Making Boost: Inside Modern High Performance Turbochargers

The modern era of technology has been very kind to the drag racing world, allowing for the production of weapons-grade levels of power that were merely a fantasy just a decade ago. Some of the biggest leaps in technology have come in the power adder world — especially when it comes to turbocharging — which were little more than a niche application that was largely misunderstood not long ago. We sat down with Tim Coltey of Honeywell Garrett, one of the leading manufacturers of high-end racing turbos, about modern turbocharger technology and how they are able to make so much power today.

The progress of turbo performance has been staggering to say the least, and racers have been able to harness that progress and translate it into real-world results. Big-block turbo combinations are now running in the 3.80s in the eighth mile under the hood of Radial vs The World Cars, and have run deep into the five-second zone in the Pro Modified ranks. These gains are due in large part to the use of turbochargers and their continued development by manufacturers across the globe.

Radial tire star Marty Stinnett has been able to lay down some incredible passes with a pair of Garrett turbos under the hood of his small-block Mustang.

The World Of High Performance Turbos

If you think of an engine as nothing more than an air pump, adding a turbo is how you pump ever-larger amounts of air through the engine to create more power when combined with the proper amount of fuel. It sounds simple, but there is a lot of hard work and science that goes into improving the process of how a turbo makes power while still being as efficient as possible.

The modern high-performance turbo that’s used in racing is much different than the one that might be sitting under the hood of the car in your driveway. It’s all about what they’re designed for. The turbochargers used in drag racing are designed to make upwards of 3,500 horsepower when used in twin applications. The goal with these monster turbochargers is to generate as much horsepower as possible while remaining efficient. It’s easy to build a large turbocharger to make tons of power, but it also needs to build boost quickly on the starting line to help the car launch.

High-performance turbos aren't burdened with the restrictions of OEM turbos on passenger cars; they're built for maxium effort at the track.

As part of the design process that goes into a turbo, Honeywell Garrett will conduct multiple tests to ensure the turbo can deal with the stress racing can put on it. They will look at things like shaft motion, thrust bearing capacity, rotor inertia, shaft critical speed, wheel fatigue, and turbo vibration to make sure the turbo is capable of surviving the most extreme conditions that racing can put it through.

Advancements in bearing design have allowed companies like Honeywell Garrett to coax some impressive performances out of high-performance turbos.

According to Coltey, these tests have allowed Honeywell Garrett to come up with ways to make their racing turbos more durable, specifically in the bearing department. “Ball bearing innovation began as a result of work with the Honeywell Garrett Motorsports group for several racing series, where it received the term the ‘cartridge ball bearing’. The cartridge is a single sleeve system that contains a set of angular contact ball bearings on either end, whereas the traditional bearing system contains a set of journal bearings and a thrust bearing.”

These upgraded cartridge bearings in the turbo help to make the throttle crisper and have a better overall throttle response, which is great for drag racing applications. Another advantage of the ball bearing turbos is the ability to spool nearly 15 percent faster than the traditional journal bearing turbos. The improved response and quicker spooling help to add more performance to a racecar, allowing it to see better 60-foot times, and more usable power at all areas of the powerband.

The ball bearing design reduces the required amount of oil needed to provide adequate lubrication. -Tim Coltey, Honeywell Garrett

The bearings advantages go beyond turbo response, as they make the turbo more durable overall.“The ball bearing design reduces the required amount of oil needed to provide adequate lubrication. This lower oil volume reduces the chance for seal leakage. Also, the ball bearing is more tolerant of marginal lubrication conditions and diminishes the possibility of turbocharger failure on cold starts. The ball bearing cartridge gives better damping and control over shaft motion, increasing reliability for both everyday and extreme driving conditions. In addition, the opposed angular contact bearing cartridge eliminates the need for the thrust bearing — a common weak link in the turbo bearing system,” Coltey says.

Turbo Innovation

Nothing spurs innovation in the motorsports world like the need to go faster, and that has been a huge driving force behind the use of turbos in drag racing. Engineering developments from racing like Formula 1, CART, and other motorsports have found their way into drag racing as turbo use has increased in popularity. Now that experience, data, and knowledge is being used to develop drag racing-specific turbos that have produced record performances at the track.

The need for turbochargers that were designed specifically for drag racing began over a decade ago, and has grown exponentially ever since. “About 15 years ago, companies were piecing together turbochargers that were designed for diesel tractor engines and trying to use them in drag racing. You had heavy components that weren’t optimized for performance and were being used on all kinds of different drag racing cars, especially the imports. Racers were pushing the product to the limits and this huge influx of enthusiasts helped to really bring turbos into their own in the drag racing world,” Coltey says. 

This new push for turbochargers that could be used specifically for drag racing led to the development of the previously-discussed cartridge ball bearings, better housings, new impeller designs, and improved compressor wheels. As more innovation flowed into the development of turbos, it allowed racers to make more power efficiently with turbos and spin then upwards of 84,000 rpm.

With the help of Computer Aided Engineering (CAE), we were able to really re-engineer the compressor wheels to optimize them specifically for drag racing. -Tim Coltey, Honeywell Garrett

The materials used in turbos that you see at the race track are different from those used in the OEM market. The compressor wheels are typically forged, and the compressor housings feature fully-machined ported shrouds to improve surge resistance and increase operating range. The turbine wheels are made using a high nickel super-alloy, so they can remain strong during the exposure to the high exhaust temperatures seen in drag racing.

