Step 1: Check for Boost Leaks
A boost leak is the most frequent cause of lower-than-expected boost. This happens when pressurized air escapes from the intake tract after the turbo compressor but before it enters the engine.
What to do: Carefully inspect every connection from the turbo's compressor outlet all the way to the engine's throttle body.
Firstly, please check the following 4 points before inspection of the turbocharger.
1. Compressor housing outlet, intercooler circuit, and connections.
2. Turbine Housing inlet, manifold circuit, gasket, and connections.
3. Turbine Housing outlet, dump pipe circuit, gaskets and connections.
4. Compressor housing inlet, air filter clean situation and connections.
Waring: The troubleshooting guide may only be conducted with the vehicle in drivable condition. Please stop the trials at signs of engine malfunction such as black smoke, excessive oil consumption, or run-away engine.
A small, hard-to-see leak can bleed off a significant amount of boost. The best way to be certain is to perform a boost leak test using a specialized tester that pressurizes the system with compressed air, allowing you to listen for leaks or spray soapy water on connections to see bubbles.
Step 2: Verify the Wastegate Actuator Preload
This is an extremely important step and a very common source of low boost if not set correctly. The wastegate actuator requires a specific amount of "preload" to ensure the wastegate flap in the turbine housing stays completely sealed until the desired boost pressure is reached. If the flap is even slightly open, exhaust gas will bypass the turbine wheel, and the turbo won't be able to build proper boost.
What to do: Your Kinugawa universal actuator is designed to have 1.5mm of preload applied to the rod during installation.
- To set this: When you attach the actuator's end fitting (the clevis) to the wastegate arm on the turbine housing, you should have to slightly pull or extend the rod by about 1.5mm to get it to line up with the hole on the arm. This creates the necessary tension.
- Our installation guide provides a great tip: "one full turn of the nut equals to approximately 0.75mm change in rod extension". After hand-tightening the adjustment nut to hold the wastegate flap shut, turn it two additional full turns in the clockwise direction to set the 1.5mm of preload. Please confirm that this 1.5mm preload was set during the installation. Without it, the wastegate will leak exhaust pressure, preventing the turbo from spooling up correctly.You can preload the actuator rod to get a higher boost pressure. please check the following 2 videos
BTW, Please make sure the manifold and the inter-cooler pipe that connected with the turbocharger without leak.
Step 3: Inspect the Wastegate System and Connections
Even with the correct spring and preload, a leak in the control system can prevent the actuator from working as it should.
What to do: Check the Boost Signal Hose: Inspect the small hose running from a pressure source (like the compressor housing) to the nipple on the wastegate actuator. Make sure it's not cracked, split, melted, or disconnected.
- Confirm the Boost Source: Ensure the hose is connected to a pressure-only source. It should be taken from somewhere
- after the compressor outlet and before the throttle body.
- Test the Actuator Diaphragm: With the engine off, you can disconnect the hose from the actuator and carefully apply compressed air from a regulated source. Apply just over 14.5 PSI (1 bar) and confirm that the actuator rod moves smoothly.
- Do not apply more than 3 bar (40 PSI). If you hear air escaping from the actuator body itself, the internal diaphragm may be damaged.
- Check the Wastegate Flapper: With the actuator arm disconnected, manually move the wastegate arm on the turbine housing. It should move freely without binding. Ensure the internal flapper seats firmly and creates a good seal when in the closed position.
Step 4: Check for Pre-Turbo Exhaust Leaks
The turbo is powered by exhaust gas energy. Any leaks in the exhaust system before the turbo will reduce this energy, leading to slower spool and lower boost.
What to do: Look for any signs of black soot or exhaust residue around the following areas:
- The gasket between the cylinder head and the exhaust manifold.
- Any welds on the exhaust manifold.
- The gasket or fire-ring between the exhaust manifold and the turbo's turbine housing inlet.
- An exhaust leak here means less power is available to spin the turbine wheel, which directly results in the compressor not being able to build your target boost.
If you go through these steps, you will almost certainly find the culprit. The most likely issues are a boost leak or incorrect wastegate preload.
Please take a look at these items, and don't hesitate to reach out if the issue persists. We are dedicated to ensuring you are 100% satisfied and that you get to enjoy the full performance of your new Kinugawa turbo!