Understanding the Tial QR Series 44/50 Turbo System

The Tial QR Series 44/50 compound turbo system is engineered for enthusiasts who demand significant power gains without sacrificing drivability. Unlike single-turbo setups, compound configurations pair a small high-pressure turbo (the 44mm wastegate-integrated unit) with a larger low-pressure turbo (the 50mm compressor) to achieve high boost levels across a wider RPM range. The result is improved airflow, reduced turbo lag, and the ability to support well over 800 horsepower on many four- and six-cylinder platforms.

The “QR” designation refers to Tial’s quick-release turbine housing, which allows for tool-less servicing of the hot side. The 44/50 pairing is popular because it balances spool characteristics with top-end flow—ideal for street-driven cars that see track time. Key components include:

  • High-quality stainless steel construction for corrosion resistance and durability under extreme heat.
  • Optimized compressor wheel aerodynamics that deliver high mass flow rates while maintaining efficiency.
  • Integrated wastegate design that simplifies plumbing and improves boost control accuracy.
  • Oil and water-cooled center sections to manage thermal loads during prolonged high-load operation.

This compound system is compatible with most inline-four, V6, and inline-six engine platforms, though custom fabrication is often needed for manifold integration. For further technical specs, refer to the manufacturer’s product page.

Pre-Installation Planning

Assess Your Current Setup

Before purchasing the Tial QR 44/50 kit, evaluate your engine’s condition and supporting modifications. The turbo system will stress fuel, ignition, and cooling systems. Ensure you have:

  • High-flow fuel pump and larger injectors (e.g., 1000cc or higher).
  • Upgraded intercooler and charge pipes with adequate flow area.
  • Strong bottom end (forged pistons, rods, and main studs).
  • Aftermarket engine management (standalone ECU or piggyback).

Gather Tools and Components

Thorough preparation prevents delays and ensures a clean installation. A typical tool list includes:

  • Metric and standard wrench sets, socket set with extensions.
  • Torque wrench (capable of 10–150 ft-lb).
  • Thread chasers and tap set for cleaning bolt holes.
  • Pry bars, hose clamps, and a vacuum pump for oil priming.

Necessary components beyond the turbo kit itself:

  • Oil supply and drain lines: Use -4AN for supply and -10AN for drain to ensure adequate flow after a hot shutdown.
  • Gaskets and O-rings: Always replace crush washers and turbo-to-manifold gaskets.
  • Heat shielding: Reflective wrap or ceramic coating for downpipe and turbine housing.
  • Boost control solenoid: A MAC valve or Tial MVR wastegate actuator for precise boost regulation.

Workspace and Safety

Work in a clean, well-ventilated area. Disconnect the battery and drain coolant and oil before beginning. Have a fire extinguisher rated for Class B and C within reach. Plan for at least two full days of installation time for a first-timer.

Step-by-Step Installation Guide

Removing the Old System

Carefully remove the existing turbo and manifold assembly. Label all bolts and vacuum lines for reassembly. Inspect the exhaust ports and manifold mounting surface for warping or cracks. If your old turbo had oil leaks, clean the oil pan return bung thoroughly to prevent debris from entering the new turbo’s oil drain.

Installing the Tial QR 44/50

  1. Mount the low-pressure turbo first, using the supplied brackets and gaskets. Torque manifold bolts to the OEM specification for your engine (typically 35–45 ft-lb for cast iron).
  2. Install the high-pressure turbo (QR 44) onto the secondary manifold section. The quick-release mechanism should face outward for easy access. Tighten the V-band clamp to 10–12 ft-lb—do not overtighten.
  3. Route oil feed lines from the engine oil pressure port to both turbo center sections. Use a restrictor if the oil pressure exceeds 60 psi at idle. For the drain, ensure gravity flow with no kinks or uphill sections.
  4. Plumb coolant lines (if water-cooled) in series or parallel as per the manual. Bleed the system to prevent air pockets.
  5. Connect intercooler piping and charge pipes. Use silicone couplers with T-bolt clamps rated for 35+ psi. Check for clearance with the chassis and suspension components.
  6. Install the wastegate and blow-off valve supplied in the kit. The QR 44’s integrated wastegate simplifies this step, but you must still route the boost reference line from the compressor outlet to the wastegate cap.
  7. Add heat management: wrap the downpipe and turbine housing with DEI Titanium wrap or install a turbo blanket. Secure all heat shields.

