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So, I came across this, yes yes Facebook but I believe Mark Roberts is a tuner- Sonic Tuned. Here is the link, not sure if it was already discussed- also put the text below.

Facebook Groups

My question before the read is, BOVs good or a waste of money (I don’t care about the chirp)?

Here is the text in case you can click the link-

Mark Robert’s—
I see a lot of questions lately concerning blowoff valves for these cars. The simple and short answer is, they don’t work. Here’s why:

A typical turbo car, let’s say the GTR for instance, uses mechanical wastegates and recirculating blowoff valves to reduce boost when letting off the gas and sometimes between shifts. Whenever you see a GTR using a standard VTA (vent to atmosphere) blow off valve, you’ll find the car has been converted to speed density. It doesn’t use filter maf signals for fueling but a volumetric efficiency(VE)table precisely tuned by your tuner which doesn’t monitor active airflow but uses other calculations for proper engine fueling.

A recirculating blowoff valve is REQUIRED when used in a system that places the MASS AIR FLOW SENSOR(MAF) in front of the valves(which is how most systems are setup).
A recirculating valve relieves pressure but doesn’t “waste” the airflow simply recirculates and pumps it back into the intake tract POST MAF) The reason for this is the MAF pre-fuels the engine which means ANY AIR passing by the MAF has to go into the engine. If it doesn’t, the ecu still adds fuel for that amount of air going into the engine. Extra fuel/less air= rich dips in air fuel. This won’t blow your engine up but it will cause your drivability to suffer and things like your spark plugs/AF sensors to degrade/foul over time.

The VR30 ECU’s logic is much different than the GTRs and other older systems. It uses the electronic wastegates and throttle bodies to limit/decrease boost. When you let off the gas, instead of relying on a recirculating blowoff valve (which is what it would need being that is a MAF car) to reduce spikes, it completely opens the wastegates and momentarily holds the throttle bodies open(sometimes up to 0.25 seconds) to give the small turbos time to slow down through exhaust turbine pressure relief NOT compressor pressure relief.

The two main reasons the VTA BOVs DONT work on these cars is because they are not currently able to be tuned in speed density and even after adding them, any pressure spikes you think you might be limiting, aren’t limited enough or even at all to make a difference in extending the turbo life due to the throttle body logic and how it hesitates closing once more than stock boost is added to the car.

In order for blow off valves to work, the valve has to be subjected to a positive pressure to vacuum condition to suck the piston up into the head of the BOV to allow air to escape the bottom portion of the valve. The throttle body logic limits this transaction completely and you end up with a small double spike every time. I have taken back to back logs and if I posted the boost pressure spikes after letting off the throttle, no one (including myself) would be able to tell you which log did and didn’t have the BOVs. The throttle let off spiking remained almost identical. This is something built into the logic that has yet to be(or able to be) solved by ECUTEK. -Mark Roberts- SonicTuned”
 
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Well that answers a few questions I had. Seeing as how manufacturers make their cars with reliability in mind, most of the time anyway, I was curious why the VR30 didn’t come with BOVs.
 

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2021 Q50 RedSport, ARK Cat-Back. HKS BOV, AMS LDP, Mishimoto Catch Can
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I've heard from multiple people stating that it is not good for the vehicles, But have also heard good things as well. There was a post a while ago with a video of a guy explaining why not to get them so if you want more explanations, just search at the top. At the end of the day, I love the sound it produces, nothing like zooming up next to a car that thinks he's hot s**t and letting off the throttle. Not everyone here likes the sound, they prefer the sleeper style.
 

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I read the SonicTuned post as I'm part of that FB group. In my experience the off throttle is much faster ..no 1/2 second surge that the OEM system uses to bleed off the extra pressure. Z1 has a good read on the pros of running their HKS BOV's. Bottom line nothing bad, but better responce. I like mine.
 

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I read the SonicTuned post as I'm part of that FB group. In my experience the off throttle is much faster ..no 1/2 second surge that the OEM system uses to bleed off the extra pressure. Z1 has a good read on the pros of running their HKS BOV's. Bottom line nothing bad, but better responce. I like mine.
AMS and Goracebox, 2 of the top tuners for the VR say not to run them. I don't know how much more evidence you need.
 

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@IridiumRS400 runs BOV's and likes them. He puts down excellent #'s. They may not be needed, but I don't see any real downside.
 
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Yes, MAF engines need a recirculated BOV to function correctly, since what you "blow off" is metered, accounted air to the ECU. People obviously run the atmospheric, just that is not the proper, nor an optimal method.

