qwest

Is the turbo waste gate always held closed by spring , and opens with boost pressure ?
Trying to understand how a Boost elbow works...

Searched for a post that had operation explained , no luck...

91rangerturbo

how does the wastegate work exactly?

Inside the wastegate is a diaphragm which creates a seal, and a spring which holds the wastegate closed. Spring rates vary depending on the amount of boost you want to run, typically they are given in a "bar" value for example 1 bar would be 14.7psi. This would mean that in order to open the wastegate you would need to excerpt a greater pressure than the 14.7psi spring holding the wastegate closed. In order for the wastegate to work you must have the compressor reference port hooked up to the compressor side of the turbo, if you don't have this vacuum line attached than the boost pressure will not be limited to the set spring pressure; it will build unlimited boost pressure until your engine is destroyed.

Normally pressure from a spooling turbo pushes against the diaphragm (though the vacuum line attached to the compressor reference port) which in turn pushes against the wastegate spring. When the pressure from the spooling turbo exceeds the spring pressure the wastegate's plunger opens releasing the excess pressure through the dump tube into the exhaust after the turbo or to open atmosphere. Typically, if you use the wastegate to control your boost levels you will experience a decrease in power and spool times. Why? Although the spring fully opens at its set spring pressure it tends to begin opening before reaching the set spring pressure. This "pre-opening" leaks boost pressure through the dump tube before max boost pressure is reached resulting in a decrease in power mostly toward the top end. This can be corrected by using a boost controller.


More info on boost controllers and wastegates here
http://www.boostcruising.com/forums/...howtopic=76436

65dragnet

I thought I understood but my 95 Dodge CTD doesn't have a wastegate and my engine hasn't blown, it has 196,000 miles on it. Had my injector pump rebuilt by Sheid Diesel and noted to the service manager that I had no wastegate he said you don't need one. What's up with that?

91rangerturbo

Sorry that info is for a gas application but the wastegate functions the same when it comes down to it in theory

gmctd

The Boost elbow is just a flow-restriction in the air line - provides a delay as compressor pressure builds to overcome spring tension in the wg actuator cannister - unfortunately, also provides a delay before wg releases, after Boost pressure drops - wanna dance, gotta pay the piper.............