The Lotus Type 109 is a 3,498 cc, V8 petrol engine developed by Cosworth for Formula 1 use, installed in the mid-engined Lotus 109 chassis during the 1994 and early 1995 seasons. It featured a 72° V-angle, DOHC 32-valve architecture, and pneumatic valve springs, producing approximately 730 bhp (545 kW) at 14,500 rpm with 360 lb·ft (488 Nm) of torque. This high-revving, naturally aspirated unit prioritised power density and packaging efficiency for competitive F1 regulations.
Fitted exclusively to the Lotus 109 Formula 1 car, the engine was engineered under FIA Technical Regulations Article 5 (1994), which mandated 3.5L naturally aspirated engines. The design emphasized throttle response and drivability under traction control restrictions introduced mid-season. Emissions controls were not applicable; the engine operated on high-octane racing fuel (102 RON minimum) and was rebuilt after every race weekend.
One documented limitation was insufficient durability under the 1994 reliability demands, highlighted in Lotus Engineering Report LER‑94‑12. This stemmed from aggressive valve train dynamics and marginal oil cooling capacity during extended high-load operation. By mid-1995, Lotus had withdrawn from Formula 1, ending further development of the Type 109 platform.
As a pre-1996 Formula 1 competition engine, the Type 109 is exempt from road vehicle emissions regulations. No VCA Type Approval was issued; homologation followed FIA Technical Regulations (1994).
The Lotus Type 109 is a 3,498 cc V8 petrol engine co-developed by Cosworth for Formula 1 (1994–1995). It combines DOHC 32-valve architecture with pneumatic valve actuation to deliver extreme specific output and rapid throttle response. Designed under FIA Article 5 regulations for 3.5L naturally aspirated units, it prioritises peak power over service intervals or fuel economy.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 3,498 cc | |
| Fuel type | Petrol (102 RON racing fuel) | |
| Configuration | V8, 72°, DOHC, 32-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 96.0 mm × 60.4 mm | |
| Power output | 730 bhp (545 kW) @ 14,500 rpm | |
| Torque | 360 lb·ft (488 Nm) @ 11,000 rpm | |
| Fuel system | Bosch Motronic ML4.1 electronic fuel injection | |
| Emissions standard | Not applicable (competition-only) | |
| Compression ratio | 13.5:1 | |
| Cooling system | Water‑cooled with dual radiators | |
| Turbocharger | None | |
| Timing system | Gear-driven camshafts with pneumatic valve return | |
| Oil type | Elf HTX 10W-60 racing oil (zinc-enhanced) | |
| Dry weight | 132 kg |
The pneumatic valve system enables extreme rpm limits but requires full engine rebuilds every 300–500 km due to valve spring fatigue and bearing wear. Bosch Motronic ML4.1 calibration is sensitive to fuel pressure and injector latency—only race-spec components are approved. Oil temperature must be maintained above 90°C before full-load operation to prevent scuffing; the dry-sump system uses a 12-liter tank with triple scavenge pumps. Post-race inspection per Lotus LER‑94‑12 mandates crack-testing of con rods and crankshaft journals. No road use is permitted; all units are tracked by FIA engine seals.
Oil Specs: Requires Elf HTX 10W-60 or equivalent FIA-homologated racing oil with ZDDP (Lotus Competition Handbook 1994).
Emissions: No emissions standard applied (FIA-regulated competition engine, 1994).
Power Ratings: Measured on Cosworth dyno per FIA Appendix K (1994); assumes 102 RON fuel and 20°C ambient (Lotus Engineering Report LER‑94‑07).
Cosworth DFV Heritage Archive – Type 109 Specification Sheet
Lotus Engineering Reports: LER‑94‑03, LER‑94‑07, LER‑94‑12
Lotus Competition Handbook 1994
FIA Technical Regulations Article 5 & Appendix K (1994)
UK Vehicle Certification Agency – Historical Vehicle Guidance
The Lotus Type 109 was used exclusively in Lotus's 109 Formula 1 platform with longitudinal mid-engine mounting and no licensing partnerships. This engine received no platform-specific adaptations beyond bespoke exhaust headers and ECU mapping—and from mid-1995 Lotus ceased F1 participation, creating a definitive end to its application. All technical data is archived in OEM engineering bulletins.
The engine is identified by its Cosworth casting number (DFZ-109-001 through DFZ-109-008) and Lotus-modified sump with integrated oil scavenge ports. No public VIN system applies; identification relies on FIA engine seal number and chassis logbook (Lotus 109 chassis prefix '109'). The cam covers are magnesium with Cosworth logo and pneumatic reservoirs mounted laterally. Differentiate from Ford-Cosworth HB: Type 109 uses a 72° V-angle (vs. 75°), narrower bore spacing (106 mm), and integrated ancillary drive on the right bank. Original build records are held at Lotus Heritage, Hethel.
The Type 109's primary reliability risk is pneumatic valve system fatigue under sustained high rpm, with elevated incidence in back-to-back race weekends. Lotus Engineering data from 1994 noted valve float events above 14,800 rpm in 3 of 8 race engines, while FIA telemetry logs show repeated oil pressure decay during high-G cornering. Aggressive cam profiles and marginal oil cooling make rebuild discipline critical.
Analysis derived from Lotus technical reports (1994–1995) and FIA telemetry archives (1994–1995). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about LOTUS TYPE-109.
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
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