F430 Air Intake Resonators
This page is a chapter in the book F430.
Some may know that Ferrari has stopped producing the original air intake resonators.
This is quite a big change because the difference between the old and new air intake resonators is huge.
Before developing the entire subject, if you have the old air intakes like I have, please DO KEEP THEM! The best sound is with the old intakes.
I will explain why there is such a big difference comparing the results with a spectrum analyser. I hope to give also some understanding on how important air intake is in the overall engine sound.
The old intake is made of a one unique molded plastic part. The manufacturing of this part is of very high quality using thick plastic and it must have been quite expensive to make such a mold. When you blow air in it, this air intake resonator sounds like an music instrument and resonates perfectly well.
Unfortunately, Ferrari stopped using this part on the F430 (the exact year is unknown) and replaced it by a very cheap air intake resonator. The same cheap air intake resonator is also used on the Scuderia and 16M (although the shape is slightly different). When you touch the newer air intake, you can feel immediately that is made of thin cheap plastic. This air intake is an assembled part and is no more molded in a unique complete part. There are several air leaks especially around the resonator box which is just riveted on the air intake. Blow air in it, and you’ll discover that it will not make any sound at all. It just doesn’t resonate. Unfortunately, only this part is now only available (even as a spare part).
Here are 2 pictures comparing both versions of the air intake resonators.
When I had both versions in my hands (thanks to Richard), and could feel the huge difference of quality, I was wondering if a difference of sound with be really noticeable on the F430. The only way to find out is the use a spectrum analyser because ears are well to subjective.
I made all the sound tests on my F430 which had at that time still a complete stock exhaust from the headers to the exhaust tips.
To understand the following images, here are a couple of guidelines :
All spectrum images have 3 dimensions :
- Time (from left to right) : represents the evolution of sound in time
- Frequency (from bottom to top) : sound frequency expressed in Hz. Low values represents bass tones while high values represents high pitches tones
- Sound Pressure (in colour) : dbV expressed in different colours from blue to orange. Blue is soft while orange is very loud.
Let's take as an example the following spectrum result picture:
This picture represents the harmonic spectrum of a warm F430 engine revving 2 times from idle to 3000rpm with the exhaust valves opened.
You can see very well the double rev on it. All the blue lines from bottom to top (low to higher tones) have an identical curve. What is interesting is that in the range of 107Hz-177Hz, we have a yellow colour instead. Yellow = 0dbV=maximum sound pressure. So our ears will hear most this part of the sound. But this range of sound has a little loud brother, which is at a higher tone (avg 350 Hz). Harmonic spectrum is really like a digital signature of the sound. The smallest change in sound, which can't be always heard but felt, will be seen in the digital signature. All the blue dots on the image are part of that signature, they reflect the resonances with are accompanying the main sound. Remove all the resonant frequencies and your engine would sound horrible. The resonant frequencies will make a basic noise more pleasant to hear.
The difference here is that the second image shows all the real frequencies of the sound. But you can see that the loudest part of the sound in red is in the lower range of frequency (low tones). You need much more energy to generate loud low frequency sounds compared to high tones. Evolution in time is also very interesting especially before and after the revs. You can see that the engine idle sound is very quickly restored as soon as the second rev is done but only after a couple of small distortions in the red zone the time needed for the engine to restore a stable idle.
Using spectrum analyses is another approach to diagnose the engine as it may show issues which can't be heard directly. Our ears (or brain) don't have the capacity to extract specific frequencies in an accurate way even for trained musicians
When we compare the first image (MK1) and the second image (MK2), we can clearly see that MK2 is quieter at warm idle. Indeed, the line on MK1 (first picture) at 129Hz is much stronger as well as at 193Hz. But with MK1 there is an additional sound line at 322Hz which is missing on MK2. In the lower tones, the MK2 does not generate any sound at all (blue lines missing under 129Hz).
These results are not surprising and confirm what I've heard during a test drive with the MK2 intakes.
To conclude, not always later MY cars have better options or improvements ;) In this case, the 2005 F430's and maybe also the MY 2006 have a much better air intake resonator ;)
MK2 workaround to improve intake sound
Although, there is a way to improve the MK2 air intakes. I report here what have been researched by my local Swiss friend Richard. As he got very upset with the MK2 air intakes on his Scud, he has been trying many things to make the Scud sounding as good as his F430 Spider. I can say that he did put a lot of efforts to reach his goal. Eventualy, he found out that there existed also a "Valid for Noise" of the air intakes (not available anymore). This intake has several slots on the top of it and is wrapped in some kind of material:
To improve the sound, he wrapped his air intakes and confirmed a great improvement of sound. He didn't made the slots though but maybe someone will test it out? With the slots, the resonance effect should be even more amplified. The small box, used for the Helmholtz resonance should be wrapped too and silicone must be applied where the box is attached to the leg to make it air proof.
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