Toyota 3A-U / 3A-LU Engine 1.5 Specs, Problems, Reliability

The old engines of the 3A line were developed in 1979 and were the successors of the 1A series , which by that time was already very outdated.

This is not the most massive generation of engines, but it left its mark on the history of the development of Toyota Corporation. In particular, on some modifications, advanced systems for increasing environmental cleanliness and reducing fuel consumption were tested at that time.

Engines 3A-U and 3A-LU are almost identical in their parameters. These two modifications differed only in one parameter – the location in the engine compartment. The letter L means transverse engine. Otherwise, these two modifications are completely identical.

Read Also: Toyota 4E-FTE Engine 1.3 Turbo Specs, Problems, Reliability

Main technical characteristics of engines 3A-U and 3A-LU

Despite the rather ancient development, many engine of the line have survived to this day. This indicates a good design and high reliability. This is the golden age of Toyota engines, when engines were made for long-term operation without problems. Today, there are quite a few such engine.

The main characteristics of the installations are as follows:

Working volume1.5 l
Number of cylinders4
Number of valves8
Timing system drivebelt
Fuel supply systemcarburetor
Cylinder diameter77.5 mm
Piston stroke77.0 mm
Engine power83 HP at 5600 rpm
Torque118 Nm at 3600 rpm
Fuelgasoline 92, 95
Fuel consumption:
– urban10 l / 100 km
– suburban7 l / 100 km

A cast iron cylinder block and an aluminum block head were an optimal combination for that time, which also made it possible to overhaul the engine, improve its performance and engage in various types of tuning.

Technical characteristics can be called optimal, given the development time of engines. However, of today’s obsolete systems, only the carburetor turns out to be, which, with such an age of the engine, will certainly cause discomfort to the owner.

3A-U Engine Performance Summary

Here, we will investigate the characteristics of this engine by referring to the data of the 3A-U type naturally aspirated engine installed in Toyota’s AL21 type Corsa EX 1988/05 model.

toyota CORSA 3A-u Engine
Toyota’s AL21 type Corsa EX
Vehicle modelE-AL21 type
Car name & gradeCorsa
EX
Engine model3A-U
typeIn-line 4-cylinder
Displacement1452cc
Inner diameter × stroke77.5mm×77.0mm
Bore stroke ratio0.99
Single cylinder volume363.2cc
Compression ratio9.3
Intake methodNaturally aspirated
use fuelRegular gasoline
Maximum output70PS/5600rpm
Maximum torque10.9kgm/3600rpm

First of all, as a basic structure, the 3A type engine is a short stroke type engine with a bore (inner diameter) of 77.5 mm, a stroke (stroke) of 77.0 mm, and a bore stroke ratio of 0.99 (the piston diameter is larger than the stroke amount).

Strictly speaking, if the displacement and the number of cylinders are the same, it is not allowed to call yourself a square type unless the bore and stroke are exactly the same, but if the bore stroke ratio is so close to 1, “Already It’s okay to make it a square type! ”

These engines retain the flavor of short stroke type or long stroke type, but in fact, they have characteristics that are as close as possible to square type.

On this site, the model equipped with the 3A-U type naturally aspirated engine is the 3rd generation Corsa [AL21 type | 1988/05] released from 1982/05 , and there are 3 NA models, turbo. As for / SC cars, all 3 models of 0 models are registered.

Evaluation from the viewpoint of transient characteristics and liter equivalent horsepower

Image of engine performance curve
3A engine performance curve diagram
Changes in horsepower54.8PS → 70PS
Transition of torque10.9kgm → 9.0kgm
Liter horsepower48.21PS/L
Liter torque7.5kgm/L

Corsa’s in-line 4-cylinder 1452cc engine with a compression ratio of 9.3 and regular gasoline specifications, which is the reference vehicle for this time, produces a maximum output of 70 horsepower at 5600 rpm and a maximum torque of 10.9 kgm at 5600 rpm.

If you know the horsepower and the number of revolutions, you can know the torque, and if you know the torque and the number of revolutions, you can know the horsepower. The torque at 5600 rpm is 9.0kgm.

