How BAM BAM makes cars faster

If you've seen the LATEST EPISODE (get your BAM and also more BAM here) then you'll see the box of wonder, sparks and flames the boys fitted to MOOG's museum-spec 180SX. But, why do people froth on cars banging out the exhaust and popping flames? Basically, it all goes back to motorsport from 40 years ago...

The wondrous, flame-belching technology referred to as BAM BAM is actually colloquially known as anti-lag, and came from top-shelf Formula One, sports car, and World Rally Championship motorsport.

In the 1980s, back in the early days of turbocharged race cars, engines typically had low compression ratios so they could handle the boost pressure the old school journal bearing turbos would deliver (normally in one big hit). The ECUs which ran these engines were in their infancy, with very basic control of spark and fuel maps, so the combined result of all of these factors were very laggy engines when not running in the narrow RPM window where they had full boost.

Some rally classes also had to run restrictors in their intake manifolds, which caused a pressure drop at the restrictor. This meant the turbos needed to spin faster to make the same boost level in the engine as an unrestricted engine, so race teams turned to anti-lag as a way of keeping the turbo spinning fast and making all the boost needed.

So how does a turbo make the BAM BAM? Early anti-lag systems typically used modified ignition timing and enriched fuel loads to keep the turbo spinning when the throttle was closed, though the heat associated with this was brutally hard on exhaust valves and turbochargers. So where do the the flames you see come from? That is unburned fuel/air mix being ignited in the hot exhaust 

Subsequent systems used throttle bypass techniques to keep the turbo spinning while the throttle was shut, while aftermarket stand-alone ECUs of the last 15 or-so years have offered their own style of anti-lag. Retarding the ignition timing and adding extra fuel, the ECU basically ignites the air/fuel mixture much later than normal, so it partly blows out the exhaust port and keeps the turbine spinning. This style of anti-lag is more used to build boost off the line to assist launching, rather than keeping the turbo spinning when the throttle blade snaps shut.

Anti-lag systems were designed for use in high-end motorsport, so there weren't ever strong consideration for how hard anti-lag is on engine parts. This technology was used in motorsport where engines were replaced as often as the driver's underpants (and in this mega-powered days that was very common). 

In recent years the trend of having "anti-lag battles" and the rise of social media has seen new interest making cars pop, bang and blow flames. Outside of using anti-lag to launch a car at the drags, all the flame-blowing and BAM BAM is just for show... which is rad if that is your thing. Some people like skids, some people like drifting, and some people like making popbangs.