Dyno Comparisons -- Adjustable Fuel Pressure Regulator Settings

Dyno graph of stock vs. 36psi Fuel Pressure.

Here, the dyno shows a 16.6 horsepower and 14.6 ft/lbs torque difference between the stock fuel pressure (46psi) and 36psi with the LG Motorsports adjustable regulator. Actually, it was still making more power at 35psi than 36psi, but until I can measure my O2 sensors, I did not want to lean it out any further. The average gain here was 13.9 horsepower and 15.4 ft/lbs torque. Check out the Dynojet Race Routine between the stock and 36psi fuel pressure.

Something new: Dynojet is currently Beta testing their new WinPEP software for the dyno. With this software, they have the ability to graph up to 12 graphs at once. Check out the Dynojet
WinPEP Graph of all the power between the stock and 35psi fuel pressures.

NOTE: One thing that I have found after some time with this mod is that the stock computer is quite smart. After lowering fuel pressure to achieve a better air/fuel ratio, the computer sees this at part throttle and adds injector pulsewidth to compensate. Basically, horsepower fell back off to where I started from. While normal trains of thought tell us that since O2 values are not measured during wide open throttle, that fuel pressure should have a long lasting effect here. Actually, it does not. The computer uses the last known long term fuel trim integer at WOT, which is to add fuel since at part throttle it has adjusted for being too lean.

This mod is helpful for tuning the block learns to as close to 0% as possible, giving the computer the widest range of adjustment, but not for horsepower. For more horsepower, we need a computer program with a different target air/fuel ratio.


With the adjustment of the fuel pressure, the car becomes much more lively. I did not expect fuel pressure to have this much of an effect on it, but since I'm here at 5000 feet altitude, I guess it was even richer that I had suspected. I think I could even go leaner, but until I can monitor my air/fuel ratio with Hypertech's scan tool module for the Power Programmer Plus, or I buy a Diacom, I do not want to risk the consequences.