Engine Nomenclature — Decode MAN, Sulzer, Daihatsu & Spec Sheets

1. MAN B&W — Read the Code Left to Right

The maker's project guide prints the code as boxes with leader lines — each position is one fact. The pattern below is assembled from standard worked examples plus a ship spec sheet (6S80MC-C):

6S80MC-C identifies six cylinders, with firing order 1-5-3-4-2-6. S means super-long stroke, with S/B approximately 4; 80 gives the bore in centimetres (800 mm), with a 3200 mm stroke in this example.

M denotes MAN lineage and C the compact/programme concept. The suffix −C identifies the revision; TII denotes Tier II compliance. E identifies the design series, F/A the programme, and GI gas injection.

• Older prefixes: V means crosshead with V-frame, T crosshead with tie rods, and F marine propulsion.
• 774VT2BF: seven cylinders, V-frame crosshead, tie-rod engine, 740 mm bore and second-generation programme.
• 7L80GFCA: L-class, gas-fuel capable auxiliary example.
• Daihatsu direction convention: clockwise viewed from the flywheel side is normal; anticlockwise is reverse.
• Cylinder numbering runs 1, 2, 3… outward from the flywheel end.

The 6S80MC-C spec-sheet example develops 23280 kW at 76 rpm, with S/B = 4 and firing order 1-5-3-4-2-6.

2. Stroke Classes — K, L, S, G Set the Engine Speed

Stroke-to-bore ratio fixes character: a long stroke means a slow-turning engine swinging a large-diameter propeller efficiently; a short stroke means a faster, more compact engine. The bands:

• K: short stroke, S/B approximately 2.
• L: long stroke, as in 7L80GFCA.
• S: super-long stroke, S/B approximately 4, as in 6S80MC-C.
• G: ultra-long stroke, S/B approximately 4 or more; the slowest engine with the largest propeller.

For the worked example, 3200 mm stroke / 800 mm bore = 4.0, confirming S class at 76 rpm and 23280 kW. The rule of thumb runs from short and fast to long and slow: longer S/B means a slower engine and a larger, slower, more efficient propeller.

Exam move: given any MAN code, state cylinders, class, bore, then compute S/B from the spec sheet and confirm the class letter matches — a mismatch means you misread the bore.

3. Sulzer RTA & Aux Makers — Same Logic, Different Letters

Sulzer uses the identical left-to-right grammar with its own alphabet; aux makers (Yanmar, Daihatsu) add duty letters because a generator engine and a propulsion engine with the same bore are different products:

7RTA84M: 7 gives the cylinder count; R denotes the welded bedplate, T super-long stroke, A the first series, 84 the 840 mm bore, and M the modified version. Its 2800/840 stroke-to-bore ratio is approximately 3.4.

Auxiliary engine codes add duty information:

• Yanmar 6EY26LW: six cylinders, EY series, 260 mm bore, blank division (standard), L marine auxiliary duty and W Tier-2 NOx.
• Daihatsu 6DL(M)-20(L)(F)(S): six cylinders, DL medium-speed vertical series, M propulsion, 200 mm bore, L reverse, F front PTO and S sole-plate.
• Daihatsu 6N21A-L–DV: A means the 900/1000 rpm range (without A, 720/750 rpm); L means auxiliary/land constant-speed duty and DV the degree of supercharging.

Sulzer's 7RTA84M spec sheet is also the template for §4: bore 840, stroke 2800, 23000 BHP at 92 rpm — every field below appears on it.

4. Read the Spec Sheet — Five Numbers, Two Consumptions

A spec sheet answers the surveyor's five questions — how hard does it push (MEP), how hard can it peak (Pmax), how thirsty (SFOC), how fast does it wear (liner), how much oil does it drink (cylinder oil) — with the Sulzer sheet as the worked example:

Spec-sheet extras to name on sight

Generator: Daihatsu 8DK-20, 880 kW × 720 rpm, Pmax 160, FO 1356 g/kW/h-class consumption, 1000 kVA 60 Hz 440 V. Propeller beside it: 4-blade solid-skewed, 9658 mm diameter, 6776 mm pitch. Emergency set: 480 kW × 1800 rpm. When the examiner points at any one line, read maker, model, duty, speed and output in that order.