[Mk2] [Turbo] Help ! strange trumpet noise while exceeding 0.3 bar...

[allan]

Hi folks !
I've got a very strange problem on my ride:
It happen only when the engine is quite hot, after 10 mn of hard driving for exemple.
And always while driving, never if i rev up the engine in front of my house.
When the engine exceed 0.35 bars (displayed on my AVC-R), a very strange trumpet like noise appear (like the plastic trumpet used by dead drink people at new year eve's party)
While trumpeting i can't feel any difference: the boost is still here, no loss of power,nothing..only this strange noise.
I've replaced my stock dump valve by a same one, no difference..
I've checked all my pipes, hoses, nothing, everything is fine...
Can you help me to source the problem ?
Thanks !!!

[allan]

any ideas ?

[Martin F]

it may well be the pipe coming from the dumpvalve and going into the airbox, quite a common issue

[allan]

it may well be the pipe coming from the dumpvalve and going into the airbox, quite a common issue

i'm gonna check that, any other idea ?

[allan]

well...
bad news, i've checked and double-checked all the pipes and hoses, and everything is damn fine !

just a little detail: the hose from the left of the actuator of the waste gate is puggled in my avc-r solenoid, the hose from the right of the actuator is filled and blocked witjh a bolt.
Everything is tighten, and the bolt don't move.
But an hose (originaly plugged to the actuator from somewhere on the engine) is wide open. Nothing is plugged in, is that correct ?
(hope everything is clear, and everybody understand what i mean)
thanks for your help !

[Steve-O 2007]

Im sure the instructions for my MBC said to plug that pipe up as well. Might be worht blocking it and seeign what happens.

[allan]

well.....
I've unfitted, and refitted all my pipes between the turbo and the throttle body, checked and double check all the stuff....
After 1 hour of labour, and some scratchs on my hands and arms, i've made a road test: same problem...
No change....
this f.... problem don't seeem to come from the hoses and pipes...
Is it possible to have some problems with the intercooler ?
I've got a spearco intercooler, brand new, and genuine one from spearco, fitted in my ride 4 years ago.

[Martin F]

it may well be the pipe coming from the dumpvalve and going into the airbox, quite a common issue

i'm gonna check that, any other idea ?

what i meant was that when the dump valve opens the surge of air it lets out makes the noise you are referring to when it is forced into the airbox...

if you want it to stop then remove the pipe going to the airbox and block it off on the airbox side, just leave the dump valve going to atmosphere, the sound will not just be gone but be replaced by a nice wooshing sound...

that should be it anyway but if not no harm in trying

[paxo_pete]

is this not just a goose honk from an after market dump valve. i have a forge dump valve on my rev 1 tubby and it sometimes it partially opens on half throttle and makes a honk noise bit like a trumpet. dont think its anything bad tho.

[allan]

i'm still in trouble
I've checked all the clamps, hoses and pipes, everything is fine, but the problem remain.
I've also discovered that i can't reach 1 bar as usually.
between 0-15 mn : everything is fine, ans the boost reach normally.
When the engine is quite hot, after 15mn of hard driving, i can' exceed 0.65 bars, and this damn noise appear after 0.35 bars...
an another idea ?

[allan]

i think i've found my problem: may be the solenoid of my apexi AVC-R is dead.

I've tighten strongly some hoses, and for now the "trumpet like" noise had disapear,but the boost don't exceed 0.65 bars, even if i modify all the set up of the avc-r
Decreasing the boost is possible, but it's impossible to increase it over this value.

So how to check this solenoid ?
How to be sure that this part is functionning or is out of order ?

[JP1]

Try removing the boost controller from the loop completely. Just run on actuator pressure to see if it is that or not.

I guess its just a matter of joining the 2 pipes that go to and from the boost solenoid together?


John.

[allan]

I've swapped my Apexi solenoid, and nothing change, but i've discovered something else :
The A/C idle up sensor is leaking...
At idle and when the engine is cold everything is fine, but after a few minutes, an air leak appear in the middle of the sensor.
If i touch, or try to bend a little the sensor, the air leak is more important...
so i need to replace this part, and i hope, solve my problem in the same time...

So, hear my advice: check your A/C idle up sensor....and may be you gonna find an air leak right here....

to be continued...

[^Trickster^]

I dont have time to read the full thread so maybe repeating whats been said, but I had this exact annoying problem.

It was a slight gap on the pre turbo pipe between my filter and the turbo inlet, the clamps were tight, just the pipe seemed to pass air, I had to pressure test the full intake system from filter to throttle to find it, when I pressurised it sure enough it made the trumpet/whistle kind of sound

Graeme