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Old 10-10-2017, 10:11 AM   #1
02SwagonProject
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Default Modding Stock BOV vs. Aftermarket

I read through both FAQ's and tried Google, but I can't find an answer to this.

So it's obvious that an aftermarket BOV holds more boost than a stock BOV. But, looking at the "$0.16 BOV Mod," is there any reason to go with an aftermarket unit for $199.84 more?

I'm asking because I'm moving from a 20G XT-R on 93 octane at 21psi (about the limit of stock from what I can find), to a GT2860RS on E85 and expecting to be pushing a bit more boost.

What advantages does aftermarket offer over modding the stock BOV, or what disadvantages are there to modding vs aftermarket?
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Old 10-10-2017, 12:17 PM   #2
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how much boost are you thinking of running? that is a question you need to find out.if you are thinking of doing like 24 and up I would go with an aftermarket like the tial qr. what Intercooler are you running and why such a small turbo? I think the 20g xti is about the same size as a 2871 which is bigger than what you going to. just asking
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Old 10-10-2017, 01:37 PM   #3
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The $0.16 BPV modification effectively disables the ~24 psi overboost protection of the E-marked BPV. If you're only hitting 24 peak, I wouldn't bother with an aftermarket BOV and I would avoid vented valves entirely if not converting to speed density.
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Old 10-10-2017, 03:11 PM   #4
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Quote:
Originally Posted by subaru_gc8 View Post
how much boost are you thinking of running? that is a question you need to find out.if you are thinking of doing like 24 and up I would go with an aftermarket like the tial qr. what Intercooler are you running and why such a small turbo? I think the 20g xti is about the same size as a 2871 which is bigger than what you going to. just asking
I don't have a target boost, but I'm looking to hit 300whp. Went with the Disco potato for a quicker spool and low end response. It's an EJ207, so I don't quite have some of the advantages for spooling that the ej25s do.

There's an APS 50/50 on the forums right now for a good price that I was considering, but even at almost half the cost of most new BOVs, it's still much much more than a tap and a set screw. But I'm wondering why aftermarket BOVs are a thing at all besides sound if the stock one can just be tweaked to do the exact same.
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Old 10-10-2017, 03:13 PM   #5
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Quote:
Originally Posted by mrsaturn7085 View Post
The $0.16 BPV modification effectively disables the ~24 psi overboost protection of the E-marked BPV. If you're only hitting 24 peak, I wouldn't bother with an aftermarket BOV and I would avoid vented valves entirely if not converting to speed density.
I've seen a lot of people saying that stock only holds 20-22psi, will it go all the way to 24?

And I thinks I can guess what it is, but explain for the noob - overboost protection? Where do I look to see if I have E-Marked, or is that just a given if it's an 02 or not plastic?
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Old 10-10-2017, 05:39 PM   #6
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Quote:
Originally Posted by 02SwagonProject View Post
I don't have a target boost, but I'm looking to hit 300whp. Went with the Disco potato for a quicker spool and low end response. It's an EJ207, so I don't quite have some of the advantages for spooling that the ej25s do.
You've chosen wisely.

Quote:
Originally Posted by 02SwagonProject View Post
I've seen a lot of people saying that stock only holds 20-22psi, will it go all the way to 24?

And I thinks I can guess what it is, but explain for the noob - overboost protection? Where do I look to see if I have E-Marked, or is that just a given if it's an 02 or not plastic?
The STi BPVs are all pretty much the same design, and there is a large letter stamped on the top of them. E-marked BPVs have been the same since about 2004. They all contain the same safety device - it is not an open/shut switch, but will be fully open by about 24 psi (~20% overboost on a stock EJ207).
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Old 10-10-2017, 07:16 PM   #7
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Originally Posted by mrsaturn7085 View Post
You've chosen wisely.



The STi BPVs are all pretty much the same design, and there is a large letter stamped on the top of them. E-marked BPVs have been the same since about 2004. They all contain the same safety device - it is not an open/shut switch, but will be fully open by about 24 psi (~20% overboost on a stock EJ207).
So if I don't have an STI BOV, does that change anything? Got the engine as a full block, but both manifolds and all other attachments were pulled from the 205 that the previous owner had ruined with 24psi on a homebrew tune.
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Old 10-11-2017, 10:49 AM   #8
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Aren't there differences in the USDM vs JDM valves as well? The E marked valve was the USDM, one correct? The 02-07 USDM ones were the same, whether from a WRX or STi. But you'll have to decide between the ones that came with the 205 and the 207.

https://forums.nasioc.com/forums/sho....php?t=2008706

FWIW, I've been running 22psi for several years on a stock WRX valve with the $.16 reference signal mod. You can also crush the valve slightly to increase the internal spring preload, but that's going to be pretty unscientific.
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Old 10-11-2017, 01:26 PM   #9
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Originally Posted by T-37 View Post
Aren't there differences in the USDM vs JDM valves as well? The E marked valve was the USDM, one correct? The 02-07 USDM ones were the same, whether from a WRX or STi. But you'll have to decide between the ones that came with the 205 and the 207.

https://forums.nasioc.com/forums/sho....php?t=2008706
That thread has some things right, and some things wrong... early 2000's JDM valves have no over-boost safety device and a different spring. Later models (including the Spec C) got the E-marked valve.

