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  • Insights on Performance Turbocharger Systems and Components for Today’s Diesels

Insights on Performance Turbocharger Systems and Components for Today’s Diesels

Boost Reference

Jason Sands
May 3, 2016
Photographers: Jason Sands
The EPA has an exact tally of the number of diesel-powered vehicles currently offered in the U.S., and all 43 diesel-powered cars and trucks on that list are turbocharged. “Turbodiesel” is the popular term for the engine/power-adder combination, which has been pretty much the standard for many, many years. Why does turbocharging work so well on diesel engines? We’re going to try and answer that.
Diesel Engines: Naturally Aspirated, Supercharged, and Turbocharged
Naturally aspirated diesels can often be found chugging along in farm machinery or in cars and trucks from the ’80s. Unfortunately, these diesels are a one-trick pony—they can achieve good fuel economy but can't do much else. They're typically smoky, noisy, and limited in power output.
When it comes to diesels and supercharging, Detroit Diesel engines (and other oil-burning engines of the late 1930s) are the powerplants that are widely remembered. The early two-stroke oil-burners used a Roots-type blower for scavenging, but boost pressures were only slightly above atmospheric. Although a 6V-71 (7.0L) Detroit could make more than 200 supercharged horsepower in most applications, its mammoth 2,000-pound weight made it ill-suited for anything other than industrial or boating applications.
Photo 2/15   |   014 Turbo Performance Cummins Individual Runner Intake
More and more diesel enthusiasts are doing everything they can to create the greatest volume of airflow into the engine. We're starting to see more and more modified intake manifolds, like this individual runner design built for an I-6 Cummins powerplant.

Which brings us to our third option: turbocharging. In the ’90s, production cars and trucks experienced a shift, in which turbochargers started becoming optional or standard equipment on virtually all diesel offerings. Dodge stepped up its truck program for the 1989 model year with the turbocharged 5.9L Cummins in its Ram. GM offered turbocharged 6.5L engines in 1992, and Ford entered the space with a vengeance with its ’94 7.3L Power Stroke. The automotive set also made a shift to turbos, most notably on the ’92 Volkswagens, which hit the market with the famous 1.9L TDI engine.
Turbochargers are cost-effective to produce, will last the life of an engine (if maintained), and support making excellent power without the same parasitic losses associated with a supercharger. Variable-vane technology, which has become almost standard issue in the last decade, has also enabled turbos to work as exhaust brakes or emissions helpers. As power demands increased, turbocharging really became the only solution.
Turbo System Basics: The Major Components
Regardless of whether it’s a lawn mower engine or a container ship’s powerplant, turbodiesels have a few basic components that are universal in all applications. These parts include exhaust manifolds, downpipes, air intakes, turbochargers, and intercoolers.
Photo 3/15   |   002 Turbo Performance Steed Speed Manifold
Many exhaust manifold options are available for today’s Cummins, Ford Power Stroke, and GM Duramax engines. This stainless steel Steed Speed manifold is incredibly tough and is proven in engines making up to 3,000 hp. Many options such as wastegates and straight or angled flanges are also available for custom-mount applications.

Exhaust Manifolds
In addition to the turbocharger itself, perhaps the hardest-working part on a turbodiesel engine is the exhaust manifold. Under loads or while towing, a manifold can see sustained temperatures of more than 1,000 degrees. Combine this with ambient temperatures of less than zero in some locations, and you definitely have a hardworking piece of equipment. The exhaust manifold’s actual job is quite simple: It funnels the exhaust gases from the engine to the turbocharger. The exhaust manifold is also often used for mounting the turbocharger on inline engines such as the 5.9L and 6.7L Cummins. On V-8 powerplants (like the 6.6L Duramax and 7.3L, 6.0L, and 6.4L Ford Power Strokes), twin manifolds direct exhaust through up-pipes to the top of the engine, where the turbo is mounted in the valley on a pedestal. It should be noted that some engines (like the 6.7L Power Stroke) use a swapped intake/exhaust arrangement, which puts the exhaust in the valley of the engine, making for a short path to the turbocharger.
Performance Applications
There are a number of companies that offer viable alternatives to the stock hardware. Stainless steel manifolds offer greater heat tolerances, three-piece units are more flexible and less prone to cracking over time, and oversized pieces match larger turbo configurations. Finally, wastegate manifolds are available for those who want to maximize turbo efficiency or are afraid of overboosting due to excessive rpm or power-adders like nitrous oxide.
Downpipes and Exhaust
Once the engine’s exhaust powers the turbocharger, the leftover gases must also be vented. In most applications, the spent exhaust goes through a tube that bends sharply by the firewall and extends down below the car or truck. This is called a downpipe. From there, exhaust is routed toward the back of the vehicle through mufflers and various after-treatment systems like diesel particulate filters (DPFs). Modern diesel exhaust setups are actually quite complex, with pressure sensors, temperature sensors, and a number of large bends.
Photo 4/15   |   004 Turbo Performance OBS Exhaust
Getting exhaust gases out of the turbocharger can be especially challenging on older trucks. Fortunately, for most applications, a 3.5- or 4-inch downpipe and exhaust tubing are large enough and offer little to no restriction.

