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Old 03-30-2016, 06:36 AM   #401
ride5000
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I will gladly exchange my modded usdm valve for a jdm sti version.
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Old 03-30-2016, 12:12 PM   #402
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Quote:
Originally Posted by 4eat05 View Post
Now Im even more confused on this modded usdm vs factory modded jdm lol
Buy both, see which you prefer. They aren't the most expensive parts to pick up and they take all of 5 minutes to swap out.

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Originally Posted by ride5000 View Post
I will gladly exchange my modded usdm valve for a jdm sti version.
They're easy enough to import - let me know (ASAP) if you need one, as I've got a JDM pump and fuel tank on order that haven't shipped to me yet. I'd hold on to that modded valve so you can compare them, however...
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Old 04-04-2016, 02:22 PM   #403
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Quote:
Originally Posted by mrsaturn7085 View Post
Buy both, see which you prefer. They aren't the most expensive parts to pick up and they take all of 5 minutes to swap out.



They're easy enough to import - let me know (ASAP) if you need one, as I've got a JDM pump and fuel tank on order that haven't shipped to me yet. I'd hold on to that modded valve so you can compare them, however...
I know the stock usdm bpv is cheap, easy to find, easy to mod and easy to swap out for testing, but I cant seem to find Jdm bpv's. Most of the "jdm" ones I see dont seem to have the external hole, and the 1 I see every blue moon is super expensive for an oem bypass valve, plus usually expensive shipping

And Im having a hard time figuring out if the higher spring pressure plus external boost reference port, or if the lower spring pressure with external boost reference port would be better for my car. (2005 Wrx ej205. Cobb sf intake+box/maf hose, Perrin turbo inlet, Samco tmic hoses, Cobb catless uppipe, Cobb catted downpipe, oem Sti catback, Cobb Accessport stage 2 93 octane. Only future engine plans are vf39/34, Sti tmic/injector, Walbro fuel pump and tune) I know I dont NEED a modded usdm or jdm or aftermarket bpv since Im not passing 20 psi or leaking, I just want to try one, but not sure which to try first.

Last edited by 4eat05; 04-04-2016 at 02:28 PM.
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Old 04-04-2016, 07:25 PM   #404
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Quote:
Originally Posted by 4eat05 View Post
...I cant seem to find Jdm bpv's. Most of the "jdm" ones I see dont seem to have the external hole, and the 1 I see every blue moon is super expensive for an oem bypass valve, plus usually expensive shipping
These have not been installed on a new car in approximately 10 years. I'm pretty sure I can still order them new... but personally, I still don't see why you'd want to. I get it though - you want a side-by-side comparison, just like I did

If you aren't going to run over 24 psi, then you don't need to change a thing. Buy a second USDM valve and mod it just to give it a shot, but don't drive yourself nuts trying to locate the older JDM valve.
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Old 04-05-2016, 01:10 AM   #405
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Quote:
Originally Posted by mrsaturn7085 View Post
These have not been installed on a new car in approximately 10 years. I'm pretty sure I can still order them new... but personally, I still don't see why you'd want to. I get it though - you want a side-by-side comparison, just like I did

If you aren't going to run over 24 psi, then you don't need to change a thing. Buy a second USDM valve and mod it just to give it a shot, but don't drive yourself nuts trying to locate the older JDM valve.
Yeah, I just figured if im going to go ahead and buy another stock usdm bpv to mod, I might as well try to find the Jdm bpv that already has the "mod", then I could mod my stock usdm bpv after I put the Jdm bpv on. Seems to make more sense to me than buying another stock usdm bpv, modding it, swapping it with my current stock bpv and then looking for the correct Jdm bpv.

How exactly would I be able to tell it is the correct Jdm bpv other than hoping to see the external boost reference port in pictures?

Random Q, do you know if, or think it would be possible to tap/thread the external boost reference port on the Jdm/modded usdm bpv to add a small vacuum line fitting like the Greddy type s had? I personally think that would be neat. (90's inner ricer coming out of me)
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Old 04-05-2016, 08:55 AM   #406
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From running both, I would say to save your money and mod the USDM one and run it. If you have a drill, tap and metric grub screw, you can literally be done in a half an hour hood open to close. It's that simple.

In regards to your question of making the atmospheric port fancy: no point. You can but I chalk it up to a solution in search of a problem when a simple hole will suffice.

