We all know that BMW, as well as most other automakers, are switching from larger naturally-aspirate engines to smaller displacement turbocharged engines, in nearly all of its vehicles. The reasoning behind the switch is efficiency, as turbocharged engines offer far better fuel economy and better emissions that naturally-aspirated engines. Turbocharging also allows for more power out of smaller engines, in turn making cars faster buy bumping power and reducing weight. So there are some serious benefits to adding gas-driven snails to smaller engines. But there are several drawbacks as well.
Lag was always the number one complaint about turbocharged engines. If you’ve ever driven an ’80s or ’90s turbocharged performance car, you’d know that you stop the throttle and the engine does nothing for a second or two as it waits for the turbo to spool up. This turbo lag is the primary reason why so many performance car makers put off using turbocharging until the absolute last minute, when governments stepped in. But lag isn’t really a big issue anymore, as automakers, BMW especially, have figured out how to virtually eliminate turbo lag. Stomp the throttle in an F80 BMW M3 and it will immediately rip its rear tires to bits with a tidal wave of boost-powered torque.
Another big complaint about turbocharging is the way the engine feels, in comparison to free-breathing engines. With a naturally-aspirated engine, the powerband is more linear, meaning power increases in a smooth upward fashion as the revs rise all the way to redline. Whereas in a turbocharged car, power is a bit flat, even in the most lag-free cars, early on in the rev-range until boost kicks in. Once full boost is in, the torque curve becomes high and broad until it drops off a couple thousand revs before redline. So turbocharged engines have a nice meaty mid-range, while naturally-aspirated engines have a smooth linear powerband that’s easier to control.
But the biggest complaint about turbocharged engines is the noise. We can live with the minute amount of lag in turbo’d performance cars nowadays, as the car is usually in its mid-range while driving along anyway, and we can live with the power dropping off slightly before redline, as most people generally don’t take their engine to redline much. But turbocharged engines simply do not sound as good as free-breathing ones and that’s an absolute fact.
Now, some automakers have been able to work some magic and makes some good sounding turbo-powered cars, but it’s fake exhaust trickery that makes this happen. There’s something about the way a naturally-aspirated engine, specifically a BMW Inline-Six, revving all the way to its peak sounds that even the best sound turbocharged cars cannot match. There’s a snarl and a wail at the top end that sends shivers down your spine that exhaust gas-sucking turbochargers will never be able to replicate.
Unless you’re putting bread on your table with pink slips, power and performance are not the ultimate metrics for performance cars. The way they feel is the true metric. And hearing a snarling BMW I6 or wailing Porsche flat-six scream their way to redline is something that makes owning a performance car worth it. That’s what I’ll miss the most when turbos fully take over. What about you?