Here’s how Mazda goes about reducing turbo lag

Mazda hasn’t been shy about its dedication to the internal combustion engine. After all, the Japanese company will likely arrive first to market with a homogeneous charge compression ignition engine (HCCI), which will provide tremendous fuel economy improvements without the loss of performance.

But today we’re talking turbo lag, and how Mazda aims to reduce it. Jason Fenske of details how the automaker accomplishes just that. Specifically, Jason takes a look at the 2.5-liter turbocharged inline-4 found in the Mazda CX-9 and Mazda 6.

First and foremost is the exhaust manifold. It’s short, so the exhaust gas holds on to as much energy as possible as it travels through various pipes. The gas is, ultimately, heading to the turbocharger. The second part of the process to keep turbo lag at bay is the valve design. Jason says it’s similar to a variable geometry turbo, but the components are built into the exhaust manifold. Below 1,620 rpm, the valve closes and becomes more constrictive for the exhaust flow.

The process increases the velocity of airflow to spool up the turbocharger quickly, though it sacrifices efficiency. The engine also runs a 10.5:1 compression ratio to help make up for some lost efficiencies. Above 1,620 rpm, the valve opens up to allow for higher gas flow and the need to spool up the turbo more quickly isn’t as necessary.

Finally, the cylinder firing strategy and 4-3-1 exhaust help the process. In a 4-cylinder engine, the firing order performs as 1-3-4-2. Mazda chose to split the exhaust in a unique manner to maxmize scavenging. When the exhaust valve opens, peak pressure and energy occur. The process forces the exhaust gas out, but some gas remains at a lower pressure. A suction effect to pull out the remaining gas at the end of the stroke would be ideal, and that’s what Mazda has done.

Read also:
First look at new Opel design language, GT X Experimental concept

The cylinder next to the other (in this example its cylinder one beside cylinder two) creates the suction effect to pull out low-pressure exhaust gas. High pressure and low pressure are always beside each other to help one another evacuate the exhaust gases.

It’s complicated, so see the entire explanation in the video right up above.

Check Also

Isle of Man TT documentary captures the beauty and danger of the race

It's just a small rock in the middle of the Irish Sea, but for those who love motorcycle racing, the Isle of Man is an almost magical place. This is the home of the Snaefell Mountain Course, which is a twisting road circuit that unfolds over the course of 37.75 miles. The speeds are high, and the risks are higher. Many flock to this Manx mainstay to capture...

1955 Ferrari 500 Mondial Series II visits Jay Leno’s Garage before heading to Pebble Beach auction

Rear Admiral Robert Phillips has owned his 1955 Ferrari 500 Mondial Series II for 58 years. That means he has owned a racing Ferrari longer than anyone. That's set to change as Admiral Phillips' car is heading to auction during Monterey Car Week. Before it gets there, the Admiral brought the car over to Jay Leno's Garage to tell us all about why it's such a...