The one thing I would advise is to drill the atmospheric port on the bottom of the valve where it mounts versus the side for water ingress. Wish I knew that before I did mine.

In my posts, I purchased a new E-code (and is now sitting in the box) JDM BPV and the biggest difference between the two was the near non-modded USDM performance. The modded USDM valve has more of a surge in boost as the spring pressure plus atmospheric reference holds the charge much moreso than the JDM valve. After spoolup and max boost, both perform the same. Both hold max boost the same, at least on my turbo (max pressure is 21psi). I did this for better response and not the fact that the valve itself will hold more. That was a bonus to me.

YRMV, especially if your screen name holds true (auto) but for cost of entry, mod the USDM valve. It is reversible if you don't like it and you're only out the cost of the grub screw if you have everything else. I went metric as it's pretty much all I have these days and stainless so that if I were to revert, the screw would be exposed to the elements.

-Randy
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Old 04-05-2016, 11:12 AM   #407
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Originally Posted by tomacGTi View Post
From running both, I would say to save your money and mod the USDM one and run it. If you have a drill, tap and metric grub screw, you can literally be done in a half an hour hood open to close. It's that simple.

In regards to your question of making the atmospheric port fancy: no point. You can but I chalk it up to a solution in search of a problem when a simple hole will suffice.

The one thing I would advise is to drill the atmospheric port on the bottom of the valve where it mounts versus the side for water ingress. Wish I knew that before I did mine.

In my posts, I purchased a new E-code (and is now sitting in the box) JDM BPV and the biggest difference between the two was the near non-modded USDM performance. The modded USDM valve has more of a surge in boost as the spring pressure plus atmospheric reference holds the charge much moreso than the JDM valve. After spoolup and max boost, both perform the same. Both hold max boost the same, at least on my turbo (max pressure is 21psi). I did this for better response and not the fact that the valve itself will hold more. That was a bonus to me.

YRMV, especially if your screen name holds true (auto) but for cost of entry, mod the USDM valve. It is reversible if you don't like it and you're only out the cost of the grub screw if you have everything else. I went metric as it's pretty much all I have these days and stainless so that if I were to revert, the screw would be exposed to the elements.

-Randy
I see you say "save your money and mod the USDM one", but what if money were of no issue, or say I had access to the Jdm valve?

Are all oem usdm 02-07 Wrx/Sti bpv's the exact same, or should I do this mod to a certain year(s) or model? How can I tell the difference between the Jdm bpv that I want and the Jdm valve that I don't want?

Could you show a pic of where you feel the atmospheric port should be drilled in comparison to where most people drill the port? Im having a hard to visualising where your are talking about.
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Old 04-05-2016, 11:37 AM   #408
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If you want to try the JDM valve, you can buy mine. It was used for a total of a month and is brand new. I ordered it and had to wait for it for about a month from Japan Parts. All total I have $140 into it, if you're interested, I'll let it go for less than that shipping included. PM me.

If you look at the USDM BPV, the 1/16" hole you drill into the vein is usually in a casting flash on the side of the valve. Don't drill it there, instead, drill it on the bottom of the vein. The images of the holes in the Cota valve as well as the JDM valve show this clearly. You do not want to go larger than this either.

Like this:

http://minkara.carview.co.jp/en/user...6175/note.aspx

Like I said, after running both, I am running the USDM valve modified. My tuner has also indicated that the STi valve is sprung more stiffly as well. I haven't bothered trying as I have three options already: Stock, modded and JDM.

My .02$.

-Randy

Also, read carefully through this thread..

This modification to the valve is to hold more boost and gain additional response: this does not necessarily apply to stage 2 levels. A good deal of feedback through all of the posts through the years have indicated compressor surge with a modified valve. I cannot provide any feedback because in the days when I was stage two with near similar mods as yourself, I found no need for a beefed up BPV. I certainly don't need one now either but it helps with the slight bit of lag from a slightly larger turbo. The stock setup (stage 2/turbo) is as responsive as the car will ever be so hence the possibility of surge.

Again, YRMV.

Last edited by tomacGTi; 04-05-2016 at 12:13 PM.
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Old 04-05-2016, 12:18 PM   #409
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Originally Posted by tomacGTi View Post
...I purchased a new E-code (and is now sitting in the box) JDM BPV and the biggest difference between the two was the near non-modded USDM performance...

