Upgrading the turbocharger on a Duramax diesel engine is one of the most effective ways to unlock substantial gains in horsepower, torque, and towing capability. Among the aftermarket options available, Bullseye Power Turbo has earned a strong reputation for building durable, high-flow turbos that are purpose-engineered for the LB7, LLY, LBZ, LMM, and LML Duramax platforms. This article provides an in-depth look at the benefits of upgrading to a Bullseye Power Turbo, walks through the installation process in detail, and shares real-world performance results you can expect. Whether you're building a daily driver that hauls heavy loads or a competition truck chasing big numbers, understanding what a Bullseye turbo offers will help you make an informed decision.

Why Upgrade Your Duramax Turbo?

The factory turbocharger on a Duramax is designed to meet a broad range of conditions—emissions compliance, fuel economy, and reliability under stock power levels. Once you add a tuner, larger injectors, or increase fuel delivery, the stock turbo becomes a bottleneck. Exhaust backpressure rises, intake temperatures climb, and the turbo can no longer supply enough air to safely burn the extra fuel. This leads to excessive smoke, high EGTs (exhaust gas temperatures), and a loss of power. A larger, more efficient aftermarket turbo like a Bullseye Power unit resolves these issues by flowing more air at lower pressure ratios, keeping EGTs in check and allowing the engine to make clean, sustained power.

Benefits of Upgrading to a Bullseye Power Turbo

Bullseye Power offers a range of turbos specifically for Duramax engines, including the popular Bullseye S472, S475, and S480 models, as well as their BAT (Bullseye Air Technology) series. Each model is designed with specific performance goals in mind. Below are the key benefits you can expect from upgrading.

Significant Horsepower Gains

A properly sized Bullseye turbo can add 100 to 300+ horsepower to a Duramax, depending on supporting mods and tuning. For example, an S472 with a 1.10 AR turbine housing paired with a mild tune can deliver 500–550 rear-wheel horsepower on an otherwise stock LB7 or LLY. With a built transmission, larger injectors, and a performance tune, the same turbo can push well past 700 hp. The key is that Bullseye turbos use high-flow billet compressor wheels and race-proven journal or ball bearing centersections that maintain efficiency across a wide operating range.

Improved Torque and Low-End Spool

Contrary to what some believe, a larger turbo does not have to sacrifice low-end response. Bullseye's BAT quick-spool technology uses a patented waste gate design and optimized turbine housings to reduce lag. Many owners report a noticeable improvement in low-end torque from 1,500 to 2,200 RPM, which translates to stronger pulling power when towing. Even the larger S480 can light quickly when paired with the right exhaust housing and a proper tune.

Better Fuel Economy Under Load

Efficiency is a direct result of the turbo's ability to deliver the correct air-to-fuel ratio. When a Duramax is lugging under heavy load with a stock turbo, the engine often runs richer (more fuel, less air), wasting diesel and increasing EGTs. A Bullseye turbo, with its larger compressor and turbine, provides surplus air, allowing the engine to burn fuel more completely. This can improve highway fuel economy by 1–3 MPG when towing, and even more during unloaded cruising on the interstate.

Durability and Reliability

Bullseye Power turbos are built to withstand the extreme heat and vibration of a Duramax engine. They use CNC-machined billet compressor wheels (not cast), which are stronger and more balanced than stock wheels. The bearing systems—whether journal bearings for budget builds or ball bearings for ultra-fast spool—are assembled with high-temperature clearances and premium synthetic grease. Many Bullseye turbos also feature upgraded thrust bearings that resist thrust loads from high boost pressures over 45 psi.

Customizable Sizing and Configurations

Bullseye offers multiple sizes, A/R ratios, and turbine wheel options so you can tailor the turbo to your specific use. For a daily-driven truck that tows occasionally, an S472 with a 0.90 or 1.10 housing is a popular choice. For a race-oriented truck aiming for 800+ hp, an S480 or even an S485 with a larger housing may be ideal. Bullseye also offers T6 and T4 flanged turbos for custom setups, and some models come with integrated waste gates or provisions for external waste gates.

Installation Process: Step-by-Step

Installing a Bullseye Power Turbo on a Duramax is a job that requires mechanical experience, the right tools, and attention to detail. The following guide provides a comprehensive overview. Always refer to the specific instructions included with your turbo kit, as some models have unique requirements.

Preparation and Tools

  • Tools needed: Metric and SAE socket set, torque wrench, wrenches, flathead and Phillips screwdrivers, turbo removal tool (or pry bar), gasket scraper, vacuum pump (for coolant system), wire brush.
  • Parts to have on hand: Bullseye Power turbo, turbo installation kit (gaskets, o-rings, copper washers, lock nuts), new oil feed and drain lines (recommended), new coolant lines (if applicable), anti-seize compound, threadlocker.
  • Optional but recommended: upgraded intercooler boots, aftermarket intake elbow, PCV reroute kit, new V-band clamps.
  • Safety precautions: Disconnect both batteries, ensure engine is cool, working on a level surface, have a fire extinguisher nearby, wear eye protection.

