Greddy Turbo - Should I Weld on External BOV?

[No Limit Motorsport]

Originally Posted by jamesm

You understand that the main benefit of not stalling the compressor, aside from not damaging it, is that it helps spool between shifts right? It makes no sense at all that not having a bov would help spool, or anything else other than your wallet.

I am not here to argue it, nor do I have a mechanical or automotive engineering background to get into real specifics. However I have observed many turbocharged race cars that choose to not run a blow off valve for performance reasons. It was explained to me that it helps with response by keeping the pipes pressurized during gear changes.

Here is an educated guess on my part - The benefits of keeping the pipes pressurized, outweighs the stalling/slowing of the compressor wheel?

I understand how a blow off valve functions.

I know Crawford doesn't run one on there time attack STI, or there turbo kits. A lot of rally cars don't run them, so on and so forth

[jamesm]

Originally Posted by No Limit Motorsport

I am not here to argue it, nor do I have a mechanical or automotive engineering background to get into real specifics. However I have observed many turbocharged race cars that choose to not run a blow off valve for performance reasons. It was explained to me that it helps with response by keeping the pipes pressurized during gear changes.

I understand how a blow off valve functions.

I know Crawford doesn't run one on there time attack STI, or there turbo kits. A lot of rally cars don't run them, so on and so forth.

Here is a race car, no BOV
http://www.motoiq.com/MagazineArticl...-update-1.aspx

i can't say i've every heard of or seen the same, but i suppose in a racing application you wouldn't mind the potential for damage to the compressor wheel, so that wouldn't be an issue. i really can't fathom how stalling the compressor would help spool, but who knows? maybe it does...

[SmsAlSuwaidi]

Originally Posted by jamesm

i can't say i've every heard of or seen the same, but i suppose in a racing application you wouldn't mind the potential for damage to the compressor wheel, so that wouldn't be an issue. i really can't fathom how stalling the compressor would help spool, but who knows? maybe it does...

Not here to argue too but a friends built tb48 nissan engine has been running no BOV for over 1 year ( daily driver) and we recently pulled apart the turbo to inspect it and seemed to have a few years in it left.

Now I'm not saying running no bov has no harm, but based on the experience we've been having it seems like it's ok if you don't mind messing up your turbo

[shiro]

All valuable inputs! So I appreciate it. For now, I'm not racing my car especially since we are hitting winter soon (in the midwest) and grad school takes up most of my time and $$, lol. I'm just looking for a fun car that sounds cool and gets some good performance.

Even without the BOV I love the car and setup. I wouldn't mind adding a little bit of sound to her. One of my friends would rather hve me keep the fludder sound than the BOV. Furthermore, I can just order a replacement pipe from Greddy if I don't like it or the car isn't doing well.

I'm curious what it will sound like with the BOV and the TRD exhaust together. I don't think anyone has done that application before. If anyone is curious I might be able to post a sound clip and take some pictures too. Overall, this is my project car so swaping parts and having fun is a must...until someday I get that ol' ball and chain HAHA!

[Element Tuning]

Most of the racers that choose to forego a BOV are usually for reliability issues at very high boost levels where a BOV can fail (vent). Many drag racers do not need a BOV because they never lift off the throttle, therefore near maximum boost is maintained.

Because they don't lift the compressor won't slow down or stall. Here is a video of me launching with the Hydra EMS Launch control and flat-foot shift. Watch the boost gauge as I lift on the 1-2 shift and then keep the throttle WOT on the others.

https://www.facebook.com/photo.php?v...type=3&theater

No BOV required but for road racing in sections you lift between shifts it does help to keep the compressor wheel moving and it makes an appreciable difference as I've tested both.

[shiro]

Originally Posted by Element Tuning

Most of the racers that choose to forego a BOV are usually for reliability issues at very high boost levels where a BOV can fail (vent). Many drag racers do not need a BOV because they never lift off the throttle, therefore near maximum boost is maintained.

