Exhaust sound and chiptuning

[dutchie01]

I learned something new yesterday. I guess most of us will know the irritating sound in today's hot hatches when the gearbox shifts to the next gear something between a firecracker and a gunshot. Loud anyway. Well, this can be added to your car by chip-tuning! ( provided you have a turbo) They even gave it names you can choose from ! Pops/Bangs/Crackle/Burble on overrun/ Schubblubbern. No idea what these are but if you are under 25 you will know.

Any interest?

[Linas.P]

Yes, that is fairly simple assuming you car ECU can be tuned, which isn't the case with most Lexus cars.

There are 3 basic reasons for this:

1. Oversaturated fuel mix - the pop and bangs happed naturally on old cars when you let off the gas, this would close throttle, but because old cars had carbs or very basic injection they would still deliver some fuel. In short bangs and pops are result of inefficient fuel delivery/delivering fuel after throttle is already closed. Turbo is absolutely not required, this could be achieved on any car by updating fuel maps and programming ECU to incorrectly deliver some fuel after you let off the gas pedal (basically waste it). If you car is diesel then you will get nice puff of black smoke as well 😁
2. Are race derived technology - so called "anti-lags", these do require turbo and actually have purpose on racing cars (to keep turbo on boost). Mostly on older turbo cars or cars with very large turbos there are loads of "lag" (the time it takes to spool-up the turbo), as such "anti-lag" system would dump the fuel on low throttle input to keep turbo spooling by literally dumping fuel and exploding it in turbo, but they would absolutely destroy factory turbo.
3. Again race technology called "2-step" launch system, this is basically secondary rev limiter which one could engage on start (usually in turbo car, but could be NA), this would be dialled in to RPM at which either engine delivers most torque or car grip limit is. So when you press the accelerator in 1st gear with clutch depressed, instead of going to say 7500RPM, the revs would stop at say 3500RPM - drop the clutch and car is in it's most powerful RPM already. It could as well be dialled for every gear if needed. And this sounds like machine gun firing. Overrun is pretty much same principle, just happens on actual rev limit.

I personally think, such tricks sounds cool, but they inherently shows that your car is running rich and inefficiently. The gases rich with fuel would go into hot exhaust (or turbo) then and explode resulting in pops bangs and crackles.

[rob_clio172]

I have my 2step launch control as Linas.P described set up to the right hand "down" tip tronic button on the steering wheel, I knew those buttons would come in handy after the manual swap.

[scudney]

Sorry to old for that sort of stuff lol,why bother?trying to look cool 😎 eh really,doesn't do the engine any good either 🤔

[rob_clio172]

10 minutes ago, scudney said:

Sorry to old for that sort of stuff lol,why bother?trying to look cool 😎 eh really,doesn't do the engine any good either 🤔

Oh yeh when it serves no purpose just farts and bangs on over run, 2step on the other hand can serve as a useful tool to spool up a huge Borg Warner turbo before taking off.

[scudney]

Just boys being boys and men being men i suppose lol 😆 

[Linas.P]

Sure it is silly when 1.1 Fiesta sounds like little cannon with anti-lag on the turbo which is the same size as peanut. 

But it is not like rally drivers are boys for having 2-spet or anti-lag, those have the purpose on properly built car, but the first one is just for fun. To be fair I liked pops and bangs more when I didn't know why and how they happen, now that I know it is no longer so fascinating 🙂

 

Actually on IS250 with "sort of 2-step" I was able to do ~7s 0-60, the "sort of" I mean is building some revs whilst holding the brake - say ~3500RPM, then at the same time releasing the brake and pressing accelerator all the way, this rev "boosting" for launch easily shaves off a second. The problem is that you can't hold the car on the brake for more than few seconds without hurting in too much. The difference is that 2-step does it for your consistently and every time - you just press the accelerator all the way and as soon as brake is released car is launches.