Compressor Surge? Flutter? 16t Hybrids

Jeffman

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Jan 7, 2017
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Is your VS Vader TMAP BOV line connected to your intake manifold or your charge pipe? (It should be intake manifold)
 
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Zbottoroff

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Using a stiffer spring to fix these issues is not the right solution. If you can't use a light spring, there is a problem with your tuning, plumbing or the supporting hardware you've chosen.
You are very well known throughout the N54 forums and I have actually ordered the black spring to try it out. Am wondering if maybe it’s just bad turbos at this point. Thanks for all your help. The tune is from doc vu and he said he has never seen this before.
 

Zbottoroff

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Is your VS Vader TMAP BOV line connected to your intake manifold or your charge pipe? (It should be intake manifold)
Intake manifold. Wondering if it’s just something stupid such as o2 sensors hooked up backwards or too small of an intercooler etc.
 

Threetirtyfive

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Jan 9, 2019
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A couple of things -with that cold start- does the noise defo come from the dump valve not the turbos? (if it's from the turbos it sounds like siren a bit where compressor hits the housing), hopefully just the BOV.

secondly:
Something to point out, MHD doesn't have a separate gauge for the manifold MAP sensor and the chargepipe TMAP sensor. Only the manifold sensor will ever see vacuum, and with the throttle blade closed, you could actually have boost in the chargepipe and engine vacuum on the other side simultaneously. So despite there being boost displayed during that throttle closure, that is only an indicator of the chargepipe side of the blade. If there is vacuum building up on the manifold side, that will pull the bov plunger up and it may not even register as vacuum in the log.
The CP DOES see VAC especially under coastdown from high speed in low gears- CP vac is roughly minus 10 max whereas manifold is up to minus 22. Not sure if you're talking actual or measured vac, but if you connect a manual boost gauge to the inlet manifold it will register over -20, whereas MHD displays up to around minus 10 ( which therefore must be coming off the CP TMAP).
But yes any pressure differential CP side to inlet manifold side of the butterfly will potentially cause the BOV to open. Incidentally the HKS SSQV doesn't run different size springs and shouldn't get this issue.

If the noise is coming off the BOV- run a harder spring.
 
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Zbottoroff

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A couple of things -with that cold start- does the noise defo come from the dump valve not the turbos? (if it's from the turbos it sounds like siren a bit where compressor hits the housing), hopefully just the BOV.

secondly:

The CP DOES see VAC especially under coastdown from high speed in low gears- CP vac is roughly minus 10 max whereas manifold is up to minus 22. Not sure if you're talking actual or measured vac, but if you connect a manual boost gauge to the inlet manifold it will register over -20, whereas MHD displays up to around minus 10 ( which therefore must be coming off the CP TMAP).
But yes any pressure differential CP side to inlet manifold side of the butterfly will potentially cause the BOV to open. Incidentally the HKS SSQV doesn't run different size springs and shouldn't get this issue.

If the noise is coming off the BOV- run a harder spring.
So I should see what vacuum is on both sides instead of just the intake manifold side?
 

doublespaces

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Oct 18, 2016
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The CP DOES see VAC especially under coastdown from high speed in low gears- CP vac is roughly minus 10 max whereas manifold is up to minus 22. Not sure if you're talking actual or measured vac, but if you connect a manual boost gauge to the inlet manifold it will register over -20, whereas MHD displays up to around minus 10 ( which therefore must be coming off the CP TMAP).
But yes any pressure differential CP side to inlet manifold side of the butterfly will potentially cause the BOV to open. Incidentally the HKS SSQV doesn't run different size springs and shouldn't get this issue.

So I should see what vacuum is on both sides instead of just the intake manifold side?

No,

What was said above isn't accurate. There is a difference of units between 20 inches of mercury and 10 psi(they are aproximately equivalent) and likely he is mixing them.

Mhd combines the negative vacuum reading from the manifold MAP sensor with the positive boost reading from the chargepipe TMAP (two totally different sensors) and displays it on one parameter/gauge. For those with a JB4 it's possible you'll actually see their boost gauge display 0.1 as the minimum as that is only showing the chargepipe TMAP.

Just from the physical placement of the chargepipe TMAP sensor, it is impossible to get any meaningful vacuum reading there as there are no obstructions to the path such as another throttle blade.
 
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doublespaces

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You are very well known throughout the N54 forums and I have actually ordered the black spring to try it out. Am wondering if maybe it’s just bad turbos at this point. Thanks for all your help. The tune is from doc vu and he said he has never seen this before.

I didn't recognize any of the sounds in that video. I highly doubt you've got bad turbos causing those sounds, it is possible to have turbos with really bad compressor/turbine combination making surge more likely, but I'm not the turbo expert. Does your car do this with a regular OTS map?
 
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Zbottoroff

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I didn't recognize any of the sounds in that video. I highly doubt you've got bad turbos causing those sounds, it is possible to have turbos with really bad compressor/turbine combination making surge more likely, but I'm not the turbo expert. Does your car do this with a regular OTS map?
I haven’t tuned it with a regular ots map because those tunes aren’t made specifically for those turbos.. you think it would be alright to try that?
 

doublespaces

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I haven’t tuned it with a regular ots map because those tunes aren’t made specifically for those turbos.. you think it would be alright to try that?
As far as I'm aware. Running a basic ots map should be fine for diagnostic purposes, I don't know what MAP or O2 sensors you have baked into your tune and the waste gate duty cycle will probably be way off so I wouldn't got WOT or anything. Someone else would have to chime in, I've been single turbo for years and don't remember what's involved in switching back. For me, it isn't possible due to the boost control strategy.