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Discussion Starter · #1 ·
I had a pretty big block of text here, but I didn't even want to read it all so here is the TL'DR:

I recently was driving with someone who was in a different big turbo Focus. He noticed a noise and said the other Focus did not have it. I thought it was just a quirk of the turbo and thought nothing of it until he mentioned it. I am planning on boost leak testing again but that equipment is two hours away in a frozen garage.

- Have a Mountune MRX Kit (BW 6258(a?))
- Had a boost leak test when installed, everything was perfect
- Swapped Injen exhaust with Milltek
- Noticed slight hum/whine/whistle coming from the firewall after Milltek install
- Can't hear it from outside
- Really only noticeable below 3k rpm, otherwise exhaust drones noise out
- Not boost dependent, happens in vacuum as well
- Doesn't sound like any boost leak I have ever heard.
- Car runs fine, boost still builds up quick and holds.
- No oil loss, smoke and no play in the turbo flywheel (Checked that last night)

It took me forever to catch it on audio, but you should be able to hear it here:


So until I get the motivation to sit out in a frozen garage: What do you think the noise is?
 

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Sounds like a little siren or whistle. Are you sure its coming from the engine? Almost sounds like a bad ground wire the whines with the rpm climb. Subbed to see if someone can figure this out.

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It's not the sound of an exhaust leak is it? Sounds like you didn't mention that as a possibility so most likely not the case, but throwing a suggestion out there since you mentioned the Milltek exhaust install. Maybe during install the pipes sagged or were moved a certain way and the downpipe slipped slightly out vclamp and is causing a whistle?
 

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Discussion Starter · #5 ·
It's not the sound of an exhaust leak is it? Sounds like you didn't mention that as a possibility so most likely not the case, but throwing a suggestion out there since you mentioned the Milltek exhaust install. Maybe during install the pipes sagged or were moved a certain way and the downpipe slipped slightly out vclamp and is causing a whistle?
Hmm, I didn't think to check the vband. I am pretty sure that isn't the case, as a pre-o2 sensor leak would wreak havoc on the logs but I will check it out either way!

It almost sounds like a loose clamp in the intake side of the turbo to me but I could be wrong.
Good point, I will recheck the intake piping. It looks 'secure' but it's also the hardest to look at.

Thanks for the tips! I will most likely be testing things this weekend, weather depending.
 

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Hmm, I didn't think to check the vband. I am pretty sure that isn't the case, as a pre-o2 sensor leak would wreak havoc on the logs but I will check it out either way!



Good point, I will recheck the intake piping. It looks 'secure' but it's also the hardest to look at.

Thanks for the tips! I will most likely be testing things this weekend, weather depending.
If it's causing a whistle then there is a chance that it's such a small minor little pinhole level of a leak that it isn't throwing off AFR or anything, since it's an easy check it shouldn't hurt to look! Hopefully it's something that simple. My old 2.slow Jetta (2000) had a minor exhaust leak at the cat which caused a whistle so everyone thought it was the 1.8t model when I stepped on the gas.
 

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If it's causing a whistle then there is a chance that it's such a small minor little pinhole level of a leak that it isn't throwing off AFR or anything, since it's an easy check it shouldn't hurt to look! Hopefully it's something that simple. My old 2.slow Jetta (2000) had a minor exhaust leak at the cat which caused a whistle so everyone thought it was the 1.8t model when I stepped on the gas.
Why did you ruin your profile pic!!?? Lol

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OP, I have the same mountune turbo kit and mine makes the exact same noise! I hadn't noticed any other side effects so I've been living with it. I can't find anything wrong either. It's definitely NOT a boost leak.

I haven't yet re-seated the v-band connection but I don't expect to find anything. I do think it's rather odd that the EFR doesn't utilize a fire ring connection to the downpipe like the stock turbo did.
 

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I had an exhaust leak here on my turbo which made a similar sound. Also made my heater smell like complete **** because the exhaust fumes would go into the cabin. Had to buy new turbo adapter studs and nuts and completely drop the turbo and resemble. 20170108_191838_1483926467126.jpg FB_IMG_1483924474430_1483926493360.jpg
 

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Discussion Starter · #15 ·
OP, I have the same mountune turbo kit and mine makes the exact same noise! I hadn't noticed any other side effects so I've been living with it. I can't find anything wrong either. It's definitely NOT a boost leak.

I haven't yet re-seated the v-band connection but I don't expect to find anything. I do think it's rather odd that the EFR doesn't utilize a fire ring connection to the downpipe like the stock turbo did.
Hmm, good to know I'm not the only one! Thanks for chiming in. If do find out where the noise is coming from and can fix it I will let you know.

Have you check every hose line, tubes, connections?
I went through and inspected what I could the weekend before posting this. Hopefully when I can get an actual boost leak test done it will tell me more.

I had an exhaust leak here on my turbo which made a similar sound. Also made my heater smell like complete **** because the exhaust fumes would go into the cabin. Had to buy new turbo adapter studs and nuts and completely drop the turbo and resemble. View attachment 200577 View attachment 200585
Just curious, but how did you find the leak there? It looks like there is some carbon spray on the second picture? Were your fuel trims or AFR acting up? I can't say I notice any smell out of the heater vents, and I have been using them quite a bit. I sure hope it doesn't come to that, I may just park it until spring if that is the case.
 

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I ended up throwing a lean CEL and then started fishing around. I actually missed this until about the second time under there. I ended up shaking the turbo and then I noticed it sounded like it was lose somewhere. Ended up finding it after that.
 

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I had a pretty big block of text here, but I didn't even want to read it all so here is the TL'DR:

I recently was driving with someone who was in a different big turbo Focus. He noticed a noise and said the other Focus did not have it. I thought it was just a quirk of the turbo and thought nothing of it until he mentioned it. I am planning on boost leak testing again but that equipment is two hours away in a frozen garage.

- Have a Mountune MRX Kit (BW 6258(a?))
- Had a boost leak test when installed, everything was perfect
- Swapped Injen exhaust with Milltek
- Noticed slight hum/whine/whistle coming from the firewall after Milltek install
- Can't hear it from outside
- Really only noticeable below 3k rpm, otherwise exhaust drones noise out
- Not boost dependent, happens in vacuum as well
- Doesn't sound like any boost leak I have ever heard.
- Car runs fine, boost still builds up quick and holds.
- No oil loss, smoke and no play in the turbo flywheel (Checked that last night)

It took me forever to catch it on audio, but you should be able to hear it here:


So until I get the motivation to sit out in a frozen garage: What do you think the noise is?
I have the MRX kit and the same sound.... I am thinking that its characteristic of the cold side housing and integrated bpv. The sound only exhibits itself at high (LOW?) vac levels and low boost levels....I also notice a whistle at high boost part throttle.

My theory is the integrated bpv is transient during this spool period causing a whistle
 

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Discussion Starter · #19 ·
I figured I would give a final update on this, now that the turbo is off.

We did a boost leak test while we had everything apart and no leaks were found. Additionally, there were no signs of leaks around the exhaust flange. I am not really sure where else we would of found a leak, so I would have to agree with the others that this is a "normal" noise. Why mountune's turbo is louder than others is still a mystery, although one I probably won't be solving.
 

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I have a SBD turbo and I have a similar sound as well haven't dismounted the turbo but haven't found any leaks. But only makes the noise during initial spool
 
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