Why Upgrade to BPM Power 3 Downpipes?

The 6G72 twin-turbo engine, found in the Mitsubishi 3000GT VR-4 and Dodge Stealth R/T Turbo, is a capable powerplant, but its factory exhaust system chokes high-end flow. The stock downpipes are particularly restrictive, with cast-iron sections and narrow internal diameters that create backpressure and limit turbo efficiency. BPM Power 3 downpipes are engineered to address these bottlenecks using mandrel-bent 304 stainless steel, smooth transitions, and larger diameters—typically 2.5 to 3 inches depending on your setup.

Replacing the restrictive factory pieces with BPM Power 3 downpipes yields several measurable benefits:

  • Reduced Exhaust Backpressure – The smoother, larger-diameter flow path allows exhaust gases to escape the turbochargers faster, lowering the pressure gradient the turbos must work against.
  • Faster Turbo Spool – With less restriction, the turbine wheels spin up sooner. Many owners report noticeable spool improvements as low as 100–200 RPM earlier than stock.
  • Horsepower and Torque Gains – On a dyno, a properly tuned 6G72 with BPM Power 3 downpipes typically sees gains of 15–25 whp and similar torque increases, depending on supporting mods.
  • Aggressive Exhaust Note – The larger piping yields a deeper, more aggressive tone without becoming overly droning when paired with a quality cat-back system.
  • Heat Management – Many BPM Power 3 downpipes feature a ceramic coating or come with thermal wrapping options. This keeps under-hood temperatures lower, reducing intake air temps and protecting nearby components.

For enthusiasts serious about extracting power from the 6G72, downpipes are one of the highest-return bolt-on modifications available. Before you begin, ensure you have a clear understanding of the installation process, required tools, and potential pitfalls.

Tools and Materials Needed

Installing downpipes on a 6G72 twin-turbo is an intermediate-level job. You will need the following items to complete the installation safely and efficiently:

  • Socket and wrench set – 10mm, 12mm, 14mm, 17mm sockets and wrenches. A flex-head ratcheting wrench is very helpful for tight spaces near the turbos.
  • Torque wrench – 3/8″ or 1/2″ drive, capable of reading 20–60 ft-lbs for bolts and nuts on the turbo-to-downpipe flanges.
  • Jack and jack stands (or a lift) – You need at least 18 inches of clearance under the front of the vehicle to access the exhaust system comfortably.
  • Penetrating oil – Brands like PB Blaster or Kroil are essential for freeing rusted bolts, especially on older vehicles.
  • Gaskets – BPM Power downpipes usually include new gaskets for the turbo flange and the midpipe connection. If not, purchase OEM-grade or multi-layer steel (MLS) gaskets. Never reuse old gaskets.
  • New exhaust hardware – Stainless steel flange nuts and bolts are recommended to prevent corrosion.
  • O2 sensor socket – A 7/8″ or 22mm O2 sensor socket with a cutout for the wire harness.
  • Anti-seize compound – Copper-based or nickel-based anti-seize for bolt threads and O2 sensor threads.
  • Safety gear – Safety glasses, mechanic gloves, and hearing protection (exhaust work is loud).

Optional but highly recommended: A breaker bar or impact wrench for stubborn bolts; a mirror-on-a-stick for inspecting hidden fasteners; and an exhaust hanger removal tool if your vehicle has stubborn rubber hangers.

Step-by-Step Installation Guide

1. Preparation and Vehicle Lifting

Park the car on a level surface and set the parking brake. If your car has a manual transmission, leave it in gear. Disconnect the negative battery terminal—this eliminates any risk of shorting tools against the starter or alternator. Lift the front of the vehicle using a jack placed under the front subframe crossmember, then place jack stands under the factory lift points. Never rely on a jack alone.

2. Accessing the Stock Downpipes

From underneath, identify the two downpipe sections. On the 6G72, each turbo has a separate downpipe that merges into a single pipe (or connects to a test pipe/catalytic converter). You will need to remove the heat shields that cover the turbo-to-downpipe flanges. These shields are secured with 10mm bolts that may be rusted. Spray penetrating oil on all fasteners 15–20 minutes before removal.

3. Removing the Stock Downpipes

Start with the O2 sensors. Unplug the sensor connectors (usually located near the firewall or on the frame rail) and carefully thread the sensors out of the stock downpipes using the O2 sensor socket. Label which sensor came from which side to avoid confusion later. Next, remove the bolts connecting the downpipes to the turbocharger outlets. These are often 12mm or 14mm hex head bolts. Expect them to be tight—use penetrating oil and a breaker bar if needed. Once the turbo flanges are free, unbolt the downpipe-to-midpipe connection (typically 14mm bolts) and maneuver the stock downpipes out from above the subframe. You may need to rotate the pipes to clear the steering shaft on the driver’s side.

Pro tip: If a bolt snaps (common on old 6G72s), drill it out or have a shop extract it. Avoid using an extractor that jams unless you are experienced—snapped extractors are a nightmare. Always replace with new high-tensile bolts.

4. Preparing the Turbo Flanges

Inspect the exhaust outlet face each turbo. Wire brush away any carbon buildup or debris. Verify the studs are intact and threads are clean. If you stripped a stud during removal, replace it with a new stud and nut from the dealer or a specialty fasteners store. Apply a thin layer of anti-seize to the stud threads to prevent future seizing.

