thoughts on turbo flutter?

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OneTwenty
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Re: thoughts on turbo flutter?

Post by OneTwenty » Mon Oct 16, 2017 2:16 pm

DGJ123d wrote:
Mon Oct 16, 2017 12:54 pm
OneTwenty wrote:Trying to make a boggo 4 pot diesel sound decent is a waste of time IMO. I've nothing against BOV's, had a nice one of my old Focus ST, but don't see the point with a diesel.
It sounds like a BOV was suggested as a solution to something that the op wasn't asking for.

As I said above and the owner confirmed, he wants the lift-off "coooo" sound which is a result of the veins of the turbo being held open after giving it full power then taking your foot off the accelerator quickly (usually at about 2.5krpm).

This sound can be heard once the backbox is removed or with a straight through exhaust and is in no way related to a wastegate (which a diesel doesn't have) or a blow-off or recirculating valve (which a diesel doesn't have/need)

Edit: also a diesel with a straight through has quite a nice rasp on full-throttle! It's all personal preference though and agreed you'll never make it sound like a 5-pot petrol like in the ST
It wasn't that great on the ST though either tbh, sounded like a hamster sneezing although with the other mods it all added up to sounding half decent!! :D The only decent BOV and chatter/turbo stall sounds come from the big engined Jap motors IMO, 2JZ Supra, GTR etc.
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Re: thoughts on turbo flutter?

Post by drifterr » Tue Oct 17, 2017 9:58 pm

This is one hell of a confusing thread :lol:
Removing a back box has nothing to do with turbo flutter..
This is turbo flutter, is that what you are after? (Video below).
If so then it's heard through the intake.
When I installed my bov it was a bit tight, the n54 has a pretty decent sounding turbo flutter (on my car anyway) :D but as much as I wanted to keep it that way it's no great for the turbo as it's basically air going back against the compressor wheel.

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Re: thoughts on turbo flutter?

Post by DGJ123d » Wed Oct 18, 2017 8:33 am

drifterr wrote:This is one hell of a confusing thread Image
Removing a back box has nothing to do with turbo flutter...
You're right, it has nothing to do with turbo flutter. However the op drives a diesel which doesn't have a blow off valve and wouldn't make a turbo flutter noise in any case. I think wires have been crossed by people mentioning BOVs in a diesel thread Image

He wants the closing veins sound like you can hear on this one from about 10 seconds in...



This is achieved by removing the backbox or going straight through.

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Re: thoughts on turbo flutter?

Post by fmn716 » Wed Oct 18, 2017 2:45 pm

Sounds awesome on a sr20


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Re: thoughts on turbo flutter?

Post by docwra » Wed Oct 18, 2017 2:51 pm

Are there only like 2 people who have owned a turbo car before here? :lol:

I assume we are all talking about this noise:

https://www.youtube.com/watch?v=m2xkcS3v9i8

A Dump valve is nothing to do with turbo "flutter"/"chatter"/compressor surge/owl noises which I will refer to as the pigeon noise from now on, it actually reduces the noise as air is venting elsewhere in the system. That said, some BOV's replicate the pigeon noise, this is usually your best route on a diesel (see below)
The noise comes from the pressurised air that has travelled through the turbo but has nowhere to go when the throttle plate is closed, so it comes back out the front of the turbo, through the blades which makes the noise.
All turbo cars with a throttle plate make the noise, but most cars have a suppressor fitted somewhere near the air filter so you dont hear the noise, in the case of the N54 the closed inlets do the job pretty well too. As someone else has said, a turbo without a wastegate will just keep producing boost until it blows up so unsurprisingly it doesnt happen.
Diesel cars often dont have throttle plates to close the system so its a lot more difficult to get the noise, I believe very high boost can do it though.

Size of engine is irrelevant, level of boost, hard intake pipes and type of air filter make a lot more difference.
It used to be said that it damages a turbo but Ive never seen hard evidence of this, as it happens the other route to the noise through atmospheric BOV's is worse as they can cause fuelling issues.

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Re: thoughts on turbo flutter?

Post by drifterr » Wed Oct 18, 2017 3:28 pm

docwra wrote:
Wed Oct 18, 2017 2:51 pm
Are there only like 2 people who have owned a turbo car before here? :lol:

I assume we are all talking about this noise:

https://www.youtube.com/watch?v=m2xkcS3v9i8

A Dump valve is nothing to do with turbo "flutter"/"chatter"/compressor surge/owl noises which I will refer to as the pigeon noise from now on, it actually reduces the noise as air is venting elsewhere in the system. That said, some BOV's replicate the pigeon noise, this is usually your best route on a diesel (see below)
The noise comes from the pressurised air that has travelled through the turbo but has nowhere to go when the throttle plate is closed, so it comes back out the front of the turbo, through the blades which makes the noise.
All turbo cars with a throttle plate make the noise, but most cars have a suppressor fitted somewhere near the air filter so you dont hear the noise, in the case of the N54 the closed inlets do the job pretty well too. As someone else has said, a turbo without a wastegate will just keep producing boost until it blows up so unsurprisingly it doesnt happen.
Diesel cars often dont have throttle plates to close the system so its a lot more difficult to get the noise, I believe very high boost can do it though.

