Efi Engines; Throttle Body; Mass Air Meter; Fuel Injectors - Factory Five Racing Mk4 Roadster Assembly Manual

EFI Engines

There are three things an engine needs; air, fuel and spark. If you allow more of each of these
into the engine, it will make more power.

Throttle Body

Stock Mustang size: 58mm
A 65mm throttle body work well up to 350hp. Ford Racing, BBK, Jegs, Summit Racing etc... sell many
other sizes.

Mass Air Meter

Stock Mustang size: 55mm
In order to increase the flow of air above 5000 rpm, upgrade from the stock mass air sensor.
Aftermarket 70 mm or 75 mm mass air units are an excellent choice and have proven effective. If the
mass air meter is changed make sure it is calibrated for the injectors you are using or you will have to
change the injectors too. Pro-M or Ford Motorsport meters work the best. Usually the mass air meter is
larger than the throttle body.

Fuel Injectors

Stock Mustang size: 19lb/hr.
The stock injectors are good for exactly that, a stock engine. If upgrading parts, step up to 24 lb/hr
injectors. They are good up to about 400hp. Make sure that you have the mass air sensor calibrated to
the injectors you use.
Rear end gears.
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