2014 Engines: Do they sound right?

[WhiteBlue]

In that design it clearly is. But the design may be schematic. The compressor and the turbine should be dual flooded and they are not. IMO the Merc final version can look very different to what we see now. But it is an entirely legitimate design to have the MGU between the two turbo machines. It has the added benefit that you can use one cooling system for the MGU and the shaft bearings. A hint that this is not the real thing is the lack of elements that could hold the bearings. Caterpillar btw. uses the same design. It sure minimises the shaft length. I have my doubts if the volume of the unit shown in this rendering is appropriate for the power the MGU is supposed to handle. It looks smallish to me.

Why should both the compressor and turbine be dual flooded?? They turbine surely should as the exhaust comes from two exhaust manifolds. But the compressor housing would only be "dual flooded" if there is two intercoolers. I don't think they will run two intercoolers. Of course they could but IMO they wont.

You are right. The compressor outlet should split into the two banks after it has passed the inter coolers. So no need to have two exit floods there. But the turbine needs two which I do not see either.

[Holm86]

In that design it clearly is. But the design may be schematic. The compressor and the turbine should be dual flooded and they are not. IMO the Merc final version can look very different to what we see now. But it is an entirely legitimate design to have the MGU between the two turbo machines. It has the added benefit that you can use one cooling system for the MGU and the shaft bearings. A hint that this is not the real thing is the lack of elements that could hold the bearings. Caterpillar btw. uses the same design. It sure minimises the shaft length. I have my doubts if the volume of the unit shown in this rendering is appropriate for the power the MGU is supposed to handle. It looks smallish to me.

Why should both the compressor and turbine be dual flooded?? They turbine surely should as the exhaust comes from two exhaust manifolds. But the compressor housing would only be "dual flooded" if there is two intercoolers. I don't think they will run two intercoolers. Of course they could but IMO they wont.

You are right. The compressor outlet should split into the two banks after it has passed the inter coolers. So no need to have two exit floods there. But the turbine needs two which I do not see either.

I agree with you on the turbine side. But I see you believe the engine will have two intake plenums. One for each bank.

I believe there will only be one intake plenum with one intake. But either one of us could be right.

[xpensive]

Gentlemen please, we have not yet seen anything but animations from Renault an MHPE, the former's xhaust and intercooler looks grotesque and the latter's MGU-H reminds me of a belt-drive sprocket, why would a "recording" be any different?

I'm certain that Ferrari will soon release a recording that barks like big-block chevy on roids.

[Holm86]

Gentlemen please, we have not yet seen anything but animations from Renault an MHPE, the former's xhaust and intercooler looks grotesque and the latter's MGU-H reminds me of a belt-drive sprocket, why would a "recording" be any different?

I'm certain that Ferrari will soon release a recording that barks like big-block chevy on roids.

Of course we have seen other than renders from Renault. They showed the engine unit for real at the Paris Air Show earlier. Though the engine showed for real didn't have the intercooler mounted.


And I think its pointless discussing if that's the real intercooler or not. As the teams will surely design those themselves. Just as the radiators.

And when it comes to the size of the intercoolers I think they will be large. At least taking up one entire sidepod.

Some people say that the cooling requirements of the new IC engine itself will be lower than current V8's. That seems to be true as the total output of the new engines are lower than today. But the ERS system will require even more cooling than today. So the total engine cooling requirements adds up to something almost like today. But then again in 2014 we have ERS-H which is harvesting some energy from heat. This removes a bit of cooling requirements as this heat is converted into energy. Though that is not much. So radiators should be somewhat the same as today size wise. But as they discuss in the Racers edge video in the engine thread they are looking at running the engines hotter which means smaller radiators.

There is also an aspect we haven't really discussed much. Which is coatings on pistons and cylinder sidewalls.

The standard low friction coatings on the sidewalls and piston sides is a given I believe. But I also believe that the top of the pistons will be coated with thermal barrier coatings. And even the entire combustion chamber would be coated with these. This will reduce the heat transfer to the engine block and cylinder heads. Which also decreases the heating requirements of the engine. This also means that the exhaust gasses will be even hotter. Bringing more energy for the turbine. And again you can reduce the size of the radiators.

