Turbo flutter MMP twins

[Jordi992]

Hey I have posted on FB pages, and JB4 help threads, Still no luck solving my issue.

I am getting turbo flutter when I release the gas. I can hear the bov going off, but also hear the air chirping back through the turbos. Currently running JB4, with the Pump backend flash.


Mods,
7.5" fmic,
Catless DP, 3.5" HPF V2 exhaust
HKS BOV, with ER CP, (Also tried a synapse CP and bov, Both work fine in a stock car.)
Upgraded 6mm vacuum line to BOV
MMP inlets, MMP outlets
MMP S3 turbos
JB4 with PUMP BEF

I used to have a twisted tuning port injection kit on the car, but I have removed that because i thought it was causing my issue. I was forced to leave 2 of the aluminium studs in the block, because they got stuck and I dont want to drill them out.

I will post photos with my JB4 settings, and links to some logs. Another question I had is if I connected the PCV hose properly. Seems odd that I can just connect that hose and run it down the side of the transmission like that.

https://datazap.me/u/jordi992/log-1536947063?log=0&data=1-3-4&zoom=131-188&mark=171-178
In this log you can see the boost doesn't drop fast. I think that is showing the sound im hearing.

 

[pdxbimmertech]

Correct me if I'm wrong but isn't the stock vacuum line for the recirc/BOV 6mm?

The line to the BOV needs to be much larger especially when running aftermarket valve and higher boost than stock. Most people elect to tap the intake manifold with a barbed fitting same size as the barb on the BOV.

 

[DCook]

Correct me if I'm wrong but isn't the stock vacuum line for the recirc/BOV 6mm?

The line to the BOV needs to be much larger especially when running aftermarket valve and higher boost than stock. Most people elect to tap the intake manifold with a barbed fitting same size as the barb on the BOV.

I deleted my post cause i thought the same, but 6mm is .23 which is close enough to 1/4. Factory is smaller than that iirc

 

[veer90]

If you already have a 6mm vac line might be helpful to adjust the spring. I know for Tial you run the 11 psi spring unless you have issues, and only change the spring as a last resort.

 

[veer90]

Correct me if I'm wrong but isn't the stock vacuum line for the recirc/BOV 6mm?

The line to the BOV needs to be much larger especially when running aftermarket valve and higher boost than stock. Most people elect to tap the intake manifold with a barbed fitting same size as the barb on the BOV.

Factory is way smaller that's why 6mm or 1/4" is an upgrade.

 

[pdxbimmertech]

I guess it really depends on if we are talking ID or OD on the hose. If the ID of the vacuum reference line to the BOV is 6mm or 1/4" then all is well. When looking online at vacuum hoses for most euro vehicles they often refer to it as "6mm hose" which is why I asked. If the hose is bigger than OE then I agree with trying a lighter spring and/or shimming the one you have if needed to get the BOV setup properly.

 

[Jordi992]

Hey thanks for the response. Its 6mm ID. Much larger then stock. Stock is about 3.5mm ID.

 

[Jordi992]

the issue im having with the HKS BOV is it only accepts a 3.5mm vacuum line. I could maybe fit a 4.5mm with a zip tie but a 6mm didn't clamp on tight.

 

[Jordi992]

I got lots of photos here if anyone can spot something wrong. I took photos while i was putting everything together.

https://photos.app.goo.gl/JfOGB1xNVuBJ4QOg1

 

[matreyia]

This is a bov issue sounds like. If your bov can't take bigher hoses that may be a problem. Also i used spring less than 11psi on a tial and it works perfect.

 

[Jordi992]

This is a bov issue sounds like. If your bov can't take bigher hoses that may be a problem. Also i used spring less than 11psi on a tial and it works perfect.

Ok i placed an order for a Tial and charge pipe. So i will wait for that. Thanks

 

[matreyia]

I got lots of photos here if anyone can spot something wrong. I took photos while i was putting everything together.

https://photos.app.goo.gl/JfOGB1xNVuBJ4QOg1

Just saw your bov... it's all jacked up. Replace that setup with tial. Are these the new mmp or old?

 

[Jordi992]

Just saw your bov... it's all jacked up. Replace that setup with tial. Are these the new mmp or old?

Whats jacked up about it?

 

[Zhelyazkov]

Get the Tial with the black spring and if you don't want it open at idle shim it a bit. The response is much better with the black spring.

 

[matreyia]

Whats jacked up about it?

Your hose set up with the zip tie. that won't do. Especially on upgraded turbos. And you didn't have a charge pipe before the turbos? Man...you should have had the charge pipe, downpipe, port injection, intake, intercooler, and upgraded trans all before the turbo.

Or are you saying the ER CP had a HK custom fitting and you have to get a Tial ER CP?
That doesn't sound right. In this case, then it's definitly your spring rates and not the bov.

 

[N54gasm]

As others have stated, it's a bov problem. Spring rate isn't correct, or a bov malfunction. Go with a Tial, proven and cant go wrong

 

[Chris@VargasTurboTech]

If you already have a 6mm vac line might be helpful to adjust the spring. I know for Tial you run the 11 psi spring unless you have issues, and only change the spring as a last resort.

You really want the black spring, I don't care what the Tial chart says.

Get the Tial with the black spring and if you don't want it open at idle shim it a bit. The response is much better with the black spring.

Yes, 1000x over.

This gets re-hashed every 6-8 months and someone will point out that the Tial chart would indicate the plain spring is the right one for the N54. Use the black, shim if it being open at idle bothers you (it doesn't bother me), and use a dedicated line.

 

[matreyia]

I ended up using on my particular car the white one at 8psi.

The black at 6psi was too soft and the bov was open like almost an inch.
The Uncolored one at 10psi was too hard and at high acceleration introduced super high whistling noises...sounded awful.

The White one at 8psi for my car was perfect as the bov is BARELY open and I can drive like a Klingon and it is steady as a rock without any inappropriate noises besides the bov release.

Others have used the black or Uncolored spring...it depends on your vacuum levels I suppose. Better to have it open than closed to be sure you have good reaction times on the BOV. Nothing can fly into the opening since air is being pushed out.

 

[Erichale77]

The HKS has no spring to adjust and it can only dump a small amount of boost. Just ditch the HKS and get a Tial. I had flutter as well with HKS and switched to 50mm Tial. Problem solved

 

[Jordi992]

Your hose set up with the zip tie. that won't do. Especially on upgraded turbos. And you didn't have a charge pipe before the turbos? Man...you should have had the charge pipe, downpipe, port injection, intake, intercooler, and upgraded trans all before the turbo.

Or are you saying the ER CP had a HK custom fitting and you have to get a Tial ER CP?
That doesn't sound right. In this case, then it's definitly your spring rates and not the bov.

I already have all the supporting mods. I ordered a tial so I dont need that reducer fitting thing to make it work.

You really want the black spring, I don't care what the Tial chart says.

The HKS has no spring to adjust and it can only dump a small amount of boost. Just ditch the HKS and get a Tial. I had flutter as well with HKS and switched to 50mm Tial. Problem solved

Thanks. My CP, and bov are ready for pickup tomorrow it sounds like. I will pick them up and take the car out again when I get a chance.

But what I dont understand is why did i not have this issue on stock turbos? Im still only doing 15ish PSI. Shouldn't it be the same?