One is a required amount. The other is the delay of a desired amount.
There’s a big difference between knowing the stats of every high-performance car out there, and knowing the mechanical hardware and processes, such as turbos and direct fuel injection, that create those stratospheric output numbers. Being a passionate car nut isn’t the same as being an engineer well-versed in the operations of complex automotive systems. That’s OK. Professionals such as Jason Fenske of Engineering Explained are here to help.
According to Fenske, many people often get the terms “boost threshold” and “turbo lag” confused with one another. It turns out they’re wildly different. Regarding boost threshold, Fenske says, “So this is the engine speed at which you have sufficient exhaust gas flow in order to create boost, boost of course being when your intake manifold pressure is above atmospheric pressure.” The higher your rpms and the more your pistons move, the more exhaust gases they create, which in turn spool up the turbo. If your engine isn’t operating at a fast enough speed, it’s starving the turbo of the fuel it needs to help your engine generate more power.
Fenske goes on to explain the infamous concept of turbo lag, stating, “This is the time delay above boost threshold when you are operating at an RPM high enough that you can create boost — the time delay between when you open up the throttle from closed to when you actually start to receive boost.”
Both types of occurrences can trick you into thinking your engine is snoozing when you want it to shoot you down the road. Fenske says, “If you are operating an engine, you know, in this lower RPM where you aren’t above the boost threshold and you floor it, you may think, ‘OK, I’ve got this enormous amount of turbo lag because it takes until 4,000 rpm,’ when, in reality, you just don’t have enough gas flow in order to spool that turbo up.”
So the next time you’re winding up your Porsche 911 Turbo or Bugatti Veyron, keep this lesson in mind. It might bring you closer to your car and make you understand it more.
Derek Shiekhi's father raised him on cars. As a boy, Derek accompanied his dad as he bought classics such as post-WWII GM trucks and early Ford Mustang convertibles.
After loving cars for years and getting a bachelor's degree in Business Management, Derek decided to get an associate degree in journalism. His networking put him in contact with the editor of the Austin-American Statesman newspaper, who hired him to write freelance about automotive culture and events in Austin, Texas in 2013. One particular story led to him getting a certificate for learning the foundations of road racing.
While watching TV with his parents one fateful evening, he saw a commercial that changed his life. In it, Jeep touted the Wrangler as the Texas Auto Writers Association's "SUV of Texas." Derek knew he had to join the organization if he was going to advance as an automotive writer. He joined the Texas Auto Writers Association (TAWA) in 2014 and was fortunate to meet several nice people who connected him to the representatives of several automakers and the people who could give him access to press vehicles (the first one he ever got the keys to was a Lexus LX 570). He's now a regular at TAWA's two main events: the Texas Auto Roundup in the spring and the Texas Truck Rodeo in the fall.
Over the past several years, Derek has learned how to drive off-road in various four-wheel-drive SUVs (he even camped out for two nights in a Land Rover), and driven around various tracks in hot hatches, muscle cars, and exotics. Several of his pieces, including his article about the 2015 Ford F-150 being crowned TAWA's 2014 "Truck of Texas" and his review of the Alfa Romeo 4C Spider, have won awards in TAWA's annual Excellence in Craft Competition. Last year, his JK Forum profile of Wagonmaster, a business that restores Jeep Wagoneers, won prizes in TAWA’s signature writing contest and its pickup- and SUV-focused Texas Truck Invitational.