Step 1: Remove the Stock Turbo

  1. Disconnect negative battery cables and drain the coolant from the engine block drain plug or lower radiator hose to reduce coolant loss.
  2. Remove the intake tube, intercooler pipes, and air filter assembly. On LMM/LML trucks, you may need to remove the duct from the intercooler to the throttle body.
  3. Detach the exhaust downpipe from the turbo outlet. On some Duramax models, the downpipe is bolted to the turbo with a V-band clamp; on others, it's a 4-bolt flange. Use penetrating oil if necessary.
  4. Disconnect the oil feed line from the top of the turbo and the oil drain line from the bottom. Be prepared for some oil spillage—place a catch pan underneath.
  5. Disconnect coolant lines at the turbo; plug both ends to prevent debris entry.
  6. Remove the turbo mounting bolts (usually 4 bolts on the exhaust manifold flange). On some Duramax engines, the turbo is also supported by a bracket. Withdraw the turbo from the engine bay, taking care not to damage the oil drain tube or surrounding wiring harnesses.

Step 2: Install the Bullseye Turbo

  1. Clean the exhaust manifold flange and turbo mounting surface thoroughly. Use a gasket scraper and brake cleaner to remove old gasket material.
  2. Install the new Bullseye turbo onto the exhaust manifold, using new gaskets (ensure correct orientation). Hand-thread the mounting bolts, then tighten to the specified torque (typically 35–45 ft-lbs for M10 bolts; check your kit).
  3. Attach the oil drain line. Bullseye turbos often use a larger drain than stock (e.g., -10 or -12 AN). Reuse or replace the drain tube gasket/o-ring. Use thread sealant on pipe threads for the drain line fitting into the turbo center section.
  4. Connect the oil feed line. Use a new supply line with a restrictor if recommended (Bullseye provides specifications for journal vs. ball bearing). Tighten banjo bolts with new copper washers.
  5. Reattach coolant lines. On water-cooled turbos, ensure hoses are routed correctly and not kinked. Use new o-rings at the turbo connections.
  6. Reinstall the exhaust downpipe with a new gasket. Tighten V-band clamps to the manufacturer's torque spec (often 60–80 inch-pounds).
  7. Reconnect intercooler pipes and intake boot. Ensure all clamps are clean and secure. If you upgraded to aftermarket silicone boots, they may require slightly different clamp torque.

Step 3: Final Checks and First Start

  • Double-check all connections: Oil and coolant lines, exhaust clamps, intake pipes, electrical connections (if any, such as waste gate solenoid or MAP sensor source).
  • Prime the oil system: Before starting, disable the fuel injection (pull the fuse or unplug the injector harness) and crank the engine for 15–20 seconds in 5-second intervals until you see oil pressure on the gauge. This prevents dry starts on the turbo bearings.
  • Check for leaks: Start the engine and let it idle. Listen for exhaust leaks (ticking noise) and inspect all oil/coolant connections. Rev the engine gently to 2,000 RPM and check for boost leaks at the intercooler boots.
  • Test drive: After confirming no leaks, take a short test drive, keeping boost under 15 psi for the first 50 miles to allow the turbo bearings to seat. Do not operate at full throttle until the turbo bed-in is complete.

Performance Results: Real-World Gains

After upgrading to a Bullseye Power Turbo, Duramax owners consistently report dramatic improvements across multiple performance metrics. Below are typical results based on common configurations and independent dyno testing.

Dyno Proven Horsepower and Torque

On a stock or mildly modified Duramax, a Bullseye S472 with a 1.10 housing and a performance tune (e.g., 5-position chip set to the highest power level) can produce 450–500 rear-wheel horsepower and 850–950 lb-ft of torque on 91 octane diesel. This represents a gain of 100–150 hp over the stock turbo. When combined with 30% over injectors and a lift pump, the same turbo can exceed 600 rwhp and 1,000 lb-ft. A Bullseye S480 on a fully built engine with 72% injectors, an S&B intake, and a 5-inch exhaust can push 700–750 rwhp while maintaining driveable spool characteristics.

Acceleration and Response

Owners report that 0–60 mph times drop by 1.5 to 2.5 seconds compared to a tuned Duramax with the stock turbo. The low-end spool of the Bullseye BAT series is particularly praised: full boost (30–35 psi) arrives by 2,000 RPM on an LBZ, making the truck feel responsive even in stop-and-go traffic. When towing a 12,000 lb trailer, the turbo maintains boost with less lag than the stock unit, resulting in fewer downshifts and lower EGTs.

