2015 Lexus RC F: Making It Louder With Office Supplies
June 4, 2015
One good thing about our long-term 2015 Lexus RC F? It gets loud.
Under heavy throttle load and around 3,600 rpm, the RC F's 5.0-liter V8 goes from its soft-spoken idle to a booming roar. This change is controlled by a vacuum-actuated flap on the passenger side of the airbox. Vacuum holds the flap shut until you cross that throttle load/engine speed threshold. When you do, the flap opens and broadcasts that wonderful intake sound all around the car. When the engine's off, you can move the flap with your fingers. This gave me an idea.
I once owned a late-90s BMW 3 Series that had a setup like the RC F's. Under similar conditions, a flap in the muffler would open up and play that sweet I-6 exhaust sound just a bit louder. My inner car guy asked, "Why isn't it louder all the time?" An online search revealed the Golf Tee Mod: Pull the vacuum line off and plug it with a golf tee. Apparently, BMW owners have more golf equipment lying around that vacuum caps.
The RC F? We couldn't find any golf tees here at the Edmunds office, but raiding the supplies closet netted a few plastic clips.
We pulled the vacuum line off, clipped it twice to avoid a leak, and fired the car up. As expected, the flap stayed open. The result? A hugely satisfying bark at low engine speeds.
Happy with our test, we returned everything back to normal. But I'll be stopping by a parts store soon for a vacuum cap.
Unless I find a golf tee first.
Carlos Lago, Road Test Editor @ 9,800 miles