Performance Applications
With the explosion of diesel performance came literally hundreds of exhaust options. Since tubing size is closely associated with the size of a turbocharger, turbo upgrades are often accompanied by an exhaust swap. Truck exhaust systems are also unique, in that they have become fashion statements of sorts, with various exit options available. From miter-cut stacks and dual tips to chrome center dumps, there are endless options available.
Air Intake Systems
Compared to exhaust manifolds, air intake systems have the relatively easy job of filtering and directing outside air into the turbocharger. Unlike exhaust manifolds, which are connected directly to the turbo, air intake systems usually have a filtered airbox at the front of the engine compartment, with tubing that directs fresh outside air into the turbo. Cooler intake air helps promote lower intake charge temperatures and better engine efficiency, usually resulting in more power.
Photo 5/15   |   007 Turbo Performance SandB LLY Mouth
GM Duramax LLY engines built from ’04½ to ’05 have a very restrictive air intake mouthpiece that hurts both power and turbo efficiency. Fortunately, companies like S&B Filters make upgraded versions that allow a smooth airflow path to the turbocharger.

Performance Applications
Air intake systems are arguably the most popular performance upgrades for diesel engines. Whenever boost is increased through a new turbo or tuning, adding a performance intake is always a good idea.
Turbochargers: The Heart of a Turbo System
Of course, the heart of a turbodiesel engine is the turbocharger, which can be configured in a variety of ways. The simplest system is commonly known as a “single-turbo” setup, which features one exhaust-driven turbocharger.
Photo 6/15   |   003 Turbo Performance ATS 67 Exhaust
On V-8 (or V-6) diesels, the turbo is often mounted in the valley of the engine. Despite the crowded area, upgrading is still possible. This ATS exhaust kit for 6.7L Fords features bellows and heat-wrapped up-pipes and can be used to mount an Aurora 4000 turbo in the valley of the engine.

While the term “twins” is often used as a nickname for a compound-turbocharger system, there are actually quite a few different arrangements that incorporate two turbos. A parallel twin-turbo setup includes two same-sized ’chargers that independently feed each bank of a V-style engine. A true compound setup consists of a large turbo that feeds a smaller unit. A sequential twin-turbo setup is the final dual-turbocharger configuration. It consists of a small, single turbo that is used for low rpm, and a larger unit (the smaller is bypassed completely) that provides boost at high rpm.
Single-turbo setups are common on many diesel vehicles, although Ford, GM, BMW, and Audi each have experience producing compound- and sequential-turbocharged engines. Audi even has a triple-turbo powerplant in its stable, and BMW is experimenting with a quad-turbocharged diesel (although one of those turbos will be electrically, rather than exhaust, driven.
Photo 7/15   |   006 Turbo Performance No Limit Intake
Whenever a larger turbocharger is installed, adding a new cold-air-intake setup is also a good idea. This No Limit Fabrication system for a 6.4L Ford Power Stroke features a high-flowing AFE filter with a pre-filter and can be ordered in either polished aluminum or stainless steel.

Performance Applications
The aftermarket has pushed the boundaries of turbocharging even further, with numerous high-end systems designed for a variety of applications. There are quick-spooling ball-bearing turbos; tough, 360-degree–bearing large-frame turbos; advanced compressor wheel designs; and heat-treated, powdercoated, or polished versions. Often, some units (like Garrett’s GTX-series or BorgWarner's SX-E) will have advanced wheels, upgraded bearings, and a wide variety of housing options.
Larger-than-stock single- or compound-turbo setups consisting of two or even three turbochargers are the most popular options among diesel enthusiasts, with horsepower ranging from stock-type power (around 350 to 440 hp) to 2,000hp or even 3,000hp turbo systems. Since turbo size is the main factor in dictating horsepower capability, most aftermarket offerings are much larger than OEM turbochargers.
Intercoolers
Just as turbochargers have become vital in diesel applications, intercooling is now an integral part of virtually every turbodiesel system. But it hasn’t always been that way. Diesel-equipped Dodge Rams were non-intercooled when they were introduced for ’89. While this was a cost savings, it also limited power. Hotter intake air results in less air in the combustion chamber due to expansion, which limits how much fuel can be burned. Lower exhaust gas temperatures are a benefit of intercooling, but the main advantage is more air going into the engine. One way to drastically increase engine efficiency and power-making potential is to add an intercooler, which passes a turbo’s discharge through a system of cooling tubes and fins, drastically lowering the air’s temperature. With modern trucks pushing 30 psi of manifold pressure (which can create temperatures of more than 250 degrees), using an intercooler is mandatory at today’s power levels.
Photo 8/15   |   012 Turbo Performance Banks Intercooler
Banks Power offers several small and large intercoolers that can be used for various applications, from everyday tow vehicles to race diesels making 80 psi of boost.

