8:1 or 10:1
Posted: May 3rd, 2006, 3:09 pm
Dose anyone know which ones better for a 1.6 DOHC b6. 8:1 or 10:1, for an FMU ? gonna be running 8 - 12 psi. which one is a richer mixture ? Thanks
What turbo are you using (wheel sizes, trims, housing A/R sizes)? Also what size injectors are you using?
The compressor map for your specific turbo will help you determine about how much HP it can support at “X” psi of boost pressure. Once you know that then you can mathematically figure out your fueling needs base on the size of your injectors you are using. RC Engineering has a calculator that is handy for this http://www.rceng.com
First you need to calculate what size injectors in cc's or lbs/hr that you should be using according to RC Engineering’s Calculator. Start with your base line fuel pressure (set with no vac. line on regulator) and add the “X” psi of boost you used on that compressor map to find the amount of HP you need to support.
Base Fuel Pressure + "X" psi = Fuel Pressure input into RC Eng.'s Calculator
Now use RC Engineering’s calculator to see how much fuel pressure it will take to make your fuel injectors flow as many cc's or lbs/hr as the injector size you just calculated previously. Take the new pressure you'll need on your injectors and subtract it from your base line fuel pressure you were using in the first calculation. This is how many psi the fuel pressure will have to raise over "X" psi of boost you used to get your HP number in the first injector size equation.
RC Engineering's Injector size Fuel Pressure - Your Injector size Fuel Pressure needed = total fuel pressure rise needed
Take the total fuel pressure rise needed now and divide it by that "X" psi of boost you used on the compressor map earlier. Now you have your rising rate needed per psi of boost.
Total Fuel Pressure Rise Needed / "X" psi = Rising Rate Needed
Note!...10:1 rising rate...is 10psi of fuel pressure increase for every 1psi of boost pressure increase.
Note! Use this information at your own risk and always try to stay on the rich side for initial tuning. Also be sure to use the proper gauging equipment to monitor your engine until it is properly tuned. Continued use of such equipment after proper tuning is finished is HIGHLY recommended!