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post #1 of 16 (permalink) Old 03-04-2017, 05:27 AM Thread Starter
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Wastegate and bov?

Internal/external Waste gates and blow off valves, recirculating/venting to atmosphere and boost controllers?

Now, I have (quite) a few questions, that may or may not be somewhat rhetoric, but haven't seen anything else on the forum that really addresses this (particularly in regards to the turbo setup in the 4c). Also may be for the benefit of some members who are still getting confused, particularly in highlighting, not only the benefits of mods, but the difference between what a

-Turbo waste gate/actuator is, and what a
Diverter blow off valve is, and

-Whether both are internally recirculating, or

-"Dumped/vented to atmosphere,

Both wastegate and bloff off valve in our cases are recirculating are they not?

-Any point in adding aftermarket mechanical or electronic boost controllers?
i.e what are the
benefits in boost/power?

benefits in better quality/longevity over OEM plastic parts and weak springs/components? For an aftrmarket blow off valve,, i like more sound i.e
the benefit of controlling the sound of how loud the blow off valve vents to atmosphere?


and

What sounds do we hear from the engine,?? Is the distinctive "barp" sound between shifts coming from the waste gate recirculating (or venting ) exhaust to control turbo boost, or is it the diverter/blow off valve recirculating (or once again venting to atmosphere) the pressurized intake air?

Now a lot of people are confused with the difference between a waste gate and a blow off valve. They are two complete different things as we may or may not know..


WG: Regulates pressure on the exhaust side i.e turbo boost
BOV: Regulates pressure on the intake side. Stops excessive flow back pressure on the turbo vanes after the throttle plate close

As far as i know, This limit is controlled by the waste gate , which "sees" the intake pressure and opens up when the limit is reached to vent off or bypass the exhaust gas around the turbo (vented to the catalytic converter or atmosphere), thus preventing it from spinning faster and creating more boost. It doesn't vent out the intake air.
Hence , the waste gate controls the maximum boost pressure (limited by how much your engine can take/ turbo rev limit etc).
Changing how much your waste gate "sees" can allow you to increase this limit (increase maximum boost)


A blow off valve, on the other hand, lies on the intake side and is meant to open up when the throttle is closed (by sensing engine vacuum). This vents out the pressurized intake air to the atmosphere. This is required because as you rev the engine up , the turbo spools up as well. The instant the throttle is let go, the turbo continues to create boost which now has no where to go. This causes the turbo to quickly spool down which creates a lot of impulsive stress on the turbo. Consequently , the turbo (now having spooled down) will take time to spool up when the throttle is re-applied.
Hence the blow-off valve protects your turbo by allow it to continue to spin (rotational inertia) and vent out the un-required air, when the throttle is closed. A consequence of which is reduced turbo lag eg. between gear shifts etc. Installing high flow blow off valves may improve turbo spool performance to a perceivable extent.

Poor bov design chirping

like when the throttle closes during a shift. When a BOV is vented to atmosphere, it produces a distinctive hissing sound, and when a BOV isnít used or is of insufficient size, the compressor surges and makes a chirping or rattling sound. Compressor surge can put stress on the compressor and its bearings, shortening its life. I hear this chirpping all the time, meaning the oem blow off valve, being plastic is not that good...i.e plastic

Quote,

For cars with metered air (a flapper valve or hot wire MAF sensor), it is best to route the vented air back into the pipe between the MAF sensor and the turbo to avoid a moment of rich mixture caused by the missing air. For a car that does not have an air flow meter, you can just vent the air to the atmosphere with no ill effects on the mixture.

So any point in afternarket actuator, or at least bov, or adaptor plate ,, at least for sound and or reliability?

