TOYOTA 4AG ENGINE

Toyota 4A-GE Engine

Toyota’s distinguished small high performance engine, the 4A-GE, was introduced in May 1983. In a short period of time 4A-GE became very popular among import tuners with its reliability, high performance, light weight and compact design. 4A-GE was displacing 1587cc with bore and stroke dimensions of 81mm and 71mm respectively. Though 4A-GE was lacking torque with its relatively small displacement, it was renowned for high revving abilities.

DOHC head was driven by a single timing belt. Cross flow type intake and exhaust layout was coupled with pent-roof combustion chambers for improved combustion efficiency. Engine was fed through an electronic multi-point fuel injection system which was very rare back then.4A-GE was intended to be used mainly in compact performance models as well as racing applications. Therefore keeping the engine weight to a minimum was crucial. In order to reduce the weight, 4A-GE was equipped with aluminium head and aluminium pistons. Despite the weight disadvantage, iron was chosen as the block material instead of aluminium. Thanks to enhanced casting techniques, and a very well thought design, Toyota managed to manufacture strong yet lightweight block.

Toyota continued developing 4A-GE through out its life span to keep it up to date. Although there is no such official classification from Toyota, 4A-GE enthusiasts generally consider that a total of 5 generations of 4A-GE were produced.

First Generation

The first generation 4A-GE was produced between May 1983 and May 1987. First generation was the only 4A-GE version that was available both as RWD and FWD. 4A-GE was mounted longitudinally in RWD models (AE86 Corolla GT/Corolla Levin/Sprinter Trueno and AA 63 Celica) whereas FWD models (AW 11 MR2 and AE 82 FWD Corolla) were fitted with transversally positioned 4A-GE. To mount the engine in longitudinal form, throttle body was moved to flywheel end of the inlet manifold.

First generation 4A-GE was equipped with a 16 valve head and the compression ratio was 9.4:1. The air drawn into the engine was measured either with a Manifold Absolute Pressure (MAP) sensor or Air Flow Meter (AFM) depending on the market. Inlet manifold was featuring Toyota Variable Intake System (TVIS). TVIS was operated by ECU and utilized a set of butterflies that manipulated one of the intake valves per cylinder. In order to improve mid-range torque, TVIS blocked the flow of air through the valve below 4500RPM and opened it above 4500RPM. First generation 4A-GE with a MAP sensor were putting out 115 4A-GE’s fitted with an AFM were delivering 120hp at 6600RPM.

Second Generation

The second generation 4A-GE was released in May 1987. Performance wise, second generation 4A-GE was almost the same with first generation, however structurally; the second generation engines were much stronger. Engine block was reinforced with seven external ribs opposed to three found on first generation. Connecting rod bearing size was increased to 42mm from 40mm and a stiffer crank shaft was used. The reason behind all these changes was the release of supercharged 4A-GZE. In order to withstand the extra loads generated by the supercharger, these modifications were necessary. To reduce the tooling costs, Toyota engineers decided to use same components on both 4A-GE and 4A-GZE where possible. MAP sensor was not employed anymore, hence it was replaced with AFM on all markets. 4A-GE was found under hood of AE92 Corolla, Levin/Trueno and facelifted AW11 MR2 models and was only available in transverse layout. Second generation was delivering 115hp at 6600RPM.

Third Generation

In May 1989 third generation of 4A-GE was released. Improvements made on the third generation were aiming to increase the power output of the engine. The first move was increasing the compression ratio from 9.4:1 to 10.3:1; which was the easiest and the most efficient way to increase power. In order to achieve this; pistons were replaced with higher compression ones. These new pistons were also featuring oil cooling channels. Oil jets underneath the pistons were supplying oil to these channels to cool down the pistons. Cam timing and lift was also revised. The new cams had 7.1mm of lift and 232° of duration lift whereas earlier generations had 7.56 and 240° respectively. Redline was now at 7200RPM.

Intake system also received some serious attention. AFM used on second generation engines was restricting the air flow through intake manifold; therefore AFM was reverted back to MAP sensor for improved intake capabilities. Because of the strict emissions, US version 4A-GE’s were equipped Mass Air Flow (MAF) sensors instead of MAP sensors. Most radical change was at the intake manifold. TVIS was discarded and the intake port design was revised. The intake ports on 3rd generation 4A-GE were utilizing a narrower design that generates a smaller cross sectional area compared to intake ports on previous generations. Third generation 4A-GE was used in AE92 Corolla GT and Carina models. Thanks to mentioned modifications third generation 4A-GE was delivering 140hp.

Fourth Generation

June 1991 saw the release of fourth generation 4AGE. The fourth generation is famous for being the first 20 valve variant of 4AGE. The engine was now featuring five valves (3 inlet and 2 outlet) per cylinder instead of four. The addition of fifth valve to valve train brought along an extensive list of modifications. The head was completely redesigned to accept the fifth valve. To create room for the third inlet valve, valve size was reduced to 26.5mm from 29mm found on earlier engines; however exhaust valve size was increased to 26mm from 25.5mm. Although the diameter of intake valves reduced in size, the addition of the third valve increased the total cross sectional area by 37%. Updated valves were operated by new camshafts that had wilder cam profiles. Intake cam was equipped with Toyota’s variable cam timing mechanism VVT-i.

Inlet and exhaust systems were also revised. Inlet port angle was revised for optimum air flow into the engine. Individual throttle bodies were used on each cylinder and the air drawn into the engine was measured with an AFM. Exhaust system was also revised with tubular headers for lower backpressure.

The modifications were not limited to head only. In order to reduce rotating mass connecting rods and crankshaft were replaced with lighter units. The pistons were replaced with new ones that had three flycuts for the three inlet valves and the compression ratio was raised to 10.5:1. Fourth generation 4AGE was delivering 160hp and it was only available in JDM AE101 Corolla series.

Fifth Generation

Fifth generation 4A-GE -which was also the final version- was introduced in may 1995. Fifth generation was using a 20 valve head just like its predecessor. However; intake port and exhaust port sizes of the 20 valve head were increased and the shapes were improved before being was placed in fifth generation.

In order to reduce the rotational mass pistons, connecting rods, crack shaft and flywheel were replaced with lighter ones. Compression ratio was raised to 11.0:1 and intake cam profiles were slightly modified. The duration of the cams were 250°, which was the same with previous generation 20 valve 4AGE, but the lift was increased to 8.2 mm from 7.97mm. There was no change in the exhaust cams; just like previous version 20 valve, duration was 250° and lift was 7.6mm. Intake system was also altered for better air flow. The diameter of the individual throttle bodies were increased to 45mm from 42mm and a larger intake plenum was used. Also the plastic intake trumpets were replaced with rubber ones. Once more, AFM was replaced by a MAP sensor.

Fifth generation was delivering 165hp and it was only used in JDM Corolla AE111 series. Production of 4AGE ceased with the production of AE111 in 2002.