The horsepower per liter of displacement is 48.21PS / L and the torque is 7.5kgm / L, and the horsepower per cylinder (single cylinder volume 363.2cc) is 17.5PS and the torque is 2.7kgm.

When the 3A naturally aspirated engine is applied to a 10-step evaluation based on the deviation value aggregated from all NA vehicles registered on this site, the evaluation is “I don’t mind” with a converted horsepower of [ 1 ] and a converted torque of [ 1 ]. It is categorized as ” engine of output “.

Displacement increase, compression ratio increase, bore stroke ratio change

Normal displacement and compression ratio
BoreStrokeDisplacementCompression ratioB/S ratio
77.577.01452cc9.30.99
Displacement expansion by bore up
78.077.01472cc9.40.99
78.51491cc9.50.98
79.01510cc9.60.97
79.51529cc9.70.97
80.01548cc9.80.96
80.51568cc9.90.96
Displacement expansion by increasing stroke
77.578.01472cc9.41.01
79.01491cc9.51.02
80.01509cc9.61.03
81.01528cc9.71.05
82.01547cc9.81.06

There are three factors that determine the engine displacement: the number of cylinders, the bore diameter, and the stroke amount. By increasing or decreasing these, engines with various displacements are created.

Here, regardless of whether it is actually possible, the displacement when the piston diameter is expanded from the genuine 77.5 mm to 80.5 mm in 0.5 mm increments and when the stroke is extended from the genuine 77.0 mm to 82.0 mm in 1 mm increments. And, the change of the compression ratio when it is assumed that the volume of the combustion chamber does not change is listed.

* It is easy to say stroke up, but if you want to make a long stroke, you need a crankshaft and a compatible connecting rod, and if you can not divert it, you have to make it in one-off, so it is expensive anyway. It is a menu that requires considerable preparedness to put out.

Regarding the compression ratio, in most cases, the uneven capacity of the top surface of the piston changes as the diameter of the piston increases, so the compression ratio values ​​in the list do not match, but the displacement. Please enjoy the atmosphere that the compression ratio will naturally increase as you increase the size.

The B / S ratio is an abbreviation for the bore stroke ratio, and as the bore diameter is widened, the value becomes even smaller from 0.99, and the advantages and disadvantages of the short stroke type become more pronounced. In the case of 3A type engine, the ratio changes from 0.99 to 0.96 when the bore is increased by +3.0mm from the genuine piston.

Increased displacement with engines with similar piston diameters

Since there are 15 engines with pistons that are close in size to the piston diameter of 77.5 mm for 3A type engines, let’s calculate the displacement when the piston is diverted and the bore is increased as a sideshow.

Eg typePiston diameterDisplacement
Mitsubishi
6A12 type
78.4mm
[+0.9mm]
1487cc
[+35cc]
Mitsubishi
4G91 type
78.4mm
[+0.9mm]
1487cc
[+35cc]
Toyota
5A type
78.7mm
[+1.2mm]
1498cc
[+46cc]
Subaru
FB16 type
78.8mm
[+1.3mm]
1502cc
[+50cc]
Toyota
1ZZ type
79.0mm
[+1.5mm]
1510cc
[+58cc]
Nissan
MRA8 type
79.7mm
[+2.2mm]
1537cc
[+85cc]

Engines with similar piston diameters are 6A12 type 1998cc 78.4mm mounted on Mitsubishi: E84A type Galant, 4G91 type 1496cc 78.4mm mounted on Mitsubishi: CA3A type Mirage Asti, Toyota: AE91 type Corolla Levin. 5A type 1498cc 78.7mm, Subaru: FB16 type 1599cc 78.8mm mounted on GT3 type XV, Toyota: 1ZZ type 1794cc 79.0mm mounted on ZZT230 type Celica, Nissan: MRA8 mounted on TB17 type Sylphy 79.7mm of type 1798cc is applicable.

