Contour Enthusiasts Group Archives Forums Modifications 3.0L Duratec MAF/Injector sizing for your hybrids...must read!

You have to think in percentage of increase because that is the only way to get correct perspective.
The 3L is 20% larger than the 2.5L
The 19# injectors are 11% larger than the 17# injectors and on average will flow ~10% more fuel if swapped out. So just by doing this you have increased fuel flow by 10% but remember you may not need the full 10% increase at idle.
19#'s will work and can probably by compensated for by an eManage or SAFC if you just add about 8-10% fuel AFTER you install the injectors (again, Idle is a different story).
This won't be perfect, but it will work until you get to a dyno with A/F to tune it.
However, this brings another problem up. The top end of your airflow through the stock MAF will be maxed out at about 4.5 volts. This is because the emanage will add 0.45 volts on top of the 4.5 volts from the MAF to compensate for the additional 10% fuel you are asking for. The output voltage of the emanage going to your PCM will then be 4.95 volts even though the MAF is still only putting out 4.5v.
All you have to do now is figure out what airflow voltage the 4.5 volts is equivalent to and then see if that is enough peak airflow for the new 3.0L at max RPM.

Figure out your max airflow at max RPM = 7000:
3L has an 89mm bore x 79.5mm stroke.

44.5^2*PI= 6221 mm^2
6221x79.5 = 494580 mm^3 per cylinder
Convert from cubic mm to cubic feet:

494580 / 25.4^3 (in^3/mm^3) = 30.18 in^3
30.18 per cylinder x 6 cylinders = 181.1 cubic inches and is the way you calculate engine displacement.

30.18 / 12^3 (ft^3/in^3) = 1.747x10^-2 ft^3 of air per cylinder.
0.1048 ft^3 is the engine displacement in ft^3.

How many cylinders draw air at any given rpm:
7000 rpm / 2 = 3500 (because two revolutions per firing cycle)

# cylinders x vol. per cylinder:
3500 intake cycles/minute x 0.1048 ft^3/intake cycle = 366.8 CFM (cubic feet/minute)

OK. ~367 CFM at 7000 rpm. This can help you size your MAF correctly or see if your current MAF can actually go this high. Honestly this is right around the top range of the SVT MAF calibration so I don't know if your stock duratech MAF goes this high. However if you find out that it's close then you will be able to use it because you are almost never at 100% volumetric efficiency...which is what this math calculation assumes to be true. More likely at 7000 rpm you are 80% of that.

80% of 367 = 293 CFM
Now, does the 4.5 volts on your stock MAF correspond to 300 CFM or more? If it is more than say 10% less (i.e. 270 cfm) then you will not be able to safely use your stock MAF even with the 19# injectors, and DEFINITELY not with 24# injectors.

If you change the MAF then you are now in the other category where you must get a chip because you have changed TWO VARIABLES from the engine mangagement system (MAF and INJ) and now you cannot control it very easily with a simple MAF scaling device. It is possible with lots of tuning time to use something like the emanage with rpm and throttle position and 256 data points to get a close approximation, but it is never perfect. The best I ever got was with the stock MAF and 24# injectors. When I tried a non-stock maf and 24# injectors I had CEL's popping on at random engine speeds during cruise. Not the best way.

Tom