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Discussion Starter #1
Guys--

Have you noticed that the exhaust note improves drastically when the car has been driven for a distance and the engine and exhaust are at full temps?

When cold the car fires up and revs like a luxury sedan but after I get to my destination it sounds much deeper and revs quite nicely. The drive is still quiet but the bottom end note is quite nice.

Why is that?
 

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Hi Squidward,

My setting : sport exhaust + OEM Airbox with K&N and charcoal filter removed ( 4500km - 3000 miles )

I have the meaning that you're right, we made a trip with Lotus enthusiats last week ( Elise MK1 and MK2 + Exige etc...) and while the car was at full temp, i definitively had the meaning that while accelerating it roars louder!

I was followed by a guy in Nissan GTR ( which is impressively quiet!!! ) and he told me that my Evora was having a great sound ( when i thought it was too quiet ).

Plus because my car is relatively new, i also have the meaning the sound is becoming better km after km, making me thinking i won't change anything on the car ( was thinking about removing the 3rd cat ).
 

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Discussion Starter #4
Michael, I assume you mean you swapped out the stock filter with the K&N, right? Not sure what you are referring to, regarding "charcoal filter".

And when you say "meaning the sound" I believe you mean aggressive sound (just for clarification).

Anyway did you notice that the idling sound is more serious when the engine was at full temp? If you tap on the accelerator it rumbles deeply whereas when the engine is cold, it just hisses quietly.
 

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Hiya, Squidward,

In the OEM air box, over the Airfilter, there's a charcoal filter, it's needed for US californian laws ( because while the engine is off, the gas that will stay in the cylinder will evaporate and go in the air : this filter is supposed to stop this sort of evaporation ).
But anyway, it's another piece that filters the intake air so it makes the air flow a bit worst : so i removed it ( it's "attached" to the airbox and some piece of plastic needs to be broken ).
And yep i changed my OEM filter by the k&n one.

So my car at idle, sounds the same ( i didn't really ear any difference ), but it definitively makes better noise while accelerating ( you can ear the air suction over 2000) and much better when the engine is at the good temp and over 4000 rpm, it really becomes interesting ( mature sound ).
But in 6th gear on the motorway at legal speed : i have no engine sound coming in the car, and i can drive for hours without any earplugs ( which were mandatory on the Elsie i had : 111r with Hurricane CAI + full quicksilver set including manifold, race cat and sport exhaust )
 

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I have noticed the change becomes dramatic with my non-stock exhaust. As it heats up, it gets louder, has more burbles and pops and the tone gets much better. I don't mind.
 

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I'm a fan of the burbles and pops - as it gets hotter I can get better and louder pops.
me too. I know it is kinda "boy racer" to like the pops and burbles, but just can't help myself.
The sport exhaust with the CAI added soooooo much to my car. Now i'm bitten with the mod bug. Next 3rd cat delete. must have more burbling:clap:
 

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Discussion Starter #10
My question is primarily a pondering one--- why. why doesn't the car sound like that when it starts up cold. The startup sounds aggressive when the engine is hot, but very unimpressive when it's cold on this car, (with the stock muffler, of course).

We know heat has alot to do with it, but just wondering what is exactly happening. does sound somehow reverberate more against hot metal? Or is there a physical change to the systems involved, such as expansion? Or perhaps because the engine is hot, more air is now drawn through it since the oxygen content is not as rich as cold air.. I dunno. Just pondering...
 

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If you want the most - drop the muffler and third cat completely :)
Are you still running that way with the straight out the back Tips?, what is your dealers (Park Place?) attitude on it.
 

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My question is primarily a pondering one--- why. why doesn't the car sound like that when it starts up cold. The startup sounds aggressive when the engine is hot, but very unimpressive when it's cold on this car, (with the stock muffler, of course).

We know heat has alot to do with it, but just wondering what is exactly happening. does sound somehow reverberate more against hot metal? Or is there a physical change to the systems involved, such as expansion? Or perhaps because the engine is hot, more air is now drawn through it since the oxygen content is not as rich as cold air.. I dunno. Just pondering...
When cold you will generally have much more moisture in the exhaust which has a considerable sound absorption. Once the exhaust getss warm and the moisture evaporates wou'll get a much more pronounced sound.:shift:
 

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Discussion Starter #13
When cold you will generally have much more moisture in the exhaust which has a considerable sound absorption. Once the exhaust getss warm and the moisture evaporates wou'll get a much more pronounced sound.:shift:
ah.. that makes sense! is moist air the primary/only reason or are there other factors?
 

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Hi, i don't know what our catalysor are made of, but, regarding to the 3 we have, and if they are made of iron, then maybe the dilatation makes a big difference too?
 

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Are you still running that way with the straight out the back Tips?, what is your dealers (Park Place?) attitude on it.
I'll let you know next time I head to Dallas if you want to hear it in person. I think it's fantastic :)

OU vs tx weekend It will be there btw.
 

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There is no single explanation. :confused:

Air "absorbs" less sound as it gets hotter (past a certain point) or dryer (below a certain point), but it is not linear. Low pitches are absorbed less than high pitches.


Muffler design plays a big role, as well. Old 'rodders know that some kinds of mufflers sound louder or deeper when they get hot, while others not so much.​
 

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Discussion Starter #18
There is no single explanation. :confused:

Air "absorbs" less sound as it gets hotter (past a certain point) or dryer (below a certain point), but it is not linear. Low pitches are absorbed less than high pitches.


Muffler design plays a big role, as well. Old 'rodders know that some kinds of mufflers sound louder or deeper when they get hot, while others not so much.​
Thanks, this is a good supporting point..

So the result is a combination of explanations:
-Sound waves travel faster in hotter temps. This preserves original amplitude of the wave (ie. how loud it is).
-As air heats up, it also absorbs the higher frequencies, leaving more of the lower frequencies unaffected. This results in a deeper sound.

Deeper & louder sound is the outcome of these two phenomena.
 

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I'll let you know next time I head to Dallas if you want to hear it in person. I think it's fantastic :)

OU vs tx weekend It will be there btw.
I followed behind Plackslayer on a recent drive and that exhaust sounded amazing. Burbles, pops, and lots of turned heads.

I'm curious if you ever tell strangers that it's a Toyota engine? It seems to come up when talking about my Exige, but an Evora just seems so much more refined that I would assume most (less) people wouldn't ask who makes the engine and just assumes it's a Lotus mill. Perhaps those who have owned an Evora and an Elige can chime in?
 
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