-Randy
Just as a heads-up, the valves that are E-marked are all the same. JDM E-marked = USDM E-marked. This was a standardized part in all markets between the 2005/2006 mode year. If you were referring to the GDB-E, then yeah, that's the last model year that the light spring valve was installed!

Quote:
Originally Posted by 4eat05 View Post
Are all oem usdm 02-07 Wrx/Sti bpv's the exact same, or should I do this mod to a certain year(s) or model? How can I tell the difference between the Jdm bpv that I want and the Jdm valve that I don't want?
There are three valves to concern yourself with:

#1 - The JDM STI valve used up to 2005; this used a light spring.
#2 - The USDM STI valve, which was also used on JDM STI models after 2005/2006; this was silk-screened with a "E" and used a heavy spring.
#3 - The USDM STI valve, modified to match the function of #1, with the spring pressure of #2; this was sold in the aftermarket as the Coto Sports valve.

READ ALL OF PAGE 16 OF THIS THREAD That is where the most useful information is. There's some argument about the JDM light spring valve being better - but as tomacGTi, myself, and likely the majority of tuners in Japan would tell you, the E-marked valve is the one you want. Buy a JDM valve and drive it back to back with the "E"-marked valve if you want - I already know which one you'll keep. Whether or not you need to modify it to remove the overboost safety depends solely on your need to run higher than approximately 24 psi.

Pay special attention to my comments about TiAL valve on page 16, and selecting spring pressures. TiAL will tell you to run the hardest one that matches your idle vacuum on a reference chart, while random people online will tell you to just run the light spring... light audible surging is not gonna grenade your turbo - selecting the proper BPV/BOV spring pressure is a balancing act between performance and longevity.

Last edited by mrsaturn7085; 04-05-2016 at 12:29 PM.
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Old 04-05-2016, 02:51 PM   #410
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surely a claim of increased performance using ever stiffer spings would be backed up with data...
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Old 04-05-2016, 03:14 PM   #411
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surely a claim of increased performance using ever stiffer spings would be backed up with data...
I can explain the theory all day (as I tried to on page 16), but as I mentioned, a back-to-back test is all you should need. I get it - we disagree, and I'm fine with that.

You're welcome to provide data as well; at the moment, I think you're the one disagreeing with the majority, including companies that have done such testing, such as TiAL, Tomei, and others. What specific data are you looking for?

Also, given this topic of this thread (modifying a late-model BPV) cannot even apply to the early JDM valve... what are you even doing in here aside from stomping the thread?
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Old 04-05-2016, 09:42 PM   #412
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Originally Posted by mrsaturn7085 View Post
Just as a heads-up, the valves that are E-marked are all the same. JDM E-marked = USDM E-marked. This was a standardized part in all markets between the 2005/2006 mode year. If you were referring to the GDB-E, then yeah, that's the last model year that the light spring valve was installed!



There are three valves to concern yourself with:

#1 - The JDM STI valve used up to 2005; this used a light spring.
#2 - The USDM STI valve, which was also used on JDM STI models after 2005/2006; this was silk-screened with a "E" and used a heavy spring.
#3 - The USDM STI valve, modified to match the function of #1, with the spring pressure of #2; this was sold in the aftermarket as the Coto Sports valve.

READ ALL OF PAGE 16 OF THIS THREAD That is where the most useful information is. There's some argument about the JDM light spring valve being better - but as tomacGTi, myself, and likely the majority of tuners in Japan would tell you, the E-marked valve is the one you want. Buy a JDM valve and drive it back to back with the "E"-marked valve if you want - I already know which one you'll keep. Whether or not you need to modify it to remove the overboost safety depends solely on your need to run higher than approximately 24 psi.

Pay special attention to my comments about TiAL valve on page 16, and selecting spring pressures. TiAL will tell you to run the hardest one that matches your idle vacuum on a reference chart, while random people online will tell you to just run the light spring... light audible surging is not gonna grenade your turbo - selecting the proper BPV/BOV spring pressure is a balancing act between performance and longevity.

Brain farted: I have the earlier JDM valve that has the lighter spring and sealed to the intercooler chamber. Sorry for the confusion.

https://www.japanparts.com/parts/detail/14352

The actual BPV I purchased.

