In professional motorsport, lap records are the ultimate validation of engineering decisions. The 2025 Time Attack season saw Tegiwa’s Honda NSX, ‘Tsuki’, secure the Championship title and reset six Pro 2WD lap records.
While the results on the tarmac were headline-grabbing, they were the product of a rigorous engineering programme in the workshop. The powertrain, electronics architecture, and calibration strategies were all designed and executed by Bourne HPP.
Crucially, this dominance was delivered with absolute reliability. The Bourne K22 power unit completed the entire 2025 season—every practice, qualifier, and final—without requiring a single rebuild. It is a testament to the robust engineering standards we apply to every motorsport application.
Here is a technical deep-dive into the engine package that delivered the 2025 Time Attack Pro 2WD Championship.
The Power Unit: The Bourne K22 Turbo
The brief for the NSX was specific: raw power was necessary, but driveability and transient response were critical. To achieve the required rate of acceleration of revs, we moved beyond standard tuning methods to re-engineer the K-Series platform using high-grade motorsport components.
We utilised a standard 2.0L block, bored and stroked to 2.2L, engineered to withstand the extreme cylinder pressures of a high-boost application.
1. F1-Grade Piston Design
We collaborated with Pankl Racing Systems to develop a bespoke piston solution.
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Design Philosophy: The pistons feature a thick, bowled crown design—a topography typically found in WRC and endurance racing. This allows for significantly higher cylinder pressures than a standard K-Series piston.
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Specification: The assembly includes beryllium bearings and DLC-coated gudgeon pins to minimise friction and maximize durability under load.
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The Result: A piston that offers Formula 1-grade resilience within a Honda architecture.
2. Rotational Mass & Block Integrity
To manage the torque output from the Garrett G-Series 950 turbocharger, we focused on the bottom end's stability and rotational speed.
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Crankshaft: We selected an Arrow Precision crankshaft machined from 722M24 nitriding steel. By reducing the counterweight count from eight to four, the crank weight was dropped to just 12kg. This reduction in rotational mass is key to the engine’s rapid throttle response.
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Liners: The standard dry liners were machined out and replaced with Bourne's one piece liner set, featuring an F1 style head gasket that incorporates a coopers ring design, ensuring the block maintains structural integrity during high-load hot laps.
3. Cylinder Head & Valvetrain
To handle the extreme boost and RPM requirements, the cylinder head is built around our own proprietary Bourne HPP Valve & Spring Set.
Designed entirely in-house and manufactured in the UK from high-heat resisting austenitic steel, this package is engineered specifically to prevent valve float and ensure reliability in forced induction applications. We paired this set with our 32R billet high-lift cam and increased valve sizes by 1mm on both inlet and exhaust. This combination allows the head to flow enough air for 1,000HP+ while maintaining the precise valve control required for technical circuits.
Advanced Electronics & Data Acquisition
Managing the powertrain is a complete electronics suite centred around a Life Racing F88 ECU, with a closed loop wide band in order to keep everything in check. This unit handles all engine strategies, gearbox control, and traction management. The engine also features a Bosch 68mm drive-by-wire throttle and 2x Bosch knock sensors which allows for closed loop knock control.
A key differentiator in this build is the CAN bus integration. Originally developed by Siemens for military applications, the system used on Tsuki transmits 14,000 channels of data across just two wires!
This high-density data stream allows for seamless integration with the Bosch Motorsport ABS and ECUMaster dash, providing our engineers with high-resolution telemetry. This data is critical for refining traction control maps, ensuring that power delivery is optimised for the specific grip levels available at each corner.
Remote Engineering Support
Building the car is the first step; optimising it across a season is where championships are won. Throughout 2025, Bourne HPP provided comprehensive remote trackside support.
By plugging directly into the car’s telemetry systems remotely, our engineers monitored engine health and performance data in real-time. This allowed us to execute precise calibration changes and adjust traction control strategies to suit changing track conditions and weather, ensuring the driver always had a predictable and potent platform.
This meticulous management of engine vitals is the reason the engine remained sealed and untouched all year. Delivering championship-winning pace is one thing; delivering it with an engine that survives a full season of Time Attack abuse without a rebuild is the Bourne HPP standard.
2025 Track Record
The reliability and performance of this package were demonstrated by the lap times achieved across the UK’s premier circuits:
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Cadwell Park: 1:27.311 (Pro 2WD Record)
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Donington Park National: 1:06.793 (Pro 2WD Record)
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Brands Hatch Indy: 45.556 (Pro & Pro 2WD Record)
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Snetterton 300: 1:49.220 (Pro & Pro 2WD Record)
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Oulton Park International: 1:37.878 (Pro & Pro 2WD Record)
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Knockhill: 48.617 (Pro & Pro 2WD Record)
1Motorsport Programmes by Bourne HPP
The engineering principles applied to Tsuki are the same we apply to every client project. Whether you require a high-performance engine build, a bespoke motorsport wiring harness, or a full calibration and support package, we have the in-house capabilities to assist.
Discuss your programme requirements. Contact Bourne HPP to speak with our engineering team.
