As I was reading the 500 Abarth autocross thread, and after remembering what they sounded like in person, I have always kind of wondered....
If you wanted to replicate that type of sound ( "mini Ferrari", etc... ) on a different car, what factors would be involved ? and how would you do it ?
My thinking is that it's a combination of things:
--partly exhaust (pipe lengths, soundwave reflections, resonators or no resonators, cats, surely some degree of acoustical research was budgeted for by the manufacturers)
--perhaps partly something to do with the engine configuration and it's tuning ? as in, maybe the ECU mapping on those cars actually has something built-in to monkey with the ignition timing, valve timing, and mixture to purposely create little tastefully musical pops and burbles when you lift off the throttle, not for any performance reasons but specifically engineered to sound the way it does, for the driver's enjoyment ...
Has anyone here with exhaust building skills ever attempted to take their existing "non-Ferrari" (I know not all of them sound that way, but...) and experiment with different pieces, lengths, dimensions, to replicate that type of sound ?
just wondering, since I don't yet have the means to experiment with these things just yet.
grazie !
some examples for fun:
Jag F-Type
A run-of-the-mill Ferrari
The pops and burbles are done by the ECU. In an unrestricted exhaust they occur naturally, but many ECUs dump pulses of fuel into the exhaust on purpose to create them artificially. I know for a fact that the F-type does this.
Retarded ignition timing at closed throttle and a little fuel into the exhaust can definitely produce some nice cracks and pops.
ah, very interesting. that is what I kind of suspected.
I recall a past car of mine did something like this when it was once tuned a little rich and had a possible air leak upstream in the exhaust.
The way I figure it, much like styling, the Italians just know how to make a car sound good...Even 4's and turbo-4's. It's something in their DNA, that the Americans (among others) just don't have. Because if even for all their engineering might Ford was entirely unable to figure it out for the Ecoboost Mustang, then I doubt I would have the resources to do much better. 
as much as I can appreciate a car's performance and cold hard technology, the sound sure can connect with the emotions.
I wonder if the other manufacturers just aren't concerned with that aspect ? or maybe it's the first thing to go when production cost enters the picture ? ("eh, there's aftermarket support, let them buy what we make and then customize it on their own...").
Or, maybe the actual target buyers don't seem to care ? who knows I guess :P
I can see a huge market for this type of add-on as cars continue to become more computerized.
like downloadable ringtones for your car.
And for those quiet electric vehicles, that need to make more noise on the outside (to alert pedestrians),
I will be first in line to get the Jetson's sound ;D
How entertaining would that be ! honestly ?
https://www.youtube.com/watch?v=4NgSZ8sjDgU
I want a Tesla that sounds like a TIE Fighter.
I like where this is going !
muffler's do a pretty good job of... well... muffling the off-throttle burbles. I know on my 5.4 5 speed f250 with the muffler on it it would never burble when off throttle in gear, but after i removed the muffler (so basically a straight pipe with the cat still in it) it gets a good burble and popping when off throttle. Same story with my 1.8t audi a4 that had a cutout, with it closed no burble, with it open lots of shotgun pops and burble for full race car effect.
with a little tuning and a decent flowing muffler im sure you could make it happen to just about any car
Glasspack or other "straight through" muffler, a branch resonator* or two to handle any drone issues. On a V8 car you'll want a flat plane crankshaft or 180 degree headers (gives the same exhaust order as a flat plane crank would) to sound really "Italian". Camshaft choice and compression ratio also play a role, but I don't know much about it beyond more is usually better.
This is a F type muffler. This SAE article goes into some detail on how they made the car sound the way it does.
Ignoring all the quiet mode stuff, you'll see this is more or less just a pair of blown out glasspacks and a couple kinda sophisticated branch resonators right at the tailpipe.
* A dead end pipe Teed into the exhaust pipe, length tuned to 1/4 the wavelength of your drone frequency so the exhaust pulses go in, bounce off the end, and get injected back into the stream 180 degrees out of phase, canceling the drone.
cool article.
I knew that there was some attention paid to keeping it from droning (like a regular big pipe all the way back might).
And it always seemed to me, that on these cars with the nicely tailored crackly exhaust, they weren't always just loud...
it's like they were crackly, but with a somewhat controlled volume,
and as you mentioned, minus the drone (cancelling out those lower frequencies).
