How do engines get their sound?

[Deleted member 37751]

Was at a meeting this morning and got chatting to what turned out to be another petrolhead who's just bought a brand new M4. He loves the car but the sound that emits from the exhaust is actually quite offensive and it's starting to take the gloss off the ownership quite quickly for him.

So it got us wondering, how do car manufacturers make an engine sound good? Some are famous for consistently making great soundtracks (Mercedes/Jaguar/Maserati), whereas others just don't seem to get it right (BMW/Audi). And yes there will be exceptions to the rule, but is it just a case of certain manufacturers don't put it high on their priorities?

 

[moonloops]

1.Petrol
2.Oxygen
3. Cylinder layout I4 F4 V5 I6 V6 V8 V10 V12 W......etc
4. Exhaust manifold length(s)
5. Post cat(s) exhaust flow and silencer levels
6. Proximity of accelerator pedal to carpet
7. The local environment e.g. giving it welly through a tunnel or the local high street

 

[MancMike]

It has to be thought about from the very beginning, and maybe BMW are designing a powerful engine, then handing it over to the "exhaust guys", "here, make that sound good".

Those doing it right, AMG for one, must have the final sound as a priority throughout engine design.

You can tell, as even those changing manifolds, down pipes, and other exhaust components to aftermarket ones, generally only makes it louder, it still has the characteristic AMG growl low down and snarl up high.

 

[PobodY]

1.Petrol
2.Oxygen
3. Cylinder layout I4 F4 V5 I6 V6 V8 V10 V12 W......etc
4. Exhaust manifold length(s)
5. Post cat(s) exhaust flow and silencer levels
6. Proximity of accelerator pedal to carpet
7. The local environment e.g. giving it welly through a tunnel or the local high street

I'd add turbo/supercharger in there, but otherwise that's pretty close to what I was going to say.

Some manufacturers (McLaren comes immediately to mind) actually devote time to tuning the engine and exhaust note to get it just right. - I think BMW take the opinion that you make the exhaust as quiet as you can, then pipe in noise to keep the customer happy.

I wish my CLK was a little more "growly". - I quite like the V6 sound (admittedly not as nice as the V8), but I'd like more of it when I plant my foot.

 

[KillerHERTZ]

All done on computer these days, check out Chris Harris's video on the AMG GT the engineers calculated the sounds using bespoke software

 

[Deleted member 113659]

I was told that the raw sound of the TVR's was just a reasult of the package and not a manufactured noise. Love the rumble of those cars.

 

[developer]

Fuel air explosion makes noise, silencer reduces noise.

It's all about what level of silencing the manufacturer wants.

 

[The _Don]

How do engines get their sound -

When perfection is achieved M156 ;0))

 

[Bobby Dazzler]

There are many factors which influence the sound of an engine, much of which can be tuned, but at it's heart the sound is influenced by how many times the engine fires for each revolution of the crank (ie how often there's a bang), and the firing sequence (ie the order in which cylinders produce bangs).

Thinking of V8s specifically as that's what's fitted to some of the best sounding Mercedes/AMGs. They have a cross plane crank which makes it growl and burble, like an old-school American V8. Ferrari's sound completely different as they have a flat plane crank, which gives them a wail or shriek.

The M156 6.2 AMG is a marvel because it can growl down low, and hit the high notes too (for a cross plane), it has a remarkable vocal range.

 

[rockits]

I would be very interested to know how/where engines get their characteristics from. There are some truly great engine noises. AMG have quite a few. The SL60 I had sounded good & the E55K & SL55 another step up. Deep & bassy.

The E60 M5 I had....what a noise. That banshee screaming/howling V10 was one of my favourites. Had a bit of low breaking into mid finishing at the top end howl....awesome.

The Ferrari F36 engine in my 4200 now that also is a peach. I have it secondary decatted with rear box delete with straight through rears....now that sounds epic too....oh & very loud!

All of these are all mechanical & no fake electronic gimmitry on these. We are starting to lose this with so many smaller turbo engines. Boxsters with 2.0 turbos....really....how very dare you.

The Scooby boxer, Porsche flat 6....there are so many characterful engines....even the tranverse Yamaha V8 in my XC90 sounds pretty good but different & full of unique character I've not heard anywhere else.

We must fight not to lose them forever

 

[rockits]

I was told that the raw sound of the TVR's was just a reasult of the package and not a manufactured noise. Love the rumble of those cars.

The Speed6 in the TVR Tuscan I drove the other week.....awesome. So raw, so natural and organic. Awesome car.

 

[PobodY]

Ironically that characteristic sound of a Scooby flat-four is due to unequal length headers; when you fit performance manifolds they don't burble nearly as much... but they do make more power on boost.

 

[brucemillar]

Once an engine is built then the sound can only really be altered in two ways.

1) The most obvious and cheapest. The exhaust design and materials used.

2) Adding bits to the engine, superchargers, bigger turbo's, cams etc.

Some manufacturers consider sound to be at the heart of the driving experience. They will spend a huge amount of R&D to get that sound.

Others see it as by product of their engine and will spend what is required to get it to meet country legislation.

 

[Lotiman]

On the subject of engine noise, I was driving home on the 50 mph restricted section of the motorway during the week, minding my own business, when I started to hear a low pitched growl that was steadily increasing in volume. I looked in the mirrors to see a lovely highly polished black MB approaching slowly in the outside lane from behind. As he slowly came past, I saw it was a beautifully kept AMG CL600 V12, so I quickly wound down my window to hear an exhaust note to die for emanating from the 4 big chrome tipped exhausts.

I remember Clarkson commenting many years ago that his AMG SLK55 sounded like a Supermarine Spitfire engine, but this CL really did sound that good. Even though we were both doing only c.50mph, it was still a lovely exhaust note with an almost menacing 'Don't f*** with me' character to it. I would love to have heard him open it up but, unfortunately, I had to leave the motorway before we were back up to the national speed limit.

If Beelzebub drove a car, this CL would be it!

 

[TheFoX]

And there was me thinking that modern cars are completely silent, and that the sound the car makes is from 6 hidden woofers underneath the vehicle.

 

[PobodY]

And there was me thinking that modern cars are completely silent, and that the sound the car makes is from 6 hidden woofers underneath the vehicle.

That's just for hybrids isn't it?

 

[leef44]

I was told that the raw sound of the TVR's was just a reasult of the package and not a manufactured noise. Love the rumble of those cars.

This is true. TVR do not have the funds to develop sounds for exhaust. In fact, they didn't even have the funds to tune the chassis/suspension set up. They use the customer as the development tool for feedback.

So how come TVR can make a good sounding exhaust without significant development, while modern car manufacturers struggle with this? What's going on?

 

[Bobby Dazzler]

This is true. TVR do not have the funds to develop sounds for exhaust. In fact, they didn't even have the funds to tune the chassis/suspension set up. They use the customer as the development tool for feedback.

So how come TVR can make a good sounding exhaust without significant development, while modern car manufacturers struggle with this? What's going on?

What's changed since TVR made cars? Regulations and shifting customer expectations mean that engines and even the rest of the must be designed differently in order to sell in any real volume.

And of course even then TVR didn't need to sell in any real volume, which would mean that even today they could take a different approach to the bigger manufacturers but that's risky: some win (eg Morgan) ans some lose (eg TVR).

 

[PobodY]

Isn't part of the story with TVR that they don't make enough cars to have to conform to EU legislation about exhaust noise?

 

[Bobby Dazzler]

Isn't part of the story with TVR that they don't make enough cars to have to conform to EU legislation about exhaust noise?

I recall they were even not road-legal in Switzerland.