Because they don't lift the compressor won't slow down or stall. Here is a video of me launching with the Hydra EMS Launch control and flat-foot shift. Watch the boost gauge as I lift on the 1-2 shift and then keep the throttle WOT on the others.

https://www.facebook.com/photo.php?v...type=3&theater

No BOV required but for road racing in sections you lift between shifts it does help to keep the compressor wheel moving and it makes an appreciable difference as I've tested both.

How about this method?:

What if I make the BOV a little more stiff so that mid-range RPMs tend to maintain the boost internally longer; thus this could make the internal waste gate dump if needed and only at high RPM's the BOV will dump? My apologies if this is an ingnorate question.

BUT, I do understand where you are coming from for keeping the compressor spun up during high RPM and shifting. Also, this turbo is smaller so it might not lag as much as a lager one? Thanks!

[Sportsguy83]

Originally Posted by shiro

How about this method?:

What if I make the BOV a little more stiff so that mid-range RPMs tend to maintain the boost internally longer; thus this could make the internal waste gate dump if needed and only at high RPM's the BOV will dump? My apologies if this is an ingnorate question.

BUT, I do understand where you are coming from for keeping the compressor spun up during high RPM and shifting. Also, this turbo is smaller so it might not lag as much as a lager one? Thanks!

The BOV reliefs the Compressor of a turbocharger. The Wastegate modulates the amount of exhaust gases going through the Turbine side of the turbo charger.

BOV and Wastegate do not interact with the same air/gases. Wastegate deals with exhaust gases, BOV deal with intake air.

[STV3]

Originally Posted by shiro

How about this method?:

What if I make the BOV a little more stiff so that mid-range RPMs tend to maintain the boost internally longer; thus this could make the internal waste gate dump if needed and only at high RPM's the BOV will dump? My apologies if this is an ingnorate question.

BUT, I do understand where you are coming from for keeping the compressor spun up during high RPM and shifting. Also, this turbo is smaller so it might not lag as much as a lager one? Thanks!

The BOV is only supposed to release boost when you lift off the gas pedal and go into vacuum it is not meant to regulate boost, that is what the wastegate is for. If your BOV is venting while in boost then you just have a boost leak.

[shiro]

Originally Posted by Sportsguy83

The BOV reliefs the Compressor of a turbocharger. The Wastegate modulates the amount of exhaust gases going through the Turbine side of the turbo charger.

BOV and Wastegate do not interact with the same air/gases. Wastegate deals with exhaust gases, BOV deal with intake air.

Yeah, but after looking at the design of the turbo isn't the waste gate on this setup the one that dumps to the exhuast? That's what it looks like? I could be just getting that confused since I'm thinking they both (BOV or Waste gate) dump the extra boost.

[shiro]

Originally Posted by STV3

The BOV is only supposed to release boost when you lift off the gas pedal and go into vacuum it is not meant to regulate boost, that is what the wastegate is for. If your BOV is venting while in boost then you just have a boost leak.

With that said, does that mean the compressor will constantly be spun up if I did not have a BOV? So I would always be at the PSI that the system is set up as (unless at idle)?

Furthermore, understanding that the waste gate regulates boost (PSI) level, why do I get a fudder noise when I let off on the gas at a high RPM with no BOV installed? I'm guessing that is because the waste gate is dumping the extra gasses not needed to produce the boost. Hence, would it still dump with a BOV installed?

[whitefrs]

@King Tut

road trip to LJ for tuning lol

Great work

[Sportsguy83]

Originally Posted by shiro

Yeah, but after looking at the design of the turbo isn't the waste gate on this setup the one that dumps to the exhuast? That's what it looks like? I could be just getting that confused since I'm thinking they both (BOV or Waste gate) dump the extra boost.

You are going up in RPMs, the exhaust gases are spinning the Turbine, the shaft connecting the turbine to the compressor moves the compressor and the compressor builds boost. If you keep feeding exhaust gases to the turbine, it will keep spinning up the compressor and bulding boost until you hit 30 PSI or whatever... BOOM.

