The Honda B20A engine series, known as the B20A and B21A was an inline four-cylinder engine family from Honda introduced in 1985 in the second-generation Honda Prelude. Also available in the contemporary third-generation Honda Accord in the Japanese domestic market, along with the Accord-derived Vigor, the B20A was Honda's first line of multivalve DOHC inline four-cylinder engines, focused towards performance and displacing 2.0 to 2.1 litres.
The third-generation Prelude was exclusively powered by the B20A engine family and production of the B20A engine family ended with the conclusion of the production of the third-generation Prelude in 1991.
It would be succeeded by the Honda B engine. Although sharing similar nomenclature and some design elements, the earlier B20A substantially differs from the later B-series in architecture enough to be considered two different engine families and must not be confused with other B-series engines and the B20B, a 2.0 liter DOHC engine introduced alongside the Honda CR-V in 1994.
There were two versions of the B20A:
The first generation of B20A engines was available in the 86–87 Prelude 2.0SI in Japan and Europe, the 86–89 Honda Vigor and Accord. It leaned towards the front of the car just like the A20A engine found in the same cars. This B20A produces 160 hp (119 kW) and 140 lb·ft (190 N·m) torque in Japan. In Europe this is called B20A1, produces 137 hp (102 kW) and 127 lb.ft (172 Nm).
There was also a similar engine named B18A for the 86–89 Accords. It was a destroked B20A powered by two sidedraft Keihin carbs.
The second generation of B20A was found in the 88–91 Prelude. The 88–91 Prelude B20A and B21A blocks are cast so they lie at an 18-degree angle leaning towards the firewall. This was done to please the exterior specifications for the 1988–1991 3rd Generation Prelude due to its ultra-low hoodline which Honda dubs the "engineless design" and also for handling reasons due to placing the engine at an angle gives it a lower center of gravity (similar to straight 6 designs in older BMW's).
The B20A, B20A3, and B20A5 engines consisted of closed-deck aluminum blocks with thicker-than-average iron sleeves whereas the B21A1 had FRM (fiber reinforced metal) cylinder liners.
The B21A1 was basically a re-worked B20A5 with an increase in bore to 83 mm (3.3 in). The external block dimensions had to stay identical (although there was increased external strengthening and webbing on the B21) to the B20A5 block so Honda called upon Saffil to create a thin but strong cylinder liner called FRM (fiber reinforced metal) which basically consisted of a carbon fiber matrix, aluminum alloy, and aluminum oxide to make a very strong cylinder sleeve. The sleeve is so strong, in fact, that it wears out the piston rings causing low compression numbers, severe smoking, and high oil usage. It is possible in many situations to merely replace the worn rings in order to revive the motor's former output. Many machine shops will not attempt to re-hone or re-bore the FRM sleeves, as this type of sleeve will de-laminate during machining operations.
(16-Valve, 4 Cylinder, DOHC, PGM-FI)
"Honda" logo in center of valve cover – Filler cap on left side of cover.
Found in:
Serial numbers 1000001~, 1500001~ and 1550001~
1985–1986 Honda Prelude Non-U.S.
1985–1986 Honda Accord Non-U.S.
1985–1986 Honda Vigor Non-U.S.
Serial numbers 1600001~ and 1640001~
1987–1989 Honda Vigor Non-U.S.
Displacement: 1958 cc
bore: 81 mm (3.2 in)
stroke: 95 mm (3.7 in)
Compression: 9.4:1; 9.5:1
Power:
(JDM GOLD TOP B20A 1986–1987) 160 hp (119 kW) @ 6300 rpm & 137 lb.ft (186 N·m) @ 4000 rpm, using PH3 ECU
(JDM BLACKTOP B20A 1988–1989) 160 hp (119 kW) @ 6200 rpm & 137 lb.ft (186 N·m) @ 4000 rpm, using PH3 ECU (Some think this engine have same spec as black top from 88–91 Prelude, but this is not. This engine is still 160 hp. just like the gold top.)
