Electronic Engines — Camless Fuel, Exhaust & Start-Air Control
No camshaft, no chain, no timing gears — software decides when fuel fires, valves open and air starts, and pressurised lube oil does the muscle work.
Key Principles at a Glance 5 points
- Camless means no camshaft, chain or timing gears for fuel, exhaust and start air — on-off NC electronic valves plus software set every event.
- Fuel metering is by injection duration, not pump stroke: a low-voltage signal opens the electro-hydraulic servo (ELFI) valve, servo oil from the accumulator fires the fuel valve.
- Exhaust valves run on the same 300-bar servo oil through the ELVA valve — timing and lift are free variables, not cam-profile prisoners.
- One cylinder controller per cylinder plus a standby engine controller means a single failure costs one unit temporarily, never the engine.
- Camless freedom has one dark side: fuel can enter a cylinder without any cam event — leakage alarms, deflection monitoring and double-walled HP pipes are the price of that freedom.
1. The Camless Idea — Software Replaces Steel Timing
On a conventional engine the camshaft is the timetable: fuel cams, exhaust cams and start-air distributor all cut in steel, phased once at build. Electronic engines delete that entire drive — no camshaft, no chain, no timing gears for these functions — and replace each cam event with an on-off NC (normally closed) electronic valve plus a crank-angle input. Timing becomes a number in software, changeable per revolution:
What software gains
Injection timing, rate shaping, pre-injection and exhaust open/close angles become free per load, per revolution — including slow steaming and crash-stop patterns stored in memory.
What steel loses
No cam means no cam-event interlock: a leaking valve can admit fuel with no timing signal at all — the hydraulic-lock hazard of §5.
2. Fuel Injection — Duration Meters, Servo Oil Fires
Metering is no longer delivery-volume-per-stroke. The microprocessor takes engine speed and crank angle, selects an injection pattern, and fires a low-voltage signal at an electro-hydraulic servo (ELFI) valve. That valve connects the fuel valve to the servo-oil accumulator — pressurised, cool, clean lube oil at about 300 bar from a common engine-driven pump block — and accumulator pressure drives the injection. Quantity equals open-time, so slow initial injection and pre-injection shape the burn and cut sac-volume dribble:
Two or three injection valves per cylinder cover (bore decides the count), each with pre-sharpened edges — and the nozzle hardware in this family is what the slide-valve zero-sac injector of the emissions lesson refines. The injector-side tests and overhaul rhythm live in Fuel Injectors — Atomisation, 7 Tests & Overhaul.
3. Exhaust Valve — Hydraulic Muscle, Free Timing
The same servo-oil system drives the single central exhaust valve in each cover. An ELVA (exhaust-valve control) proportional valve meters 300-bar oil to the valve's activation piston through an actuation pipe with dampers — so opening moment, closing moment and lift profile are all software-set, and the classic early/late/opening trade-offs of cam profiles disappear:
4. Controllers — One Per Cylinder, One Spare for All
Control is layered so no single box can stop the engine. Each cylinder has its own cylinder control unit (CCU) driving its fuel, exhaust, start-air and lube functions; above them sit engine control units and an interface unit tying plant control, safety and alarm systems together; multi-purpose controllers (MPC) stand redundant — and a standby engine controller takes over a failed unit with no performance change:
| Box | Owns | Fails like this |
|---|---|---|
| Cylinder control unit | All four functions of its cylinder | That unit alone loses power until standby takes over |
| Engine control unit | Whole-engine situation, plant + safety + alarms | Supervised by interface logic and redundant MPCs |
| Local terminal + MOP | Main operating panel commands and readouts | HCU local boxes mirror per-unit fuel pressure and exhaust data |
5. ME vs RT-flex — and the Uncontrolled-Fuel Hazard
| Feature | MAN B&W ME | Sulzer RT-flex |
|---|---|---|
| Control brain | ECS with EICU / ECU / CCU per cylinder | WECS-9520 electronic control |
| Fuel drive | Servo-oil accumulator + ELFI per unit, rate shaping | Common-rail supply, rail valves per unit |
| Exhaust drive | ELVA hydraulic actuation, free timing | Hydraulic open and close (cam Sulzers: hydraulic open, gas-spring close) |
| Cylinder lube | Load-timed dosage off the same controllers | Alpha lubricator, load-proportional pulse feed |
The hazard both share: with no cam event gating the fuel, a leaking injection valve or HP line can feed fuel into a cylinder uncontrolled — and liquid does not compress, so the unit heads for hydraulic lock. The defences are layered: fuel-leakage collection with alarms, crankshaft-deflection monitoring that catches the overloaded throw, double-walled HP pipes that contain bursts, and scavenge-space design that keeps stray fuel away from hot steel:
Reversing and starting logic for these engines extends the cam-engine story in Starting & Reversing; exhaust-valve hardware detail sits with Four-Stroke Aux Design and timing practice in Valve Gear & Fuel Injection.