Wastegate questions for turbo guru's...
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The basic Tial 35/38mm wastegate will do just fine for your/our application. The larger wastegates are more for higher boost vehicles, such as 300ZXs, Supras, DSMs, etc. If you want to run 5-7 psi, then you would need the applicable 5-7 psi spring, depending on the model wastegate you get. But, if you get a Tial, they are (for the most part), non adjustable. So whatever spring you put in, that is all you will get until a different spring is put in. A Deltagate or Racegate are "somewhat" adjustable for the spring that you have in there.
The boost controller would allow you to run as much boost as you want, well dependant on the limit of the boost controller itself, and ultimately the limit of the motor.
You are correct, the min. amount of boost you can run will depend on the wastegate spring. However, the rating on the spring will probably not be the amount of boost you will get from it. There will be some pressure loss in the system, ie the piping and/or the intercooler etc. This lose could range anywhere from 2-4 psi. So that 4 lbs spring in the wastegate might only equate to 2 psi when it finally reaches the motor. This however, varies between every setup.
UltimaSE
You are correct, the min. amount of boost you can run will depend on the wastegate spring. However, the rating on the spring will probably not be the amount of boost you will get from it. There will be some pressure loss in the system, ie the piping and/or the intercooler etc. This lose could range anywhere from 2-4 psi. So that 4 lbs spring in the wastegate might only equate to 2 psi when it finally reaches the motor. This however, varies between every setup.
UltimaSE
Bolt in compatibility.
The 38mm and 46mm gates are made to be direct bolt in replacements for existing wastegates as well as custom setups. The 38mm gate is dimensional equivalent to the Turbonetics delta gate with many features not found in the delta gate. The 46mm gate is a drop in for the 930 Porsche turbo cars.
Flow capacity.
Contrary to popular belief, larger higher HP applications do not necessarily require the largest wastegate available. The lower the boost pressure you are gunning for the larger your wastegate needs to be. An engine/turbo combination that is set to 25+psi has a smaller wastegate flow requirement than the same application set to 7 psi. This is because the wastegate is used to lower the boost not raise it, the lower the boost pressure is set the more flow the wastegate must allow.
The spring.
TiAL wastegates are not adjustable. To change the boost pressure at which the valve opens requires changing the spring within the wastegate. Springs range from .3 Bar to over 1 Bar are available. The most common way to select your spring size is to pick a pressure rating that is a couple tenths or a bar or a few psi lower than the boost pressure you intend to operate the turbo/engine combo at. This way a boost controller can be used to adjust the opening point of the wastegate and help you fine tune to the exact pressure that is desired. This also allows adjustments to compensate for changes in atm pressure, altitude and temperature, which will all effect the way your wastegate does it's job.
Mounting the wastegate.
this is one of the most overlooked areas of boost control. In a perfect world you would select a mounting location for our wastegate that allows the gate equal access to all cylinders or rotors. This promotes equal exhaust port pressures between cylinders/rotors and avoids mysterious tuning problems resulting from uneven exhaust port back pressures. Another aspect to keep in mind is the high velocity of the exhaust gas inside the exhaust manifold, sometimes exceeding 800ft sec. Gas that is traveling at such high velocities will not easily make 90 degree turns of zero radius into the wastegate inlet. Remember Newton's second law, "bodies in motion tend to stay on motion". That particle of air is not particularly inclined to make a 90 degree turn and 800ft/sec. It must be persuaded to do so by giving it a gentle radius and easy access to the exhaust flow. Simply welding the gate to the side of a tube may work in some cases where the manifold back pressure is thru the roof, but in modern high efficiency turbochargers the pressure inside the manifold can be quite low and special through should go into wastegate runner geometry. The penalty for poor gate placement and poor gate runner design is having to use a larger gate.
The 38mm and 46mm gates are made to be direct bolt in replacements for existing wastegates as well as custom setups. The 38mm gate is dimensional equivalent to the Turbonetics delta gate with many features not found in the delta gate. The 46mm gate is a drop in for the 930 Porsche turbo cars.
Flow capacity.
Contrary to popular belief, larger higher HP applications do not necessarily require the largest wastegate available. The lower the boost pressure you are gunning for the larger your wastegate needs to be. An engine/turbo combination that is set to 25+psi has a smaller wastegate flow requirement than the same application set to 7 psi. This is because the wastegate is used to lower the boost not raise it, the lower the boost pressure is set the more flow the wastegate must allow.
The spring.
TiAL wastegates are not adjustable. To change the boost pressure at which the valve opens requires changing the spring within the wastegate. Springs range from .3 Bar to over 1 Bar are available. The most common way to select your spring size is to pick a pressure rating that is a couple tenths or a bar or a few psi lower than the boost pressure you intend to operate the turbo/engine combo at. This way a boost controller can be used to adjust the opening point of the wastegate and help you fine tune to the exact pressure that is desired. This also allows adjustments to compensate for changes in atm pressure, altitude and temperature, which will all effect the way your wastegate does it's job.
Mounting the wastegate.
this is one of the most overlooked areas of boost control. In a perfect world you would select a mounting location for our wastegate that allows the gate equal access to all cylinders or rotors. This promotes equal exhaust port pressures between cylinders/rotors and avoids mysterious tuning problems resulting from uneven exhaust port back pressures. Another aspect to keep in mind is the high velocity of the exhaust gas inside the exhaust manifold, sometimes exceeding 800ft sec. Gas that is traveling at such high velocities will not easily make 90 degree turns of zero radius into the wastegate inlet. Remember Newton's second law, "bodies in motion tend to stay on motion". That particle of air is not particularly inclined to make a 90 degree turn and 800ft/sec. It must be persuaded to do so by giving it a gentle radius and easy access to the exhaust flow. Simply welding the gate to the side of a tube may work in some cases where the manifold back pressure is thru the roof, but in modern high efficiency turbochargers the pressure inside the manifold can be quite low and special through should go into wastegate runner geometry. The penalty for poor gate placement and poor gate runner design is having to use a larger gate.
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