Ford F150 Pickup. Manual - part 1617

2003 ENGINE PERFORMANCE

Theory & Operation - CNG, Flex-Fuel & Gasoline 

INTRODUCTION 

This article covers basic description and operation of engine performance related systems and components. 
Read this article before diagnosing vehicles or systems with which you are not completely familiar. To identify 
vehicles and engines, see FORD MOTOR CO. - INTRODUCTION - CARS or FORD MOTOR CO. - 
INTRODUCTION - TRUCKS article. 

AIR INDUCTION SYSTEMS 

SUPERCHARGER (F150 LIGHTNING 5.4L SC & MUSTANG 4.6L SC) 

Supercharger Assembly 

Supercharger assembly is a positive displacement pump designed to supply an excess volume of intake air to 
engine by increasing air pressure and density in the intake manifold. Supercharger assembly incorporates a by-
pass system to reduce air handling losses when boost is not required, resulting in better fuel economy. See Fig. 
1 . Supercharger can increase torque across entire engine operating range from 25-50 percent without 
compromising driveability or emissions. 

Supercharger is matched to engine by its displacement and belt ratio, and can provide excess airflow at any 
engine speed. Drive gears for supercharger are pressed into place and are not serviceable. Supercharger must be 
replaced as a unit. Supercharger contains 2 belt driven 3-lobed helical cut rotors which are supported by ball 
bearings in front and needle bearings at the rear. The rotors helical shape and internal specialized porting 
provide a smooth discharge flow and low noise levels during operation.

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline

  

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline

  

Fig. 1: Exploded View Of Supercharger & Intercooler System 
Courtesy of FORD MOTOR CO. 

Supercharger By-Pass System 

Supercharger By-Pass (SCB) system allows high pressure air at outlet of supercharger to vent back to inlet side 
of supercharger. This equalizes pressure and eliminates boost for times when supercharger function is not 
required. Descriptions of supercharger by-pass system components are as follows:  

Vacuum By-Pass Actuator 
 
During normal operation engine vacuum is applied to upper port of vacuum by-pass actuator. Lower port 
of vacuum by-pass actuator references air pressure in clean air tube, cancelling out any pressure 
difference in intake air system. Actuator opens during engine high vacuum conditions (by-passing 

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline

  

supercharger). As throttle is opened and engine vacuum decreases, vacuum by-pass actuator closes to 
allow supercharger to pressurize air in intake manifold. 

SCB Solenoid/Thermactor Air Control Solenoid 
 
SCB solenoid is used to control intake manifold vacuum to vacuum by-pass actuator. The SCB solenoid 
is de-energized during normal operating conditions. The Powertrain Control Module (PCM) will transmit 
an output signal to activate SCB solenoid to apply stored vacuum from vacuum reservoir assembly to 
vacuum by-pass actuator when an undesirable condition occurs in the engine. Once engine condition is 
corrected, SCB solenoid will be deactivated by PCM allowing engine intake manifold vacuum to control 
vacuum by-pass actuator. 

Vacuum Reservoir Assembly 
 
Vacuum reservoir assembly stores vacuum that is applied to the vacuum actuator when a condition such 
as overheating or critical sensor failure is generated.  

Supercharger Intercooler (Charge Air Cooler) System 

Intercooler system is designed to cool induction air which has been heated by the supercharger. Removing heat 
from pressurized air through an intercooler increases air density, which results in increased combustion 
efficiency, engine horsepower and torque. 

Intercooler system consists of the following components: an additional radiator and coolant reservoir 
(independent from engine cooling system), an intercooler (charge air cooler) located in lower intake manifold 
and a charge air cooler pump (electric water pump) located at right front side of engine compartment and 
intercooler coolant hoses. See Fig. 2 . 

Charge air cooler pump is controlled by PCM and charge air cooler pump relay to maintain a desirable intake 
air temperature signalled by a second intake air temperature sensor (IAT2) located in lower intake manifold.

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline

  

Fig. 2: Location Of Intercooler System Hoses (F150 Lightning 5.4L SC) 
Courtesy of FORD MOTOR CO. 

VARIABLE INDUCTION SYSTEM 

Intake Manifold Runner Control - Focus 2.0L (VIN P), Econoline & Pickup 4.2L (VIN 2) & Windstar 3.8L (VIN 4) 

On 3.8L & 4.2L engines, Intake Manifold Runner Control (IMRC) system consists of a remote mounted electric 
actuator with an attaching cable or linkage to operate the housing butterfly valve plate levers located between 
intake manifold and cylinder head(s). See Fig. 3 -Fig. 6 . On 2.0L, IMRC uses a motorized actuator mounted 
directly to a single housing, between intake manifold and cylinder head, without use of a cable or linkage. PCM 
uses a positive change in Throttle Position (TP) sensor along with the increase in engine RPM from Crankshaft 
Position (CKP) sensor to open butterfly valve plates. 

IMRC housing is an aluminum casting with 2 intake air passages for each cylinder. One passage is always open 

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline