A growing number of specialty and race vehicle builders and tuners are turning to modern direct fuel injection engines as their powerplant of choice. While stock direct-injection engines produce more horsepower and torque with smaller displacements than their traditional port-fuel-injected counterparts, the performance racing industry is asking for ways to safely and reliably generate more power.

Companies have focused on modifying gasoline direct injection (GDI) fuel pumps to generate more power by providing more fuel at higher pressures. However, reconfiguring service pumps isn't the best way to solve the problem. Unique operational challenges need addressing to safely and dependably deliver the flow and pressure the industry is demanding to push the output boundaries of today's GDI engines, like the AMG, BMW B58 and the GM LT4. Increasing flow and pressure comes with significant issues that only purpose-designed-and-built pumps can resolve, like managing the extreme force on the camshaft and maintaining long-term structural integrity at high pressures.

Using OEM Pumps for the Performance Aftermarket

Stanadyne has been producing high-performance GDI pumps for automotive applications since 2007, with the introduction of the SP1250, commonly referred to as an "LT1". It is used across a range of original equipment manufacturer (OEM) applications and has a plunger diameter of 10.5 mm with a standard plunger stroke of 5.7mm and a pressure capability of 150 bar. The SP1250 has an advertised volumetric delivery of 1250 mm3/rev utilizing a three-lobe camshaft providing a 5.7 mm plunger stroke at 2400 pRPM (pump rpm) at minimum delivery.

In 2014, Stanadyne introduced the SP1550 (commonly referred to as an "LT4") for high-performance automotive applications. It has a plunger diameter of 11.5 mm and a volumetric delivery of 1550 mm3/rev at 200 bar utilizing a three-lobe camshaft providing a 6.0 mm stroke at 2400 pRPM at minimum delivery. It currently is the largest displacement GDI fuel pump used in OEM automotive applications.

Performance aftermarket companies have been modifying these Stanadyne OEM GDI fuel pumps to offer increased fuel-flow products. In 2023, Stanadyne partnered with performance vehicle tuning customers to design, build, and deliver aftermarket SP1250 and SP1550 pumps. These specialty pumps have a variety of options on the inlet and solenoid mounting, allowing for custom applications on a wider range of engine platforms. In addition, the pressure capability on the SP1250 was increased to 250 bar and on the SP1550 was increased to 350 bar.

Going Bigger with Goliath

The desire for higher flow and pressure led Stanadyne to develop a larger volume, 350-bar-capable pump for high-horsepower applications. This second-generation design is externally analogous to the original SP1550 pump but is fitted with a 12-millimeter plunger, has important internal modifications, and can accept up to an eight-millimeter plunger stroke. It has a SP2100 designation and is referred to as the "Goliath." It can deliver up to 2,100 mm3/rev at 350 bar using a three-lobe camshaft with up to an eight-millimeter plunger stroke.

"Protect your engine by choosing the trusted original," said Stanadyne Chief Engineer Srinu Gunturu. "Avoid knock-offs and modified pumps flooding the market. Insist on the patented Stanadyne Goliath pump—engineered to deliver original equipment quality and unmatched reliability, proudly built in the USA."

More Volume, Same Pressure

The Stanadyne pumps perform extremely well at 200 and 250 bar throughout the speed range, with minimal drop in delivered volume at higher pressure. The SP1550's delivered volume is approximately 24% higher than the SP1250. The Goliath's delivered volume is approximately 22% more than the SP1550 and about 50% greater than the SP1250. The SP1550 and Goliath perform exemplary at 250 and 350 bar throughout the speed range, with minimal drop in delivered volume at higher pressure. The Goliath's delivered volume is approximately 12% higher than the SP1550 at 350 bar.

More Volume, Higher Pressure

The Goliath pump provides significantly higher delivery than the SP1550 throughout the speed range at up to 350 bar. However, extreme power applications require even greater delivery. This led to the development of a higher lift capability for the Goliath's 12-millimeter plunger and the ability to run with up to an eight-millimeter stroke. As a result, an increase of approximately 29% in delivered volume can be realized by going from a six- to an eight-millimeter plunger stroke.

Understanding the Challenges

Moving to such high plunger strokes is not without issues, making implementing this operational change quite challenging. Given the existing space constraints when using the required larger diameter plungers and higher displacements, it is difficult to design a plunger spring with adequate force to maintain cam/roller contact on the downward stroke. The Goliath's large plunger combined with an increased stroke results in higher mass, and plunger velocities and accelerations. The greater inertial loads associated with increased lifts need to be understood. In addition, a spring with the appropriate force needs to be installed prior to the implementation of an increased pump stroke. An increased stroke results in greater loads being generated between the cam and the roller follower. Maintaining sufficient contact force throughout the cycle necessitates complimentary plunger return springs to maintain minimum contact force.

To achieve the spring force required for the Goliath high lift plunger in the allowable package size, a nested spring design was developed. This is a "spring within a spring," providing a very high-force solution to be installed in the available area.

Contact forces were thoroughly analyzed, internal flows and pressures were modeled and optimized to ensure an acceptable pumping chamber pressure and minimize losses, and finite element analysis ensured the pump was structurally sound.

Proving Out The Pump

After completing analysis and testing, it was time to see how the Goliath performed on-engine. Performance vehicle tuning partners fit the pump on various engines to measure performance improvement, especially horsepower gains.

Dorch Engineering installed the Goliath pump in a BMW 340i and achieved 823.7 hp and 765.6 ft-lbs. of torque. The Goliath pump enabled this engine to gain a 264% horsepower increase and a 242% torque increase over the stock engine baseline of 311.8 horsepower and 315.7 ft-lbs. of torque. Spool Performance fitted a Goliath pump in a twin-turbo Mercedes M177 LS2 engine and measured 1,040 WHP with 1,000 ft-lbs. of torque using E85 fuel. Katech Performance equipped the Goliath pump on a General Motors 388-cubic inch LT V engine. The engine ran a 7.82-millimeter cam lift using race gas to generate 1,475.3 horsepower with 1,173 ft-lbs. of torque. The same engine was fueled with E85 and achieved 1,254.9 horsepower with 996 ft lbs. of torque. Check out the results in the graphs below and read the full paper here. 

The Next Performance

Stanadyne continues to listen to the industry. Customers are asking for a 350-bar GDI fuel injector to accompany high-flow, high-pressure pumps. The Goliath high-flow, high-pressure GDI injector currently is undergoing performance and durability testing. The full Goliath system is expected to be on Stanadyne's display vehicle at the 2024 PRI Show, Booth #1936. The pump-injector set will offer tuners and racing enthusiasts with huge performance and dependability gains. 

Stanadyne testing results:

Stanadyne
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USA Corporate Headquarters: (860) 525-0821
Visit Stanadyne at the PRI Show in Booth #1936 in the Green Hall.
To read the full paper, click here. 

Srinu Gunturu leads Stanadyne's team of global engineers pioneering cleaner, more efficient fuel injection technology for engines moving our world, the aftermarket components keeping them operating, and the high-performance products fueling the passion for the industry. He is the driving force behind the company's new Performance Product, Systems, and Solutions.