5. Installing the BPM Power 3 Downpipes

Place the new gaskets onto the turbo flanges. The gasket should be oriented so the metallic side faces the turbo (if using MLS gaskets). Hold the BPM Power downpipe in place and loosely thread the flange nuts onto the studs. Do not tighten yet—you need a few millimeters of movement to align the pipe with the rest of the exhaust. Connect the lower end of the downpipe to the midpipe or test pipe. If the flange holes do not align perfectly, loosen the midpipe hangers to gain slack. Once everything is loosely connected, tighten the turbo flange nuts from top to bottom, applying 30–35 ft-lbs in a crisscross pattern. Next, tighten the midpipe connection to the same torque spec. Finally, reinstall any heat shields you removed, but check for clearance—new downpipes may sit closer to the frame or steering shaft.

6. Reinstalling O2 Sensors

Apply anti-seize to the threads of each O2 sensor (avoid getting it on the sensor tip). Thread them into the bungs on the new downpipes. BPM power downpipes typically have bungs located in similar positions to stock. Hand-tighten until snug, then use the O2 sensor socket to give an additional 1/8 turn. Over-tightening can strip the bung or damage the sensor.

7. Checking Clearances and Leaks

Before lowering the car, crank the engine over (without starting) to check that nothing is rubbing against the steering shaft, subframe, or suspension components. Adjust as needed by loosening bolts and repositioning. Then start the engine and let it idle. Place your hand near each flange—you should not feel any puffs of exhaust. A smoke test or soapy-water spray on the joints can reveal small leaks. If you detect a leak, tighten the bolts a little more (but do not exceed 40 ft-lbs on turbo flanges, as the studs can snap). Listen for unusual rattling or buzzing—this often indicates the pipe is contacting a chassis component. Wrap the area temporarily with heat-resistant tape to dampen vibration until you can relocate the pipe.

8. Final Torque and Lowering

After the engine has idled for 5 minutes, check the torque on all fasteners again. The heat cycle can cause some bolts to relax. Let the engine cool, then lower the vehicle. Drive gently for the first 10 miles, then re-check the downpipe bolts for proper torque.

Common Challenges and Solutions

Even with a straightforward installation, 6G72 twin-turbo cars have quirks that can frustrate first-timers:

  • Stuck or Sheared Bolts – Use penetrating oil the night before. If one snaps, drill and tap or take the car to a machine shop. Do not try to weld the new pipe in place as a band-aid.
  • Clearance Issues with the Steering Shaft (Driver’s Side) – Some aftermarket downpipes need a small dimple or notch for clearance. If your BPM Power downpipes rub, you can use a hammer and a block of wood to carefully create a dimple—or contact BPM Power for a warranty replacement. Never cut the steering shaft.
  • Check Engine Light (CEL) After Installation – The 6G72 uses narrow-band O2 sensors that can trigger a CEL if they sense a change in exhaust flow due to increased pipe diameter. This is normal. Install O2 sensor spacers (also called “defoulers”) on the rear O2 sensors if your car has a secondary O2 system. For primary O2 sensors, a tune is the only permanent fix.
  • Exhaust Leaks at Turbo Flange – Usually caused by an incorrect or damaged gasket. Always use new gaskets and ensure the flange surfaces are flat. A warped turbo flange requires resurfacing by a machinist.
  • Drone or Resonance – Removing catalytic converters can produce drone in the 2,500–3,000 RPM range. Consider adding a resonated test pipe or a quality resonator if drone becomes objectionable.

Performance Expectations and Tuning Considerations

BPM Power 3 downpipes are not a standalone performance solution. To fully exploit the improved exhaust flow, your 6G72 should have a supporting list of modifications: a free-flowing intake, upgraded intercooler, and a tune. On an otherwise stock engine, you can expect 10–15 horsepower at the crank. But with a boost controller, fuel pump, and a proper ECU remap (using software like ECUTek or a standalone like Haltech), the gains multiply. Dyno results from community-build 6G72s show whp increases of 25–35 whp when paired with a 3-inch cat-back exhaust and a conservative tune. The turbines spin more freely, so boost comes on faster and holds flatter to redline.

Important: Downpipes that eliminate the catalytic converters will cause your car to emit an OBDII readiness fault on some regions. If you live in an area that requires emissions testing, keep your stock downpipes to swap back, or use high-flow cats integrated into the downpipe system. BPM Power offers catted versions of their downpipes for exactly this reason.

After installation, we highly recommend getting a custom tune. The increased flow alters the boost curve and can push the fuel trims lean. A tune not only maximizes power but also ensures reliability. Many experienced tuners recommend adding a wideband O2 sensor if you plan to push the boost above 16 PSI.

Final Thoughts

Installing BPM Power 3 downpipes on your 6G72 twin-turbo is a rewarding project that dramatically improves the car’s character. The sound alone is worth the effort for many enthusiasts, but the real value lies in the unrestricted flow that unlocks higher horsepower and faster spool. With the right preparation—quality tools, new gaskets, patience with rusted hardware—the installation can be completed in a weekend. Just remember to plan for a tune and consider your local emissions laws before removing catalysts.

For further reading on 6G72 tuning and exhaust upgrades, check out these resources:

Treat the installation as an opportunity to inspect your entire exhaust system, including hangers, flex sections, and heat shields. A little preventive maintenance now will keep your boosted 6G72 running strong for many miles to come.