Turbocharger Boost Pressure - Manual Revision
88ford15
TURBOCHARGER - REVISED BOOST PRESSURE SPECIFICATIONS - SHOP MANUAL REVISION
Article No. 88-14-13
FORD: 1987-88 THUNDERBIRD
MERKUR: 1985-88 XR4Ti
This article is being republished in its entirety to correct the information listed in the "OPERATION" section.
ISSUE: The turbocharger and boost control solenoid diagnostic procedures as published in the 1987 and 1988 Car Shop Manual, Volume D, Section 24-47 "Turbocharger Boost Control System" and the Merkur XR4Ti Shop Manual, Section 24-01 are incorrect. This incorrect information may have been responsible for the unnecessary replacement of turbochargers and boost control solenoids.
ACTION: If service is required, use the boost pressures specifications listed below along with the following Turbocharger Boost Control System procedure to diagnosis for a "loss of power" condition.
OTHER APPLICABLE ARTICLES: Supersedes 88-11-13
WARRANTY STATUS: "INFORMATION ONLY"
24-47-1 Turbocharger Boost Control System 24-47-1
SECTION 24-47 Turbocharger Boost Control System
SUBJECT PAGE
DESCRIPTION ............................. 24-47-1
DIAGNOSIS ............................... 24-47-2
OPERATION ............................... 24-47-1
REMOVAL AND INSTALLATION
Fuel Selector Switch ..................... 24-47-1
SUBJECT PAGE
REMOVAL AND INSTALLATION (Cont'd)
Solenoid Assembly ....................... 24-47-1
SPECIFICATIONS ............................ 24-47-4
VEHICLE APPLICATION ........................ 24-47-1
FIGURE 1 - TURBOCHARGER BOOST CONTROL SYSTEM LAYOUT:
VEHICLE APPLICATION
Thunderbird Merkur/XR4Ti
DESCRIPTION
The turbocharger boost control system is designed to provide electronic variable boost control on the 2.3L electronic fuel injected turbocharged engine. The boost control system provides regulation of the wastegate actuator signal allowing turbo boost pressures up to 89.6-110.3 kPa (13.0-16.0 psi) on manual transmission vehicles and 55.1-75.8 kPa (8.0-11.0 psi) on automatic transmission vehicles. The system includes a control module, solenoid/hose assembly, calibrated "T" fitting and all controlled by the EEC module (Fig. 1). The boost control system is activated in the PREMIUM fuel selection position only, on manual transmissions. On automatic transmissions, it is activated in both the REGULAR and PREMIUM positions. See Note (A).
OPERATION
Refer to Fig. 1.
On vehicles equipped with manual transmissions, with the fuel selector switch in REGULAR position, boost pressure is limited by the wastegate to approximately 69 kPa (10 psi). When boost pressure reaches 69 kPa (10 psi), the wastegate is opened, bypassing exhaust gases away from the turbine blades, limiting turbo boost pressure.
When the fuel selector switch is in the PREMIUM position, the EEC module sends open and close commands to the turbo boost control module which, in turn, energizes or de-energizes the solenoid. When the solenoid is energized, a portion of the pressure signal to the wastegate actuator is diverted to the inlet side of the boost solenoid. This will result with higher boost pressures 89.6-110.3 kPa (13-16 psi) maximum. Boost pressure varies between 68.95 and 110.3 kPa (10 and 16 psi) depending on rpm, vehicle, speed and transmission gear selection. See Note (B).
On vehicles equipped with automatic transmissions, the boost control solenoid operation is identical with the fuel selector switch in either REGULAR or PREMIUM position. Solenoid operation is similar to the operation described earlier for PREMIUM position on vehicles equipped with manual transmissions, except boost pressures are lower 55.1-75.8 kPa (8-11 psi) maximum. Boost pressure varies between 41.3-75.8 kPa (6-11 psi) depending on RPM and vehicle speed. See Note (B).
NOTES:
(A) Merkur/XR4Ti does not have an Octane Switch. Boost control is activated at all times on automatic and manual transmission.
(B) Merkurs with manual or automatic transmissions operate the same as Turbo-Thunderbirds with the Octane Switch in the premium position.
24-47-2 Turbocharger Boost Control System 24-47-2
FIGURE 2 - TURBOCHARGER BOOST CONTROL MODULE AND SOLENOID:
REMOVAL AND INSTALLATION
Solenoid Assembly
Removal and Installation
1. Remove air cleaner assembly. Refer to Section 24- 41.
2. Remove control solenoid hose clamps at turbocharger. Carefully pull hoses away from fittings on turbocharger.
3. Remove two screws holding solenoid assembly to fender (Fig. 2).
4. To install, reverse Steps 1, 2 and 3.
Fuel Selector Switch (1987-88 Thunderbird only)
Removal and Installation
1. Remove switch assembly. Refer to Chassis/Electrical Manual, Section 35-21.
2. Turn switch assembly over, disconnect electrical connectors and remove switch.
3. To install, reverse Steps 1 and 2.
DIAGNOSIS
NOTE: Before beginning any diagnostic testing on this system, ensure that:
1. Fuel is premium grade unleaded with an octane rating of 91 or greater.
2. Engine is fully warmed up.
3. Battery voltage is 11.5-volts or greater.
4. An auxiliary vacuum/pressure gauge is attached.
SPECIFICATIONS BOOST PRESSURE TABLE
ROTUNDA EQUIPMENT
Model Description
021-0001 Radiator and Core Pressure Tester