Variable-length intake runners aren’t a particularly new concept, but Ferrari’s system in its LaFerrari is next-level fascinating. Let Engineering Explained give you the rundown.
You see variable intake runners in all sorts of cars; BMW has a system called DISA, Toyota has TVIS and Fiat Chrysler has its own Active Intake Manifold found in big V8 Chargers, Challenger and Grand Cherokees. But these systems usually just contain a valve that diverts air from a short to a long intake runner. Ferrari’s system is a bit different.
Its intake runners’ lengths are infinitely variable instead of restricted to just two sizes, and the runners get longer by “telescoping” instead of using flaps or valves.
Here’s a look at Ferrari’s Continuously Variable Length Intake Tracks in a Formula One Application:
The purpose of the system is to maximize both volumetric efficiency and to ensure proper air/fuel mixing. As Engineering Explained mentions, at low RPMs, funneling air through thin, long intake runners creates turbulent airflow, which facilitates better mixing with fuel, yielding more complete combustion and higher efficiency.
At higher RPMs, the engine needs lots of air, so the variable intake system reduces the length of the runners, decreasing the pressure drop across them, and allowing for improved flow to the cylinders.
Another factor that Engineering Explained mentions is a “light supercharging effect,” that can actually increase volumetric efficiency above 100 percent by regulating intake lengths to take advantage of pressure waves created by the intake air charge bouncing off the closed intake valve and inside the manifold.
It’s a fascinating system that doesn’t get nearly enough credit. I, for one, think Ferrari should put a nice CVLIT badge on their cars to tell the world of their engineering brilliance.