Engine and Transmission Tech

Quote:

If you are going to use E85 or alcohol as a fuel, you need a fuelcompatible pressure regulator. Holley’s selection is a good place to start, but if you want to expand your range, check out Summit’s large selection. When alcohol is used, you need a large needle valve and adequate fuel pressure to flow enough fuel for maximum power. Fuel pressures need to be adequate at WOT and maximum RPM, but these higher pressures are often too much for the float to accurately control the fuel flow at idle. If the pressures are set for idle, the engine starves of fuel at the top end. This situation is by no means universal, so it depends on the design of needle and seat used in the fuel bowl as well as its effective diameter. I have a friend who has just wrapped up a championship with his dragster and has not run a single pound over 3 psi all season. Therefore, if the needle and seat pressures are good enough, high pressures are not needed. However, it may take a while to sort through your fuel system to get to this happy state.
The best way to run strong while still in the process of making adjustments is to have a vacuum-referenced pressure regulator, such as one made by Mallory. A few other companies, such as Aeromotive, also make vacuum/boost-referenced, fuel-pressure regulators worthy of consideration. All these regulators compensate linearly, and that means for every 1 psi the intake pressure changes, the regulated fuel pressure changes the same amount. Here is how this works for an alcohol-fueled engine. If, at idle, there are 6 inches of vacuum (3 psi), the pressure regulator reduces the pressure delivered by 3 psi. So if the base pressure is set at, say, 6 psi, then, at idle, it is 3 psi.

[www.musclecardiy.com]