[Juicehead]

Ok, so I started a thread a while back about my HKS SSQV BOV not venting between shifts at full load/throttle. (I am Manual).

It vents well at all other boost psi except at full throttle between shifts, etc. If the BOV was sticking, I assume it would stick at other boost levels as well.

I have read comments where, due to the drive-by-wire, it keeps the throttle open momentarily.


Can anyone validate this? I am not getting any flutter or adverse effects, but don't want to potentially damage my turbos as well...

[Jeff@TopGearSolutions]

Originally Posted by Juicehead

Ok, so I started a thread a while back about my HKS SSQV BOV not venting between shifts at full load/throttle. (I am Manual).

It vents well at all other boost psi except at full throttle between shifts, etc. If the BOV was sticking, I assume it would stick at other boost levels as well.

I have read comments where, due to the drive-by-wire, it keeps the throttle open momentarily.


Can anyone validate this? I am not getting any flutter or adverse effects, but don't want to potentially damage my turbos as well...

If you have a tune most of them can log the DBW or BT Tool and see what is going on with the throttle. You could also log to see how much boost you hold through the shift.

My BOV releases after full throttle but if I shift fast enough sometimes it doesnt because I actually maintain boost through the shift.

So people are partially correct if you do a quick 2nd to 3rd or 3rd to 4th WOT it may not blow off.

But if you just floor it in 3rd gear and release the pedal all the way it should blow off entirely.

Does the clear up any confusion?

[Juicehead]

Originally Posted by Jeff@topgearsolutions

If you have a tune most of them can log the DBW or BT Tool and see what is going on with the throttle. You could also log to see how much boost you hold through the shift.

My BOV releases after full throttle but if I shift fast enough sometimes it doesnt because I actually maintain boost through the shift.

So people are partially correct if you do a quick 2nd to 3rd or 3rd to 4th WOT it may not blow off.

But if you just floor it in 3rd gear and release the pedal all the way it should blow off entirely.

Does the clear up any confusion?

A bit...

If I go full throttle in 2nd gear then left off, the blow-off is delayed.


I should mention that I am FBO with Cobb Stage 2+FMIC

[Syndicategt]

It's no different than an AT car with a BOV....it will not let off when the tranny shifts between gears (unless you let off and the throttle plate closes).

[ECSTuning]

Flat foot shifting, super quick shifts, shifting with partial throttle, etc all cause the BOV to not make a sound. The throttle plate is staying open enough for air to flow and not create the pressure differential needed to open the valve.

[Juicehead]

Originally Posted by Syndicategt

It's no different than an AT car with a BOV....it will not let off when the tranny shifts between gears (unless you let off and the throttle plate closes).

So, unless I am getting flutter/compressor surge, there should be nothing to worry about...

[Syndicategt]

Originally Posted by Juicehead

So, unless I am getting flutter/compressor surge, there should be nothing to worry about...

That depends too. Is your BOV sequential like TiAL or Synapse? Those can release some air during part throttle plate closure, which might sound like flutter.

[Juicehead]

Originally Posted by Syndicategt

That depends too. Is your BOV sequential like TiAL or Synapse? Those can release some air during part throttle plate closure, which might sound like flutter.

It is the HKS SSQV, so yeah, it is...

[Syndicategt]

Originally Posted by Juicehead

It is the HKS SSQV, so yeah, it is...

Sounds to me like everything is fine, but the only way to know 100% is to data log the car (which is a good idea on any tuned/upgraded car). Do a few 2-3-4 pulls and look at your boost graph, it should taper off but you shouldn't see any spikes at WOT (you should during shifts).

[Tzu]

6MT here. I spent quite a lot of time diagnosing this same issue. The BOV would hiccup near redline, about 70% of time. It sounded like it would blow off half, reseat, and release the rest. This was for any gear, and complete accelerator letoff at the end of the pull.

Regardless of the time, adaptation, weather, vacuum lines, spring stiffness etc. this would occur. After many hours troubleshooting, fiddling with engine bits, custom springs, shims, making my own BOV/DV test stand, a simple look at that DBW throttle illustrates the DME closing the throttle, and blipping it between gears. It's completely repeatable. Probaby a default soft shifting technique integrated from factory.

[bigdnno98]

Thanks guys. I have the same issue with my AP BOV. I'll be installing my JB4 and CPS this weekend. I'll post up logs since I really have no idea what you're talking about.