The gold-colored valve that came on the USDM STI is the one we are interested in, but it came on more than just the STI or Spec C in Japan. Let's just call it the performance BPV for the sake of simplicity.

It looks like this:



The E-marked model is the one used across all performance motors from 2004+ in the USA, and 2006+ in Japan. It's a waste of time and effort to try and source anything beyond the E-marked valve (specifically, the early JDM valves are not worth seeking out).

Quote:
Originally Posted by T-37 View Post
FWIW, I've been running 22psi for several years on a stock WRX valve with the $.16 reference signal mod. You can also crush the valve slightly to increase the internal spring preload, but that's going to be pretty unscientific.
Don't crush your valve... you're not working on an SR20 motor in 1990 here.

Quote:
Originally Posted by 02SwagonProject View Post
So if I don't have an STI BOV, does that change anything? Got the engine as a full block, but both manifolds and all other attachments were pulled from the 205 that the previous owner had ruined with 24psi on a homebrew tune.
Get the E-marked 'performance' valve. This is the one you want to start with unless you're going with an aftermarket part.

On MAF-fueling:

If you're running up to 24 psi, just leave it alone - keep it routed to the intake.

If you're running above 24 psi, disable the over-boost protection - keep it routed to the intake.

Avoid aftermarket valves (even recirc. type) - you should prioritize converting to speed density long before you care about making more noise.

On speed density:

If you're running up to 24 psi, just leave it alone - route to intake or atmosphere.

If you're running above 24 psi, disable the over-boost protection - route to intake or atmosphere.

I you REALLY want an aftermarket valve (you probably don't *need* one) - I'd recommend the TiAl with a correctly selected spring.

Lastly... you can always just block-off the BPV port. Yeah, it's not ideal, but you need to weigh the pros and cons...

1. It will completely solve ALL boost leak issues through the BPV/BOV.
2. It will stall the compressor when you come off high boost and make some noise.
3. It will NOT cause surging in a way that damages the compressor like crossing the surge line under boost.

FWIW, I blocked off the BPV on my motor 50k miles ago to enhance the anti-lag performance and I've had zero issues. Subaru installs these to try to get 200k miles out of their turbos... but honestly, does anyone really think an IHI turbo is going to last that long, anyhow?
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Old 10-11-2017, 01:45 PM   #10
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Quote:
Originally Posted by mrsaturn7085 View Post
That thread has some things right, and some things wrong... early 2000's JDM valves have no over-boost safety device and a different spring. Later models (including the Spec C) got the E-marked valve.

The gold-colored valve that came on the USDM STI is the one we are interested in, but it came on more than just the STI or Spec C in Japan. Let's just call it the performance BPV for the sake of simplicity.

It looks like this:



The E-marked model is the one used across all performance motors from 2004+ in the USA, and 2006+ in Japan. It's a waste of time and effort to try and source anything beyond the E-marked valve (specifically, the early JDM valves are not worth seeking out).



Don't crush your valve... you're not working on an SR20 motor in 1990 here.



Get the E-marked 'performance' valve. This is the one you want to start with unless you're going with an aftermarket part.

On MAF-fueling:

If you're running up to 24 psi, just leave it alone - keep it routed to the intake.

If you're running above 24 psi, disable the over-boost protection - keep it routed to the intake.

Avoid aftermarket valves (even recirc. type) - you should prioritize converting to speed density long before you care about making more noise.

On speed density:

If you're running up to 24 psi, just leave it alone - route to intake or atmosphere.

If you're running above 24 psi, disable the over-boost protection - route to intake or atmosphere.

I you REALLY want an aftermarket valve (you probably don't *need* one) - I'd recommend the TiAl with a correctly selected spring.

Lastly... you can always just block-off the BPV port. Yeah, it's not ideal, but you need to weigh the pros and cons...

1. It will completely solve ALL boost leak issues through the BPV/BOV.
2. It will stall the compressor when you come off high boost and make some noise.
3. It will NOT cause surging in a way that damages the compressor like crossing the surge line under boost.

FWIW, I blocked off the BPV on my motor 50k miles ago to enhance the anti-lag performance and I've had zero issues. Subaru installs these to try to get 200k miles out of their turbos... but honestly, does anyone really think an IHI turbo is going to last that long, anyhow?
I agree with everything here.

It's worth noting that if you do mod the BPV, there will be some compressor surge at low boost pressures. The only time you're going to notice this when lifting off the throttle (changing gears) during moderate acceleration at low boost pressures (0-~5psi). You can reduce this effect by not lifting fully off the throttle when shifting if it bothers you.
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Old 10-12-2017, 12:46 AM   #11
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Originally Posted by mrsaturn7085 View Post
Don't crush your valve... you're not working on an SR20 motor in 1990 here.

