Choosing the Right Wastegate
Choosing the right size wastegate can be a very in depth process, but for this purpose we will give you a basic guide to choosing the right size wastegate for your build.
What is a wastegate?
A wastegate is simply a pressure control valve used to divert hot exhaust gasses away from your turbo which in turns controls the turbo shaft speed and ultimately to control boost pressure.
Different engine and turbo size combinations require varying sizes of wastegates to control the boost pressure.
Factors to consider:
Displacement: The larger the motor is typically the larger wastegate you will need.
Target RPM: If you plan to be running your car at higher RPMS your wastegate will need to be larger to keep up with the increased flow demands at higher RPMS.
Fuel: E85 and Alcohol based fuels increase the flow demand on the wastegate more so than Pump Gas.
Target Boost Pressure: Wastegates work the hardest at low boost, so depending on what boost you plan on running your wastegate selection will need to fit your target boost plan.
Estimated Power: The ultimate combination involving all variables above
Turbo Sizing Chart:
Small Frame Turbos: Up to 60mm Compressor Size
Medium Frame: from 60mm to 70mm Compressor Size
Large frame: 70mm Compressor Size up
Wastegate Sizing Chart:
Small Frame: 40-45mm
Medium Frame: 45mm- 50mm
Large Frame Wastegate: 50mm-60mm
Pros and Cons:
Larger Frame wastegates offer the widest range of pressure. Simply you can control low boost setting while also being able to handle high boost targets. Also Larger Frame Wastegates flow most efficiently, allowing the exhaust gasses to be flowed much quicker. Large Frame Wastegates however, are heavier, larger in the engine bay, and ultimately more expensive.
Smaller Frame Wastegates work the best if you are only going to be running at higher boost levels, if you are running a larger A/R turbine Housing. Conversely, twin scroll turbochargers work great with smaller trim twin wastegates. Smaller frame wastegates weigh less, are smaller in the engine bay, offer the most control on boost pressures, and ultimately are the least inexpensive.
Wastegate Size Examples:
Big Block V8: Twin 60mm
Small Block V8: Twin 50mm
Six Cylinder: Twin 45mm (twin scroll) or Single 50mm
Four Cylinder: Single 45 or Twin 40mm (twin scroll)
13B Rotary: Single 50mm or twin 40mm
20B Rotary: Single 60mm
The rule of thumb is when in doubt choose one size bigger.
Ultimately, reach out to your tuner, turbo manufacture or engine builder on choosing the right size wastegate for your specific application.