This is how>>>

This is how>>>
Posted By: Rick V. (205.188.197.31)	Posted on Date: November 14, 1999 at 20:54:17
In Reply to: Re: Hmmm.... PACKIN 5.0 on November 14, 1999 at 20:13:33:
Message Text:
Take your MPH and divide by 234. Cube the result and multiply by your car's weight. This is the HP your car is making at the transmission tailshaft. In your case, it comes to around 423 horsepower. To figure minimum injector size, multiply the HP figure from the first equation by .6 (which is a conservative approximation of brake specific horsepower in supercharged cars), divide by eight and then divide again by .85 (a conservative injector duty cycle.) Working the figures for your car yields an ideal injector size of 37.32 lbs per hour. You can get your 30 pounders to act like 37 pounders by raising your fuel pressure with an FMU. The target pressure can be calculated by dividing the ideal injector size by your current ijector size and squaring the result. Multiply this by 39 psi and you know how much fuel pressure youi will need out of your FMU at max boost. The answer in your case is 60.36 psi, which, as you said, is about what your 6:1 FMU is giving you at max boost in the lower gears. To calculate fuel pump size in liters per hour, multiply your HP by .6 and then again by your BSFC of 0.6. Divide the result by .8 (for safety margin purposes) and this is the minimum flow capacity for your setup. In your case this comes to around 194 lph. The problem with using an FMU to raise fuel pressure is that most aftermarket pumps lose flow capacity as a function of increased pressure. At 60 psi, your 190 lph pump is probably only pumping out 85% of its rated capacity. Bottom line: you need more pump if you want to keep running 30 pounders and an FMU. The easiest way to maintain fuel flow at high pressure is to install a T-Rex. You might also be able to get by with a 255 lph pump. Safest route: 255 lph pump AND a T-Rex. Hope this helps.

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Comments: : Take your MPH and divide by 234. Cube the result and multiply by your car's weight. This is the HP your car is making at the transmission tailshaft. In your case, it comes to around 423 horsepower. : To figure minimum injector size, multiply the HP figure from the first equation by .6 (which is a conservative approximation of brake specific horsepower in supercharged cars), divide by eight and then divide again by .85 (a conservative injector duty cycle.) Working the figures for your car yields an ideal injector size of 37.32 lbs per hour. : You can get your 30 pounders to act like 37 pounders by raising your fuel pressure with an FMU. The target pressure can be calculated by dividing the ideal injector size by your current ijector size and squaring the result. Multiply this by 39 psi and you know how much fuel pressure youi will need out of your FMU at max boost. The answer in your case is 60.36 psi, which, as you said, is about what your 6:1 FMU is giving you at max boost in the lower gears. : To calculate fuel pump size in liters per hour, multiply your HP by .6 and then again by your BSFC of 0.6. Divide the result by .8 (for safety margin purposes) and this is the minimum flow capacity for your setup. In your case this comes to around 194 lph. : The problem with using an FMU to raise fuel pressure is that most aftermarket pumps lose flow capacity as a function of increased pressure. At 60 psi, your 190 lph pump is probably only pumping out 85% of its rated capacity. Bottom line: you need more pump if you want to keep running 30 pounders and an FMU. : The easiest way to maintain fuel flow at high pressure is to install a T-Rex. You might also be able to get by with a 255 lph pump. Safest route: 255 lph pump AND a T-Rex. : Hope this helps.