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RB25DET Whistling

Moistcat

By Moistcat,
in Engines & Forced Induction

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Moistcat Apprentice

Moistcat

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Posted
RB25DET Whistling

Hey all.

I've recently had an a new issue with the RB25det in my Series 1 C34 Stagea. Last week I changed the plugs and coils, which solved the misfire problems I was having. After getting everything back together I'm now getting what I can only describe as a 'kettle whistle' it's noticable from 70km/h and quite loud at 100km/h ( a speed in which the car drives at a lot), and I do get slight hints of it at around 60km/h.

Tonight after double checking the plugs it did feel like it wasn't boosting as much as it normally did.

I put in Irridium sparkplugs, and Splitefire coils.

Have doubled checked all connections and everything appears to have a good connection, and couldn't spot any lines with fatigued lines.

Wanting to know if you guys could suggest anything to check.

Mods to car;

3inch split pipe dump

3 inch ehaust, but retaining the stock 2inch cat

GFB plumb back BOV

K&N Pod filter

Return flow front mount intercooler

Turbo smart bleed valve set to boost the car to about 9-10psi

All these mods have been on the car for at least 3 weeks before the whistling started, and was planning to remove the bleed valve, and put the factory diverter valve back on tomorrow morning before I need the car for work.

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https://www.sau.com.au/forums/topic/467920-rb25det-whistling/
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iruvyouskyrine Grand Master

iruvyouskyrine

Posted
Posted

Exhaust gasket is my first guess. Mine sounded exactly like this and got worse and worse. One time it was the turbo gasket and the second time was the exhaust manifold gasket.

Does volume increase with RPM?

89CAL Grand Master

89CAL

Posted
Posted

If its speed dependant not rpm or engine load/boost dependant, i would say something is physically making the noise, like a panel gap or something hanging down/out

Your post gives the impression it is only related to speed

Moistcat Apprentice

Moistcat

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3 hours ago, 89CAL said:

If its speed dependant not rpm or engine load/boost dependant, i would say something is physically making the noise, like a panel gap or something hanging down/out

Your post gives the impression it is only related to speed

That was my first thought, especially as I've installed a CB radio, and cut up the front bar for the intercooler.

Since writing the post I've pretty much lost all boosting ability, not even getting wastegate pressure (5psi) now, got a spare turbo laying around so gonna change the turbo later this arvo.

The exhaust has new OEM gaskets from the turbo through to the front of the cat when I put in the 3inch dump and front pipe and I can't hear any exhaust leaks.

GTSBoy Grand Master

GTSBoy

Posted
Posted
1 minute ago, Moistcat said:

Since writing the post I've pretty much lost all boosting ability, not even getting wastegate pressure (5psi) now, got a spare turbo laying around so gonna change the turbo later this arvo.

The exhaust has new OEM gaskets from the turbo through to the front of the cat when I put in the 3inch dump and front pipe and I can't hear any exhaust leaks.

 

The only exhaust gaskets that matter when it comes to whistling noises and ability (or lack thereof) to make boost are on the high pressure side.  That's manifold to head and manifold to turbo.  And as I said before, they won't whistle like you describe if you're running at low load at a given speed.  You need exhaust manifold pressure to make them scream.

You can also get whistles from boost leaks.  Again though, they won't whistle at a constant road speed - only when you have pressure inside.  But if you do have some stupidly large gaping hole in your inlet tract then you could get all sorts of weird noises and apparent inability to make boost.  And probably lean running off boost and rich running on boost and all the bad things that can happen as a result of those.

You can get weird noises from the turbo if the turbine is falling apart, which can lead to loss of ability to make boost.  They normally fail totally in a split second though.

All in all, we still can't diagnose this one across the 'net.

89CAL Grand Master

89CAL

Posted
Posted

While that is not good, It's on the suction side so will not stop the car boosting - unless the open pipe (if thats how you found it) has sucked something into the turbo and 're-adjusted' the comp wheel

Pull your suction pipe of and check the turbo for damage and shaft play etc. It is usually fairly obvious when you have a turbo issue.

 

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Moistcat Apprentice

Moistcat

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56 minutes ago, 89CAL said:

While that is not good, It's on the suction side so will not stop the car boosting - unless the open pipe (if thats how you found it) has sucked something into the turbo and 're-adjusted' the comp wheel

Pull your suction pipe of and check the turbo for damage and shaft play etc. It is usually fairly obvious when you have a turbo issue.

 

I took that photo after removing that hose, just sitting there as point of reference as to where it came.

The compressor wheel is good, very little shaft play and spins freely. Yet to check the turbine as I'm aware they can end up in the cat.

 

6 hours ago, KiwiRS4T said:

Start by pressure testing the inlet system. Its hard to spot some boost leaks.

Sadly, I don't have the equipment to test pressure and compression. The downside about moving out of home :P

Moistcat Apprentice

Moistcat

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Posted
13 hours ago, KiwiRS4T said:

Bit off topic but why on earth would you fit a 3in exhaust and restrict it with a 2in cat?

I hadn't gotten around to that, it was actually my plan to fix that within the next couple weeks. That's about it really.

 

I did also notice that when I stopped getting boost the normal turbo spool noises wasn't happening. Turbo will be out tomorrow so I can check that and the manifold properly.

89CAL Grand Master

89CAL

Posted
Posted
On 28/11/2016 at 10:33 AM, 89CAL said:

If its speed dependant not rpm or engine load/boost dependant, i would say something is physically making the noise, like a panel gap or something hanging down/out

Your post gives the impression it is only related to speed

No worries

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