So this became a little of a long story. But my point is that the intercoolers will take up one of the sidepods. And the radiator the other. Perhaps ERS cooling could be in the same sidepod as the intercooler but behind it.

[xpensive]

Never seen that picture before actually, but if that is the true shape of the xhausts, Newey can't have been consulted yet?

Not in this lifetime.

[Holm86]

Never seen that picture before, but if that is the true shape of the xhausts, Newey can't have been consulted yet?

Not in this lifetime.

Well the exhaust would probably also be designed inhouse at the teams. What I don't understand with this exhaust is the shrouding in carbon. There would be more efficient ways of doing it wouldn't there?? Such as thermal coatings and wraps. They would take up less space. But I do get the idea of insulating the exhaust as much as possible. To get as much heat as possible to the turbine.

[xpensive]

With the heat-recovery MGU-H and all, I doubt if the teams will be given much freedom with the xhausts?

But believe me, the contraption in the picture will never find its way into a Newey-car.

[Holm86]

With the heat-recovery MGU-H and all, I doubt if the teams will be given much freedom with the xhausts?

But believe me, the contraption in the picture will never find its way into a Newey-car.

Its just the routing of the exhaust. I cant see why they shouldn't be free to do whatever they want with that.

[xpensive]

So why in the world is Renault showcasing something like that, the piping on each side takes up as much room as the engine?

[Holm86]

So why in the world is Renault showcasing something like that, the piping on each side takes up as much room as the engine?

I really don't know. Perhaps its just a form of smokecover. Or perhaps they are actually hiding something?

Is thermal generators legal next year?? Perhaps the exhaust manifold are covered with some kind of thermal generators.

[timbo]

As I've seen this thread only after it was pointed to me and I'm a bit late to the party, I want to add a few things on summing waveforms.
There is a point being raised (backed by some F1 engine specialists) that splitting exhaust into two banks reduces pitch, i.e. the fundamental pitch is being equal to the pitch that a single bank of cylinders produce.
That is equal to the statement that summing of waveforms does not alter perceived pitch.
This statement is correct only for sines and very simple combinations of sines.
But the exhaust note that we perceive is far from that. In fact it is periodic train of short noise bursts and the tone perception only comes from this periodicity. So if you sum two train of pulses which have period t and shift one by t/2 you have a new train of pulses with a period of t/2, and the pitch changes accordingly.
In fact even relatively simple waveforms like saw-waves behave like that. If you have two phase-aligned saw-wave generators and you delay one by half a period, the pitch will shift up an octave.
So splitting exhausts of an 8-cylinder engine does not make it sound like 4-cylinder.
Now, I'm talking about pitch perception. Of course manipulation with exhaust manifold may alter timbre much like changing shape of a violin body. But the pitch is not a timbre.


PS Mods, the thread should be moved it is absolutely in the wrong forum!

[WhiteBlue]

Timbo, as far as I can see you are not talking about the same thing here. White and Cowell have not said that exhaust splitting exactly halfes the perceived frequency. They also never said that a v8 with split exhaust sounds like an I4. I'm not an expert in sound theory but I can compare your assertions with the sources and they do not match.

If I understand those guys right they both claim that there is a shift in perceived pitch when you compare a split exhaust with a common exhaust, and the shift is towards a higher perceived frequency in the case of the common exhaust.

I ask myself why two senior F1 engineers both mentioned such a phenomenon if it is completely false as you seem to assert. Do you have an explanation? Are they deliberately spreading disinformation?

[timbo]

If I understand those guys right they both claim that there is a shift in perceived pitch when you compare a split exhaust with a common exhaust, and the shift is towards a higher perceived frequency in the case of the common exhaust.

First of all, there is just no way to have a partial shift in such system, as the pitch is based on one frequency -- the revs of engine. The pitch can only be based on the harmonics of that frequency. Shifting by variable amount without changing base frequency is only possible by some rather complicated digital algorithms. So if any shift in pitch happens it should happen in octaves.

I ask myself why two senior F1 engineers both mentioned such a phenomenon if it is completely false as you seem to assert. Do you have an explanation? Are they deliberately spreading disinformation?

