GTI MK7 BOV

[GTI_Owner]

Did you get a custom tune for the bov? If not log your fuel trims after upshifting. You’ll notice they’re gonna be loose. You should also notice a loss of acceleration after an upshift. I’m referring to a bov the vents to atmosphere

What do you mean by fuel trim will be loose?
So the difference I'm looking for is with the stock DV after a shift acceleration is greater than with the BOV installed?
What variable do you recommend recording for the acceleration value?
Does a custom tune eliminate these issues attributed to the BOV?

I'm repeating what I've read in the forum from guys who know. Also I rarely see anyone post a problem with the stock DV but I see problems posted for a lot of the aftermarket DV 's. I've seen so many responses to people to just put the OEM DV back in when they reported a problem.

Ok

Ran a BOV on my previous car, a 16 GTI 6MT. Sounded great but spit crud all over the back of my engine. Transient response went to shit, plus the loss of boost on shifts. Would not recommend.

What variable do you suggest logging for transient response?
When you say loss of boost on a shift, what should I be looking for to change with the boost?

 

[Keehs360]

What do you mean by fuel trim will be loose?
So the difference I'm looking for is with the stock DV after a shift acceleration is greater than with the BOV installed?
What variable do you recommend recording for the acceleration value?
Does a custom tune eliminate these issues attributed to the BOV?

Ok

What variable do you suggest logging for transient response?
When you say loss of boost on a shift, what should I be looking for to change with the boost?

Short term and long term fuel trims, air fuel and air fuel learning. That’s what u would log in a Subaru. In a vw you’d log those things too but they might be called different things. Sorry I can’t be specific. But hopefully it can point you towards a definite answer in the future.

 

[Square1]

Buy it you'll like it.

 

[Reggie Enchilada]

What do you mean by fuel trim will be loose?
So the difference I'm looking for is with the stock DV after a shift acceleration is greater than with the BOV installed?
What variable do you recommend recording for the acceleration value?
Does a custom tune eliminate these issues attributed to the BOV?

Ok

What variable do you suggest logging for transient response?
When you say loss of boost on a shift, what should I be looking for to change with the boost?

The DV recirculates the compressed air back into the intake tract, that's why there is no or very little boost loss during shifts. The BOV that vents to atmosphere dumps the compressed air to atmosphere, so the boost has to build back after the shift.

Put simply, with an atmospheric BOV (aka dump valve) the turbo will need to spool up after each shift. The DV loses almost no boost during shifts, so the turbo won't have to spool up after the shift.

As for logging, you can log the boost pressure, wastegate duty cycle, and possibly the recirc valve (DV) voltage/position.

 

[NBMK7GTI]

Yeah, I've seen that comment made a few times. What makes the stock DV best? I'm using the Forge BOV and don't notice any problems. I still have the stock DV and don't mind re-installing it to look for a difference. I have an AP so I can log the different parts. What should I log to see where the stock DV outperforms the Forge?

Because time and time again they cause nothing but problems. Most tuners claim the oem is fine in big power applications and they’re usually pretty resilient unlike the mkv diaphragm days.

 

[jimlloyd40]

Ran a BOV on my previous car, a 16 GTI 6MT. Sounded great but spit crud all over the back of my engine. Transient response went to shit, plus the loss of boost on shifts. Would not recommend.

Must have been something else wrong because I've had a spacer on mine that I got for free for 70,000 miles without any problems.

 

[Keehs360]

Must have been something else wrong because I've had a spacer on mine that I got for free for 70,000 miles without any problems.

Weren’t u custom tuned with that spacer on?!? If so, then there u go

 

[jimlloyd40]

Weren’t u custom tuned with that spacer on?!? If so, then there u go

Yeah always custom tuned.

 

[Keehs360]

Yeah always custom tuned.

If u remove the spacer. Your car will run a bit off I bet. If your tuner is any good, he obviously compensated for the spacer.

 

[jimlloyd40]

If u remove the spacer. Your car will run a bit off I bet. If your tuner is any good, he obviously compensated for the spacer.

EQT was the tuner and he wasn't aware I was using a spacer but I suppose he didn't need to since he had the logs to tune from. It was a remote dyno tune.

 

[Keehs360]

EQT was the tuner and he wasn't aware I was using a spacer but I suppose he didn't need to since he had the logs to tune from. It was a remote dyno tune.

Next time u get a second. Get a log for me. Just 3-4 miles of stop and go traffic. No wide open throttle plz. I’ll text u my email. I’ll take a look.

 

[GTI_Owner]

Short term and long term fuel trims, air fuel and air fuel learning. That’s what u would log in a Subaru. In a vw you’d log those things too but they might be called different things. Sorry I can’t be specific. But hopefully it can point you towards a definite answer in the future.

Cobb lists these:

• LTFT Long term fuel trims stored by ecu. ( Value of 1 = 0% correction | Value of 1.1 = 10% fuel added | Value of 90 = -10% fuel removed)
• STFT Current fuel trim stored and calculated by the ECU.
• AFR Air/fuel ratio based on the front oxygen sensor.
• AFR Set Point Target Air/Fuel Ratio

I don't understand what you meant by the readings will be "loose" after shifting.

