Exhaust Sound

[S14]

There's been considerable discussion in and around Formula One regarding the exhaust sound of the new 1.6 liter turbo V6s. Some have worried that the cars will lose the high pitched shriek the cars currently have, or that the engines will be too quiet, or that some other change will occur, to the detriment of the fans' experience and the F1 "brand." This has me wondering what aspects of engine design affect the exhaust sound produced? And though I suppose that 'exhaust sound' may be something of a misnomer, given that induction noise and the noise produced by the valvetrain and other moving parts aren't generated by the exhaust, strictly speaking, I would include them in 'exhaust sound' if only for ease of use.

I'm sorry if this is too broad a topic, or if it has already been discussed (and I have simply missed it with the search function). If there are resources already extant which cover this subject, please link them for me.

Anyhow, my question is this: in an engine, what affects exhaust sound, and in what way?

[chunder]

To be perfectly honest the sound of previous turbo cars has hardly been quiet.

WRC cars are fairly loud, but WSPC cars were sometimes quite quiet, maybe coz a lot of the exhaust was side exit and inside the bodywork.

Modern rallycross cars are powerful, but quite quiet, though their wastegate chatter is very loud due to high boost. And the nearest comparison are things like high boost drag cars which basically have the exhausts open after the turbines, this is proably what F1 exhausts wil be like, and they are not that quiet.

80's turbo cars were pretty loud, depending on the model, OK, compared to a V10 or a V8 they are quiet, but in this day and age I think there are good reasons for having quieter cars.

And a V6 turbo does sound good, but maybe not to everyones taste.

What I really want is wastegate chatter, dump valve and pop off noise. Anti Lag would be great too, would sound just like modern exhaust diffuser rattle, but more frequent and poppy.

But not sure if it will be allowed as its really loud in rally cars and they have silencers! In an F1 car it might be too loud.

[GORDON STREETER]

Whatever they sound like I would doubt if anything engine wise will sound as good as the BRM 16cyl or the Honda 6 GP bike of years gone by !!!
Look up Youtube.

[BertMk2]

Originally Posted by chunder

What I really want is wastegate chatter, dump valve and pop off noise. Anti Lag would be great too, would sound just like modern exhaust diffuser rattle, but more frequent and poppy.

And flames too. Got to have flames on the overrun.

[Al Weyman]

I once watched Nigel Mansell do some demo laps around Brands in the Renault F1 Turbo and I can honestly say it was one of the most ear damaging painful sounds I have ever heard, and they want the rest of us to poodle round at 105db.

[S14]

I guess I should clarify - I'm not overly concerned about the sound the new F1 engines will make. I'm asking the broader question of what influences and affects the exhaust sound of a given engine/vehicle.

For example, listening to a Ducati, there's a great deal of noise coming from the desmodromic valve train at idle, producing this very tappety sound. That I can identify pretty easily.

Listening to this Matra V12, as it drives away (around the 1:12 mark) it sounds almost fizzy. Is that an auditory artefact of the V12 layout? Is it because the exhausts go from 12 pipes to six?

Or, to use a non automotive example, the Rolls-Royce Merlin, here heard in the legendary Spitfire. Why is it so deep, especially after it has passed the listener/audio equipment? Is it because the massive displacement (27 liters), or its supercharger? Some cars have a similarly low register; the McMerc SLR and the Morgan Aero 8. What allows their engines to be as deep as the Merlin?

[GORDON STREETER]

A small cc multi cylinder engine that can rev very high will always "scream" simply because of the number of cylinders firing per revolution, whereas a single cylinder or big cc (lower revs) engine will sound lower.
The noise change on passing the person listening/recording is simply the "Doppler effect" caused by the frequency change because of the speed of the vehicle making the frequency change from + to -

[chunder]

Basically, the new F1 cars will run open silencers as always, but they will be quieter as the turbocharger naturally quieten the engine sound.

Some turbo cars are very loud, so it mght be cool!

[GORDON STREETER]

What you may also be talking about are "harmonic resonances" in that case you would have to have a read on the subject (it will take a while to fully understand)
This is why some road cars have a heavy weight fixed on the exhaust system.

[S14]

Originally Posted by GORDON STREETER

A small cc multi cylinder engine that can rev very high will always "scream" simply because of the number of cylinders firing per revolution, whereas a single cylinder or big cc (lower revs) engine will sound lower.
The noise change on passing the person listening/recording is simply the "Doppler effect" caused by the frequency change because of the speed of the vehicle making the frequency change from + to -

I get that the "scream" seems to come primarily from high RPMs, but I have doubts regarding the lower pitch being primarily due to larger capacity engines. For example, the Honda Varadero 125 and the Honda RC149 are both 125cc four-strokes, but they produce markedly different exhaust notes - is this due to the different capacity of the individual cylinders (in addition to the obvious differences in RPMs)? Even if it were, why does that Varadero sound deeper than the 2.7 liter straight six in my BMW, which has much larger capacity and similar RPMs?

As far as the Doppler effect, I am well aware of it and its effect on the perception of sound, I was simply pointing out that the low pitch was more apparent when the Spitfire had gone past, while still present as it approaches.

Originally Posted by GORDON STREETER

What you may also be talking about are "harmonic resonances" in that case you would have to have a read on the subject (it will take a while to fully understand)
This is why some road cars have a heavy weight fixed on the exhaust system.