Cheers
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2016 Australian delivered Giallo Prototipo (Yellow) 4C Spider, full clear Hexis wrap, dry carbon fibre 3m wrap on:rear spoiler, roof halo, rear engine black plastic vents, front air intake,Red Aussie rimskins covers on 18 and 19 inch dark spider alloys,

Previous cars:

2006 Alfa 959 Spider 3.2 V6 Q4 manual,Blue/two tone tobacco and blue interior
1999 VT Series II HSV R8 sedan
1974 HQ GTS 253 Monaro sedan
1969 Holden HG GTS 350 Bathurst Monaro coupe

Last edited by 4Canada; 03-04-2017 at 10:22 AM. Reason: Missed some items
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post #2 of 16 (permalink) Old 03-04-2017, 10:24 AM
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Moved To technical section, and fixed typo in your title (my OCD acting up again).
I have to admit, I understand about 30% of this, so I think there will be some learning going on today!
Intesting questions

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post #3 of 16 (permalink) Old 03-04-2017, 10:50 AM
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Interesting article. I'm somewhat new to turbos, so this description/breakdown is informative for me. I'm interested to hear more information from others about this. I'd always thought that a WG and BOV where one in the same.

My Fiat 500 Abarth was this first car I ever owned with a turbo, 4C being second. There's a big difference between the two in how they perform and sound. The Abarth had enough lag that I had to plan ahead and get on the gas before I needed power, ie passing another car. The 4C has virtually no lag.

Quote:
Originally Posted by Ivanivnk View Post
WG: Regulates pressure on the exhaust side i.e turbo boost
BOV: Regulates pressure on the intake side. Stops excessive flow back pressure on the turbo vanes after the throttle plate close

As far as i know, This limit is controlled by the waste gate , which "sees" the intake pressure and opens up when the limit is reached to vent off or bypass the exhaust gas around the turbo (vented to the catalytic converter or atmosphere), thus preventing it from spinning faster and creating more boost. It doesn't vent out the intake air.
Hence , the waste gate controls the maximum boost pressure (limited by how much your engine can take/ turbo rev limit etc).
Changing how much your waste gate "sees" can allow you to increase this limit (increase maximum boost)
From a logical stand, I must disagree. The exhaust can't bypass the catalytic converter. Our government won't allow that. Aside from the legalities, it's not even safe. Any gasses escaping from anyplace except the tailpipe are a potential problem.
1) This could allow poisonous gasses into the cabin.
2) This could put heat in places we don't want heat. Melting car parts.

I can follow the logic of adjusting the pressure on the exhaust side as well as on the intake side. Bypassing the turbo (exhaust side) by feathering the vanes or a bypass line work in concept. It would stand to reason that it would be a problematic turbo to have a vane feather system. That would be vain. (haha, I made a pun) I think the corrosive gasses would destroy the bearings and mechanism needed.

Reliability in this type of system must be first. It's already a system that has a high fatality rate (common to all turbos).
Performance second and cosmetics last. Sound is part of the cosmetic thing.

Rac
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post #4 of 16 (permalink) Old 03-04-2017, 11:29 AM
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Quote:
Originally Posted by 4Canada View Post
Moved To technical section, and fixed typo in your title (my OCD acting up again).
I have to admit, I understand about 30% of this, so I think there will be some learning going on today!
Intesting questions


Good thread. Great information.
I'm at about 20%.
Now I know the the rattlesnake sound is BOV chirping sound.

But I'm still confused what the dog bark sound in between shifts is, whether it is the wastegate or the blow off, or them both together.

I know what the wheeee sound is..... it's me enjoying the ride and sounds.

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post #5 of 16 (permalink) Old 03-04-2017, 03:00 PM
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Just wait for Greg to get here
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post #6 of 16 (permalink) Old 03-04-2017, 10:37 PM
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Just wait for Greg to get here
Thanks, I'll respond to all of OP's questions. In the meantime, I do have two related tech articles on this subject.

https://shopeurocompulsion.net/blogs...harging-system

https://shopeurocompulsion.net/blogs...t-tech-article

Sorry I haven't posted in a while. I have been very busy, with the 124, Giulia, and new stuff for the 4C.

