Overview of the BorgWarner EFR 6758 Turbocharger for the Chevy Cobalt SS

The Chevy Cobalt SS, particularly the 2008–2010 LNF model, is already a capable platform from the factory with its direct-injected 2.0L turbocharged engine. However, the stock turbo (a Mitsubishi TD04 variant) leaves performance on the table. Upgrading to a BorgWarner EFR 6758 turbocharger transforms the car into a serious street and track performer. The EFR (Engineered for Racing) series is renowned for its advanced metallurgy, dual ceramic ball bearings, and integrated boost control features. The 6758 model – with a 67mm turbine wheel and 58mm compressor wheel – offers a great balance of quick spool and high top-end power, making it ideal for the Cobalt SS 2.0L engine.

This guide provides a comprehensive, production-level walkthrough for installing the BorgWarner EFR 6758 on your Cobalt SS. We cover everything from required tools and safety precautions to torque specs, oil routing, and post-installation tuning. Whether you are a seasoned enthusiast or a dedicated DIYer, following these steps ensures a reliable and high-performance installation.

Tools and Materials

Essential Hardware

  • BorgWarner EFR 6758 Turbocharger (typically with T25 or T4 divided inlet; for Cobalt SS, the T25 .80 A/R is a common fitment)
  • Turbo installation kit (gaskets, studs, nuts, hardware specific to Cobalt SS)
  • Oil feed line kit (stainless braided -3AN or -4AN) and oil drain line (-10AN or -12AN)
  • Coolant lines (if using water-cooled bearing housing; EFR is oil-cooled but some variants have coolant)
  • Intercooler piping kit (2.5” or 3” aluminum, with silicone couplers and T-bolt clamps)
  • Front-mount intercooler (upgrade recommended to support increased flow)
  • Wideband O2 sensor (for tuning feedback) and boost gauge (electronic, 30 psi capability)
  • Vacuum lines and fittings (for boost reference and wastegate control)
  • New spark plugs (colder heat range, e.g., NGK 6510 or 6619, gapped to ~0.028” for higher boost)

Tools Required

  • Metric socket set (8mm–19mm) and wrenches
  • Torque wrench (ft-lb and in-lb ranges)
  • Pry bars, screwdrivers, pliers, pick set
  • Tap and die set (for cleaning threads on manifold and turbo studs)
  • Coolant drain pan and oil drain pan
  • Jack stands, floor jack, wheel chocks
  • Multimeter and wiring supplies (heat shrink, connectors, wire loom)

Preparation and Safety

Before touching the car, disconnect the negative battery terminal to prevent accidental shorts. Let the engine cool completely – the exhaust manifold and stock turbo will be extremely hot. Raise the vehicle securely on jack stands placed at the factory lift points. Drain the engine oil and coolant into appropriate containers. It is also wise to remove the plastic engine cover and intake ducting for unobstructed access.

Take photographs of the stock turbo layout and vacuum lines. This reference will help during reassembly. Label all connectors and hoses with tape and marker. A well-organized workspace prevents lost hardware and confusion.

Removing the Stock Turbocharger

Step 1: Disconnect Lines and Hoses

Start by disconnecting the stock turbo oil feed line from the engine block (banjo bolt at the oil filter housing) and the oil drain line from the pan. Also disconnect the coolant lines (if present) from the stock unit. Next, remove the intake pipe and the downpipe connection at the turbo outlet. On the LNF engine, the stock downpipe is bolted to the turbo with three 12mm nuts and a V-band clamp. Use penetrating oil if the nuts are rusted.

Step 2: Remove Turbo Support Bracket and Manifold

The Cobalt SS LNF has a cast-iron exhaust manifold that bolts to the cylinder head. Unbolt the manifold from the head (six 10mm stud nuts, difficult to access) and from the turbo support bracket. Carefully lift the entire manifold and stock turbo assembly out as one unit. This is heavy – a helper is recommended. Use a scissor jack to support it if working alone.

Step 3: Separate Turbo from Manifold

Place the assembly on a clean workbench. Unbolt the stock turbo from the manifold (four 12mm bolts or studs). Note the orientation of the oil drain port. The stock turbo uses a specific gasket; discard it. Inspect the manifold for cracks or warpage. Have the manifold resurfaced if needed.

Installing the BorgWarner EFR 6758

Step 4: Prepare the Manifold and Turbo

Clean the manifold flange thoroughly with a wire brush brake cleaner. Install new studs from your installation kit. Apply anti-seize to the threads that go into the manifold and copper-based lubricant to the nut threads. Mount the BorgWarner EFR 6758 onto the manifold using a new gasket (many EFRs use a 5-bolt pattern, but the 6758 with T25 flange uses a standard T25 gasket). Torque the fasteners to 35–40 ft-lb in a crisscross sequence.

Step 5: Install the Manifold/Turbo Assembly

Lift the assembly back onto the engine. Install the manifold nuts (six 10mm) and torque to 18–22 ft-lb using a short 12-point socket. Reattach the turbo support bracket to the engine block. Tighten to 28–32 ft-lb. At this stage, do not fully tighten the V-band clamp or downpipe connections – leave them loose to allow alignment later.

Step 6: Oil Feed and Drain Lines

Run the oil feed line from the block (use the existing port or a sandwich plate if necessary) to the turbo oil inlet. EFR turbos are oil-cooled only; the bearing housing has a 1/8” NPT inlet. Use a braided stainless line with proper fittings. Torque the banjo or AN fitting to 12–15 ft-lb – do not overtighten. The oil drain line must slope continuously downward from the turbo drain flange to the pan. The recommended drain is -10AN or -12AN line with a 1/2” NPT fitting into the oil pan. Use a new oil pan gasket and torque to 18 ft-lb. Ensure no kinks or low points in the drain line – this is critical for turbo longevity.

