The forced induction knowedge thread
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Joined: Oct 2000
Posts: 30,809
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From: Sydney
Moderator
Joined: Oct 2000
Posts: 30,809
Likes: 15
From: Sydney
A wastegate is a valve that lets exhaust gas bypass the turbine. It is a way of limiting the speed of the turbo. Wastegates are traditionally mechanical devices which use a spring to hold the valve closed, and pressure from the turbo to push it open. The spring is a set tension. The valve remains closed as the pressure increases. When it reaches the set pressure of the spring it pushes the valve open and exhaust gas bypasses the wastegate, the turbo slows (or at least stops accelerating) and pressure levels out or drops.
This is fine, but you only have one single finite limit on pressure. The tension of the spring. ANd like any mechanical device it is prone to delays and fluctuation. A boost controller overcomes these limitations by controlling the boost line from the compressor housing (it can open and close it) and also the other side of the wastegate which has to release air when the wastegate opens. By closing the pressure supply there is no force working against the spring. also by capping the air release the wastegate cannot open.
The boost control solenoid is controlled by the boost controller (in many of our cases, the AEM EMS). The LoveFab turbo kit comes with a 6psi spring. It will open at 6psi (although with our exhaust flow plenty still drives the turbo and boost can 'creep' up over 7psi). By blocking the line from the compressor the boost control solenoid can let it run as high as we require.
When using a boost controller the ideal set up is to use a weaker spring (say 4psi) then have several control levels such as 6 and 10 psi. You then switch between these as required. The AEM takes this even further. It can alter boost based on RPM and speed. This is useful if you suffer traction problems at certain levels.
This is fine, but you only have one single finite limit on pressure. The tension of the spring. ANd like any mechanical device it is prone to delays and fluctuation. A boost controller overcomes these limitations by controlling the boost line from the compressor housing (it can open and close it) and also the other side of the wastegate which has to release air when the wastegate opens. By closing the pressure supply there is no force working against the spring. also by capping the air release the wastegate cannot open.
The boost control solenoid is controlled by the boost controller (in many of our cases, the AEM EMS). The LoveFab turbo kit comes with a 6psi spring. It will open at 6psi (although with our exhaust flow plenty still drives the turbo and boost can 'creep' up over 7psi). By blocking the line from the compressor the boost control solenoid can let it run as high as we require.
When using a boost controller the ideal set up is to use a weaker spring (say 4psi) then have several control levels such as 6 and 10 psi. You then switch between these as required. The AEM takes this even further. It can alter boost based on RPM and speed. This is useful if you suffer traction problems at certain levels.
