Intermittant Fluttering Sound

[lagbort]

OK this is a bit of a weird one, I have a pretty much stock (engine wise) V7 sti.

relatively regularly I will be cruising along the motorway and I will start to get a strange fluttering sound from the turbo area (sounds like its coming from right in front of the driver) this can vary from quiet to quite loud and goes up and down in rhythm with the boost level turning into a whine at high boost levels, during this I notice no loss of power or performance.

The weird thing is it isn\'t constant, some days I can drive around happily with no noise, other days it starts up pretty much as soon as the engine is warm. Initially I was thinking boost solenoid but the ebc screen shows no solenoid duty at the time the noise starts. Boost is built and held pretty much as it should.

I had the car in at speedtech for a warrant and during this time they took it for multiple test drives without the noise occurring once, I picked it up this afternoon and the noise started as soon as I hit the motorway, I turned around to head back and the noise stopped shortly before I arrived back at the workshop...

Does anyone have any idea what could cause such an intermittent noise?

[Kiwi_Fozze]

That\'s the EBC doing it\'s thing. Mine does the same ;-) some days are audable, some not so much, if you don\'t pay attention you\'ll hear it, listen for it and you won\'t. Murphys law ;-)

Whats your gain and duty cycle set to?

[lagbort]

its seriously loud though, I had the same ebc in my last v7 that was stolen and that didn\'t make this noise. it also starts before the solenoid kicks into action.

How would I check my gain and duty cycle? , its an Apexi AVCS

[Kiwi_Fozze]

Eek, never played with one of them. I have a GFB ebc, fantastic unit but yeah, it can get rather loud, depends on how your solenoid is placed i\'d imagine, as it\'s releasing pressurised air. Try moving it and see?

[lagbort]

OK, just had a poke around in the menu, what I can find is:

Duty:

3000rpm -> 6000rpm = 70%

>6500rpm = 69%

Boost:

<6000rpm 1.25

>6500rpm 1.3

the other thing I noticed is that the value for the throttle position sensor didn\'t move when I pressed the throttle pedal

[lagbort]

Just noticed it has a second setting (setting A and B), the second one seems to be broadly similar except boost is set to 1.0 across the board and more of the other settings have a value rather than "**"

[Pappu1]

Any chance of a video of it

The sound I mean

[lagbort]

i tried to record a video of it with my phone but despite being very obvious when you are in the car it didn\'t show up at all over the engine noise on the video.

I went for a long drive today and the noise only showed up 3 times in 1/3 of a tank of fuel, each time lasting for no more than a minute, during that time i can control it entirely with my right foot, as the turbo spools up the sound spools up and vice versa but no loss of performance is noticed.

[Pappu1]

Hmm maybe as kiwifoze said may the boost solenoid

Is there a way u can relocate the solenoid and see if makes a difference in sound

Also maybe the up pipe gasket but that is there all the time u set boost

U don\'t have any boost or vac leaks u can see?

Maybe tighten all hoses and bov etc as a precaution anyway

[boon]

Could be compressor surge?

[Pappu1]

 boon said:

Could be compressor surge?

Yea man was thinking that but on a stock tune it will be near impossible as it\'s not aggressive enough ....

[Marky]

 SP00N']

[quote name='boon said:

Could be compressor surge?

/quote]

Yea man was thinking that but on a stock tune it will be near impossible as it\'s not aggressive enough ....

But... AVCR does closed loop - could it be maybe managing to make it surge by waking up super fast?

Just throwing the idea out anyway

[Pappu1]

That will be a first but yea could be .... Lol y not...

Have gotten a cheap tap to surge on a v8 so this cud be in the relm...

If u change ur settings to say lower duty cycle - does that still do it?

[lagbort]

I cycled through setting A, B and off while it was making the noise and it didnt make any difference to the noise at all. Fairly certain it isnt the solenoid, the noise starts before the AVC-R screen shows any solenoid duty and if I listen carefully I can hear the solenoid when it does activate as a separate noise.

[Pappu1]

on solenoid off does it run wastegate pressure?

cos if u can confirm that on wastegate pressure u getting the noise then it wont be surge..at least that kinda points to other things anyweay

do try a vid man...

[lagbort]

I have no idea what pressure it runs when I switch the ebc off sorry, I\'m not very good with these kind of things ???

As I say I recorded the sound a few times but it doesn\'t show up on video over the sound of the engine, depsite being very noticeable in cabin

[Pappu1]

does it slower when ebc is off?

(possibly lower boost)

[lagbort]

No there seems to be no difference in the sound no matter what setting the ebc is in

[Pappu1]

but when having the ebc off - does the car feel slower (as compared to having it on)

[Marky]

Course we\'re assuming it is boost control related - could be a tiny air leak flittering open a bit with pressure? (again just throwing a random idea out there)

Or as said a sporadic kinda exhaust leak

[boon]

A V7 will surge in bog-standard form... just point it up a hill, put it in 6th and stick your foot up it.

[Pappu1]

 boon said:

A V7 will surge in bog-standard form... just point it up a hill, put it in 6th and stick your foot up it.

hahahah im sure he is not doing that kinda antics hahaha but that wud be pretty epic

but tbh i really dont think a stock v7sti will surge even if u tried that ..

they are tuned pretty slow....

[boon]

 SP00N']

[quote name='boon said:

A V7 will surge in bog-standard form... just point it up a hill, put it in 6th and stick your foot up it.

/quote]

hahahah im sure he is not doing that kinda antics hahaha but that wud be pretty epic

but tbh i really dont think a stock v7sti will surge even if u tried that ..

they are tuned pretty slow....

Trust me, I\'m speaking from experience, put it in 6th and point it up a hill at about 85kph, put your foot hard to the floor, it will pull about 20psi in a couple of seconds and the engine can\'t swallow it fast enough. With an EBC involved I imagine it would be easy peasy to push it into surge.

[Pappu1]

on a vf30??

but the stock setup does not get to 20psi..

around 18 is what the stock setup is...

i think ur referring to ur vf34 and some mods thrown in?

stock v7sti wont bro...the stock tune is not that aggressive at all on the low rpm end to do that

did u get ur one to surge on a full stock setup tho??

[boon]

 SP00N said:

on a vf30??

but the stock setup does not get to 20psi..

around 18 is what the stock setup is...

i think ur referring to ur vf34 and some mods thrown in?

stock v7sti wont bro...the stock tune is not that aggressive at all on the low rpm end to do that

did u get ur one to surge on a full stock setup tho??

Yeah, I could make it surge completely stock (mine was stock as a rock when I got it, apart from a panel filter). You just have to be a bit dumb with it. Like I said, 6th gear up a hill, chuff chuff chuff.