The Forgotten Turbocharger Killer!

In the early 1990s, Japan was doing something no one else on earth was doing. Engineers at Mazda, Toyota, and Nissan were building turbocharged engines that had almost no lag. Not less lag. Almost none. And they did it without changing the basic turbocharger itself. Instead, they rewired the entire logic of how a turbo system works. That technology was called sequential twin turbocharging. It ran in some of the most legendary engines ever put in a production car. The 2JZ-GTE in the Supra. The 13B-REW in the RX-7. Today, those cars sell for six figures at auction. Collectors fight over them. But almost nobody talks about the actual engineering that made them special, or why that specific approach to turbocharging was eventually abandoned. This is that story. And it starts not with a car, but with a country drowning in money. To understand why Japan's car industry exploded with innovation in the early 1990s, you need to understand the decade that came before it. Between 1985 and 1991, Japan's economy entered what economists now call the asset price bubble, a period of almost delusional growth where real estate and stock prices climbed so fast and so high that they lost all connection to reality. The Nikkei Stock Index hit 38,915 yen at the close of 1989. Land prices in Tokyo had risen over 300% in just 6 years. Japanese corporations were awash in cash. Banks were giving out loans with almost no scrutiny. And the entire country felt invincible. It was, by any measure, one of the most spectacular economic booms any developed nation has ever produced. For the car manufacturers, this translated directly into engineering freedom. Research and development budgets grew to a scale that simply didn't exist anywhere else in the world at the time. The mandate from the boardrooms at Toyota, Nissan, Honda, and Mazda wasn't to build something cheap. It was to build something better than anything Europe or America had ever put on the road. And critically, their engineers had the budget to try absolutely anything. Honda developed an all-aluminum F1-inspired mid-engine supercar, the NSX, with actual input from Ayrton Senna on the handling. Nissan packed four-wheel steering in the R32 Skyline GTR alongside their Atessa ETS all-wheel drive system. Mitsubishi put active aerodynamics and all-wheel steering in the 3000 GT VR4. Even entry-level cars got insane treatment. Toyota put five valms per cylinder and individual throttle bodies into a Corolla variant that could rev to over 9,000 rpm. Ferrari didn't use that technology until years later. But the most fascinating and the most consequential engineering problem these companies were trying to solve was turbocharging. Because by the late 1980s, turbochargers were the weapon of choice for making power in a small displacement engine. But they came with a serious flaw, and Japan was determined to fix it. Before we talk about the solution, we need to understand the problem. A turbocharger works by using exhaust gases to spin a turbine, which in turn spins a compressor, which forces more air into the engine. More air, more fuel, more power. In theory, it's free energy. You're harvesting exhaust heat that would otherwise go to waste. The catch is response. The turbine needs exhaust pressure to spin up, and exhaust pressure builds with rpm. At low engine speeds, there's not enough exhaust flow to get the turbo spooled up quickly. Press the throttle from idle or low rpm, and you get nothing. Then suddenly, as the engine climbs through the rev range, boost arrives hard. That delay is turbo lag, and on a performance car, it means unpredictable power delivery exactly when you need to be most precise. Coming out of a corner, overtaking on a highway, or navigating a mountain pass. The engineering solution at the time was to use a smaller turbocharger. A small unit spins up faster because its turbine wheel has less mass to accelerate. Smaller turbo, faster spool, less lag. The problem is that a small turbo runs out of breath at high rpm. It simply can't flow enough air to maintain strong boost when the engine is demanding maximum airflow. So the power band gets narrow. You either have fast response with weak top-end power, or strong top-end power with sluggish response. Pick one. Japanese engineers in the late 1980s looked at that choice, and decided they didn't want to pick. They wanted both. The answer they came up with was sequential twin turbocharging, running two turbos of different sizes, one after the other, so each handled the part of the rev range it was optimally sized for. One small turbo for instant low rpm response, one larger turbo for high rpm power. The clever part was making