We got into diesel when GM sent us early 6.2L diesel engines to find out whether they could live with turbocharging. In stock form, those engines were weak and smoky. With boost, they cleaned up, made better mileage, and finally had the torque a truck owner could use. The 6.2L didn’t hold up the way a marine engine has to, but in pickup service it made sense, and that opened the door. From there, we moved fast. We released turbo systems for the 6.2L, then for Ford’s 6.9L, and worked directly with GMC on a dealer-specified ship-through program. Banks Sidewinder Turbo Systems were installed for GMC dealers and sold through about 2,500 dealerships, putting a Banks-turbo diesel pickup on the market a year before Dodge offered the Cummins turbo diesel. The bigger point is simple: diesel performance at Banks started with air. More air let the engine burn cleaner, make usable power, and become a better truck engine. That early shift into diesel also helped carry the company through a brutal downturn in the marine market and set the direction for decades of diesel development that followed.
In this episode of Speed School, Gale Banks and Walt Ware trace how Banks first moved into diesel work in the late 1970s. Until then, Banks had been focused on twin-turbo gasoline marine engines, including four-cylinder, small-block, and big-block combinations for pleasure boats, jet-drive boats, and race boats. Diesel was not yet part of the company's core business. Banks notes that some of the engineering lessons from earlier Oldsmobile marine racing programs, including a national championship jet-boat effort built around the Oldsmobile 455, later informed thinking around diesel durability and airflow.
Banks also recalls influence from Oldsmobile engineer Rodney Rask, whose work on intake-tract tuning and snorkeled air-cleaner systems pushed him toward deeper thinking about Ram-Air, air density, and intake tuning. Those ideas would become central to Banks' later diesel philosophy. The turning point came when Chevrolet's end-products group sent Banks two pre-production 6.2-liter diesel engines, asking whether they could tolerate turbocharging in marine service. That effectively pulled Banks into the diesel business around late 1978 or early 1979.
The original goal was ambitious: determine whether a turbocharged GM 6.2-liter diesel could compete in marine use against Caterpillar's 3208, which at the time was naturally aspirated and produced roughly 180 horsepower. The comparison was difficult from the outset. The Cat was a much larger and heavier engine, around 1,500 pounds versus roughly 600 pounds for the GM diesel, so equal horsepower would not imply equal durability.
Banks says the 6.2 easily reached the target power level and actually exceeded 200 horsepower, climbing to about 215 horsepower before the fuel pump became the limiting factor. In a marine environment, however, engines face near-continuous heavy load, and that exposed the weakness of the light-duty GM platform. The 6.2 failed as a durable marine engine, but the turbocharging work revealed something important: in pickup-truck use, the same engine responded very well. Turbocharging improved performance, reduced smoke, and delivered better fuel economy. That discovery helped redirect Banks' diesel efforts away from marine propulsion and toward light-truck applications.
By the early 1980s, Banks had begun offering turbo systems for diesel pickups. A kit for the GM 6.2 arrived in late 1981, followed by a kit for Ford's 6.9-liter International Harvester diesel in late 1982. Banks and Ware describe the Ford 6.9 as naturally aspirated, robust, and capable of 500,000 miles in pickup service, which made it a formidable competitor to GM's lighter-duty diesel.
Around 1985, GMC executive John Rock contacted Banks about formalizing a ship-through or dealer-specified option program for turbocharged 6.2 trucks. Rock's motivation was blunt: the 6.2 engine plant in Moraine, Ohio, was reportedly operating at only 17 percent capacity, while Ford's diesel pickups were taking market share. GMC needed something fresh that would attract press attention and help preserve the diesel truck program. Banks worked out an arrangement under which trucks were equipped through dealers, with installations handled in Almont, Michigan, through the Rinke organization.
The program lasted several years and became historically significant. Banks says the company had a turbocharged diesel pickup sold through 2,500 GMC dealers roughly a year before the Dodge Cummins arrived. In his telling, the first turbo in a pickup truck sold through that kind of dealer network carried the Banks name. The arrangement also had a side benefit: although Chevrolet did not participate directly, aftermarket sales for Chevrolet-branded trucks doubled as GMC's diesel-turbo publicity spread.
A recurring engineering theme throughout the discussion is that diesel engines respond exceptionally well to increased airflow. Banks summarizes it simply: excess air is hard to hurt a diesel with. Ware connects that idea to his own development work at Garrett in Alameda, where by 1980 the facility had expanded to roughly 500,000 square feet and included 24 test cells, 17 of them dynamometer cells.
Ware describes experiments on Mack's undersized 676 diesel, where Garrett pursued every available efficiency gain. That included air-to-air charge cooling, a tip-turbine fan to force more air through the charge-air cooler, and back-curved compressor impellers known internally as the "Ugly Wheel," adopted because of their efficiency advantages. He pushed testing to extremely lean air-fuel ratios, including 40:1 and even 60:1, to understand how far diesel combustion could be stretched. In hindsight, he says those ratios were beyond where practical development ended up, but the work reinforced the central lesson: diesels thrive on air density and airflow, and careful turbocharger matching can unlock both performance and efficiency.
Banks ties that same principle to later experiments with nitrous oxide and supercharging, noting that once oxygen availability rises dramatically, combustion efficiency can become startlingly high. The broader point is that diesel development at both Banks and Garrett was driven by systematic exploration of airflow limits rather than by simple fuel-addition strategies.
Banks explains that the company's move toward diesel was not only technical but also economic. In the late 1970s and early 1980s, the marine business was hit hard by recession, high interest rates, and fuel-economy pressures. Prime interest rates reached 21 percent, and Banks says his SBA loan was priced at three points over prime, leaving him paying 24 percent interest. At the same time, the 55 mph speed limit and corporate fuel-economy rules were reshaping the vehicle market.