Greg
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post #7 of 16 (permalink) Old 03-04-2017, 10:55 PM
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Hi Ivanivnk: To make all these questions more manageable, I am breaking your post up into two parts

Quote:
Originally Posted by Ivanivnk View Post
Internal/external Waste gates and blow off valves, recirculating/venting to atmosphere and boost controllers?
It's all internal. The "blow off valve" is bolted into and integrated with the turbo's compressor housing. The waste gate is built into the exhaust section.


Quote:
Originally Posted by Ivanivnk View Post
Now, I have (quite) a few questions, that may or may not be somewhat rhetoric, but haven't seen anything else on the forum that really addresses this (particularly in regards to the turbo setup in the 4c). Also may be for the benefit of some members who are still getting confused, particularly in highlighting, not only the benefits of mods, but the difference between what a

-Turbo waste gate/actuator is, and what a
Diverter blow off valve is,
These are two totally different things, but they are often confused. The wastegate is on the exhaust side and bypasses exhaust around the turbine to slow the turbo and lower boost. It's the primary component for controlling boost.

The diverter valve is a pressure relieve valve on the compressor side. It doesn't by pass exhaust, it dumps boost pressure back into the turbo's inlet.

Quote:
Originally Posted by Ivanivnk View Post
and

-Whether both are internally recirculating, or

-"Dumped/vented to atmosphere,
Both are internal. The wastegate doesn't recirculate, it bypasses. once that exhaust bypasses the turbine, it exits through the exhaust system. The diverter in stock form does recirculate. It causes air to go from the compressor's outlet side back to the inlet, where it goes through again.

Quote:
Originally Posted by Ivanivnk View Post
Both wastegate and bloff off valve in our cases are recirculating are they not?
See my above response.

Quote:
Originally Posted by Ivanivnk View Post
-Any point in adding aftermarket mechanical or electronic boost controllers?
i.e what are the
benefits in boost/power?
Absolutely no benefit. The ECU controls boost, and the stock boost control system works pretty well. A mechanical boost controller would be a huge step backwards because it would not allow us to take advantage of this engine's ability to run very high mid range boost.

Quote:
Originally Posted by Ivanivnk View Post
benefits in better quality/longevity over OEM plastic parts and weak springs/components? For an aftrmarket blow off valve,, i like more sound i.e
the benefit of controlling the sound of how loud the blow off valve vents to atmosphere?
The OEM parts seem to be of reasonable quality. Our V2 intake will allow you to hear the stock diver valve. If you want more sound that's the way to go. At the moment I don't think there are any aftermarket diverter valves/blow off valves on the market, although there are some that could be adopted.


Quote:
Originally Posted by Ivanivnk View Post
and

What sounds do we hear from the engine,?? Is the distinctive "barp" sound between shifts coming from the waste gate recirculating (or venting ) exhaust to control turbo boost, or is it the diverter/blow off valve recirculating (or once again venting to atmosphere) the pressurized intake air?
What you hear is the diverter valve throwing air back into the intake. That's why it's so much louder with our V2 intake.

Quote:
Originally Posted by Ivanivnk View Post
Now a lot of people are confused with the difference between a waste gate and a blow off valve. They are two complete different things as we may or may not know..
Yup!

Quote:
Originally Posted by Ivanivnk View Post
Cheers
Cheers

Greg
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Last edited by greg@eurocompulsion; 03-04-2017 at 10:57 PM.
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post #8 of 16 (permalink) Old 03-04-2017, 11:27 PM
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Quote:
Originally Posted by Ivanivnk View Post

WG: Regulates pressure on the exhaust side i.e turbo boost
BOV: Regulates pressure on the intake side. Stops excessive flow back pressure on the turbo vanes after the throttle plate close
That's all correct, but I'll add one more thing. The BOV (AKA Diverter valve) provides a secondary safety function, the ECU can command it open anytime it's wants to lower boost if it doesn't see what it wants from manipulating the wastegate.

