i bought one off a board member and am unsure how to adjust it.. what i mean is turning the needle valve thing does what when you turn it in or out?

thamks, george

 

The needle valve adjusts the boost reference signal to the fmu. When you turn it in the signal is stronger and produces a quicker rise in fuel pressure. As the boost gets higher the adjustment has less of an effect due to the higher pressure in the line.

 

Fully closed will be about 90psi at 8 psi boost and stock injectors. You should start with it fully closed and adjust it a half turn at a time until you achieve the proper AF ratio. Each 1/2 turn counterclockwise will decrease fuel pressure and lean the engine.

 

Without a wide band O2 sensor to measure your true air/fuel ratio, you're just guessing at FMU settings and risk blowing up your engine from a lean condition. Professional tuning on a dyno with a wideband O2 system is the best way to tune, including changing your fuel pressure if necessary.

 

Don't forget about the 8 porcelin soldiers that are available. They have stories to tell, if only we're willing to take them out and listen.

 

I agree that your spark plugs are good indicators, but they're lagging indicators, not the real time feedback of a wideband O2 sensor. Also you need to pull the plugs right after the WOT run so as not to change the color of the plug on the drive home.

 

Thats why you floor it up your street, kill the engine, and coast into the driveway/garage