The acoustic resonance of a pipe is something I'm actually pretty up on (as both a student of physics and a student of woodwinds) and that is what is being affected by affixing a mass to the exhaust pipe itself (adding mass changes the resonant frequency). Some degree of tuning of the exhaust note is possible by changing the length, diameter, wall thickness, material, &c., but is that the primary cause of the differences in exhaust notes?

There may be something to that. Do any of the cars which have valves fitted to their exhausts (to allow quieter operation at lower speeds) change the pitch of their exhaust independent of engine speed?

Beyond the architecture of the exhaust system, though, what other components of "exhaust sound" are we hearing?

[chunder]

Exhaust note has a lot to do with resonance, firing order, engine type and pretty mucb the whole thing!

Who can explain why a Ferrari V8 doesnt sound like a River V8, just coz of the flat plabne crank apparently, but no Ferrari V8 sounds like an AMerican one?

Subaru flat fours in the WRC era sounded lovely and barky, then in their wide body WRC form the engine note changed completely. and that fomr the same engine, same basic car and design, just changed the way the exhausts worked.

Lencer WRC car sounds very odd, almost a sort of pulsing exhaust note, sounds nothing like ay other WRC car I ahve heard.

Yet a Porsche flat 6 sound largey similar to how it always has, despite 4 valvaes per cylinder, water cooling etc.

Certain engines alwys sound the same, 5 cylinder Volvo and Audi sound the same. A straight six has a different kind of sound to a V6.

To original question, my huge sadness is that they are not allowing 4 cylinder F1 engines next year, that would open up a whole new area of tuning, and also be far more relevant to road cars, as in reality there are very few V6 1.6 litre road cars using turbos!!

[GORDON STREETER]

The two Hondas that you have chosen are obviously worlds apart, one being a cooking V twin and the other a 5 cyl inline out and out racer with smaller cc's per cylinder! so the 5 cyl will have more firing strokes per revolution/rev higher and give a higher exhaust note.
That's all I can say on the matter and not being an "anorak" on exhaust notes I suggest you try another forum that might suit your needs unless someone on tenths knows more sorry.

PS I note that you are a student of woodwind instruments so in effect you have answered one part of it as a thin instrument gives a higher note than a thicker one .

[GORDON STREETER]

http://www.team-integra.net/forum/bl...cts-noise.html
In open exhaust engines (F1 etc) obviously this won't apply but exhaust pipe size/length does.

[SidewaysFeltham]

Originally Posted by S14

There's been considerable discussion in and around Formula One regarding the exhaust sound of the new 1.6 liter turbo V6s.

Exhaust sound?

Worth considering from where IC engined noise emanates....

Both Intake and Exhaust systems create noise due to the Standing Wave in, respectively, the exhaust pipe/s and the Inlet system.

Think about the noise of a very high powered modern motorcycle: exhaust noise is significantly limited by traffic laws: viz, Construction and Use Regs.

However modern super 'bikes makes the most delicious noise at speed (at a distance) which reminds me of F2 in the early 1970s.

Most of this is intake noise; not exhaust.

The higher the RPM, then the higher the frequency of the standing wave. At low speed and thus frequency, the standing wave is heard as a series of mini-explosions. Since the air rushes in and the inlet valve slams shut and stops the gas dead, so it reverses. And then reverses again when the inlet valve reopens. Same for exhaust, except the outgoing gas is very hot and seeks to expand (escape) and cool as it hits ambient air. Still a classic standing wave.

Tuning exhausts and inlets is all about harnessing harmonics and the natural frequency of the associated pipework to gain "free stuffing".

Next we have simple mechanical noise: loads of bits whirring around.

Finally turbo shriek: or, with older race cars, supercharger.

As Gordon suggested earlier, nought much more blood stirring than a 1952/3 BRM V16 two stage supercharged at full chat.

Bearing in mind it was just 1.5 Litre............. pistons like thimbles.

Good sound here: http://www.youtube.com/watch?v=OnEA-m8cVcE

(I have precisely the same audio file)

Listen to the two stage supercharger shriek when the car is at the far side of the circuit at full chat.

Regarding noise, remember whilst most people think the "noise" of a Supermarine Spitfire is generated by its open stub exhausts, much of the noise one hears is generated by the prop.

http://www.dtic.mil/dtic/tr/fulltext/u2/a801118.pdf

Thus an F1 car's noise (or indeed any other car or bike) is a mixture of components, not simply exhaust.

Footnote: For me, a pretty spine tingling sound was Willie Green, pedalling Tony Bamford's ex-Le Mans V12 "Bread Van" Ferrari through the grandstand/pits straight on Silverstone club circuit one cold windy afternoon on open pipes, in a public practice session. Since the circuit and grandstand were all empty the sound echoed delightfully.........

[knighty]

if you go to this link below you can now listen to Renaults 2014 engine noise........its obviously been taken in a dyno cell as you can really hear the boost hissing away as well as the engine.......in the magazine feature they are saying the rules are dictating they must rev to the higher limit to hit the second minimum fuelflow point.......otherwise the they would be able to make a lot of power at low engine rpm and the engines would just drone around........so looks like the FIA have got something right whereby it will sound half decent to the fans.......listen to the last years GP3 cars for a definition of drone racing........enjoy

http://www.racecar-engineering.com/n...2014-revealed/


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