(EDM, B20A1 Gold Top) 137 hp (102 kW) @ 6000 rpm & 127 lb.ft (172 N·m) @ 4000 rpm, using PJ5(602,603,752),PJ7,PH3 ECU w vac. advance
Transmission: B2K5(86–87), F2K5(88–89)
This is for the B20a that came in 88–91 Preludes, not the same motor as listed above. (16-Valve, 4 Cylinder, DOHC, PGM-FI)
Found in:
1988–1991 Honda Prelude Non-U.S.
Power: 143 hp (107 kW) @ 6000 rpm
Torque: 128tq @ 4500 rpm
Compression ratio: 9.4:1
(16-Valve, 4 Cylinder, DOHC, PGM-FI)
Found in:
1987–1989 Honda Accord Non-U.S.
Power: 142 hp (106 kW) @ 6200 rpm
(12-valve, SOHC, dual side-draft carburetors)
Found in:
1988–1990 Honda Prelude 2.0 S
Power: 109 hp (81 kW) @ 5800 rpm (MT)With cata, 115 hp (86 kW) @ 5800 rpm without cata
Torque: 111 lb·ft (150 N·m) @ 4000 rpm
It was PGM-CARB microprocessor controlled (pk-1)
(12-Valve, SOHC, dual side-draft carburetors)
Found in: 1988–1991 Honda Prelude Non-U.S.
Fuel system: 2 carburetors
Displacement (cm3): 1958
Bore x Stroke (mm): 81 x 95
Compression ration: 9.2:1
Maximum power: 114 hp @ 5800 rpm
Maximum torque: 116 ft lb @ 4500 rpm
Catalytic converter: no
ECU: no
(16-valve, DOHC, PGM-FI)
Found in:
1988–1991 Honda Prelude 2.0Si
Power: 135 hp (101 kW) @ 6200 rpm
Torque: 127 lb·ft (172 N·m) @ 4000 rpm
Engine cc: 1958.14
Cylinder cc: 489.535
Deck cc: 13.885
Head cc: 47.3
Compression Ratio: 9.0:1
(16-Valve, DOHC, PGM-FI)
Found in:
1988–1991 Honda Prelude Non-U.S. New Zealand, and Australian Domestic Market
142 hp (106 kW)@6000 rpm 174 Nm@4500 rpm KY model is one of them
(16-Valve, DOHC, PGM-FI)
Found in:
1988–1991 Honda Prelude Non-U.S. UK, France, Holland, Norway, South Africa
Power 150 hp (112 kW)@6000 rpm
132tq (180 Nm) @ 5500rpm
Compression ratio 10.5:1
(16-Valve, DOHC, PGM-FI)
Found in:
1988–1991 Honda Prelude Non-U.S. Russian, Swedish Domestic Market
1988–1989 Honda Accord Non-U.S.
Power 167 hp (125 kW)
(16-Valve, 4Cylinder, DOHC, PGM-FI)
Found in:
1990–1991 Honda Prelude Non-U.S. Finland, German, Norway, Netherlands, Russia, Argentina
Power 139 hp (104 kW) @ 6000 rpm
Torque 129tq (175 Nm) @ 4500 rpm
Cylinder cc: 489.535
Deck cc: 13.885
Head cc: 47.3
Compression ratio 9,3:1
(16-valve, DOHC, PGM-FI)
Found in:
1990–1991 Honda Prelude Si States
Very rare, it was only produced for the "Si States" models in Japan
Power: 145 hp (108 kW)
Torque: 186 N·m (137 lb·ft)
Compression Ratio: 9.4:1
engine using a pk-3 honda ECU
(16-valve, DOHC, PGM-FI)
Found in:
1990–1991 Honda Prelude SI USDM
1990–1991 Honda Prelude SR Canadian Market
Power: 140 hp (104 kW) @5800 rpm
Torque: 135 lb·ft (183 N·m) @5000 rpm
Engine cc: 2056.03
Bore 83 mm
Stroke 95 mm
Cylinder cc: 514.0075
Deck cc: 10.191
Head cc: 51.0
Compression Ratio: 9.4:1
