With the mods in my sig, what does anyone think the optimum fuel pressure would be for me? I have been running it at about 39psi vac on.. sound good to anyone?
thanks
With no heads you should be fine with stock fuel pressure ( 38 -41 lbs).
However, you should be measuring your base fuel pressure with vacuum off. Vacuum, even at idle, changes the fuel pressure. So take the vacuum line off and reset it between 38-41 psi. Right now you're probably running a base fuel pressure of about 46 psi or so, which is a wee bit too much for a stock headed car.
Get one of your buddies to ride along with you. Find a level stretch of road where you can do some testing. Don't choose a speed range that will make you shift gears, the shift quality & speed will affect your results. Use 2nd or 3rd gear and do a run from 2000 RPM to 5800 RPM. Call out the RPM as it increases and have you buddy record it and the elapsed time. If you have one of those cheap digital watches like I do, a stop watch is built in. Start the fuel pressure at 36 PSI, vacuum off and make a run. Turn it up to 37 and make another. Be sure to reconnect the vacuum every time you set the pressure. Keep turning up the pressure and making runs until you notice a drop off in time. If your bud was careful to record the results, you'll have a nice chart to use to find the optimum pressure.