The DV recirculates the compressed air back into the intake tract, that's why there is no or very little boost loss during shifts. The BOV that vents to atmosphere dumps the compressed air to atmosphere, so the boost has to build back after the shift.

Put simply, with an atmospheric BOV (aka dump valve) the turbo will need to spool up after each shift. The DV loses almost no boost during shifts, so the turbo won't have to spool up after the shift.

As for logging, you can log the boost pressure, wastegate duty cycle, and possibly the recirc valve (DV) voltage/position.

Isn't the DV directing the excess air back into the turbo through the opening shown in this picture? (The opening inside the compressor housing before the compressor wheel)

If that's the case it is being mixed with the air coming from the air box, so it has to be compressed again. I don't understand how the DV would lose very little boost between shifts but the BOV does.

When comparing boost pressure, I assume it will be lower following the shift with the BOV?
When comparing WGDC, is that going to be higher with the BOV?
Options for logging the DV are:

• Recirculation Actuator Position
• Recirculation Actuator Setpoint

What are these going to show to indicate the DV performing better than the BOV?

Because time and time again they cause nothing but problems. Most tuners claim the oem is fine in big power applications and they’re usually pretty resilient unlike the mkv diaphragm days.

What are the problems you are saying they cause?

 

[NBMK7GTI]

Cobb lists these:

• LTFT Long term fuel trims stored by ecu. ( Value of 1 = 0% correction | Value of 1.1 = 10% fuel added | Value of 90 = -10% fuel removed)
• STFT Current fuel trim stored and calculated by the ECU.
• AFR Air/fuel ratio based on the front oxygen sensor.
• AFR Set Point Target Air/Fuel Ratio

I don't understand what you meant by the readings will be "loose" after shifting.

Isn't the DV directing the excess air back into the turbo through the opening shown in this picture? (The opening inside the compressor housing before the compressor wheel)

If that's the case it is being mixed with the air coming from the air box, so it has to be compressed again. I don't understand how the DV would lose very little boost between shifts but the BOV does.

When comparing boost pressure, I assume it will be lower following the shift with the BOV?
When comparing WGDC, is that going to be higher with the BOV?
Options for logging the DV are:

• Recirculation Actuator Position
• Recirculation Actuator Setpoint

What are these going to show to indicate the DV performing better than the BOV?

What are the problems you are saying they cause?

I don’t recall exactly what issues they cause but there’s definitely a strong correlation of people told to stay stock, they go aftermarket, post nonsense issues, and go back to stock and the problems usually stop. Fwiw I don’t really have a horse in the race but it’s been time and time again since early 2016 on here and the various Facebook groups. Not saying they don’t work trouble free for some but I’m just calling it how I see it and I know others share the same sentiments.

 

[Keehs360]

I don't understand what you meant by the readings will be "loose" after shifting.

so lets say you're running a bov that vents 100% to atmosphere. You shift from 2nd to 3rd, part throttle, no wide open stuff.

the ecu has metered the air that is expected to recirculate. it has accounted for that surge to return. instead your car blew it off into the atmosphere. guess what happens to your air fuel mix immediately after an upshift. and it does that, each and every time the car upshifts. over and over. every day.

 

[Reggie Enchilada]

Cobb lists these:

• LTFT Long term fuel trims stored by ecu. ( Value of 1 = 0% correction | Value of 1.1 = 10% fuel added | Value of 90 = -10% fuel removed)
• STFT Current fuel trim stored and calculated by the ECU.
• AFR Air/fuel ratio based on the front oxygen sensor.
• AFR Set Point Target Air/Fuel Ratio

I don't understand what you meant by the readings will be "loose" after shifting.

Isn't the DV directing the excess air back into the turbo through the opening shown in this picture? (The opening inside the compressor housing before the compressor wheel)

If that's the case it is being mixed with the air coming from the air box, so it has to be compressed again. I don't understand how the DV would lose very little boost between shifts but the BOV does.

When comparing boost pressure, I assume it will be lower following the shift with the BOV?
When comparing WGDC, is that going to be higher with the BOV?
Options for logging the DV are:

• Recirculation Actuator Position
• Recirculation Actuator Setpoint

What are these going to show to indicate the DV performing better than the BOV?

What are the problems you are saying they cause?

Losing very little boost was a bad way for me to explain it. It's really more about keeping the turbo spooled up.

The DV directs the air back into the compressor inlet through the return port that you pointed out. That's why it loses almost no boost on shifts. The compressed air loses some pressure, but it's still moving fast enough to help keep the rotating assembly spinning. Think of it like recycling the compressed air to prevent turbo lag. Since the rotating assembly only slows down slightly, it doesn't need to spool up after the shift. It's a very clever way to prevent compressor surge and recapture some of the energy that would otherwise be lost.

The BOV blocks off the return port and vents the compressed air to atmosphere. Since the air isn't recycled and isn't helping to keep the compressor spinning, the turbo will need to spool up after each shift.