Intercooler and Charge Piping

Step 7: Install a Larger Intercooler

The stock intercooler will be a restriction with the EFR 6758. Upgrade to a bar-and-plate front-mount intercooler (approx. 24” x 12” x 3”) with 2.5” or 3” inlet/outlets. Remove the bumper cover and crash bar for access. Mount the intercooler securely using brackets provided in the kit. Attach the crash bar if it does not interfere; otherwise, use a crash bar relocation kit.

Step 8: Connect Hot and Cold Side Piping

Route the hot side piping from the turbo compressor outlet to the intercooler inlet. Use silicone couplers and T-bolt clamps (5.1–5.3 psi clamp pressure). The cold side piping goes from the intercooler outlet to the throttle body. On the LNF, the throttle body faces the driver’s side; a 90-degree coupler typically works. Verify all connections are tight and that the piping does not rub against frame members – use rubber hose wrap at contact points.

Install a 3.5 or 4 bar MAP sensor (if tuning beyond stock boost levels). The Cobalt SS LNF uses a 2.5 bar sensor stock; a 3.5 bar sensor allows up to about 30 psi. Adapter harnesses are available from tuning vendors.

Boost Control and Wastegate Setup

Step 9: Configure the EFR’s Integrated Boost Control (IBC)

The BorgWarner EFR 6758 often features a conical wastegate with a port for a boost controller. For the simplest setup, connect the wastegate port directly to the compressor outlet (using -4AN or silicone hose) for mechanical boost control (typically 15–18 psi spring pressure, depending on the actuator). For electronic boost control, plumb a two-port or three-port boost solenoid (like a GM or MAC valve) between the compressor and wastegate. Reference vacuum lines from a clean source on the intake manifold.

If your EFR uses an external wastegate (puck & port), ensure the dump tube recirculates back into the downpipe to maintain proper exhaust flow and reduce noise. Weld a 1.5” tube into the downpipe at a 45-degree angle to avoid turbulence.

Exhaust System and Downpipe

Step 10: Downpipe and Exhaust

The stock downpipe will not fit the EFR turbine outlet. Purchase or fabricate a 3” downpipe with a V-band or 4-bolt flange matching the turbo adapter. A catless downpipe (or high-flow cat) is necessary for performance. Use a downpipe that clears the transmission bellhousing and steering shaft. Torque the V-band clamp to 40–50 in-lb (four turns after snug). Connect the cat-back exhaust; a 3” cat-back is recommended for minimal back pressure.

Electrical and Sensors

Step 11: Boost Gauge, Wideband, and Wiring

Install an electronic boost gauge (0–30 psi or 0–2 bar) in the A-pillar pod or gauge cluster. Connect the signal wire to a vacuum tee at the intake manifold. For accurate air/fuel monitoring, install a wideband O2 sensor (AEM X-series or similar) in the downpipe or mid-pipe, at least 18” downstream of the turbo. Route the wideband signal to the ECU’s analog input (if using HP Tuners or HPTuners pro link) or to a standalone gauge.

Tuning – The Critical Step

Step 12: Engine Calibration

Installing the EFR 6758 without proper tuning will likely damage the engine. The LNF ECU requires changes to fuel, timing, boost targets, torque management, and MAF/VE tables. Use HP Tuners VCM Suite or EFILive (with LNF support) to flash a custom calibration. Key areas to adjust: scalar injector flow (for larger injectors if used), boost target tables (aim for 22–25 psi initial, then taper to 20 psi at redline), spark advance (retard 2–4 degrees from stock under boost), and wastegate duty cycle.

Work with an experienced LNF tuner or research established EFR 6758 tunes on forums like CobaltSS.net or ZZPerformance. Always datalog parameters (knock, AFR, boost, fuel pressure) during the first pulls.

Final Steps and First Startup

Step 13: Reassembly and Fluid Refill

Fill the engine with 5W-30 full synthetic oil (use a high-quality brand like Mobil 1 or Amsoil) and coolant (50/50 Dex-Cool). Reconnect the battery. Before starting, prime the turbo oil feed by cranking the engine with the fuel pump fuse removed for 10 seconds, then reinstall the fuse. Start the engine and let it idle for 30 seconds; immediately check for oil leaks at the feed and drain connections. Listen for unusual turbo noise (whistling is normal, but scraping indicates misalignment).

Step 14: Bleed Cooling System and Check for Boost Leaks

With the engine warm, allow it to cool and top off the coolant. Use a boost leak tester (a cap with a Schrader valve) after the intercooler piping to pressurize the system to 20 psi. Listen for hissing – fix any leaks with additional clamping or realignment.

Step 15: Street Tune and Driveability

Take the car for a gentle test drive. Keep boost below 10 psi until the tune is finalized (use a wastegate spring only or reduced duty cycle in the base map). Gradually increase boost as you log and refine the calibration. The BorgWarner EFR 6758 will happily support 400–450 whp on the Cobalt SS with proper fueling and tuning.

Conclusion

Installing a BorgWarner EFR 6758 on your Chevy Cobalt SS is a gratifying upgrade that substantially boosts power and response. The key to a successful installation lies in meticulous preparation, correct oil flow, secure charge piping, and professional calibration. With careful attention to the steps outlined here – including torque specs, line routing, and tuning setup – your Cobalt SS will deliver reliable, high-performance driving. For further resources, consult the BorgWarner official turbocharger page, HP Tuners for calibration software, and community guides on CobaltSS.net.