounds too good to be true, right? Allow me to explain!

An initial dyno pull showed the engine going lean at higher RPM. The Holley Terminator X Stealth system was doing its job, however, there was an oversight during installation. The system was setup for 44psi of fuel pressure. This engine is capable of making the maximum HP supported by the EFI system, but to do that, it needs the full 60psi of fuel pressure. The reduced fuel pressure of 44psi was not providing enough fuel to the injectors, the injectors maxed out on their duty cycle, there was no more the system could do, and the engine was going lean. An excessive lean condition not only kills power, but also creates intense heat and can cause detonation, especially under full power or heavy load.

In this case, the increase in fuel pressure delivered 15% more fuel, putting the engine back into the target range, increasing power and removing the risk of damage caused by a lean condition.

Having your vehicle properly tuned is always a good idea, Holley EFI systems have amazing capabilities, but they also need the right inputs and settings to perform to their potential. Anytime you can increase power and reliability, it's a WIN-WIN!