A-Series Engines

Daihatsu Wiki Engines
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Daihatsu A-Series Engines

The Daihatsu A-series engine is a range of compact two-cylinder, internal combustion piston engines, designed by Daihatsu with the aid of their owner Toyota. The petrol-driven series has cast iron engine blocks and aluminum cylinder heads, and are of an SOHC lean burn design, with belt driven heads. The head design was called “TGP lean-burn”, for “Turbulence Generating Pot”. The engine also had twin-balancing shaft, which provided smoothness equivalent to that of a traditional four-cylinder engine - although it also cost nearly as much to build.

The engine was developed with some haste in order to replace the dirty two-stroke “ZM” engines used in Daihatsu’s earlier Kei cars, and was the first unit to take full advantage of the new 550 cc displacement limit in effect from 1 January 1976. It was first presented in May 1976, as the AB10.[3] Eventually, even a turbocharged version was produced. The engine was replaced by the three-cylinder EB-series in 1985.

The AB-series is a 547 cc (0.55 L) version originally installed into the 1976 Fellow Max 550 but soon found its way into Daihatsu’s entire Kei car lineup. Bore is 71.6 mm and stroke is 68 mm. Unlike the export versions, the Japanese market engines have a small catalyzer fitted.

AB10 is the code used for engines meant to be installed in an upright position, while those intended for a horizontal position (for underfloor usage) are called AB20. The AB55 is a horizontal version equipped with a turbocharger. A downtuned version with 9 PS (6.6 kW) at 2900 rpm and 2.8 kg·m (27 N·m; 20 lb·ft) at 2000 rpm was installed in Toyota’s 500 kg (1,100 lb) FG5 forklift from the late seventies.

Daihatsu Applications

  • 1976.05–1977.06 Daihatsu Fellow Max 550 (L40/L40V)
  • 1977.06–1980.06 Daihatsu Max Cuore/Cuore (L45/L40V)
  • 1980.06–1985.08 Daihatsu Cuore/Mira (L55/L55V)
  • 1976.04–1980.04 Daihatsu Hijet (S40)
  • 1977.04–1981.04 Daihatsu Hijet (S60)

Engine Variants (AB)

Varient HP KW @RPM NM @RPM Compression Fuel System Chassis
AB-10 28 21 6000 38 3500 8.7 Carb L40/L40V (Fellow Max 550)
L45/L40V (Max Cuore)
AB-20 28 21 5500 39 3500 9.2 Carb S40 (Hijet 550)
S60 (Hijet Wide 550)
AB-20 28 21 5500 41 3500 9.2 Carb S65/66 (Hijet Atari)
S65/66 (Hijet)
81.04-82.03
1981/04-03/1982
AB-20 29 21 5500 44 3500 9.2 Carb S65/66 (Hijet)
04/1982+
AB-30 29 21 6000 39 3500 9.2 Carb L40 (Cuore, Cuore Max)
AB-30 26 19 6000 37 3500 9.2 Carb L55V (Mira)
AB-30 31 23 6000 41
3500		 9.2 Carb L45 (Cuore)
L55 (Cuore)
AB-31 30 22 6000 41 3500 9.2 Carb L55V (Mira)
AB-35 41 30 6000 56 2500 8.2 Turbo L55V (Mira Turbo)
AB-50 29 21 5500 43 3500 ? Carb S65/66 (Hijet Atari)
82.04-83.09
AB-51 29 21 5300 44 3500 ? Carb S65/66 (Hijet Atari)
83.09-86.03
AB-55 39 29 5500 58 3000 ? Turbo S65/66 (Atari Turbo)
83.10-86.03

Engine Varient (AD)

The AD-series is a 617 cc (0.62 L) version of the AB-series engine. This somewhat larger engine does not meet Kei car regulations and was intended only for export markets of Daihatsu products, only the Daihatsu Cuore was ever fitted with this engine, although they were often sold as the “Domino” in export markets. Bore is 76 mm and stroke is 68 mm. The only version was an SOHC, two-valve, single carburetted unit. Innocenti also built this engine into their Mini 650, built from November 1984 until November 1987.






Original Source: https://en.wikipedia.org/wiki/Daihatsu_A-series_engine

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Thanks to @FrAsErTaG for setting this up.
Allow me to add some information.
All parts for the AB are available from Precision International. When it comes to the AD everything but pistons are available from Precision International.
There are two different thermostats for the A series.
2" (51.8mm) is commonly listed as the replacement but the 1-3/4" (45mm) is also used. The smaller is the same as CB 23 & 24 thermostat.

AB engines can be bored from 71.6 to 76 mm and fitted with CB23 pistons.
AD engines can also be fitted with CB23 pistons. Wrist pins are 18 mm like other daihatsu pistons.

Valve train is CB identical. Whatever can be used to upgrade a CB head works in AB/AD.

AB/AD connecting rods are 125.0 mm centre to centre identical to CB 23/24/60

AB flywheels are 6 bolt, AD flywheels are 4 bolt. The crankshaft flange accepts both flywheels.

AB/AD Timing belt is 90 teeth X 19 mm wide, 3/8" square tooth. Since Dayco and Gates have dropped this belt off their listings, the alternative is CB23 which is 3/8" square tooth and 91 teeth and CB24 which is 3/8" round tooth and 91 teeth. Obviously there are modifications to make, like a larger tensioner wheel to take up the slack or in the case of CB24 timing belt requires both top and bottom timing toothed pulleys.

Aftermarket Parts
ARP head studs - part number 208-4301.
Only 6 of the 10 bolts required.

Crow Cams valve springs - part number 2021-8
Similar pressure to stock N/A, when used in a boosted engine they need shining 0.120"

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Typical standard flow rates of AB/AD head.

Inlet port
IMG_20210908_170739_01

Exhaust port
IMG_20210908_170741_01

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[quote=“system, post:1, topic:305”]…The Daihatsu A-series engine is a range of compact two-cylinder, internal combustion piston engines, designed by Daihatsu with the aid of their owner Toyota…[/quote]Wikipedia is evidently not infalible. In other words, in this case, Toyota didn’t take ownership of Daihatsu, until 2016

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Everyone has permission to edit the wiki pages, feel free to correct mistakes :slight_smile:

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O rings

98.02 X 3.53 mm to suit distributor housing block that mounts on the head.

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AB flywheel has 6 bolts
AD flywheel has 4 bolts
Flywheel step for the clutch is -19mm, decreasing the step increases the preload on the clutch. Effectively increasing clamp loading.

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