Exhaust- / Sound Discussion

[sandervdw]

This is the "new" thread to discuss about exhaust sound, ask questions and request soundfiles.

Since there are a lot of people asking what exhaust to order, there is now this collection-thread.
To keep everything clear/clean, it would be useful to respond to the respective post via the "reply-button".

For aftermarket exhaust systems have a look at this discussion:
https://n-cars.net/forums/threads/aftermarket-exhaust-tips.942/





Hi,

In this video

you can see that the pops actually come from the other pipe then the normal noise. Any idea what's the reason for this?

 

[paul-h]

Hi,

In this video

you can see that the pops actually come from the other pipe then the normal noise. Any idea what's the reason for this?

Pass. maybe its the path of least resistance?

I reckon that "turning up" the exhaust just opens the secondary pipe.

 

[Gizmo]

If you find the 'active exhaust' bit of the mini-site it shows the fuel injector on the right hand pipe only.

 

[paul-h]

If you find the 'active exhaust' bit of the mini-site it shows the fuel injector on the right hand pipe only.

Can’t find it! Haha!

 

[Gizmo]

Can’t find it! Haha!

Yeah, that site isn't great and doesn't seem to work properly in Chrome - I had to use Edge to find it (knew I'd seen the picture somewhere). Find the black-backgrounded "Nth Degree Performance" section, then look at the three dots in the white section below - "Traction and stability control", "Electronic Limited Slip Differential (E-LSD)", and finally "Active variable exhaust system".

Let's see if I can link to it directly...

 

[paul-h]

Yeah, that site isn't great and doesn't seem to work properly in Chrome - I had to use Edge to find it (knew I'd seen the picture somewhere). Find the black-backgrounded "Nth Degree Performance" section, then look at the three dots in the white section below - "Traction and stability control", "Electronic Limited Slip Differential (E-LSD)", and finally "Active variable exhaust system".

Let's see if I can link to it directly...

No idea! Can’t see any of that! Haha. Doesn’t matter, I’ll have it on a ramp very soon after getting it anyway haha!

 

[sandervdw]

If you look at this, you would expect the smoke to go from 1 exhaust to 2 exhaust. In the movie it seems to go from 1 to the other. Seems to be a "loud" exhaust and a "normal" exhaust pipe.

 

[Gizmo]

If you look at this, you would expect the smoke to go from 1 exhaust to 2 exhaust. In the movie it seems to go from 1 to the other.

The pops only happen off throttle so I think I would expect something from the left pipe on throttle and the right pipe off throttle, though there must be some exhaust gas coming through the right hand pipe all the time to make it hot enough for the fuel to ignite on to actually go pop.

If (big 'if'!) that picture is actually accurate and not just marketing fluff, there's only one pipe from the engine to the back box, so it's not like there's one pipe connected to each channel of the twin scroll turbo (is it two equal sized channels or one wide and one narrow in the N? I haven't seen that information anywhere).

 

[K_N]

i found this picture of the silencer on instagram (copyright by User: mzmrgud - he also has pics of the LSD and suspension from the Vallelunga press event). It appears, that the right pipe has a direct (non resonated) exit, whereas the left pipe is "muted" due to the longer way and the smaller diameter. The exhaust gases stay "longer" in the silencer.
I'm not an expert but based on this picture you can see well why, with the valve closed, the exhaust is quieter.
I hope you understand what I'm trying to explain, non-native english speaker here...

@Gizmo I think your guess regarding the exhaust behavior is correct, I also think that with the valve open, there's still constantly exhaust coming from the right side. On IAA i could take a look under the car and there is only one pipe from the turbo to the silencer

 

[Gizmo]

Fantastic find, K_N!

 

[sandervdw]

So this is basically the same system as in the Abarth 124 spider (they do sound similar). This does clearly show that the sound is mechanical and not electronic.

 

[Howy]

so will the 5 yr warranty cover the expensive exhaust system I wonder?

 

[Gizmo]

I've got a theory.

Last Friday I put Momentum99 in, just because Tesco had run out of 95RON.

This week I haven't heard a single proper pop, only the burble-rumble, in N mode.

So... my theory is, there's just enough difference in the 99RON to stop it going bang in the exhaust, at least at current ambient temperatures.

(Yes, it's a slow day at work!)

 

[paul-h]

Wouldn’t think so, maybe your just not driving it hard enough!

That said, higher octane fuels are more resistant to detonation and knock than lower octane so it’s entirely possible!

 

[Tom Vanlimbergen]

It doesn't pop at temperatures below 4°C (give or take a few degrees). It is programmed to protect the engine, for what I don't know. Also when the exhaust temp is to high it will stop popping.
Nothing to do with the higher octane, just a coincidence.
There is an extra injector in the exhaust that causes the pops (sort of an afterburn), so the higher resistance against knocking isn't the cause.

 

[paul-h]

It doesn't pop at temperatures below 4°C (give or take a few degrees). It is programmed to protect the engine, for what I don't know. Also when the exhaust temp is to high it will stop popping.
Nothing to do with the higher octane, just a coincidence.

Good info,

How did you find this out?

Cheers

 

[Tom Vanlimbergen]

I don't know anymore, meanwhile I've read so much about the N...
I think the thing about the temperatures was on the EU-facebookgroup, the stuff about the injector was somewhere else on the net, but there was an official drawing with it. It works in combination with the throttle that stays open for a short period. The injector then sprays a bit of fuel in the exhaust wich then burns what gives the pops and bangs.

 

[Scottukl]

I only ever use shell v power or Tesco 99 and the car pops and bangs all the time, even after a 4 hour cruise so it was nice and hot.
Hopefully the pops won’t stop if it’s gets too hot but I never get the chance to drive it that aggressively for more than about an hour at a time really and track day sessions are usually 20 mins before a break which should be fine.

 

[paul-h]

Any links to the official exhaust drawing @Tom Vanlimbergen

 

[Tom Vanlimbergen]

I've been searching but can't seem to find it anymore. It was on an English forum somewhere in a thread about the exhaust pops. Wasn't a car specific forum, but something like petrolheads.