Size of engine is irrelevant, level of boost, hard intake pipes and type of air filter make a lot more difference.
It used to be said that it damages a turbo but Ive never seen hard evidence of this, as it happens the other route to the noise through atmospheric BOV's is worse as they can cause fuelling issues.
I never meant a bov is required for turbo flutter, was just stating that my bov setting was to tight causing the flutter.
When it did flutter the sound clearly came from the rear inlet pipe and not from my bov!
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Re: thoughts on turbo flutter?

Post by docwra » Wed Oct 18, 2017 3:53 pm

Dude, you were one of the few people that actually seemed to have some idea ;)

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Re: thoughts on turbo flutter?

Post by DGJ123d » Wed Oct 18, 2017 5:00 pm


docwra wrote:Diesel cars often dont have throttle plates to close the system so its a lot more difficult to get the noise, I believe very high boost can do it though.
I got the noise on my old Leon Cupra TDI when I had a Milltek straight through fitted, and also in my last car which was a Renault Laguna that I took the backbox off when one of the exhaust mounts was loose. Both only 150bhp and around 20psi of boost which is pretty normal in a diesel. As you said there's suppressors in the intake (the air filter itself being one) so to get the noise out on a diesel requires an unsupressed exhaust instead.

I think you explained it far more technically than I could though Image

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Re: thoughts on turbo flutter?

Post by jimBabyBMW » Wed Oct 18, 2017 5:43 pm

I mentioned the BOV, but not for a diesel. Someone mentioned wastegate flutter which would just mean it's broken or not working. Wastegates are controlled by an actuator on the hot side of the turbo and only open to bypass exhaust gas away from the turbo to reduce boost pressure.

As someone said, no butterfly valve so no BoV is required on a diesel. Nor will you get compressor surge, or chatter as per the videos, because it needs the butterfly valve (throttle plate) to pressurise the inlet pipe.

On a petrol car, a tight BoV will cause compressor surge. It's just the compressed air having no where to go when the throttle plate closes, so it goes back through the turbo and stalls it.

You can fit a BoV to a diesel car, but you have to add a plate to close and divert the air to atmosphere through the BoV, making the chirp. These can be added solely for that purpose, but there is no performance gain and it's a bit, well, silly really.

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Re: thoughts on turbo flutter?

Post by OneTwenty » Wed Oct 18, 2017 9:18 pm

We all know the differences, but the discussion moved from flutter/compressor stall to BOVs, which I agree is a slight tangent but that’s just the way it went. :D

Either way, it’s still a bit pointless imo making a diesel sound good.
Last edited by OneTwenty on Mon Apr 23, 2018 1:58 pm, edited 1 time in total.
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Re: thoughts on turbo flutter?

Post by Sam_M » Thu Oct 19, 2017 8:59 am

This thread is funny.

That diesel vid above, that's just the sound of a turbo spooling down.... You're never going to get flutter from a diesel because no throttle plate.

There's a guy in my local town who's fitted a BOV and big exhaust to his TDI Golf, makes me p*ss myself laughing when this half hearted ptshhh goes off as he drives by, not to mention the god awful noise from the drainpipe exhaust. :lol:

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Re: thoughts on turbo flutter?

Post by B NEGATIVE » Thu Oct 19, 2017 9:36 am

jimBabyBMW wrote:
Sat Oct 14, 2017 7:36 pm
B NEGATIVE wrote:
Fri Oct 13, 2017 8:12 pm
Turbo flutter is normal,it wont damage anything,if it bothers you then fit a wastegate. I think you are confusing wastegate flutter with turbo flutter,they are different things.
All turbos have a wastegate already (barring some Porsches etc) Do you mean diverter valve or blow off valve, sometimes called a dump valve, though dumping to atmosphere should be left to 90s Jap/ford cars.
Yes,The dump valve is what Im referring to. Thanks for the terminology correction.
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Re: thoughts on turbo flutter?

Post by DGJ123d » Thu Oct 19, 2017 9:57 am


Sam_M wrote:This thread is funny.

That diesel vid above, that's just the sound of a turbo spooling down.... You're never going to get flutter from a diesel because no throttle plate.
It seemed to go in the wrong direction pretty quickly! That's why I wanted to clarify what noise the op was after.

I think the de-spooling sound is ok when it's not too loud, I went non-res on the Milltek I had and it was only really loud when I floored it in second and changed up quickly.

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Re: thoughts on turbo flutter?

Post by MSM » Sat Oct 21, 2017 11:50 am

DGJ123d,

Some Diesel engine turbocharger systems do have wastegates to control boost. If you have a 123d, then you have wastegate in the control system on your own car.

Interestingly, If you have a LCI 123d you also have a butterfly in the intake tract that amongst other functions serves as a safety valve to prevent diesel run-on happening if the engine starts to burn its own lubricating oil.

Msm

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Re: thoughts on turbo flutter?

Post by DGJ123d » Sat Oct 21, 2017 10:18 pm

MSM wrote:DGJ123d,

Some Diesel engine turbocharger systems do have wastegates to control boost. If you have a 123d, then you have wastegate in the control system on your own car.

Interestingly, If you have a LCI 123d you also have a butterfly in the intake tract that amongst other functions serves as a safety valve to prevent diesel run-on happening if the engine starts to burn its own lubricating oil.

Msm
Cool to know I have one on mine! I know the twin scroll doesn't have one and neither did my old variable vein GT1749 so was just clarifying what the OP was after.

Is the butterfly valve on these activated on shut down like the ASV on the VAG group engines or is it self-activating? Really nice to be learning about my engine and meeting other people willing to share their knowledge, cheers MSM :-)

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