the back side of the block. It was extremely light and strong for a production engine using an all-iron block, weighing in at only - over fifteen percent reduction compared to 2T-GEU. It was also 4 dB quieter. While originally conceived of as a two-valve design, Toyota and Yamaha changed the 4A-GE to a four-valve after a year of evaluation. The 4A-GE produced at 6,600 rpm and of torque at 4,800 rpm in the American market. The use of a vane-type air flow meter (AFM), which restricted air flow slightly but produced cleaner emissions that conformed to the U.S. regulations, limited the power considerably - the Japanese model, which uses a manifold absolute pressure (MAP) sensor, was originally rated at . However, this was a gross power rating and the engine was later re-rated at net. Nonetheless, Japanese cars tested no faster than their American counterparts despite their higher power rating and a lower curb weight. Yamaha designed the engine for performance; the valve angle was a relatively wide 50 degrees, which at the time was believed to be ideal for high power production. Today, more modern high-revving engines have decreased the valve angle to 20 to 25 degrees, which allows for a more smaller and compact head. This is now believed by some to be ideal for high-revving engines with high specific power outputs. However, most high performance racing engines still employ wide valve angles which allow straighter ports and more efficient flow. The first-generation 4A-GE is nicknamed the "bigport" engine because it had intake ports of a very large cross-sectional area. While the port cross-section was suitable for a very highly modified engine at very high engine speeds, it caused a considerable drop in low-end torque due to the decreased air speeds at those rpms. To compensate for the reduced air speed, the first-generation engines included the T-VIS feature, in which dual intake runners are fitted with butterfly valves that opened at approximately 4,200 rpm. The effect is that at lower rpm (when the airspeed would normally be slow) four of the eight runners are closed, which forces the engine to draw in all its air through half the runners in the manifold. This not only raises the airspeed which causes better cylinder filling, but due to the asymmetrical airflow a swirl is created in the combustion chamber, meaning better fuel atomization. This enabled the torque curve to