Turbo flutter

[Ares3985]

Turbo flutter bad on throttle close? Or only bad while throttle open? Let’s talk about this. See so many conflicting posts about this subject. When searching the internet you get a lot of companies saying it’s bad. Guess what they sell??? Blow off valves!!! So is it really bad? Or is it a myth. I understand if you are wot and you have turbo flutter there is something seriously wrong but what about when you are off the gas? I know everyone is going to have a different opinion on this but let’s hear it. Any hard facts or data would be good also since there is absolutely none on the internet which makes me think this could be myth.

 

 

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[SageAbkatsor]

A lot of the people saying that it is bad have misperceptions about what is causing it, and say it is the turbine being driven in the reverse direction. While that’s not entirely untrue as my understanding is that the noise is from a reverse impulse being applied, the turbine is spinning incredibly fast and most definitely is not reversing direction. It is just a differential in the exhaust gas pressure and the intake air under boost. I have seen videos of professional high end performance tunes with a lot of flutter after lifting off the throttle and I can’t image these people would allow for that if it was damaging. With that said I also took those videos with a grain of salt because they were people that could afford to fix things when they blew up and were building for performance as opposed to reliability. I prefer a philosophy that says to run an adjustable 100% recirculating valve to keep all metered air within the system to avoid fuel trim spikes, and make adjustments to make the release tight to the point of flutter, and then back it off just a touch. Obviously a blow off can be properly tuned for.

 

I’m sure there are others who could shed more light on the physics of what causes the noise and if it is good or bad. From a performance standpoint I believe some flutter is good as it means you are not opening your recirc/blowoff too early so that you stay in boost more often

[utc_pyro]

It can increase load on the turbo center housing bearings accelerating wear. How much? Enough that OEM’s put BOV/BPV’s in tuned to totally prevent it, but not enough that racing teams go out of their way to make sure there is absolutely none.

 

My Evo3 16G starting making them under certain circumstances when I changed to the Grimmspeed intake. Am I worried enough about it to even bother adjusting my adjustable BOV? Nope.

[Ares3985]

A lot of the people saying that it is bad have misperceptions about what is causing it, and say it is the turbine being driven in the reverse direction. While that’s not entirely untrue as my understanding is that the noise is from a reverse impulse being applied, the turbine is spinning incredibly fast and most definitely is not reversing direction. It is just a differential in the exhaust gas pressure and the intake air under boost. I have seen videos of professional high end performance tunes with a lot of flutter after lifting off the throttle and I can’t image these people would allow for that if it was damaging. With that said I also took those videos with a grain of salt because they were people that could afford to fix things when they blew up and were building for performance as opposed to reliability. I prefer a philosophy that says to run an adjustable 100% recirculating valve to keep all metered air within the system to avoid fuel trim spikes, and make adjustments to make the release tight to the point of flutter, and then back it off just a touch. Obviously a blow off can be properly tuned for.

 

I’m sure there are others who could shed more light on the physics of what causes the noise and if it is good or bad. From a performance standpoint I believe some flutter is good as it means you are not opening your recirc/blowoff too early so that you stay in boost more often

 

 

 

Yes. This is pretty much what I’ve heard as well. I have heard of some using a block off plate to completely seal the bpv but that doesn’t sound like a good idea.

 

What bpv do you find is best? I know that some are easily adjusted from outside the housing but others you need to open up. Obviously exterior adjustment is more convenient

 

 

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[SageAbkatsor]

Go Fast Bits Mach 2 TMS Recirculating Diverter Valve

 

GFB T9101

 

Now, granted, I dont think I am the guy to ask for any advice considering my car is knocking right now. With that said, I don't think it has anything to do with this diverter valve, and this is a very nice unit.

 

I also paired it with a Samco sport BPV hose that took months for RSD to get in because I already had a perrin intercooler coupler and so I didn't want to spend the extra $60 on the kit they had in stock that included both. If you do not have an intercooler coupler already though, this kit is nice to replace some of the factory rubber with silicone. Hats off to RSD though for contacting their samco rep and special ordering this for me.