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Old 06-03-2011, 11:29 PM
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Dzchey21 Dzchey21 is offline
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Default Wastegate 101

Thanks beefy


Quote:
Originally Posted by BFT View Post
This is here for all to see, read and to give informative info. This will also be followed with some installation pics both current and old. Mike (bigrpower) let me take a couple pics of his set up with the precision wastegate, thanks Mike!
Once again all questions and input are welcome.

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.

In order to run a manual boost controller we need to tee off of the vacuum line which runs from the turbo compressor housing to the compressor reference port. The manual boost controller works using a spring and check ball, by screwing the adjusting screw into the boost controller you put more pressure on the spring which reduces the amount of airflow through the boost controller and into the boost controller port. Less airflow means less pressure will be assisting the spring to keep the wastegate plunger shut. The pressure in the vacuum line going to the compressor reference port will equal the pressure the turbo is producing. A boost controller will allow you to direct some of that pressure to the top of the wastegate diaphragm creating two opposable forces. By adjusting the spring pressure of the boost controller you can vary the amount of boost that the turbo will make before opening the wastegate's plunger. If you want to run a higher boost level than the wastegate spring allows you will need a boost controller.


The manual boost controller is a very simple device that can help you make more power from your turbo setup. Here are three additional things to keep in mind about wastegates:

Without a line running from the compressor housing to the wastegate's compressor reference port boost pressures will keep increasing forever. This will quickly destroy your engine!

Run a wastegate as close to the desired boost pressure as possible this will help the boost controller handle the pressure better.

You can't reduce your desired boost pressure lower than the spring rate.

Moderator Edit: (note this is for Elites wastgate kit only, other kits may contain different springs and may alter adjustments and proceedures) After the wastegate is installed, you should have the boost reference line from the intake or CFM elbow running to the inlet side of your manual controller. From the controler the line will run to the port on the SIDE of the wastegate. You will have one other line on top of the wastegate, that is just a vent to atmosphere, put the end of that in a clean dry place.

Set up: Easiest way to monitor drive pressure vs boost pressure is to set up your dashdaq, or livewire, to read MAP (absolute) and EBP, Both of these readings will already have atmospheric pressure (11.7-14.8 depending on altitude and ambient temp) calculated into the gauge reading. This way when you are reading data logs, or glancing at your gauges during a run you dont have to figure in atmospheric pressure on the boost side, this should speed things up as well as make it a bit more accurate. Turning the wastegate clockwise will increase the pressure to the port on the side of the wastegate, thus opening the wastegate valve earlier, and dropping back pressure. Turning counterclockwise will lower boost to the gate, and thus increase back pressure
SO
Clockwise= lower back pressure
Counterclockwise= higher back pressure

I beleive elite calls for an initial adjustment of like 2 or 2.5 turns in clock wise.

You want to try and get the boost and back pressure within about 10 psi of each other, more or less is ok depending on your liking for spool up or back pressure.


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