Get the E-marked 'performance' valve. This is the one you want to start with unless you're going with an aftermarket part.
Here's mine - https://i.imgur.com/03Bl9buh.jpg

No E mark, and it looks like it may already have been crushed in? Wouldn't be the first, second, or even the fiftieth questionable thing the PO did.

So, lemme see if I understand this:
<24psi stock, >24psi stock mod - regardless of MAF or SD.

Quote:
I you REALLY want an aftermarket valve (you probably don't *need* one) - I'd recommend the TiAl with a correctly selected spring.
I really don't care much one way or the other, I just didn't know if I'd be able to keep the stock until I saw the mod. Which then got me wondering why there's so many aftermarket options and they're so expensive if they're pointless aside from noise.

But it looks like I just need to call my tuner tomorrow and find out if he expects to climb over 24psi or not. I've had to send a turbo back twice for rebuilds and am now replacing it, and I'd like to not have to rebuild this one so I don't think I want to chance a BOV delete. But if I can save money by staying stock or modding stock, then that is definitely preferable!

Thank y'all very much for the help!
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Old 10-12-2017, 12:53 AM   #12
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Originally Posted by T-37 View Post
I agree with everything here.

It's worth noting that if you do mod the BPV, there will be some compressor surge at low boost pressures. The only time you're going to notice this when lifting off the throttle (changing gears) during moderate acceleration at low boost pressures (0-~5psi). You can reduce this effect by not lifting fully off the throttle when shifting if it bothers you.
So, wait, you're saying that if I mod the stock one, not only do I save hundreds, but it's less likely to leak, I can get a Choo-Choo sound driving around town, and enjoy the pshhh with my short ram when I'm pushing it?

I'm finding less and less reasons for aftermarket WRX BOV's to be a thing.
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Old 10-12-2017, 01:08 AM   #13
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i did the mod then reversed it. i had bad compressor surge on my vf48 at about 5psi lifting off, and really bad surge at high rpm high boost lifting off from full to about half throttle. it messed with the MAF signal and made it terrible to drive. i want to figure out some sort of solenoid situation to re rout the vacuum/boost to the underside of the valve so it can run high boost and not surge. if i had a bearing turbo and speed density i would not care about a bit of surge. it sounds friggin cool.

i tested my bpv with and without mod using compressed air and a boost gauge. with the mod done it held well over 30psi. without it it started to leak around 20psi
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Old 10-12-2017, 08:58 AM   #14
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Originally Posted by CarmelValleyWRX View Post
i want to figure out some sort of solenoid situation to re rout the vacuum/boost to the underside of the valve so it can run high boost and not surge.
Like so? http://www.jakelatham.com/1gDSM/projects/dejon_bov/


Quote:
if i had a bearing turbo and speed density i would not care about a bit of surge. it sounds friggin cool.
So is compressor surge not as rough on ball bearings as it is on journal bearings? The turbo I'm going to is ball bearing.

Quote:
i tested my bpv with and without mod using compressed air and a boost gauge. with the mod done it held well over 30psi. without it it started to leak around 20psi
I'll be honest, I never thought to just test mine. I have a huge ~7ft air compressor that can put out more than enough pressure. I can probably figure it out after messing with it, but any details on how you went about testing it?
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Old 10-12-2017, 01:18 PM   #15
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Originally Posted by 02SwagonProject View Post
Which then got me wondering why there's so many aftermarket options and they're so expensive if they're pointless aside from noise.
There are a ton of aftermarket options because there are an equal number of people designing a turbo setup around a motor that was initially N/A.

While aftermarket BOV/BPV do have a place on certain factory turbo cars that came with a BPV (built or not), you'll find most OEM BPV on factory cars from 2000-on are pretty good, as-is.

The USDM STI runs about 14.5 psi stock, while the 2006+ JDM Spec C is closer to 19.6 psi. GD GpN cars had boost targets of 24.8 psi but would usually peak out around 23-24 psi. GR GpN cars had targets of 26.5 psi (!!!), but again, probably hit 23-24 psi.

All of these examples used unmodified E-marked valves.

Use the factory E-marked valve until you pass 23-24 psi, then spend a dollar to two to modify it. If you ever reach a point where this valve no longer works, look into aftermarket options.

Quote:
Originally Posted by 02SwagonProject View Post
So is compressor surge not as rough on ball bearings as it is on journal bearings? The turbo I'm going to is ball bearing.
There are two types of compressor surge - the tiny bit of blade stalling that occurs with a disabled/modified BPV...

http://www.youtube.com/watch?v=-E5QfEE8iEk#t=01m36s

...and the kind that occurs when your loaded turbo passes the surge line of the compressor chart...

http://www.youtube.com/watch?v=nCj6Spwl1CU#t=00m34s

The former will likely take a LONG time to do any damage, even to a journal bearing. The latter will destroy a turbo in short order.

Here is Tomei's explanation for this over-boost device on SR20 motors; the function is identical to the E-marked Subaru valve:


Last edited by mrsaturn7085; 10-12-2017 at 01:35 PM.
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