Performance Applications
At some point, the factory intercooler typically becomes a restriction. Also, excess boost can actually split an intercooler’s tanks! Not only are aftermarket ’coolers higher flowing, they’re also stronger. Intercoolers for high boost pressure will often have solid rods passing through the tanks to prevent splitting, as well as to support using larger-diameter inlet and outlet tubes.
The Future of Turbocharging—More Options, More Complexity
Diesel turbo systems have evolved over the years, thanks to ever-changing diesel-engine technology. In heavy-duty commercial applications, single turbos are still popular, thanks to their simplicity and reliability. However, many twin- and compound-turbo designs are being used in commercial applications and are actually becoming more common than single-turbo setups. In the on-road world, modern turbo systems have become increasingly complex, with many incorporating two or even three turbochargers. With tightening emissions regulations, look for quicker-spooling setups, even in single-turbo applications. In the aftermarket, large singles are making a comeback, although traditional compound setups and triple-turbo systems have created their place as well. One thing is for sure: Turbodiesels are here to stay and will be more exciting than ever in the future.
Photo 9/15   |   005 Turbo Performance 62mm Turbo And Wastegate
Wastegating is crucial on applications that have lots of drive pressure. On this nitrous-oxide-injected ’89 Dodge, both an internal wastegate and Turbosmart external wastegate are used to limit boost to 60 psi when nitrous is being injected. The turbo itself is a 62mm BorgWarner S300 that has been upgraded by Majestic Turbo and has somehow survived more than five years of abuse.
Photo 10/15   |   008 Turbo Performance Garret Single Turbo
Thanks to 5,000-rpm engine speeds and a dose of nitrous, the 5.9L Cummins in Daniel Pierce's Ram is able to support an estimated 1,500 hp using a single 91mm Garrett turbocharger. With an estimated 1,500 hp (with nitrous), it just goes to show how far you can push a single-turbo setup in a race application.
Photo 11/15   |   009 Turbo Performance Traditional Compounds
The most common dual-turbocharger design is a compound-turbo setup, in which a larger turbo compresses air into a smaller one, which also compresses the air and forces it into the engine. Since the pressure ratios are multiplied in this type of setup, very high boost pressures (more than 100 psi in some applications) are easily attainable.
Photo 12/15   |   010 Turbo Performance VGT Sandrail Turbo
Variable-geometry turbochargers are known for a distinctive whistle at low- and part-throttle when the vanes are closed. These compressors are especially effective when good throttle response is needed, like in this Duramax-powered sand rail built by Merchant Automotive.
Photo 13/15   |   011 Turbo Performance BD 64 Compounds
The ’08-to-’10 Ford Super Duty is a good example of a compound-turbocharged, diesel-powered production vehicle. Upgraded versions of the 6.4L Power Stroke turbos can boost performance to as much as 750 hp and are offered by such companies as BD Diesel Performance and ATS Diesel Performance.
Photo 14/15   |   013 Turbo Performance BT Air To Water
Air-to-water intercoolers offer huge airflow while maintaining a relatively compact design. This wild unit helps support the 1,500hp engine in Big Twin Diesel's drag truck, yet it fits under the pickup’s cowl hood.
Photo 15/15   |   015 Turbo Performance Triple Turbos
The latest evolution in performance turbo systems has been the use of triple turbos in a compound arrangement (two into one). With these setups, nearly 2,000 hp can be created in trucks that are still street driven, without ever stressing the turbochargers themselves.

Sources

ATS Diesel
Arvada, CO 80002
866-490-5573
www.atsdiesel.com
Banks Power
Azusa, CA 91702
866-738-5915
http://www.bankspower.com
Advanced Flow Engineering
Corona, CA 92879
951-493-7100
www.afepower.com
Garrett Turbo
Denver, CO 80216
800-822-4332
http://www.turbobygarrett.com
Turbosmart
Rancho Cucamonga, CA 91730
909-476-2570
www.turbosmartusa.com
S&B Filters
Ontario, CA 91761
800-358-2639
www.sbfilters.com
BD Diesel Performance
Sumas, WA 98295
800-887-5030
www.dieselperformance.com
Majestic Turbo
Waco, TX 76101
800-231-5566
www.majesticturbo.com
BorgWarner
Auburn Hills, MI 48326
248-754-9200
http://www.borgwarner.com
Steed Speed Performance
250-766-7136
http://www.steedspeed.com
No Limit fabrication
800-581-8986
http://nolimitdiesel.com/

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