the transition between them seamless, and that part was anything but simple. The first mass production application of sequential twin turbocharging in Japan came from Mazda, in a car they had no business making as good as they did. The FD RX-7, launched in Japan in 1991, was built around Mazda's rotary engine, the 13B-WEW. This was a 1.3 liter twin rotor Wankel, a displacement that sounds almost laughably small for a performance car. The rotary engine has its own story worth an entire video, but the relevant detail here is this. Wankel rotaries make their power at very high rpm. They need revs. And a large, slow-spooling turbocharger paired to a rotary is a terrible match. The engine sits at the bottom of its power band, waiting for the turbo to wake up, and when it finally does, the power arrives so suddenly that the car becomes dangerous. Mazda's engineers had been working on sequential turbo systems since the mid-1980s, first on the luxury Yunos Cosmo in 1990, and they carried that work directly into the FD. The 13B-WEW used two identically sized turbos in a sequential arrangement. At low rpm, all exhaust gas flowed into the primary turbocharger alone. That concentrated exhaust stream got the small primary turbo spinning quickly, generating boost from around 1800 to 2500 rpm, much earlier than any single conventional turbo could manage. As rpm climbed toward 4500, a valve opened and exhaust gases began diverting to the secondary turbo, spinning it up in the background. At full transition, both turbos ran together in parallel, pulling the engine through to its 8000 rpm redline. The result was an engine that delivered 255 horsepower from a 1.3 liter displacement, with a power curve that felt almost naturally aspirated in character. Linear, predictable, and eager at any throttle position. From the factory, the FD hit 60 mph in about 5 seconds, which put it in a class of cars with much larger engines. More importantly, it handled those corners and mountain passes the way a performance car should, because the power was there when you asked for it, not two seconds later. But making this work required extraordinary complexity. The vacuum system controlling the transition between the two turbos used 67 individual vacuum hoses, a tangle so dense that Mazda technicians called it the rat's nest. Every one of those hoses had to work perfectly. If even one cracked or stiffened from the intense heat generated in the rotary's engine bay, the sequential system misbehaved. The secondary turbo might not engage properly, the transition might be jerky, or boost control would go wrong entirely. When the FD was maintained properly, it was one of the greatest driver's cars of the decade. When it wasn't, owners faced some of the most frustrating and expensive repairs in the enthusiast car world. That tension, brilliant when right, nightmarish when wrong, would define the sequential twin turbo era across every Japanese manufacturer that embraced it. Toyota was watching what Mazda had done. They had their own sequential twin turbo system in development for their inline-6 engines, and in 1991, it debuted in the Aristo, Japan's luxury sedan sold as the Lexus GS in export markets. But it was in 1993, bolted to the 3.0 liter 2JZ block and dropped into the fourth generation Supra, that the system became legendary. The 2JZ GTE's sequential system worked on similar logic to Mazda's, but with a notably different approach to controlling the secondary turbine. Rather than using a valve upstream of the secondary turbine housing to divert exhaust, Toyota controlled the system from downstream, choking off the secondary turbo's exit with two valves until the right RPM was reached. Fewer vacuum lines, slightly simpler transition logic. Having developed their system after Mazda, Toyota had the advantage of learning from the 13B REW's complexity and engineering around some of its more common failure points. The factory output was listed at 280 PS, 276 horsepower. That was not a coincidence. In 1989, Japan's major automakers had agreed among themselves on a voluntary power ceiling of 280 PS for domestic market cars. The official reasoning was safety. The real reasoning was more complicated. It was partially a preemptive move to avoid government regulation of performance cars, and partially a competitive truce between manufacturers who could see the horsepower wars escalating toward numbers that would draw political attention. So every manufacturer making a flagship performance car in Japan in the 1990s, Nissan, Toyota, Mitsubishi, Subaru, all officially rated their engines at exactly 280 PS, regardless of actual output. Independent dyno tests of the A80 Supra consistently showed figures