. Because of the smoothness inherent in the Wankel rotary engine, little vibration or harshness was experienced at high engine speeds, so a buzzer was fitted to the tachometer to warn the driver when the 7,000 rpm redline was approaching. The 12A engine has a long thin shaped combustion chamber, having a large surface area in relation to its volume. Therefore, combustion is cool, giving few oxides of nitrogen. However, the combustion is also incomplete, so there are large amounts of partly burned hydrocarbons and carbon monoxide. The exhaust is hot enough for combustion of these to continue into the exhaust. An engine-driven pump supplies air into the exhaust to complete the burn of these chemicals. This is done in the "thermal reactor" chamber where the exhaust manifold would normally be on a conventional engine. Under certain conditions, the pump injects air into the thermal reactor and at other times air is pumped through injectors into the exhaust ports. This fresh air is needed for more efficient and cleaner-burning of the air/fuel mixture. Options and models varied from country to country. The gauge layout and interior styling in the Series 3 was only changed for the North American models. Additionally, North America was the only market to have offered the first generation of the RX-7 with the fuel-injected 13B, model GSL-SE. Sales of the first-generation RX-7 were strong, with a total of 474,565 cars produced; 377,878 (nearly eighty percent) were sold in the United States alone. RX-7 Turbo Following the introduction of the first turbocharged rotary engine in the Luce/Cosmo, a similar, also fuel injected and non-intercooled 12A turbocharged engine was made available for the top-end model of the Series 3 RX-7 in Japan. It was introduced in September 1983. The engine was rated at (JIS) at 6,500 rpm. While the peak power figures were only slightly higher than those of the engine used in the Luce/Cosmo, the new "Impact Turbo" was developed specifically to deal with the different exhaust gas characteristics of a rotary engine. Both rotor vanes of the turbine were remodeled and made smaller, and the turbine had a twenty percent higher speed than a turbo intended for a conventional engine. The Savanna Turbo was short-lived, as the next generation of the RX-7 was about to be introduced. Second generation (FC3S and FC3C) The second generation of the RX-7 ("FC", VIN begins JM1FC3 or JMZFC1), still known