Companies like Honeywell Garrett have taken high-performance turbo development even further by finding new and innovative ways to make their turbos more powerful. Updating the compressor wheel aerodynamics, better bearings, compressor housings that are able to flow more air, machined compressor housing inlets, and ported shrouds are just a few ways these performance turbos are more powerful than ever.  

According to Coltey, the newest GTX5533R GEN II turbo from Honeywell Garrett has their full suite of new developments, and shows how much power these new turbochargers can make. “If you look at where we’ve gone from the Gen I turbo to the Gen II unit, we’ve had a pretty substantial jump in compressor stage technology. We looked at the compressor stage as a whole system, that’s the compressor wheel and compressor housing, to see where we can make improvements. With the help of Computer Aided Engineering (CAE), we were able to really re-engineer the compressor wheels to optimize them specifically for drag racing.”

Design Changes Of High Performance Turbos

The beauty of high-performance turbochargers is how simple they are when you look at other turbo machinery that are used in Honeywell’s various propulsion engines and APUs they offer. “We can capture substantial performance gains by optimizing the individual components and how they all work together. By breaking down the turbo to its individual parts and refining their abilities, greater performance has been extracted from the turbo,” Coltey says.

Since the main point of a turbo is to compress and flow air in order to generate power, making them move that air efficiently has allowed for massive gains in the horsepower they can produce. “We re-engineered the blade profile, blade count, and wheel design. This helps the turbos achieve the maximum power and efficiency over a wider operating range versus the previous generation of product,” Coltey explains.

There's not a single area of the turbo that Garrett hasn't looked at in order to try and make it produce more power efficiently.

Another area that has been addressed when it comes to turbo design is the compressor stage and its housing. By looking deeper into these parts of the turbo, more performance was uncovered that trickled down into other areas of turbo design.

Turbo Compressor Wheel Tech

 The compressor wheel innovations Garrett implemented with the GTX5533R GEN II are important and aided in its higher level of performance. The compressor wheel used on the GTX5533R GEN II flows nearly 220 pounds of air per minute and is able to compress the air to pressures over 60 psi. The key to a compressor wheel like the one used on the GTX5533R GEN II is how efficient it is inside the operating range. The most efficient wheels generate lower volumes of heat when they are compressing ambient air. By not producing as much heat, it brings the charge air temperatures down and this helps the racer to burn more fuel and make horsepower.

“We found that increasing the volute A/R (more cross-sectional area of the compressor volute) worked well with the new Gen II compressor technology and helped the compressor stage flow more air. The fully-machined and ported shrouds help improve surge resistance along with adding some eye candy to the front of the turbo. Looking at the compressor stage as a system and designing wheels and housings together produced very good results. A good example of an optimized compressor stage is our GTX5533R GEN II, which has delivered massive improvement over the GEN I product – up to 700 horsepower in some scenarios,” Coltey says.

Coltey goes into more detail about the compressor wheel technology developments from Honeywell Garrett with the GTX5533R GEN II Turbo.

“We’ve got a more efficient compressor stage and wheel that help the turbo make more power. It’s fairly common in drag racing for people to refer to turbos by the inducer diameter, and that’s what you can measure from the outside, but we’ve been able to make the exducer back disk diameter bigger and gone from 118mm to 133mm. That, combined with much more advanced aerodynamic technology and a larger compressor housing, have allowed us to see some pretty substantial increases in compressor flow and efficiency.”

Moving beyond the compressor stage of the turbo, improving the turbine wheel on a turbocharger is another way to add more performance. By tweaking the turbine wheel slightly, the benefits of improved air flow help the turbo breathe even better. “Our engineers use advanced computational fluid dynamics and finite element analysis software to maximize flow, efficiency, and durability, while minimizing inertia as much as possible with the turbo wheel,” Coltey explains.

While the size of the turbo and the parts where the air enters and exits get the most attention, the center housing of the turbo is the backbone that keeps things going. The center housing ties everything together with the turbo and can be a source of hidden power within the unit. “Although often overlooked, the center section of the turbo houses the bearing, cooling and lubrication systems of the turbo. We refined the turbo center sections and designed them for ultimate reliability and durability, so the turbocharger can make more power in a reliable way,” Coltey says.

As turbochargers have evolved, the one thing that has remained constant is the need for a high level of efficiency. “High efficiency is the key to big power for any turbo. Having a design with low efficiencies in the wheels and parasitic power losses can rob customers of their treasured horsepower and wins at the track,” Coltey explains.

The turbocharger has established itself as one of the best ways to make huge power in any form of motorsports. As its popularity has exploded in drag racing, the turbo has seen huge advancements in technology that have added fuel to its growth fire. With companies like Garrett always looking for ways to make their turbochargers more powerful, the sky really is the limit for what turbos will be capable of in the future with further development.

Article Sources

About the author

Brian Wagner

Spending his childhood at different race tracks around Ohio with his family’s 1967 Nova, Brian developed a true love for drag racing. When Brian is not writing, you can find him at the track as a crew chief, doing freelance photography, or beating on his nitrous-fed 2000 Trans Am.
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