Banks had been heavily invested in marine engines, often shipping product and waiting 45 to 90 days for payment from boat manufacturers. When the marine market collapsed during the Carter-era recession, diesel suddenly looked far more attractive because of its fuel efficiency and because turbocharging could improve both power and economy while reducing smoke. What began as an exploratory marine diesel project became a strategic pivot that helped carry the company through a difficult economic period.
Ware then shifts the story to his return from England to Garrett in 1985, just as the company was entering a turbulent period. Soon after returning, he learned that Allied Chemical had acquired Signal, which in turn controlled Garrett. He describes the takeover as a major turning point. Many long-time leaders left, including chairman Jack Teskey and executive John Kazir, and Ware says the company's culture had already been damaged by an aerospace-style management approach imposed on the turbo business while he was away.
According to Ware, Garrett's replacement leadership treated automotive OEMs with arrogance, as though they were government or airframe customers rather than commercial vehicle manufacturers. That approach badly damaged relationships with Ford and Chrysler. Teskey had previously told Ford to "pound sand" over demands for technical rights tied to turbocharger business, and by the time Ware returned, Ford had effectively sworn off Garrett turbos. Chrysler had done the same, and Ware recounts being publicly singled out at a 1985 supplier conference by Chrysler purchasing chief Dave Platt, who declared that Garrett would never do business with Chrysler again.
Ware's response was to visit customers personally and try to win back trust. He told Platt directly that he was not the man responsible for the earlier damage and intended to earn the business back. Over time, he says, he succeeded, eventually recovering Chrysler's Turbo I, Turbo II, Turbo III, Turbo IV, and later variable-geometry programs. That recovery became one of the defining achievements of his Garrett career.
One of Ware's biggest victories came with Navistar and Ford's new 7.3-liter diesel program. After returning to Garrett, he used the corporate jet to visit major North American customers and repair damaged relationships. During a meeting with Navistar CEO John Horne, Ware learned that Garrett had not even been invited to bid on the new engine's turbocharger because of the company's poor recent performance. The engine was a clean-sheet design for Ford pickups, built around advanced HEUI fuel injection, and the turbocharger had to fit a tightly defined space claim while meeting new environmental requirements.
Ware pressed for a chance anyway. Once he got the opening, he created a skunkworks operation at Lomita, fencing off leased trailers so only the core team could enter. He wanted to shield the effort from internal skepticism and from the familiar refrain that new ideas had already been tried and had failed. The team, which included Carl Walter, developed a completely new turbocharger architecture designed not for hand assembly but for robotic manufacture and assembly. That required simplifying every motion and eliminating labor-intensive procedures such as manually stretching shafts with dial indicators to achieve clamp load.
Garrett then expanded manufacturing capacity dramatically, with Ware securing $17 million in 1986 to support new machinery and production capability. The resulting contract was enormous. Ware says Garrett became sole-source supplier not only for the turbocharger but also for the charge-air cooler, exhaust brake, and even the cab heater because the system had become so integrated. A 1987 Garrett press release described it as the biggest automotive parts contract ever awarded at the time, extending through the year 2000. By Ware's account, millions of units were ultimately built, and the 7.3-liter Power Stroke remained influential decades later.
The conversation also revisits the role of press demonstrations in changing perceptions of turbocharging during the 1980s. Banks and Ware worked together to show journalists that turbocharged vehicles could be quiet, reliable, responsive, and suitable for production use. One press event featured a range of vehicles from naturally aspirated to small-turbo, intercooled, and variable-geometry configurations so visitors could feel the differences directly rather than hear them described in presentations.
A slalom course simulated city driving, while acceleration runs demonstrated how variable-geometry turbochargers could nearly eliminate traditional turbo lag by controlling exhaust-gas velocity into the turbine. Ware explains the principle as modulation of nozzle area so that available exhaust energy is never wasted but instead applied in the way the engine needs at a given speed and load. Banks emphasizes that production reliability had also become impressive, citing figures of 99.7 percent survival at 50,000 miles and 99 percent at 100,000 miles for Garrett turbochargers.
The same period included high-profile GM work such as the Buick Grand National and GNX era. Ware describes building a manual-transmission Buick V6 with variable geometry, a ceramic turbine, and a T4 compressor matched to a T3 turbine. The car became notorious at GM's Black Lake proving grounds because it could outrun Corvettes, despite corporate reluctance to let anything outperform the flagship sports car. For Ware, the demonstration value was crucial: rather than relying on PowerPoint, he preferred to let engineers and executives drive the vehicles themselves and experience the torque and response firsthand.
After leaving Garrett around 1990, Ware moved through several major roles, including Gould Pumps, Detroit Diesel under Roger Penske, and Turbodyne, where he worked on electric superchargers and electric turbochargers such as the Dynacharger. Banks notes that he later used some Turbodyne hardware in Bonneville work to improve low-speed response on a Cummins-powered dually.
In 2016, Banks brought Ware into Banks Engineering, where the collaboration continued. By the end of the discussion, both men frame their long partnership as a continuation of the same engineering mindset that shaped their diesel and turbocharger work in the 1980s: system-level thinking, direct testing, and a willingness to challenge accepted limits. They close by pointing to current military hybrid programs, including a series hybrid in which the engine drives a generator and a full hybrid project in which Banks is responsible for the electrical equipment, vehicle-control architecture, and the controller that manages both the engine and electric systems. For both men, the attraction remains the same as it was decades earlier: solving hard propulsion problems by integrating airflow, combustion, controls, and hardware into a complete system.