SteamSpeed TECH: How to Preload a Wastegate Actuator

How does one correctly preload a turbocharger’s waste actuator?

We get asked this question often, so here is a little guide on how to correctly preload a turbo’s wastegate actuator.  In general, you adjust the preload according to the pressure of the spring that is in the actuator.  Most aftermarket turbos are set to 1.0 bar.  Actuators can be adjusted up or down ~+/- 0.1 bar of their spring pressure.  Our turbos come preloaded with 0.9-1.2 bar depending on the application.

Our adjustable actuators can take a number of different springs to achieve a wide range of preloads.  We also sell them separately as a retrofit for people with stock or other brands of turbos.  Extra springs if you already have our actuator.

1. Attach the actuator to the compressor housing.

Attach the waste gate actuator to the compressor housing
Attach the waste gate actuator to the compressor housing

2. Attach the actuator to the arm of the turbine housing’s flapper arm.  Note: do not insert the cotter pin yet to the flapper arm.

Attach the waste gate actuator to the turbine housing
Attach the waste gate actuator to the turbine housing

3. Attach a boost source to the barb on the waste gate actuator.   Pictured below is a custom made apparatus that connects to an air compressor.  We also sometimes use a reversible vacuum pump (one that can be reversed to make pressure as well as vacuum) and use that to apply the target pressure.

Apply a boost source on the actuator's barb
Apply a boost source on the actuator’s barb

4. Apply the target pressure which should match the spring that is inside.  Then, apply 0.1 bar of pressure more than the target.

Add pressure to the target boost level
Add pressure to the target boost level

5. Check the flapper’s gap.  It should be open around 0.10mm at 0.1 bar beyond the target preload.  We are using a 0.10mm gap feeler to check.  If you do not have a gap checker, you can get close by watching the flapper to move ever so slightly.

Check the flapper's gap
Check the flapper’s gap

6. If the gap was correct in step 5, go to step 7.  If the gap is not correct, you fine tune by adjusting the actuator rod.  Shorten the rod to add more preolad.  Lengthen the rod to decrease the preolad.  Repeat steps 2-6 until the preload is correct.

Adjusting the length of the actuator arm
Adjusting the length of the actuator arm

7. Reattach the cotter pin.  You turbo is now correctly adjusted.

All finished
All finished

 

 

Introducing the Steam STX 67 Plus for Subaru WRX/STI

We would like to introduce you to our newest turbo to our lineup, the Steam STX 67 Plus Turbocharger aka STX 67+.

Best on our gas bench testing of our Steam STX 71 compressor wheel, we were able to estimate that our STX 67+ compressor wheel will flow 0.38 Kg/s or over 51 lbs/min.  That is a huge increase power producing flow vs stock, while still maintaining the quick response of a stock turbo.STX 67 (estimated) vs GTX2067R Compressor Map

STX 67 (estimated) vs GTX2067R Compressor Map

Our gas bench testing on the turbine section illustrates how our turbos are able to both spool quickly, and flow very well even at high RPMs.  This is how we are able to achieve both a quick response and keep building power up top.  This was measured with the STX 67+’s turbine and our 8cm^2 single scroll WRX/STI turbine housing.

STX 71 vs GTX30 turbine map
STX 67+ vs GTX30 turbine map

 

Do you have a JDM STI style twin scroll turbo setup and exhaust?  We have you covered with our STX STX 67+ Twinscroll.  Still with our up 400 WHP STX 67 compressor wheel, but now with our larger high flowing low-inertia 9-blade turbine.