Quote:
Originally Posted by Ivanivnk View Post
As far as i know, This limit is controlled by the waste gate , which "sees" the intake pressure and opens up when the limit is reached to vent off or bypass the exhaust gas around the turbo (vented to the catalytic converter or atmosphere), thus preventing it from spinning faster and creating more boost. It doesn't vent out the intake air.
That's mostly correct, but just off enough to cause of confusion. The wastegate doesn't exactly see the intake pressure. It sees whatever the ECU decides it gets to see, which is never above intake pressure, but could be a lot lower.

Quote:
Originally Posted by Ivanivnk View Post
Hence , the waste gate controls the maximum boost pressure (limited by how much your engine can take/ turbo rev limit etc).
Changing how much your waste gate "sees" can allow you to increase this limit (increase maximum boost)
What you are saying would have been 100% correct not that long ago, but it's not really accurate with the 4C. If you change the boost signal to the wastegate without allowing it to go through the ECU it will cause huge problems. As soon as the ECU notices that it's not able to control boost by manipulating the wastegate via the boost solenoid, it's going to end the fun by closing the throttle and opening the diverter valve.

Quote:
Originally Posted by Ivanivnk View Post
A blow off valve, on the other hand, lies on the intake side and is meant to open up when the throttle is closed (by sensing engine vacuum). This vents out the pressurized intake air to the atmosphere. This is required because as you rev the engine up , the turbo spools up as well. The instant the throttle is let go, the turbo continues to create boost which now has no where to go. This causes the turbo to quickly spool down which creates a lot of impulsive stress on the turbo. Consequently , the turbo (now having spooled down) will take time to spool up when the throttle is re-applied.
Hence the blow-off valve protects your turbo by allow it to continue to spin (rotational inertia) and vent out the un-required air, when the throttle is closed. A consequence of which is reduced turbo lag eg. between gear shifts etc. Installing high flow blow off valves may improve turbo spool performance to a perceivable extent.
The stock diverter works pretty well in this application. The turbo doesn't loose much speed during upshifts due to the fast shifting of the TCT and the ECU's manipulation of the throttle and diverter valve. An upgraded valve might be better, but it just hasn't been a problem yet. There are two potential advantages, faster pressure drop, and cooler air charge as a result of not putting hot boosted air back through the turbo for a second trip through the compressor. I am just not sure how much of advantage there would be in practical terms.

Quote:
Originally Posted by Ivanivnk View Post
Poor bov design chirping

like when the throttle closes during a shift. When a BOV is vented to atmosphere, it produces a distinctive hissing sound, and when a BOV isnít used or is of insufficient size, the compressor surges and makes a chirping or rattling sound. Compressor surge can put stress on the compressor and its bearings, shortening its life. I hear this chirpping all the time, meaning the oem blow off valve, being plastic is not that good...i.e plastic
Let's remember that Borg Warner, who made the turbo is the one who decided that this valve is the right size for the turbo. We certainly don't see turbos failing in the 4C, so regardless of what you think you hear, I just don't think there is a problem. I am NOT saying that what you hear isn't relevant, and I am NOT saying that there are not improvements to be made, but I don't think it's too important with the current flow requirements.

Quote:
Originally Posted by Ivanivnk View Post
Quote,

For cars with metered air (a flapper valve or hot wire MAF sensor), it is best to route the vented air back into the pipe between the MAF sensor and the turbo to avoid a moment of rich mixture caused by the missing air.
The 4C does have such a sensor, but unlike older cars, this valve is electronically controlled. I am not so sure that bypassing to the atmosphere would cause a problem because the ECU knows when it's open and when it's open the engine is in a falling condition anyway. This is nothing like the older cars where the valve was open any time the engine was off boost and thus mixture would be totally thrown off in most driving conditions if you bypassed to the atmosphere. Then again, I haven't done it on the 4C, so I can't say with absolute certainty.


Quote:
Originally Posted by Ivanivnk View Post
For a car that does not have an air flow meter, you can just vent the air to the atmosphere with no ill effects on the mixture.
No question about that.

