Why Do So Many Cars Crackle, Pop And Bang Past My House At 3am?


We’ve all heard it at this stage. Someone with an already obnoxiously loud car drives past and a series of bangs (rival gunshots) shoot out the exhaust along with the putrid stench of unburnt fuel. It’s 3am and suddenly all of the dogs and children in the neighbourhood are awake and screaming again and all because some twit doesn’t have the decency of having a civilised vehicle.

So is there a point to this madness or is it just angry teenagers with a hatred of all things decent?

These ‘pops and crackles’ tunes come from a very strange place in automotive history and were originally call a backfiring system (or anti-lag).

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As long as cars have been around, enthusiasts and racers have tried tuning their cars for the most power possible. From the early days of hot-rodding and racing, it has actually always been fairly common for a little puff of flame and a small burble come from the exhaust when properly fast cars take their foot off the throttle.

These little spirited pops changed drastically in the 1980’s and 1990’s as turbochargers began to become popular amongst racing teams (in particular in rallying).


Rallying is, for all intensive purposes, a sport for maniacs. Two people clamber into a tiny car with a tiny, high powered engine and try to drive through backroads, farmland, mountains and more to beat a fastest time from one end to the other (the same way people try to drive to work in Sydney).

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These cars were often differentiated by their engine size which meant that any way to squeeze more power from the engine was a welcome advantage over the other teams. This made turbochargers and rallying a perfect fit.

A turbocharger uses exhaust gas from the engine to spin a turbine wheel that in turn forces additional air into the engine which means that more fuel can be burnt on each revolution in turn making more power. The only downside to a turbo is a thing called lag.

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When taking off from a start or reapplying the throttle after slowing down, the turbo takes a few seconds to react, creating a lag between what you want the car to do and when it happens. While a lot of skilled drivers can overcome this problem, losing seconds per corner waiting for the turbo to work doesn't agree with the whole ethos of racing cars at all.

This is where we (finally) get to talk about anti-lag.


Because of the massive lose in drivability caused by these early turbochargers, teams began experimenting with way to keep the turbo wound up even when off of the throttle. By injecting a small amount of fuel while the throttle was closed and making sure it was late in the cycle, teams could force fuel to burn in the exhaust, which maintained the turbo’s speed while also creating a large bang from the exhaust (a backfire).

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Much the same way as todays hooligans, these systems were often obnoxiously loud and rattled off through the forests where rallies were held but, they were specifically used for racing. In fact even though it was a way to create more power more often, having fuel burn in the exhaust often reduced the life of the turbo and could even cause damage to the engine if done poorly.

The cars that we see today banging and farting up the street are really just paying homage to the original source material. And while we do support the idea of a few good burbles here and there, many of the backfiring cars today are kind of taking it over the top to a point that will probably do long term damage to their cars, sanity and eardrums.

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So should you get out there and yell back at them in the middle of the night until they stop tearing up your neighbourhood?

We honestly wouldn’t bother. Most people are acutely aware of how loud their car is and are already trying to be polite about it. Additionally, most people are just trying to make their car a little bit more like the old racing and rally cars they love and, once the tune is on the car it’s difficult and expensive to get off again.


 

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