To a small but important selection of drivers, an engine’s redline speaks to the character of the car: it’s a look into its performance, the visualization of a promise of thrilling motoring powered by a hard-working engine, and a peek at the upper limits of the model’s pulling power and fun factor.
For years, Honda has been creating engines that deliver the latter: a signature blend of small-displacement fuel economy and high-revving performance.
I spoke to Honda’s Hayato Mori for a closer look at what goes into high-revving performance, and how Honda made high-revving little engines their specialty over the years.
JP: What does the redline represent? What does it mean?
HM: In simple terms, the redline is the maximum rotational speed possible from the engine’s crankshaft, pistons and valvetrain, without damaging the engine.
JP: How does an engineer calculate the redline for an engine in question? Is there a standard across all automakers?
HM: The only real standard for a redline is “at what RPM does it fall apart?” Each engine has different limits and tolerances, so engineers base the redline on the specific engine’s limits.
JP: What sort of factors contribute to an engine’s redline?
HM: Construction of the engine, and the materials used, will dictate the amount of friction, heat and vibration tolerance, which can, in turn, dictate how fast an engine can spin before it wants to come apart.
JP: Why do some engines rev higher than others? Are there benefits for the driver in making an engine with a higher redline? A lower one?
HM: All engines are developed with different goals, but it comes down to two things: Power and Efficiency. Spinning an engine faster, or force feeding more fuel and air with a turbocharger or supercharger, allows an engine to generate more power without resorting to larger displacements.
Of course, there are limits. For instance, higher RPM engines can make more power, but use more fuel. Lower revving engines can use less fuel, but give you less power. It’s always a trade off.