So, the Wastegate has a spring set to open at say, 10 PSI so that when there is 10 psi of boost in your motor, the wastegate valve will open and release exhaust gases through another path, bypassing the turbine and preventing it from building more boost.


The BOV is connected to your intake pipe. You are going up in RPMs, Wide open throttle. When you reach 7K RPMS, there is a BIG amount of air being fed into your engine which the compressor is pushing at 10 psi of pressure. You go to shift and lift your throttle, slam shut your throttle butterfly valve. Now all this compressed air has nowhere to go but back to the compressor (which might damage it becuase the air is now coming the opposite way and will try to stop your compressor while the turbine side is still spinning with exhaust gases). The BOV has a spring that will open at high psi pressures (so that it wont open and bleed your 10 psi while you are WOT) and relief this intake air instead of it pushing your compressor to spin the other way.

A recirculating BOV takes all that compresser air and puts it pre-compressor and helps keep the compressor with air and help defeat lag on shifts.

a 50/50 BOV will recirculate half helping the compressor, but still give you the pshhhhh sound.

a 100 venting BOV will give you the psshhhhhh sound and will not put any air back in.

Originally Posted by shiro

With that said, does that mean the compressor will constantly be spun up if I did not have a BOV? So I would always be at the PSI that the system is set up as (unless at idle)?

The compressor will spin regardless, because the exhaust gases are always moving the turbine which in turn moves the compressor, the BOV is there to relief pressure from the compressor when the throttle slams shut and there is compressed air between the throttle and the compressor.


Wastegate: hot gases bypass the turbine when it opens

(Internal WG)



(External WG)



BOV: Reliefs pressure in the intake between TB and compressor.

100% Vent To Atmosphere, no connecting to any other intake pipe



100% Recirculating, notice how it recirculates to pre-compressor

[shiro]

Originally Posted by Sportsguy83

You are going up in RPMs, the exhaust gases are spinning the Turbine, the shaft connecting the turbine to the compressor moves the compressor and the compressor builds boost. If you keep feeding exhaust gases to the turbine, it will keep spinning up the compressor and bulding boost until you hit 30 PSI or whatever... BOOM.

So, the Wastegate has a spring set to open at say, 10 PSI so that when there is 10 psi of boost in your motor, the wastegate valve will open and release exhaust gases through another path, bypassing the turbine and preventing it from building more boost.


The BOV is connected to your intake pipe. You are going up in RPMs, Wide open throttle. When you reach 7K RPMS, there is a BIG amount of air being fed into your engine which the compressor is pushing at 10 psi of pressure. You go to shift and lift your throttle, slam shut your throttle butterfly valve. Now all this compressed air has nowhere to go but back to the compressor (which might damage it becuase the air is now coming the opposite way and will try to stop your compressor while the turbine side is still spinning with exhaust gases). The BOV has a spring that will open at high psi pressures (so that it wont open and bleed your 10 psi while you are WOT) and relief this intake air instead of it pushing your compressor to spin the other way.

A recirculating BOV takes all that compresser air and puts it pre-compressor and helps keep the compressor with air and help defeat lag on shifts.

a 50/50 BOV will recirculate half helping the compressor, but still give you the pshhhhh sound.

a 100 venting BOV will give you the psshhhhhh sound and will not put any air back in.




The compressor will spin regardless, because the exhaust gases are always moving the turbine which in turn moves the compressor, the BOV is there to relief pressure from the compressor when the throttle slams shut and there is compressed air between the throttle and the compressor.

David,

That was a really good explination! The picture was painted a lot better than many other forums have. I appreciate that. I will have to see what that Greddy FV BOV is capable of. Otherwise, I love the idea of a 50/50 BOV.

THANKS!

[Sportsguy83]

Originally Posted by shiro

David,

That was a really good explination! The picture was painted a lot better than many other forums have. I appreciate that. I will have to see what that Greddy FV BOV is capable of. Otherwise, I love the idea of a 50/50 BOV.

THANKS!

I have a 50/50 BOV and like it a lot. You welcome, I know I found all this stuff confusing before so its good to take the time to help someone understand.

I added pics to help explain further.