Miscommunication and mixing of terms. Often times when somebody say frequency, it isn't meant as pitch (which means the perceived fundamental) but as a characteristics of timbre.
It is totally possible that splitting the exhaust lowers the level of upper harmonics of fundamental frequency (pitch) while having a single exhaust raises higher harmonics somewhat and one can mistakenly call that "a higher frequency", but the pitch stays the same. In this case exhaust system acts like a filter with different cutoff/resonance characteristic (or an equalizer if you will).

edited typos, my English is horrible, especially at Saturday morning

[WhiteBlue]

xxchrisxx had a different position on that:

the techniques above can be used to show that V8's with two exhausts do indeed a fundamental pitch of half the firing frequency. It will also show that it's the order content that gives the sound it's character.

In the following post of this thread he compares two sound files of the single exhaust Renault V6 and a dual exhaust V8
http://www.f1technical.net/forum/viewto ... 48#p440048
His work received one of the highest votes of approval that I have ever seen on this board. +12
He concludes about the V8:

It’s fairly clear that the pitch of the engine sounds much closer to the 666Hz sine tone. Indicating that it’s the half firing frequency you hear as the fundamental note.

And finally he comes to the summary:

Summary
We can build rudimentary models using a summation of sine tones to estimate the sound from an engine.
The V8 noise, with it's two separate exhausts has a fundamental note based on 2nd order (half firing frequency).
The V6 with it's single exhaust orifice has a fundamental note based on 3rd order (full firing frequency).

People have claimed that damping would distort frequencies to provide the effects that were analysed by xxchrisxx. My limited understanding of sound damping as it is used in dyno rooms is that exhausting through sealed pipes will dampen the amplitude of the sound wave, but not alter it's frequency spectrum and the perceived pitch.
Would that 3. order based main note not be what others have found in the Mercedes sound file? I do not get my head around this discrepancies. Perhaps you can have a look at post and provide comments.

[timbo]

In that post the fundamental frequency of V6 engine is clearly overestimated. The spectral print algorithm he used apparently has lower resolution at the lower frequencies (which is to be expected for a FFT spectrum analyzer) and possibly is normalyzed towards pink noise which would exaggerate high frequencies by 6dB per octave. Here's picture I got for Renault sound

It shows a trace around 250Hz which actually dominates pitch, and you can see that by using tonegenerator set to that frequency.

Here's the graph of V8 I got from that vid

I will discuss it in a minute

And here's a graph from Renault V8 engine which possibly comes from the same dyno as V6
(from https://www.youtube.com/watch?v=Czw1pB6ZDRM)


All graphs have same vertical resolution (0-1000Hz).

My review of the graphs (and audio) is that the pitch of V6 is in fact an octave lower than xxchrisxx's estimation, so it is based on the same harmonic as in case for V8. The underestimation was caused by software xxchrisxx used for spectrum visualisation.
With that I have to note that the spectrum of the V6 differs from both recordings of V8s I reviewed here. Spectra of V8 contain significant amount of subharmonics which are absent in the V6 recording. On some throttling settings it causes the pitch to actually seem an octave lower in case of Cosworth, and sometimes there are fast timbre changes. It may appear that V6 is again not actual recording but rather a synthesized emulation. However, it can also be that different mic and pick-up position was used.

My limited understanding of sound damping as it is used in dyno rooms is that exhausting through sealed pipes will dampen the amplitude of the sound wave, but not alter it's frequency spectrum and the perceived pitch.

Damping would absolutely affect frequency spectrum because of the dispersion characteristic of the material used for damping. Lower-frequencies penetrate sound insulation much easier than high-frequencies. Sometimes a tuned dampening is used which have some frequency-dependent characteristic. However it is tough to say what affect dampening would have on frequency spectrum (a cutoff point and rolloff steepness), without knowing construction of the sound insulation and the position of the microphone, but most likely it would emphasize lower frequencies.

Would that 3. order based main note not be what others have found in the Mercedes sound file? I do not get my head around this discrepancies. Perhaps you can have a look at post and provide comments.

As it seems the 3rd order harmonic was graphing software artifact.