Towing Performance and EGT Control

One of the biggest advantages of a Bullseye turbo is its ability to lower exhaust gas temperatures. While towing a heavy load up a grade, Duramax owners often see EGT peaks above 1,350°F with the stock turbo. A Bullseye S472 or S475 typically reduces peak EGT by 150–200°F at the same power level because of increased air mass flow. This means you can tow at higher speeds or maintain speed up long hills without worrying about melting pistons.

Fuel Economy Improvements

Independent feedback from forums and fleet operators indicates a 0.5 to 2.0 MPG increase in combined driving after the upgrade, and up to 3 MPG improvement when towing heavy loads. These gains are most pronounced in trucks that were previously forced to run rich due to inadequate airflow. The turbo allows the engine to run leaner (more air per fuel) while still producing power, improving thermal efficiency.

Tuning and Supporting Mods for Maximum Results

While a Bullseye turbo alone delivers significant gains, to fully unlock its potential you must address the engine's supporting systems. Without proper tuning and fuel delivery, you can leave performance on the table or risk damaging the engine.

Engine Management Tuning

After installing a larger turbo, the factory ECU's fuel maps will be far too rich. You'll need a custom tune from a reputable tuner (e.g., EFILive, Duramaxtuner, or DSP5) that adjusts fuel tables, boost targets, and timing to match the turbo's airflow characteristics. Many tuners offer "Bullseye-specific" tunes that optimize spool and prevent overboost. Avoid generic "canned" tunes—they rarely account for the different air/fuel ratios of a larger turbo.

Fuel System Upgrades

For power levels above 500 rwhp, the stock CP3 injection pump and fuel lines become inadequate. Consider:

  • Lift pump: A FASS or AirDog system maintains positive pressure to the CP3, preventing cavitation and improving throttle response.
  • Injectors: 30% over stock for 500–600 hp, 50–72% for 700+ hp. Ensure the tune is matched to injector size.
  • CP3 upgrade: A modified CP3 or a second CP3 (dual fueler) for 600+ hp supplies enough fuel volume.

Exhaust System

To take full advantage of the turbo's airflow, upgrade the entire exhaust from the turbo back. A 4-inch downpipe and a 5-inch straight pipe (with or without a muffler) reduces backpressure and helps the turbo spool faster. For those concerned about noise, a high-flow muffler designed for diesel applications works well without significant power loss.

Intake and Intercooler

An aftermarket cold air intake (e.g., S&B, AFE, Airaid) with a dry or oiled filter improves airflow into the compressor. For trucks running over 40 psi of boost, consider an upgraded intercooler or a spearco unit to keep intake air temperatures below 130°F. Hot intake air robs power and increases EGTs.

Common Questions and Considerations

Do I need a new exhaust manifold?

Bullseye turbos are designed to bolt directly to the factory exhaust manifold on most Duramax models (LB7, LLY, LBZ, LMM). For LML trucks, a slightly different adapter plate may be required. In all cases, use a new manifold-to-turbo gasket.

Will the Bullseye turbo fit with my stock intercooler pipes?

In most cases, the outlet of the Bullseye compressor is in a similar location to stock. However, the outlet diameter may be larger (e.g., 3.5 inches vs. 3 inches). You will likely need a reducer or a custom intercooler pipe to connect properly. Many owners opt for aftermarket boots and piping to match the larger outlet.

Is this upgrade daily-driver friendly?

Yes, when properly sized and tuned. The S472 and S475 are excellent for daily drivers that tow regularly. They provide enough low-end torque to keep the truck responsive, and the increased efficiency keeps EGTs low during commutes. The S480 may be more laggy for daily use unless you have a high-stall torque converter and are aiming for 700+ hp.

How long does installation take?

For an experienced mechanic, expect 4–6 hours from start to finish. For a first-timer working in a driveway, budget a full weekend. Allowing extra time to clean flanges, replace gaskets, and route hoses correctly pays off in reliability.

Conclusion

Upgrading to a Bullseye Power Turbo is one of the most rewarding modifications you can make to a Duramax diesel. It addresses the fundamental airflow limitation of the stock turbo, freeing up substantial horsepower and torque while lowering exhaust temperatures and improving fuel economy. With models ranging from the quick-spooling BAT series to the high-horsepower S480, Bullseye offers a solution for nearly every build, from mild daily drivers to all-out competition trucks. The installation process is straightforward for a competent DIYer, and the performance results are documented by thousands of satisfied owners. Combined with proper tuning and supporting mods, your Bullseye turbo will transform the way your Duramax drives, tows, and performs for years to come. For more information on specific turbo models and pricing, visit the Bullseye Power website or consult with a reputable diesel performance shop like Diesel Power Products or Exergy Performance.