tbird turbo coupe specs
12-08-2003, 08:51 AM
#3
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Join Date: Dec 2002
Posts: 24
Re:tbird turbo coupe specs
Here's a clip from a Tbird enthusiast site:
Boost is controlled, on our cars, by a waste gate (WG). The waste gate, when closed, forces all the exhaust gas to flow over the turbine wheel and spin the compressor wheel to build boost. The WG is controlled by the waste gate actuator (WGA) which is a diaphragm driven device with a control rod on one side that is hooked to the WG. The WGA is spring loaded and set to begin opening the waste gate when it receives a certain level of boost through the hose that goes to the diaphragm (10-psi on Ford turbos). What both the factory and aftermarket boost controllers do is control when the WGA actually receives boost. The factory BCS (boost control solenoid) in conjunction with the EEC will allow up to 10 psi of boost whenever the turbo can build it but won't deliver more than 10 psi in the upper 3 gears until the engine is around 4000 rpms or a little more. It does this by sending boost pressure to the WGA when the boost is at 10 psi and rpms below 4000. When the engine reaches 4000 (approx.) the BCS bleeds or “leaks” off the boost signal to the WGA. This fools the WGA into thinking the boost pressure is lower than it actually is. When the BCS bleeds pressure off the WGA, the actual boost pressure will be about 15 psi, but the WGA will see only 10 psi. This lower 10-psi will open the WG allowing some exhaust gas to bypass the turbine wheel so boost does not build beyond 15. (This is a generalization, not all years of TCs follow this exactly as far as what boost level and what rpm) The Gillis valve and other types take control of the boost signal to the WGA away from the factory BCS and EEC. Inside the Gillis valve is a check ball and spring. The ball and spring block the flow of boost (not vacuum) through the valve and to the WGA until the preset boost level is reached. When that level is reached, the spring can no longer hold the ball over the orifice. Boost enters the valve and on to the WGA, which opens the WG. The Gillis valve doesn't know or care what the engine rpms are, it only responds to the level of boost. This is why it can allow full boost lower in the rpm range. The Gillis valve also has a very small bleed orifice that allows the pressure in the WGA to drop when the throttle is closed so the WGA doesn’t stay open.
Boost is controlled, on our cars, by a waste gate (WG). The waste gate, when closed, forces all the exhaust gas to flow over the turbine wheel and spin the compressor wheel to build boost. The WG is controlled by the waste gate actuator (WGA) which is a diaphragm driven device with a control rod on one side that is hooked to the WG. The WGA is spring loaded and set to begin opening the waste gate when it receives a certain level of boost through the hose that goes to the diaphragm (10-psi on Ford turbos). What both the factory and aftermarket boost controllers do is control when the WGA actually receives boost. The factory BCS (boost control solenoid) in conjunction with the EEC will allow up to 10 psi of boost whenever the turbo can build it but won't deliver more than 10 psi in the upper 3 gears until the engine is around 4000 rpms or a little more. It does this by sending boost pressure to the WGA when the boost is at 10 psi and rpms below 4000. When the engine reaches 4000 (approx.) the BCS bleeds or “leaks” off the boost signal to the WGA. This fools the WGA into thinking the boost pressure is lower than it actually is. When the BCS bleeds pressure off the WGA, the actual boost pressure will be about 15 psi, but the WGA will see only 10 psi. This lower 10-psi will open the WG allowing some exhaust gas to bypass the turbine wheel so boost does not build beyond 15. (This is a generalization, not all years of TCs follow this exactly as far as what boost level and what rpm) The Gillis valve and other types take control of the boost signal to the WGA away from the factory BCS and EEC. Inside the Gillis valve is a check ball and spring. The ball and spring block the flow of boost (not vacuum) through the valve and to the WGA until the preset boost level is reached. When that level is reached, the spring can no longer hold the ball over the orifice. Boost enters the valve and on to the WGA, which opens the WG. The Gillis valve doesn't know or care what the engine rpms are, it only responds to the level of boost. This is why it can allow full boost lower in the rpm range. The Gillis valve also has a very small bleed orifice that allows the pressure in the WGA to drop when the throttle is closed so the WGA doesn’t stay open.
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