What is the significance of the throttle body? How do they differ between cars?
On a fuel-injected engine, the throttle body takes the place of the carburetor. This is where the gas pedal moves a butterfly valve that varies the amount of air let into the engine, and thus determines engine speed. ATX Neons have a slightly larger bore to the throttle body than MTX Neons do. This is because a small flange was added around the rim of the MTX throttle body to restrict air flow at low throttle positions; this was done in an effort to make the manual transmission car more forgiving of poor throttle/clutch technique. Switching to the ATX throttle body may cause the car to be more jumpy and difficult to drive smoothly. If done in conjunction with a cold air intake, switching to the larger ATX TB seems to improve acceleration for the MTX car, though it has not been completely quantified. The throttle body is available from junkyards ($35-75); however, when making the swap be sure to retain the sensors that came with the original car because the different transmissions use d