(Although the number of people who find pleasure in such a quest has decreased) No matter how close the diameter is, there are factors such as the diameter of the piston pin, the height of the piston, and the convenience of valve recess, so if possible, the same manufacturer, If possible, if you choose the same fuel and the same intake method, and if possible, the one with a similar displacement, the possibility of genuine diversion may increase.

Average piston speed

strokeMaximum torque
3600rpm
Maximum output
5600rpm
77.0mm9.2m/s14.4m/s
Rotation speed / minuteper secondspeed
2000rpm5.1m/s18km/h
4000rpm10.3m/s37km/h
6000rpm15.4m/s55km/h
8000rpm20.5m/s74km/h
10000rpm25.7m / s93km/h

Next, let’s look at the average piston speed. The average piston speed at 5600 rpm, where an engine with a stroke of 77.0 mm produces maximum output, is 14.4 m / s , which is a piston speed that travels a distance of 14.4 meters per second (51.8 km / h at speed). It means that is moving up and down.

The average speed is 9.2 m / s at 3600 rpm, which generates the maximum torque, and 15.7 m / s when 6100 rpm, which is 500 rpm higher than the 5600 rpm where the maximum output is generated, is assumed to be the rev limit.

For reference, I calculated the change in piston speed when a 3A engine with a stroke of 77.0 mm is rotated up to 10000 rpm. Looking at this, it seems that the speed increases by approximately 5.15 m / s as the number of revolutions increases by 2000 revolutions.

Considering only 20.0 m / s, which is a guideline for general engines assuming mass production, it is mechanical to set the upper limit of high rpm to about 7790 rpm (whether it rotates or not). It seems to be preferred both mentally.

Advantages and main benefits of operating 3A-U and 3A-LU

Both engines proved to be reliable and durable. Their simple design and reasonable architecture made it possible to achieve a resource of 350-400 thousand kilometers. Of course, this is only possible when using normal oil with suitable characteristics and high-quality fuel with the proper octane level.

It is worth noting the following advantages of engines:

  1. simple repair, given the classic design with virtually no difficulties;
  2. the absence of complex fuel systems that will fail over such a period;
  3. timing belt drive, which for old engines can already be considered an advantage;
  4. indestructible cylinder block, there were practically no problems with wear of the main part;
  5. low power potential, which prolongs the life of the engine.

The Japanese did not squeeze the maximum out of the engine, and its 83 horses per 1.5 liter volume seem ridiculous in the modern society of turbocharged engines.

But such “vegetable” characteristics have their advantages. The engine is very difficult to kill, even considering all the shortcomings of the fuel mixture supply system.

Problems and malfunctions in this series of installations

Engine are known for their simplicity and reliability, so there were no significant troubles in operation. These engines were not supplied to several countries, today they are presented only as contract engine brought from Japan. Use them for swap in suitable models.

The disadvantages are the following:

  1. relatively high sensitivity to lubricants and fuels;
  2. the need for routine maintenance is clearly according to the requirements, otherwise there will be breakdowns;
  3. complex valve adjustment, a lot of manual work when setting up the engine;
  4. small volume and low power, even for B-class cars this is not enough;
  5. age – today 3A engine can no longer be called the best buy due to old age.

Serious breakdowns were not observed, the engine takes care of its resource up to 400,000 km even without repair. Overhaul allows you to extend the period of use, but restoration is advisable only with original spare parts. It is not difficult to bring the engine to breakdowns – you just need to pour bad oil and not pay attention to the quality of the fuel at the gas station.

Conclusions on Toyota’s 3A line of engines

The Japanese corporation systematically developed its line of engines. 3A was replaced in 1989 with the more modern 5A , which is still in demand in the secondary market today.

The demand for 3A-U or 3A-LU was influenced by the presence of a carburetor in the fuel supply system and a very honorable age. These two factors do not allow us to call the engine a good buy for a swap.

When buying a similar engine, you should make sure of its residual resource. This is not easy to do, as there are few external signs of wear. Inspect the timing system, remove the cylinder head cover and look at the condition of the main parts. This is the only way to check the estimated mileage.

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