well above the claimed 280. Some cars produced 320 horsepower in stock trim. And the 2JZ engine block was so robust, over-engineered to a degree that Toyota's own engineers probably didn't fully anticipate, that with upgraded internals and a single large aftermarket turbocharger replacing the sequential twin setup, the same basic engine could make a thousand horsepower reliably. It is still, to this day, the tuner community's benchmark for what a platform can do when it was built without corners cut. But here's what gets overlooked in all the horsepower discussion. The sequential twin turbo system in the stock 2JZ-GTE was designed specifically for drivability. It was meant to give a heavy grand tour. The Supra weighed 3,400 pounds, the kind of tractable, accessible performance that a driver could use on public roads at legal speeds. The small primary turbo gave strong boost by 2,000 RPM. The large secondary extended that power smoothly to the redline. No sudden hit. No narrow power band. Just engine. All the time. This is where the forgotten technology part of the story comes in. Sequential twin turbocharging was an elegant engineering solution to a real problem. It genuinely worked. The 2JZ-GTE and 13B-REW are proof of that. But by the late 1990s, the industry was moving away from it, not because a better philosophical approach had been found, but because turbocharger technology itself had advanced to the point where sequential systems were no longer necessary to achieve the same result. The development that ended the sequential era was the Variable Geometry Turbocharger, or VGT. The concept had existed on paper since Garrett patented a variable-vane turbine in 1953, but the materials and manufacturing precision needed to make it reliable in a production car environment took decades to develop. By the mid-1990s, variable-nozzle turbines were appearing in European diesel applications. Fiat's Chroma diesel used one in 1991, and Peugeot and Volkswagen followed quickly. The VGT solved the fundamental turbosizing problem differently from the sequential approach. Instead of using two turbos, one small for low RPM, one large for high, a single turbo with variable vanes could effectively change its own geometry in real time. At low RPM, the vanes narrowed the exhaust passage, accelerating gas flow and spinning the turbine faster than it would naturally. At high RPM, the vanes opened fully to allow maximum flow without restriction. One turbo, full power band coverage, no complex transition logic, no rat's nest of vacuum hoses. For the sequential twin-turbo system, the numbers were damning. Two turbos, two sets of bearings, two wastegates, dozens of vacuum lines, complex solenoid-controlled transition valves, and the carefully tuned plumbing to make the transition smooth. All of that versus a single, more sophisticated turbocharger with a ring of adjustable vanes. The VGT was cheaper to manufacture, cheaper to maintain, more reliable, and applicable to virtually any engine configuration. Sequential turbos required bespoke engineering for each specific engine. VGTs were comparatively modular. When tuners started getting the A80 Supra and the FD RX-7 and immediately deleting the factory sequential twin setup in favor of a single large aftermarket turbo, they weren't doing it because sequential was philosophically wrong. They were doing it because the complexity wasn't worth it for their specific purpose, maximum power, and a single large turbo is simpler to tune and maintain. That same logic, scaled up to a factory engineering level, is what killed sequential twin turbocharging as a mainstream approach. The cars from Japan's golden era were born from an economic moment that will almost certainly never repeat. The bubble funded the research, the engineers built the machines, and then the money was gone before most of the world had even noticed what Japan had done. The sequential twin turbo defined that era's approach to performance. Complex, expensive, difficult to maintain, and uniquely suited to an engineering culture willing to put 67 vacuum hoses into an engine bay if that's what the power delivery required. Better technology eventually made it obsolete, but what doesn't get replaced is the result. The 2JZ-GTE is still being built into time attack and drag cars in 2025. The FD RX-7 commands prices that would have seemed insane in 1995. The R34 GTR sells for over $100,000 at auction, and the market isn't coming down. Japan answered the question of how good a car could be when budget didn't matter. It hasn't quite answered it the same way since. If you want more of this, subscribe, and drop a comment on which golden era engine you want covered next.