Post-Installation Checks

  • Verify all bolts and clamps are tight.
  • Prime the oil system by disconnecting the fuel pump relay and cranking the engine for 10–15 seconds.
  • Check for oil leaks at every fitting before starting.
  • Reconnect the battery and top off coolant and oil.

Tuning the Compound Turbo Setup

Choosing a Tuning Method

Compound turbo systems require precise control over two wastegates (or one integrated valve) to balance boost between stages. A standalone ECU with dual boost solenoid control is recommended. Popular options include Haltech, Motec, and AEM Infinity. If you’re using a flash tune, expect limited adjustability—consider a piggyback boost controller like an AMS-500.

Fuel and Ignition Tuning

Start with a conservative base map. Key parameters to adjust:

  • Target boost: Begin at 15–18 psi total (combined). Compound setups generate high charge air temperatures—listen for knock.
  • Air-fuel ratio (AFR): Aim for 11.8–12.2 under full load for a pump gas setup. E85 allows richer mixtures (10.5–11.5) but adds complexity.
  • Ignition timing: Retard timing compared to a single-turbo map. Start with 18–22 degrees at peak torque, then advance cautiously.
  • Boost control gain: Set wastegate duty cycles to avoid oscillation. Use a data logger to fine-tune transient response.

Dyno Testing and Data Logging

A chassis dynamometer is essential for safe tuning. Log boost per stage (install pressure sensors before and after the high-pressure turbo), intake air temperature, and exhaust back pressure. The high-pressure turbo should not exceed its compressor map limit—monitor for surge. For more advanced tuning strategies, consult resources like the Engine Logics guide on compound turbo tuning.

Common Pitfalls and Troubleshooting

Oil Drain Issues

Insufficient drain causes oil seals to fail. Ensure the return line is at least -10AN and has a downward slope of 20 degrees or more. If the oil pan return bung is too high, weld a new bung lower down.

Boost Creep

If boost rises uncontrollably, the wastegate may be too small. The QR 44’s integrated 44mm gate is usually adequate up to 30 psi total. Check that the reference line is not blocked or crushed. Upgrade to a larger external gate if creep persists.

Heat Soak

Compound turbos generate massive heat. Symptoms include reduced power after repeated pulls and higher intake temps. Solutions:

  • Wrap the downpipe and turbine housing.
  • Install a turbo heat shield.
  • Use water-methanol injection pre-throttle body for cooling.

Leaks in Charge Pipes

Test the entire intake tract with a boost leak tester (DIY or commercial). Common leak points: coupler joints, blow-off valve flange, and intercooler core. Pressurize to 30 psi and listen for hissing.

Maintenance for Longevity

After the initial 500 miles, perform these tasks:

  • Oil change: Use high-quality synthetic (5W-40 or 10W-60 depending on climate). Change every 3,000 miles or after every track event.
  • Inspect V-band clamps for loosening due to thermal cycling. Retorque to spec.
  • Clean or replace air filter every 5,000 miles. Compound turbos draw more air than single setups—a dirty filter restricts flow and raises pressure ratios.
  • Check wastegate operation: actuate by hand to ensure no binding. Lubricate with anti-seize annually.

For a longer service life, consider upgrading to a Turbosmart external wastegate if your power goals exceed 900 hp.

Expected Performance Gains

A well-installed and tuned Tial QR 44/50 compound system can produce 750–900 wheel horsepower on E85 with a suitable engine. Spool characteristics: 15–20 psi by 3500–4000 RPM on a 2.0L four-cylinder, or 2500–3000 RPM on a 3.0L six. Throttle response is noticeably sharper than a large single turbo, and the system maintains power to redline without dropping off.

Conclusion

Upgrading to a Tial QR Series 44/50 compound turbo system demands careful planning, precise installation, and thorough calibration. By understanding the components, preparing your vehicle, using proper tuning methods, and performing regular maintenance, you can unlock dramatic performance improvements while retaining daily drivability. For community support and real-world experiences, browse build threads on HP Tuners forums or consult a professional tuner familiar with compound setups.