Question for teh turbo boys?

[markiii]

Having spent an age realigning exhaust and intercooler pipes tonight (as a side nte Hass could have made this so much easier if they had but another couple of bends in the intercooler pipe)

I took her out for a test run.

and for teh first time since install gave her some stick, well first thoughts were wow the redline arrives quickly but it wasn't as nutter fast as I'd expected. However I'm putting that down to having thrashed Bens tubby and Martins 350Z at teh weekend, which means I'm used to silly power at the moment.



However back to teh question. on very light or no throttle I can hear a very quit whistley fluttering sound, doers anyone else get this, could it be the BOV? or the wastegate? it's definitley not a proper BOV blow off as that is way way louder.

any thoughts?

[kanujunkie]

surely its the wastgate being actuated for some reason but correct me if i'm wrong but isn't the BOV just a pressure plate actuated by a spring when it goes over a set point, unless of course the seals on it are faulty

[markiii]

with no throttle or trailing thriottle it's not on boost so it shouldn't be the wastegate.

I'm just wondering fi it's normal?

[kanujunkie]

and with that one over to Sean, he's the only one to really comment on this then

[aaronjb]

However back to the question. on very light or no throttle I can hear a very quit whistley fluttering sound, doers anyone else get this, could it be the BOV? or the wastegate? it's definitley not a proper BOV blow off as that is way way louder.

Is it a constant noise or momentary?

If it's momentary, it's likely it's the wastegate - as you come off throttle you'll still be spinning the turbo up, but with the throttle plate (mostly) shut, boost pressure will rise and the wastegate will open to regulate it, and flutter about for a little while..

If it's constant, then it is more likely to be the BOV - is yours adjustable? It could well be that on part vacuum or total vacuum it's being pulled open (twin piston BOVs aren't meant to do this) slightly, and fluttering about a bit. If it's adjustable then .. from memory, you need to wind the adjustment screw in a bit. It could be the other way around - it's a while since I adjusted a friends  s:) s:)  (Basically, winding it one way makes it harder to open the BOV, the other makes it easier.. You want it hard enough so that it a) doesn't open leak under boost and b) doesn't leak under high vac conditions, but does vent on a hard swing from boost to vacuum).

IMHO, etc etc

[Anonymous]

It's the wastegate for sure.  s:wink: :wink: s:wink:

[markiii]

It's the wastegate for sure.  s:wink: :wink: s:wink:

so thats normal?

[Anonymous]

Actually, on a re-think it's probably not the wastegate, but yes it's normal.

[markiii]

so what is it then?

[Anonymous]

Well it seems to happen to me more so, when i let off the throttle, more than on part throttle. If i was to guess, it's the turbo wheel being stalled by the backpressure as you let off the throttle and it's still spinning(even though it's not actually on boost), trying to flow air into a closed intake, and the air seems to make the noise as it disperses, from the air filter.

Now i know what i'm trying to say but it may not be very clear from what i've just written.Sorry   s:oops: :oops: s:oops:

[markiii]

I take your point, but do you have a BOV?

When teh throttle is closed or partial the BOV will vent to the pre turbo side, and which point if teh turbo is still spinning it will be drawn back in not be expelled via the filter? surely?

[kanujunkie]

heres an idea for you, on the aircraft we have things called air cycle machines, they remove the heat in the air and are at the heart of the pressurisation system but are effectivley a massive turbo(about 2ft cubed in size), they consist of a compressor fed by bleed air running thru a shaft to run a turbine, now whilst your probably wondering what the hell i'm babling on about, one of the characteuristics of then is the noise created, the tips of the blades actually run sufficiently fast as to rip the air apart. Now these units run at a constant speed, but what if the same effect is being witnessed here, the blades in the turbo are at idle passing the point where this effect occurs.

[MR-S Turbo]

Sounds normal to me I get the same sound on light throttle.

[Anonymous]

I take your point, but do you have a BOV?

When the throttle is closed or partial the BOV will vent to the pre turbo side, and which point if the turbo is still spinning it will be drawn back in not be expelled via the filter? surely?

Yes i have a BOV to atmosphere, but it only vents when a sudden switch from positive vacuum to negative, ie from boost to letting off. On partial throttle it doesn't open to vent as there isn't the vacuum to open it.

[philster_d]

Is it not just your intake?

Mine sucks and blows like a cheap hooker.

I get an elasticky thuder after comming off boost (waste gate chatter) and the hks intake is alway sucking.

Phil

[markiii]

could well be, just remember this is my first turbo, and the first time I've had a non stock airbox, so it may be perfectly normal and just that I'm not used to it yet.

[GSB]

Have to say it sounds like every turbo'd car I've ever driven. My old Escort used to so it all the time, and a friends Elan did it an awful lot too.

[kanujunkie]

now has this settled Marks mind me wonders?

[Anonymous]

Perfectly normal on a turbo car   s:D s:D

[philster_d]

Unless your loosing cabin pressure ?    s;) s;)

[kanujunkie]

Unless your loosing cabin pressure ?    s;) s;)

  s:lol: :lol: s:lol:    s:lol: :lol: s:lol:    s:lol: :lol: s:lol:

[markiii]

probably. the roof was down  :-) :-) :-)

[Slacey]

When I see you next I'll take a ride and let you know if it's any different to mine, but I doubt it. Have you plugged that bung yet? It could be that if you haven't.

[markiii]

bung now plugged and a bit of thread lock to ensure it doesn't shift again.