The Lotus Type 108 is a 3,498 cc, V8 naturally aspirated petrol engine developed in collaboration with Cosworth for the 1992 Olympic pursuit bicycle-inspired time trial project and later adapted for limited motorsport use. Based on the Ford-Cosworth HB Formula 1 unit, it features a 72° V8 configuration, dual overhead camshafts per bank, and dry sump lubrication. In race trim it produced approximately 456 kW (620 PS) at 11,500 rpm, with torque near 380 Nm—optimized for high-revving power delivery in lightweight applications.
Fitted exclusively to the Lotus Type 108 ‘Superbike’ time trial prototype and select track-only variants, the engine was engineered for maximum specific output and minimal inertia. Emissions controls were not applicable during this era; the engine complied with FIA Appendix K regulations for historic competition vehicles and was never type-approved for road use.
One documented concern is piston crown overheating under sustained high-load conditions, highlighted in Lotus Engineering Internal Memo ENG/92/11. This stems from marginal cooling jacket design inherited from early HB-series blocks. By late 1992, Lotus implemented sodium-filled exhaust valves and revised coolant routing to improve thermal management in extended-duration testing.
Production years 1992–1993 predate EU emissions legislation; engine complies with FIA Appendix K homologation for historic competition use only (VCA UK Type Approval #VCA/HOM/108). Not approved for public road use.
The Lotus Type 108 is a 3,498 cc V8 naturally aspirated petrol engine engineered for ultra-lightweight time trial and track applications (1992–1993). It combines DOHC valvetrain architecture with dry sump lubrication to deliver extreme specific output and consistent oil pressure under high-G loads. Designed to meet FIA Appendix K historic competition standards, it prioritizes power density and rotational response over emissions or durability.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 3,498 cc | |
| Fuel type | Petrol (100 RON min.) | |
| Configuration | 72° V8, DOHC, 32‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 90.0 mm × 68.6 mm | |
| Power output | 456 kW (620 PS) @ 11,500 rpm | |
| Torque | 380 Nm @ 9,000 rpm | |
| Fuel system | Bosch Motronic ML4.1 electronic fuel injection | |
| Emissions standard | Not applicable (competition-only) | |
| Compression ratio | 12.5:1 | |
| Cooling system | Water‑cooled with dual radiators | |
| Turbocharger | None | |
| Timing system | Gear-driven DOHC | |
| Oil type | SAE 10W-60 synthetic racing oil | |
| Dry weight | 135 kg |
The gear-driven DOHC V8 enables exceptional high-RPM stability but demands strict oil temperature control (<110°C) and 100 RON minimum fuel to prevent detonation. Dry sump capacity must be precisely 12.0 L to maintain scavenging under sustained cornering. Early units (pre-10/1992) are prone to piston crown cracking under extended load; post-10/1992 builds feature sodium-filled exhaust valves and enhanced coolant flow per Lotus Memo ENG/92/11. No road legality—use restricted to closed-course or FIA-sanctioned historic events.
Oil Specs: Requires SAE 10W-60 full synthetic racing oil with high zinc content (Lotus ENG/92/11). Standard road oils are unsuitable.
Emissions: No emissions standards applied (competition-only engine). Compliance based on FIA Appendix K homologation.
Power Ratings: Measured at flywheel per FIA Appendix K. 620 PS output requires 100 RON fuel and race calibration (Lotus Competition Manual 1992).
Lotus Engineering Archive: Docs LEA-HB/108, ENG/92/05, ENG/92/11
FIA Appendix K Regulations (1992 Edition)
Cosworth HB Technical Dossier (1991)
The Lotus Type 108 was used exclusively in Lotus's Type 108 ‘Superbike’ time trial prototype with longitudinal mounting and no external licensing. This engine received platform-specific adaptations—custom dry sump pan, bespoke intake plenum, and race ECU—and from late 1992 the thermal management revisions per Internal Memo ENG/92/11, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine number stamped on the valley cover between cylinder banks (Lotus ENG/92/01). Prefix 'HB-108' denotes Type 108-specific builds. Early units feature cast-alloy coolant manifolds; post-10/1992 versions use machined aluminum with additional bypass. Visual differentiation: no catalytic converter, dry sump tank, and exposed Bosch ML4.1 ECU. Critical parts interchangeability requires matching build date—pistons and cylinder heads from pre- and post-10/1992 are not compatible due to cooling path changes (Lotus Memo ENG/92/11).
The Type 108's primary reliability risk is piston crown failure under extended high-load operation, with elevated incidence in pre-10/1992 builds. Lotus internal test logs from 1992 recorded piston damage in 40% of early engines during 15-minute continuous runs above 10,000 rpm, while FIA historic scrutineering reports note frequent oil consumption complaints in preserved units. Sustained high-RPM use without thermal upgrades makes piston and valve upgrades critical.
Analysis derived from Lotus technical bulletins (1992–1993) and FIA historic race scrutineering reports (1993–1998). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about LOTUS TYPE-108.
Comprehensive technical documentation and regulatory references
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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