How Exactly does the WasteGate work?

[MTTwister]

As I consider options for turbo boost, - "TurboMaster" versus "Vacuum fooling" I'm getting curious how the wastegate functions...

Does the vacuum can or the Turbo master - spring dealie hold the wastegate open as a default position?

What forces the wastegate closed if the vacuum can or the turbomaster spring dealie ( sorry for the technical terms here) is holding it open? Exhaust gas speed? Pressure?

Is the only function of the Vacuum pump to supply vacuum for the wastegate vacuum can? ( I don't have the EGR 'stuff' on mine).

Sould the proposed "TDP" mechanical stop ( I think it was in the 2002 reprints) be a 'good' idea on a stock diesel (21.1)- versus the project trucks 18.1 compression setup? Somehow, methinks not.

Thanks

[Kennedy]

On the 6.5 TD, the only thing that a spring loaded device can control is exhaust back psi. The factory system can hold more psi back in transient throttle positions so as to spoole the turbo more quickly, and can adjust based on actual boost rather than back psi.

[gmctd]

The wastegate is normally closed, routing all exhaust gas thru the turbine. Rising exhaust pressure blows the gate open, allowing exhaust to bypass the turbine, such that boost pressure falls.

Mechanical controllers utilize spring pressure to force the gate closed.
Bill Heath's is adjustable.

PCM , and electronic add-ons, use atmospheric pressure against a diaphragm as the motive force. Reduce pressure on control side (vacuum), and 15psi baro forces the gate closed.
Force here can be figured Baro pressure against diaphragm area in cubic inches.

Exhaust pressure against wastegate valve area can give you some idea of opposing forces at work.

Figure in the actuating arm lengths for final torque available, actuator vs wastegate.

Both add-on types have advantages and dis-advantages, as JK stated.

'92-'93 trucks, and PCM's converted to mech injection and boost, are strictly mechanical spring actuators.

PCM trucks can use either type, but spring actuators lose some PCM protection under critical conditions, such as overheating, where PCM will pull boost, then fuel.

[rjschoolcraft]

Force here can be figured Baro pressure against diaphragm area in cubic inches.[/QB]That would be square inches ;)

[gmctd]

Yep! redface.gif

Thanks :cool:
Guess I should correct that, but it would make your post and this one meaningless.
?????