E85 Injector Sizing

What size injectors to use when running E85?

This is becoming a very common question. The answer is not as easy as straight forward as I wish it was. I will try to explain a simple calculation to get an idea to guide you in the right direction.

First things first. You will need to determine your base injector size. This is the size that you should be running on gasoline. To find this size use any of the commonly found EFI injector sizer charts.

Now that you have determined your base injector size you will need to determine the difference in size to run E85 Fuel. The way to do this is to do some simple math. You are going to use the multiplying factor of 1.47 to get your size. The 1.47 number represents the difference between the stoiciometric fuel ratio of gasoline and E85. Gasoline is 14.7 and E85 is 10.0

Now that you have the factor and your base injector size, do the math. I will do one with you just to show an example. Lets say that you came up with a size of 42lb injector needed to reach your HP goals. Simply take the number 42 and multiply this by 1.47.

42 X 1.47 = 62lb Injector

No reason not to use 1.50 x the Gasoline injector for rounding up.

Fuel pump has to be sized as well � and make sure Regulator and Fuel Pump is impervious to E-85 fuel. OR"

OR MANUAL CALCULATION .6 FOR SUPERCHARGED .5 FOR UNBLOWN

HORSEPOWER DESIRED - 1000 X .6 FOR SUPERCHARGED = 600 DIVIDED BY NUMBER OF INJECTORS 600 BY 8 = 75 THEN 75 DIVIDED BY DUTY CYCLE ( WE LIKE 80% DUTY CYCLE ) SO 93.75 FOR E-85 MULTIPLY BY 150 = 140 LB FOR METHANOL TAKE YOUR 93.7S X 220% = 206 LB FOR UNBLOWN ENGINES USE .5 IN THE FIRST EQUASION