Quote:
Originally Posted by Ivanivnk View Post
So any point in afternarket actuator, or at least bov, or adaptor plate ,, at least for sound and or reliability?
I just don't think it's worth doing at THIS point in time. Now with some of the future developments, maybe.

Greg
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post #9 of 16 (permalink) Old 03-05-2017, 12:38 AM Thread Starter
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Quote:
Originally Posted by greg@eurocompulsion View Post
That's all correct, but I'll add one more thing. The BOV (AKA Diverter valve) provides a secondary safety function, the ECU can command it open anytime it's wants to lower boost if it doesn't see what it wants from manipulating the wastegate.



That's mostly correct, but just off enough to cause of confusion. The wastegate doesn't exactly see the intake pressure. It sees whatever the ECU decides it gets to see, which is never above intake pressure, but could be a lot lower.



What you are saying would have been 100% correct not that long ago, but it's not really accurate with the 4C. If you change the boost signal to the wastegate without allowing it to go through the ECU it will cause huge problems. As soon as the ECU notices that it's not able to control boost by manipulating the wastegate via the boost solenoid, it's going to end the fun by closing the throttle and opening the diverter valve.



The stock diverter works pretty well in this application. The turbo doesn't loose much speed during upshifts due to the fast shifting of the TCT and the ECU's manipulation of the throttle and diverter valve. An upgraded valve might be better, but it just hasn't been a problem yet. There are two potential advantages, faster pressure drop, and cooler air charge as a result of not putting hot boosted air back through the turbo for a second trip through the compressor. I am just not sure how much of advantage there would be in practical terms.



Let's remember that Borg Warner, who made the turbo is the one who decided that this valve is the right size for the turbo. We certainly don't see turbos failing in the 4C, so regardless of what you think you hear, I just don't think there is a problem. I am NOT saying that what you hear isn't relevant, and I am NOT saying that there are not improvements to be made, but I don't think it's too important with the current flow requirements.



The 4C does have such a sensor, but unlike older cars, this valve is electronically controlled. I am not so sure that bypassing to the atmosphere would cause a problem because the ECU knows when it's open and when it's open the engine is in a falling condition anyway. This is nothing like the older cars where the valve was open any time the engine was off boost and thus mixture would be totally thrown off in most driving conditions if you bypassed to the atmosphere. Then again, I haven't done it on the 4C, so I can't say with absolute certainty.




No question about that.



I just don't think it's worth doing at THIS point in time. Now with some of the future developments, maybe.

Greg
Thanks greg, was looking forward to your response. I too dont have much time, and this thread i started typing a few months ago, edited late last night, and got some of my facts incorrect.. essentially started it as a point of discussion,

I personally wouldnt bother with changing the actuator, it was more that i was looking at an adapter plate for the blow off valve, something that they make for the abarth 500, eg bonalume from madness 500 website) that has an adjustable slide to allow you to vent more (than none) to atmosphere To increase the sound.... i understand from all the posts that the v2 intake will increase the sound (as well as breath better), this was an additional option i was curious about

Current car:

2016 Australian delivered Giallo Prototipo (Yellow) 4C Spider, full clear Hexis wrap, dry carbon fibre 3m wrap on:rear spoiler, roof halo, rear engine black plastic vents, front air intake,Red Aussie rimskins covers on 18 and 19 inch dark spider alloys,

Previous cars:

2006 Alfa 959 Spider 3.2 V6 Q4 manual,Blue/two tone tobacco and blue interior
1999 VT Series II HSV R8 sedan
1974 HQ GTS 253 Monaro sedan
1969 Holden HG GTS 350 Bathurst Monaro coupe
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post #10 of 16 (permalink) Old 03-05-2017, 02:10 PM
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I understand the desire to hear more blow off noise. However I would be shocked if anyone with a V2 intake requested more noise. That intake sounds quite aggressive, I mean race car aggressive. It's not too loud in normal driving, but when you get on it, it's very exciting.

Greg
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