Fluidampr FR-S/BRZ Crankshaft Damper Development
Introduction
Fluidampr performance dampers originated during the mid-1980s when parent company, VibratechTVD was approached by high level race engine builders. Their goal was to bring the durability and broad frequency range protection of a viscous damper found in commercial and industrial applications to professional motorsports. Today, Fluidampr performance dampers continue to be one of the market leading premium crankshaft dampers sold for domestic, import and diesel street performance and motorsports applications.
Fluidampr performance dampers challenge the misconception that a viscous damper is only suitable for large, low rpm industrial and commercial diesel engines. Follow the design and development process, plus comparative testing of a new Fluidampr performance damper for the Subaru FA20 / Toyota 4U-GSE 2.0L opposed-four cylinder ‘boxer’ engine. The engine is featured in the popular 2013-present Subaru BRZ, Scion FR-S, Toyota GT86 and new 2015 Subaru WRX.
Design Criteria
In conjunction with Turn 14 Distribution, the process began by implementing Vibratech TVD’s ISO 9001:2008 design and development certified process. This is the same high quality company standard used in the development of viscous dampers for OEM powertrain partners in the aviation and defense industries. Objectives were first established by interviewing intended users, understanding the challenges they face and analyzing the technical specifications of the engine. Above all, the new Fluidampr would have to prove that proper crankshaft torsional vibration damping is necessary in a boxer engine and that a viscous style Fluidampr crank damper can outperform the stock tuned elastomer style damper. As a bonus, given the popular misconception that no damping is needed on a boxer engine, it would also need to be compared to a leading lightweight crank pulley alternative.
From those market and product research sessions, the following goals were established:
- The damper would need to be light weight, yet effective and durable. It would be required to pass the strict professional racing industry’s SFI 18.1 safety certification. According to SFI quality assurance specification, section 18.1 refers to crankshaft hub harmonic dampers. Article 3.0 Construction, dictates that “the damper shall be constructed in such a manner that the inertia devices shall not become disengaged during use… For inertia disc style dampers, the containment device must cover a minimum of 50 percent of the cavity containing the disc. The thickness of the containment material must be a minimum of 0.062 inch steel or 0.180 inch aluminum. Article 5.1.3 B Testing Procedure mandates that “The damper shall be driven to a rotational speed between 12,500 and 13,500 rpm and maintained at that level for one hour.” Furthermore, the steel of a SFI certified Fluidampr housing must meet a minimum 40,000psi yield strength and 60,000psi tensile strength under testing.
- The damper would need to provide broad frequency and amplitude coverage to account for a wide variety of engine modifications including changes to the bore and stroke, rod and piston composition, crankshaft composition, and the potential for much higher cylinder mean effective pressure.
- For quality conscious race teams, in addition to providing excellent torsional vibration protection, the damper would require superior longevity and no maintenance, tuning or replacement once installed.
- Through creating greater efficiency by controlling torsional vibration, the damper would need to release more lost torque and horsepower over the stock tuned elastomer damper and a lightweight pulley.
- The damper dimensions would need to remain as close to stock as possible.
- The damper would need to accommodate additional accessory drives, such as a dry sump system or supercharger.
“Viscous damper technology will provide the broad frequency range and amplitude control. The toughest challenge is going to be fitting enough inertia mass in the same amount of physical space the stock damper consumes,” remarks Aaron Neyman, Fluidampr Senior Product Engineer. Tuned elastomer style dampers bond the inertia mass to the outside diameter. Its leveraging effect provides a functional design in a smaller and lighter package. A viscous style damper carries a portion of its inertia mass in the outer housing with the remaining mass contained in the inner inertia ring. The advantage of the viscous style design is that the outer housing provides heat dissipation that contributes to overall superior damper life.
Measurements
Through membership in the Specialty Equipment Manufacturers Association (SEMA) Technology Transfer, details regarding the FA20 / 4U-GSE engine were obtained. In addition, an OEM crankshaft damper and timing cover were obtained.
Through the use of calibrated precision measurement equipment the dimensions of the OEM crankshaft damper and timing cover were configured. In combination with other data obtained, measurements confirmed that the Fluidampr performance damper would be restricted to the same 5-7/8” outer diameter dimensions as the OEM crankshaft damper.
Layout then began in computer-aided design software from the measurements collected. Detailed finite element analysis was performed to determine the damper’s resonance frequency and structural integrity. SFI requirements mandate the damper to be spun at 12,500rpm for one hour without failure to meet certification for professional motorsports. The materials and manufacturing process chosen for this Fluidampr application provide nearly four times the requirement for added safety.
Once the preliminary computer design was complete a 3D additive printed prototype was produced. The prototype was shared with established performance engine shops to verify fitment and tolerances using actual engines.
With the ABS plastic prototypes passing inspection and the design meeting the initial objectives for optimum weight, size constraint and provisions for future accessory drive changes, the team moved forward with creating fully functional test prototypes.