Secondly, a BOV is not required on an automatic like it is on a manual transmission, mostly because on auto, the TB doesn't close between shifts like on a manual. There is the odd time though that you may 'get on it' and suddenly left off in same gear, but unless you do it purposely, that scenario probably wouldn't happen enough to warrant a BOV (for that purpose).
 

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Mark and I went back and forth in that thread about the value of BOV's and some of his log pics. I'm in the camp that they're a drivability improvement to taste for those that don't like the throttle hanging open, which is only solved on a tuned car. They're not a requirement.
 

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So, I came across this, yes yes Facebook but I believe Mark Roberts is a tuner- Sonic Tuned. Here is the link, not sure if it was already discussed- also put the text below.

Facebook Groups

My question before the read is, BOVs good or a waste of money (I don’t care about the chirp)?

Here is the text in case you can click the link-

Mark Robert’s—
I see a lot of questions lately concerning blowoff valves for these cars. The simple and short answer is, they don’t work. Here’s why:

A typical turbo car, let’s say the GTR for instance, uses mechanical wastegates and recirculating blowoff valves to reduce boost when letting off the gas and sometimes between shifts. Whenever you see a GTR using a standard VTA (vent to atmosphere) blow off valve, you’ll find the car has been converted to speed density. It doesn’t use filter maf signals for fueling but a volumetric efficiency(VE)table precisely tuned by your tuner which doesn’t monitor active airflow but uses other calculations for proper engine fueling.

A recirculating blowoff valve is REQUIRED when used in a system that places the MASS AIR FLOW SENSOR(MAF) in front of the valves(which is how most systems are setup).
A recirculating valve relieves pressure but doesn’t “waste” the airflow simply recirculates and pumps it back into the intake tract POST MAF) The reason for this is the MAF pre-fuels the engine which means ANY AIR passing by the MAF has to go into the engine. If it doesn’t, the ecu still adds fuel for that amount of air going into the engine. Extra fuel/less air= rich dips in air fuel. This won’t blow your engine up but it will cause your drivability to suffer and things like your spark plugs/AF sensors to degrade/foul over time.

The VR30 ECU’s logic is much different than the GTRs and other older systems. It uses the electronic wastegates and throttle bodies to limit/decrease boost. When you let off the gas, instead of relying on a recirculating blowoff valve (which is what it would need being that is a MAF car) to reduce spikes, it completely opens the wastegates and momentarily holds the throttle bodies open(sometimes up to 0.25 seconds) to give the small turbos time to slow down through exhaust turbine pressure relief NOT compressor pressure relief.

The two main reasons the VTA BOVs DONT work on these cars is because they are not currently able to be tuned in speed density and even after adding them, any pressure spikes you think you might be limiting, aren’t limited enough or even at all to make a difference in extending the turbo life due to the throttle body logic and how it hesitates closing once more than stock boost is added to the car.

In order for blow off valves to work, the valve has to be subjected to a positive pressure to vacuum condition to suck the piston up into the head of the BOV to allow air to escape the bottom portion of the valve. The throttle body logic limits this transaction completely and you end up with a small double spike every time. I have taken back to back logs and if I posted the boost pressure spikes after letting off the throttle, no one (including myself) would be able to tell you which log did and didn’t have the BOVs. The throttle let off spiking remained almost identical. This is something built into the logic that has yet to be(or able to be) solved by ECUTEK. -Mark Roberts- SonicTuned”
This is good stuff and everything makes absolute sense.
 

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I had them on my car, and then took them off. I was hitting the rev limiter I believe, on the 2-3 shift. I could hear the BOV open when letting the trans shift for me. I adjusted them all over and would still have same issue. So I took them off.
Same thing happens, just do not hear the woosh now. I will still feel it stumble as rpms climb towards 7k. I can never really catch anything on my logs when it happens.

I will probably put them back on, I do miss the woosh, and the rpms do not seem to hang as long when shifting. I usually “tune” them. I use my brake bleeding tool to apply vac to both and adjust each so they open at same time. I have seen them open different on my logs as you can see at the end of a pull boost lines diverge.

