‘Crackle maps’, ‘Pop and bang maps’, call them what you will, they’re mega popular when it comes to car tuning. But are they safe and should you get one? Fast Car investigates…
Pops, bangs and flames; everyone likes that, don’t they? Well, hell yes you do. As a result, ECU remaps that make your exhaust pop, bang, and flame when you lift off the throttle are popular. But how do pop and bang tunes work? More to the point, are they bad for your engine’s health? Unless you’ve been living in a cave for the last few years, we’re sure you’ve heard mixed reviews. This guide will aim to answer all those questions.
As this is a slightly controversial subject, some companies declined to get involved. But thankfully, Motorsport Developments are experts when it comes to remapping all factory ECUs, and gave us their words of wisdom. A huge thanks to them. They’re certainly the guys to speak to if you want a safe, but effective map yourself!
What are pop and bang maps?
The exhausts of heavily-tuned cars have naturally popped, banged and flamed since the dawn of time. Have you noticed lately, more cars have been popping and banging from the exhaust when the driver lets off the gas? Mildly-tuned motors and factory production cars now have a cool burbling exhaust on the overrun.
This is because lots of tuners and manufacturers have realized that owners love these kinds of noises. With modern engine management being so capable, it means they are now commonly mapped into the car’s ECU.
How does it make the pop and bangs?
For this bit, let’s start with the expert words of main man Stewart Sanderson from Motorsport Developments.
“Pops and bang maps, or burbles, is simply a calibration feature within the ECU. We set up a specifically targeted, very lean misfire once you lift off the throttle.”
Normally on an engine when you close the throttle, your fuel injectors don’t fire at all. This removes all the energy from your engine, allowing it to slow down. This process is smooth, quiet, and safe. No pops, no flames, no nothing.
Back to Stu’s: “If we want to create a burbling sound while the engine slows down, we need fuel. But, burning fuel will create some piston load too, slowing the rate the engine will decelerate on the overrun. So we need to move the energy away somehow to prevent that,” he explains. “To do this we need to do two things: retard the ignition timing to reducing the torque. This allows the car to decelerate normally, and run a very lean air/fuel ratio so too much heat isn’t created, which could affect reliability.”
The heavily retarded ignition also means much of the combustion happens within the exhaust system. The fuel is ignited by the hot exhaust or catalytic converter, hence the pops and crackles you hear from your tailpipe.
What about loud pops and bangs?
“The intensity of the burbles on these set-ups varies depending on the exhaust temperature; how hard the car’s been used. The hotter the exhaust system is, the easier this tiny amount of fuel we add flashes off,” Stu explains.
But what if you don’t want subtle OEM-style burbles and fancy something crazier? Well, the methods are similar to the above, but with a little more fuel added and even more ignition retard. We’ve seen people open the idle speed control valve or opening the drive-by-wire throttle a little for more air too. In fact, these modifications are the basis of how anti-lag systems work on rally cars. But this isn’t a performance mod, this is purely to create cool noises and flames!
Can crackle maps be applied to any engine?
In a word, no. But it can be done to a hell of a lot more engines today than ever before. In theory, it can be done to any petrol engine. Whether that’s normally aspirated, supercharged, or turbocharged. Anything that has an ECU with which the fuel and ignition settings can be heavily modified.
Some cars can have their ignition retarded further still. They allow the ability to open the idle valve or open the throttle a little. This can can provide more extreme pops and bangs, if that’s what you want. Providing you can find a tuner capable of adjusting your ECU to suit. The vast majority of engines can have this applied to some extent at least.
Do pop and bang maps have any performance advantage?
No. This is done purely for the noises. As it works in a similar manner to rally anti-lag systems, really extreme set-ups could work like a mild anti-lag system on a turbocharged engine. This would help keep your turbo up to speed. But in reality, the pops, bangs and burbles usually happen only for a few seconds after you let-off the gas; purely for the sound. If you were able to set it to such an extreme level that it had a true anti-lag function, you’d be calling it anti-lag.
Are pop and bang maps safe?
This is by far the most controversial part of this subject. While the answer is sometimes yes, providing your map has been done by someone reliable, it’s highly unlikely to cause issues. Any reliability issues will come from the same thing that gave performance remapping a bad reputation; people doing it badly.
OEMs have ECU tunes that include ‘burbles’ that are reliable and designed to last 100,000+ miles of hard use. Reliability issues stem from a remap being done in an unsafe manner. Usually, they’re too extreme for what the engine can handle, and therefore doing damage.
“We offer more extreme versions of the pops and burbles, but because this requires adding more fuel, you can only have it with a catalyst-free exhaust. There is only so much fuel you can burn off before you poison the catalyst. If it smells of sulphur, it’s dying,” says Stu.
Do pops and bangs damage your engine?
Extreme heat from richer mixtures and heavily retarded ignitions can cause extreme exhaust gas temperatures, which even with a de-cat could possibly damage lambda sensors, exhaust systems, and potentially more.
What are the chances of engine internal damage with one of these maps? If you look at the internet, every man and his pet monkey has a story about a friend of a friend whose uncle has damaged an engine due to this. We’ve yet to find a case where internal damage was definitely proven to be caused by the pops and bangs mapped in to the ECU.
Certain engines have relatively weak exhaust valves – Renault F4Rs, for example, and these maps have been blamed for damaging them quite a few times. Hard used versions of these engines often end up with the same valve damage, regardless of the map, so it’s still speculation rather than proof.
Again, speaking to the guys at Motorsport Developments, Kenny has seen cars come in to their shop with quite extreme ‘crackle map’ tunes done elsewhere, with 30-degrees of ignition retard and quite rich fuelling. This is verging on the settings you’d use on an anti-lag system, albeit only happening for a few seconds at a time on a map like this. This certainly isn’t something they’d recommend on a typical engine, and would cause really high EGTs during the ‘crackle’ period. It, therefore, has more potential for damage to be caused. But still, they’ve never personally seen engine internals damaged from this.
Should you get a pop and bang map?
Some people love pop and bang maps, while others hate them as they feel they create ‘fake’ noise. But if you want one, there’s no reason to believe your engine will be destroyed if you do things correctly. There’s still a lot of debate about this, but try as we might, we’ve seen no proof at all.
This is the important bit though – you need to ensure you have the right set-up for your engine. Do you have a cat, or an engine with a known weak point in the exhaust system or exhaust valves? If so, you’d be advised to keep it to a sensible, almost OEM-style burble.
But regardless of your set-up, choose your tuner wisely. Find someone who will ensure it’s reliable and safe for your particular set-up and chosen use. Pops and bangs are fun, but an engine that isn’t broken is even more fun. Don’t just go for someone who promises the craziest, loudest fireworks display from your exhaust – that’s just asking for trouble.
Words: Stav. Thanks to: Motorport Developments for all of the info and advice.
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