Mystery of the acoustic valve

[Tin.tin]

Evening gents

Have been thinking about to the curious mystery of the acoustic valve. Many different opinions on what it actually does, each telling their own tale of what power it truly holds.

Since getting my 182 almost 3 years ago, I've had this issue where every time I start the car after letting it sit overnight, power feels restricted for maybe 2/3 minutes. Typically let it sit before driving. Took the car in to my local specialist and he couldn't work it out. Scoured the ancient scrolls & found people with a similar issue but no answer - ultimately put it down to the car being quirky. Or having a restrictor that stops engine revving too high when cold, I tell myself this version as it helps me get to sleep.

Accepted this and learnt to live it as it didn't bother me too much. Car when I bought it had some missing bits which I'd be re fitting. Got an acoustic valve off Ebay, fitted it and to my surprise, the cold start issue had disappeared. For a good 3/4 days the mystery was solved - sadly didn't last long.

Now just wondering if AV could be related to this. Have read somewhere that valve is there to restrict noise which makes sense as its in the name 'acoustic' however, after my experience I can't help but wonder if there's more to it.

What's everyone's experience after fitting AV - any notable difference?

Cheers .

 

[Mr Trailer Man]

I've heard/read somewhere that it is used during the warming up cycle/cold start.

But I can't remember where I saw that.

When you say restricted power, how do you mean? They have a cold limiter in the 6500rpm range if that's what you mean...

 

[Brigsy]

The hesitation from cold is usually due to oem mapping to warm cat up. Worse in winter when the engine takes longer to warm up, less of an issue on hotter days when engine comes up to temp fast.

 

[Flob]

The acoustic valves main purpose is when you have a wheelie bin and its not full and you're like - wow, I wish this was full so I could get as much value out of my extortionate council tax as possible then you remember that piece of s**t thing you tore out your Clio a few months before and it fits in the last little bit of bin space perfectly.

That is all it is good for.

 

[Tin.tin]

I've heard/read somewhere that it is used during the warming up cycle/cold start.

But I can't remember where I saw that.

When you say restricted power, how do you mean? They have a cold limiter in the 6500rpm range if that's what you mean...

You can put your foot down but it won't go past 20, Its almost what you get with the speed limiter feature. Can't quite remember what rpm limits at but definitely not as high 6500rpm for me

 

[Matt Cup]

The acoustic valves main purpose is when you have a wheelie bin and its not full and you're like - wow, I wish this was full so I could get as much value out of my extortionate council tax as possible then you remember that piece of s**t thing you tore out your Clio a few months before and it fits in the last little bit of bin space perfectly.

That is all it is good for.

Same for the carbon canister?

 

[Flob]

That not right at all.

My money is on a failing injector. My Clio had a failing injector for ages, when cold the car is in open loop so doesn't use the lambda sensor, when its warm it corrects for overly rich mixture using the lambda. So they run like s**t at cold, but better when warm.

Mine did this for ages before throwing an occasional EML, eventually it got bad enough that it was misfiring too.

 

[Flob]

Same for the carbon canister?

 

[Mr Trailer Man]

You can put your foot down but it won't go past 20, Its almost what you get with the speed limiter feature. Can't quite remember what rpm limits at but definitely not as high 6500rpm for me

Hmm there's something definitely not right there.

Acoustic valve or not, it shouldn't do that.

I've not seen that before 🤔

 

[Tin.tin]

The acoustic valves main purpose is when you have a wheelie bin and its not full and you're like - wow, I wish this was full so I could get as much value out of my extortionate council tax as possible then you remember that piece of s**t thing you tore out your Clio a few months before and it fits in the last little bit of bin space perfectly.

That is all it is good for.

 

[Tin.tin]

Hmm there's something definitely not right there.

Acoustic valve or not, it shouldn't do that.

I've not seen that before 🤔

Didn’t think so but gotta get to sleep somehow so I’ve made up some good theories 😂

Due to go in to another specialist soon will see what he makes of it hopefully gets sorted.

 

[Flob]

I've fixed it above, I'm a solid 80% its a failing injector

 

[Flob]

80% injector, 10% vac leak, 10% some other fuel delivery issue.

 

[Tin.tin]

80% injector, 10% vac leak, 10% some other fuel delivery issue.

Had new injectors in this year. Maybe vac leak or maybe fancy rev limiting warm up option you didn't get in yours lol will report back.

 

[Louis]

It's normal. My 182 used to pop and bang on cold start.