Snap, Crackle and Pop

‘Crackle maps’, ‘Pop and bang maps’, call them what you will, they’re mega pop­u­lar. But are they safe? Fast Car in­ves­ti­gates…

Fast Car - - Ed Speak - www.motorsport-devel­op­

We in­ves­ti­gate the noisy world of ‘Pop & Bang’ remaps. Are they a good idea? Find out here…

Pops, bangs and flames; ev­ery­one likes that, don’t they? Well, hell yes you do, and be­cause of this, ECU remaps that make your ex­haust pop, bang, and kick flames from the tailpipe when you lift off the throt­tle are hugely pop­u­lar these days. But how do they work? And, more to the point, are they bad for your engine’s health? Well, un­less you’ve been liv­ing in a cave for the last few years, we’re sure you’ve heard loads of com­ments both good and bad; it’s time for a Fast Car in­ves­ti­ga­tion into the mat­ter, so we can find out the truth for you guys.

As this is a bit of a con­tro­ver­sial sub­ject in the tun­ing scene at the mo­ment, a lot of com­pa­nies, un­der­stand­ably, de­clined to get in­volved. But thank­fully, the guys at Motorsport Devel­op­ments (­tor­sport­de­vel­op­ are ex­perts when it comes to remap­ping all fac­tory ECUs, and were more than happy to give us their words of wis­dom and help con­firm our find­ings on this sub­ject – so a huge thanks to them. They’re cer­tainly the guys to speak to if you want a safe, but ef­fec­tive map your­self!

The ex­hausts of heav­ily-tuned cars have nat­u­rally popped, banged and flamed since the dawn of time, but have you no­ticed lately, a lot more cars than ever be­fore have been pop­ping and bang­ing from the ex­haust when the driver lets off the gas? Mildly-tuned mo­tors and even quite a few fac­tory pro­duc­tion cars now have a cool bur­bling ex­haust on the over­run.

This is be­cause lots of tuners and man­u­fac­tur­ers have re­alised that own­ers love these kinds of noises. And with mod­ern engine man­age­ment be­ing so damn ca­pa­ble, it means that they are now com­monly mapped into the car’s ECU tune.

How does it make the pops and bangs?

For this bit, let’s start with the ex­pert words of main man Ste­wart San­der­son from Motorsport Devel­op­ments…

“Pops and bangs, or bur­bles as the OEM call it (yes, it’s that com­mon on pro­duc­tion cars that even the man­u­fac­tur­ers have a name for it!), is sim­ply a cal­i­bra­tion fea­ture within the ECU where 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, re­mov­ing all en­ergy from your engine, al­low­ing it to slow down: this is smooth, quiet, and safe, act­ing and sound­ing like all the sen­si­ble ‘nor­mal’ cars we’re used to. No pops, no flames, no noth­ing. Back to Stu’s words of wis­dom… “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 which 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 with the ex­haust valves open (in fact within the ex­haust sys­tem), and much of the fuel is ig­nited by the hot ex­haust and/or cat­alytic con­verter, hence the bur­bles, pops and crack­les you hear from your tailpipe.

“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 even seen peo­ple go so far as open­ing the idle speed con­trol valve or open­ing the drive-by-wire throt­tle a lit­tle for more air too. In fact, these mod­i­fi­ca­tions (al­beit with more ex­treme set­tings and for more than just a few sec­onds at a time), are ac­tu­ally 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 it be done 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 – nor­mally as­pi­rated, su­per­charged, or tur­bocharged – any­thing that has an ECU with which the fuel and ig­ni­tion set­tings can be heav­ily mod­i­fied, which these days means most of them.

Some cars can have their ig­ni­tion re­tarded fur­ther still, and al­low the abil­ity to open the idle valve or open the throt­tle a lit­tle, all of which can pro­vide more ex­treme pops and bangs, if that’s what you want. So, 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.

Does it have any per­for­mance ad­van­tage?

No. This is done purely for the noises. As it works in a sim­i­lar manor to rally anti-lag sys­tems, re­ally ex­treme set-ups could, in the­ory, work like a mild anti-lag sys­tem on a tur­bocharged engine, help­ing 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, and it’s done 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, not a crackle map!

Does it cause any re­li­a­bil­ity prob­lems?

This is by far the most con­tro­ver­sial part of this sub­ject, and while the an­swer is some­times yes, pro­vid­ing your map has been done by some­one who knows what they’re do­ing, it’s highly un­likely to cause any real is­sues. Any po­ten­tial re­li­a­bil­ity is­sues will come from the same thing that gave per­for­mance remap­ping (or chip­ping as it was known a decade or two ago) 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 (be it for pure per­for­mance or for pops and bangs) be­ing done in an un­safe man­ner – 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.

More than just the cat can be dam­aged, though, if the pops and bangs remap is too ex­treme for what your engine can han­dle. 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.

BUT what are the chances of ac­tual engine in­ter­nal dam­age with one of these maps? Well, 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. In re­al­ity, we’ve yet to find a sin­gle case where engine 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. But 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.


Some peo­ple love these 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, rather than full-on WW3 in your ex­haust.

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, so don’t just go for some­one who prom­ises the cra­zi­est, loud­est fire­works dis­play from your ex­haust – that’s just ask­ing for trou­ble.

Cheers to…

The guys at Mo­tor­port Devel­op­ments for all of the info and ad­vice.

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