Years ago now I came across the below clip on the internet. Many of you may have seen it in passing, and a lot of confusion was created at the time around what exactly was going on, and how the heck it was achieved.

In this article we’ll take a look at what’s known as the “ZeroLag” system in more detail.




How a conventional turbo setup and Anti-lag works…

In a conventional turbo setup, exhaust gasses exiting the engine are used to spin a turbine wheel, which connects to a compressor and generates positive pressure or “boost” inside the intake. This additional pressure means more oxygen is available to the engine and more oxygen means more power. The downside of this is that the turbo needs a constant high flow of exhaust gasses in order to maintain boost, so when the RPM drops so does the boost. The term “lag” refers to the time it takes for the turbo to spool up and begin to generate usable pressure inside the intake .

Conventional fire spitting Anti-lag systems use either Ignition Timing Delay, or a bypass valve along with a rich mixture to keep the turbo spinning. Both of these methods result in fuel being burnt in the exhaust manifold in order to maintain exhaust pressure and keep the turbo spooled. However both of these methods mean the engine is not running at its optimum combustion, which isn’t ideal.

So how does ZeroLag work?

As you can see in the video, the engine’s RPMs drop to idle, yet the turbo’s rotation is maintained at around 125,000RPM, producing peak boost the entire time, resulting in absolutely zero lag. Just like conventional Anti-lag systems, the turbo is being driven by maintaining exhaust pressure whilst the engine is not under load. however in this scenario, rather than altering the engine’s ignition timing or air/fuel ratios, external combustion is used. This means the engine can continue to run at its optimum the entire time. 


What is External Combustion?

External Combustion is pretty much exactly what it sounds like. Instead of the combustion process taking place inside the engine, a completely external combustion chamber, along with fuel, air and ignition source is added to the exhaust from the engine. This external system produces the exhaust gas flow required to keep the turbo spooled, much like a turbo-jet engine in fact. 

How to build a turbojet…

For the full story on this build including photos, head over to MotoIQ