Louder In Cold Weather ?

[WD Pro]

Since having a H pipe fitted to my active exhaust, it’s always been a little louder and given more burbles on the overrun (compared to the standard active) - particularly during on / off throttle at reasonably low revs.

However since the colder weather has started to move in, it’s got noticeably more pronounced (louder burbles and more of them).

Same grade fuel, same make fuel, even the same station and pump - because it’s a wide bay with no pump on the other side

Is it related to the colder weather ? Or is it something to do with one of the self learning features (the car hasn’t had a KAM reset for a while).

If it’s a factor, the DA here is low at the moment :

So I’m interested, what’s triggered the change ?

WD

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[ShadowCoyote]

So colder air means more molecules, and more air molecules means more energy released in each combustion cycle. A drop from 30 C to 0 C is roughly a 10% drop measured in Kelvin, which suggests 10% more energy for each combustion cycle --> 10% more horsepower! **per corsa performance website.

 

[MAGS1]

Colder air amplifies sound

https://www.discovery.com/science/Sound-Carries-Farther-Cold-Days

 

[Torched10]

Colder air amplifies sound

https://www.discovery.com/science/Sound-Carries-Farther-Cold-Days

The issue is when it's colder the car has more hp and more combustion means more noise. The cold air makes tires harder which make it harder to stop and easier to spin tires. The issue on the well written response it assumes the same event will travel faster in warm wather.but in this case the source of the sound is more horsepower
Ie louder exhaust

 

[Crew4991]

Umm... 94% HUMIDITY???

Your loud burble problem is nowhere near as bad as your humidity problem. I can't help you.

 

[WD Pro]

Colder air amplifies sound
https://www.discovery.com/science/Sound-Carries-Farther-Cold-Days

It sounds like that would be an interesting read

Note that we aren't really cold though, we're typically around 6°C in the mornings - and it's not like we get huge temperature swings across our seasons. OK, maybe a few outlier days, but nothing drastic (or that we have experienced yet this year).

So colder air means more molecules, and more air molecules means more energy released in each combustion cycle. A drop from 30 C to 0 C is roughly a 10% drop measured in Kelvin, which suggests 10% more energy for each combustion cycle --> 10% more horsepower! **per corsa performance website.

The issue is when it's colder the car has more hp and more combustion means more noise. The cold air makes tires harder which make it harder to stop and easier to spin tires. The issue on the well written response it assumes the same event will travel faster in warm weather, but in this case the source of the sound is more horsepower
Ie louder exhaust

Yeah I understand that, but these are low throttle opening / low rpm / low power scenarios where it's doing it most (on an off gas, slowly accelerating, slowly de-accelerating as I manage the speed humps near home (20mph limit zone with schools and shops etc).

So now I suppose we are getting down to what I was wondering ...

Yes the air is denser, but surely the ECU should account for that, giving the same burn regardless of air density. Then if you have the same burn, why the more brubley overrun (suggesting it's richer ?)

Umm... 94% HUMIDITY???

Your loud burble problem is nowhere near as bad as your humidity problem. I can't help you.

At 7°C, that's not really a problem ...

WD

 

[MAGS1]

It sounds like that would be an interesting read

Note that we aren't really cold though, we're typically around 6°C in the mornings - and it's not like we get huge temperature swings across our seasons. OK, maybe a few outlier days, but nothing drastic (or that we have experienced yet this year).





Yeah I understand that, but these are low throttle opening / low rpm / low power scenarios where it's doing it most (on an off gas, slowly accelerating, slowly de-accelerating as I manage the speed humps near home (20mph limit zone with schools and shops etc).

So now I suppose we are getting down to what I was wondering ...

Yes the air is denser, but surely the ECU should account for that, giving the same burn regardless of air density. Then if you have the same burn, why the more brubley overrun (suggesting it's richer ?)



At 7°C, that's not really a problem ...

WD

So 6C is roughly 43F, that’s cold enough that the sound will seem louder. Here’s screenshots of the article for you.

We’re typically in the 80’sF during the summer and we have cold winters (below freezing). We had a stretch the last couple weeks of temps in the low 40’sF in the mornings and I notice something similar, the exhaust does sound louder and the burbles seem to be more pronounced. It’s warmer again this week with colder temps coming next week with overnight lows at or below freezing. All that to say we can get fairly large temperature swings this time of year so a change in exhaust volume is noticeable.

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