Now thinking about the recirc issue and maf…. the point is to open when we let OFF the throttle, so running @WOT bov is closed and we are boosted, car is reading maf fine, no loss or dilution of a/f, correct?
Now we let off, boost dumps, maf gets incorrect reading right? maybe, maybe not. Throttle is closed, not really flowing much air with a closed throttle body, right? and the woosh is only for a split second, while throttle is CLOSED.
So then we open, and bov is closed already due to spring pressure and boost coming into top of bov. As that stars to happen maf is not leakinig anything right? because bov is closed as throttle starts to open, maf reading is fine.

I do not believe they are bad, unless my logic if wrong? Thoughts plz.

P.S. anyone else have the 2-3 shift bumping off rev limiter? Sport, and in sport+ mode. have not tried std.
was thinking the Syvecs trans controller to take control of that shift point, just damn expensive!
 

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BOV's require boost on 1 side and vacuum on the other. They weren't opening at WOT during a shift as an auto keeps the throttle blade open, unlike a manual transmission. If you have issues at high RPM without the BOV's then they weren't the problem. People get WAY too hung up on posts about BOV's. They only open on decel after you've been in decent boost if they're adjusted correctly. When you're on decel at higher rpm the car goes into deceleration fuel cutout, i.e. the injectors are being shut off. So all this stuff about BOV's are going to ruin your motor because the car is dumped post MAF metered air is hugely blown out of proportion. If someone wants to argue they aren't as effective as other platforms given that Infiniti hangs the throttle blade open, that's perfectly legitimate, but they aren't blowing up motors unless someone was doing something extraordinarily dumb.
 

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BOV's require boost on 1 side and vacuum on the other. They weren't opening at WOT during a shift as an auto keeps the throttle blade open, unlike a manual transmission. If you have issues at high RPM without the BOV's then they weren't the problem. People get WAY too hung up on posts about BOV's. They only open on decel after you've been in decent boost if they're adjusted correctly. When you're on decel at higher rpm the car goes into deceleration fuel cutout, i.e. the injectors are being shut off. So all this stuff about BOV's are going to run your motor because the car is dumped post MAF metered air is hugely blown out of proportion. If someone wants to argue they aren't as effective as other platforms given that Infiniti hangs the throttle blade open, that's perfectly legitimate, but they aren't blowing up motors unless someone was doing something extraordinarily dumb.
Exactly, and the 7k stumble 2-3rd gear was still there, I just thought it was the bov spring not holding boost. Yes they only open on my decel, I am holding boost and as soon as I let off I get the woosh, rpms come down. With them in I get them open at the shift. So I guess they are opening at the shift because rev limiter kicks in and is shutting off injectors, and that acts as if I am letting off and dumping boost.

So the question is, how to stop the rev limit in that 2-3rd shift @7k from happening?
(When allowing the trans to shift for me of course). My thought was the Syvkes trans controller.
Thoughts?

-J
 

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Spider is right. Mark Roberts has addressed this, offering proof along with experience. Though I already know most of this, the proof is why I won't bother:

Putting the blow-off valve debate to bed(once again) with actual data. I have posted 4 datalogs of the same car. Two logs were with the blow-off valves on and two without. For those of you who don’t know, the point of a blow-off valve is to reduce and/or eliminate pre throttle body boost spikes. These boost spikes can blow intercoolers hoses and put excess stress on the turbos compressor. Most of you have read and fully understand the write up I did on why blow-off valves don’t work on these cars specifically.

On top of them not doing the job they were intended, the rest of the car is not capable of being properly setup to accommodate them. The BOVs can only be put AFTER the mass air flow meters and because these cars are NOT CAPABLE of running speed-density, these will never work properly. In order for them to work properly, on top of the ECU logic not allowing these, they’d need to be put on before the MAFs which wouldn’t work since the MAFs are on the low pressure side. What you end up with is accelerated wear and tear on the spark plugs due to constant rich conditions which also prevent the fuel trimming in the ECU from property doing its job.

Nissan TRIED something different and found it not be be optimal so on the next version of the VR30(The Z) they have re-introduced recirculating bypass valves as it is the more effective way of eliminating these harmful boost spikes. With the Q specifically, the same ECU logic used to control boost on stock turbos works against the use of blow-off valves. Just because you hear the noises they make, doesn’t mean they are actually doing the job they were meant to do.

I know there are a few guys on here who read a lot of magazines and think they know the answers, but despite their feelings, the data doesn’t lie.

In the logs below, I selected the “double bump” boost spike area after the throttle bodies are completely closed. Blow-off valves are supposed to eliminate the spike. As you can clearly see by the actual data, they do not eliminate actual boost spikes.

Can anyone tell me which logs are with and which logs are without the BOVs?
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