-Randy

Last edited by tomacGTi; 04-05-2016 at 09:53 PM.
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Old 04-06-2016, 07:26 AM   #413
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Originally Posted by mrsaturn7085 View Post
I can explain the theory all day (as I tried to on page 16), but as I mentioned, a back-to-back test is all you should need. I get it - we disagree, and I'm fine with that.

You're welcome to provide data as well; at the moment, I think you're the one disagreeing with the majority, including companies that have done such testing, such as TiAL, Tomei, and others. What specific data are you looking for?

Also, given this topic of this thread (modifying a late-model BPV) cannot even apply to the early JDM valve... what are you even doing in here aside from stomping the thread?
Oh, certainly I do recall your theory that slowing down the shaft speed of a turbo so that you can keep excessive pressure building up in the section of intake tract between compressor and throttle body is a “good thing” for performance.

I just don’t buy it, because it doesn’t make any sense.

There have been plenty of situations where I was at a high rpm, low load operating point. Despite very low MAP there was sufficient exhaust gas flow to keep the turbo spinning quite freely. A classic example is on a highway entrance ramp. During the time when I was testing low BOV tension rates (txs rfl with no shims for example) it would CONTINUALLY vent to atmosphere under those conditions. (Obviously running speed density is a prerequisite.)

Lifting completely caused the BOV to open wider and vent faster, while additional throttle angle would make it close completely with an audible click as the heavy brass piston seated.

While at high rpm low load, that charge air was vented right to atmosphere. Had it not been, I totally agree that there would have been higher IC pressure—but that also necessarily means lower shaft speeds. You don't get one without the other.

Your position is that the compressed charge air volume between compressor and TB makes for better instantaneous throttle response.

My position is that “stored charge” not worth the tradeoff in making the turbo work harder during part throttle conditions. Instead I seek to eliminate any resistance to charge air flow regardless of whether it is flowing past the throttle plate or not.

How many milliseconds does it take for your “stored charge” pressure to drop after throttle snap open? How many milliseconds does it take to increase your shaft speed?

Since my car is off the road for repair and refreshing I cannot finish my testing, but based on everything I’ve observed first hand the ONLY time a bov must never be open at all is during WOT. (naturally if you are maf fueling there are other constraints, but they are eliminated with a recirc.)

As I asked earlier, let’s take your “explanation” to a logical conclusion: why not run no valve at all? Quirt Crawford suggested this for years. Surely if the stiffer spring is better for “performance” then an infinitely stiff spring is best? If an infinitely stiff spring isn’t best, then what is the breakpoint at which it becomes a hindrance to “performance?”
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Old 04-06-2016, 12:04 PM   #414
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Oh, certainly I do recall your theory that slowing down the shaft speed of a turbo so that you can keep excessive pressure building up in the section of intake tract between compressor and throttle body is a "good thing" for performance.
Your words, not mine. I'm advocating a balance, not a black or white extreme.

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I just don't buy it, because it doesn't make any sense.
You buying into it is not a prerequisite for it to be true. tomacGTi and I have both provided you with firsthand experience on which the better valve is. The advice is worth what you paid for it...

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Originally Posted by ride5000 View Post
Lifting completely caused the BOV to open wider and vent faster, while additional throttle angle would make it close completely with an audible click as the heavy brass piston seated.
Which BOV are you talking about? I'm not calling you out here... I just don't know of any BOV relevant to the discussion using a brass piston and I'm curious.

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Originally Posted by ride5000 View Post
Your position is that the compressed charge air volume between compressor and TB makes for better instantaneous throttle response.
Yes, partially; as the throttle is cracked, you have a small volume of air coupled with an increased shaft speed.

Quote:
Originally Posted by ride5000 View Post
My position is that "stored charge" not worth the tradeoff in making the turbo work harder during part throttle conditions. Instead I seek to eliminate any resistance to charge air flow regardless of whether it is flowing past the throttle plate or not.
You said you don't buy the momentary 'stored charge' theory above, and now you say your position is that the momentary 'stored charge' is not worthwhile... please clarify what you disagree on here, because I'm pretty sure these two positions are mutually exclusive.

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Originally Posted by ride5000 View Post
How many milliseconds does it take for your "stored charge" pressure to drop after throttle snap open? How many milliseconds does it take to increase your shaft speed?
On the former question, you could probably get a ballpark idea with some logging on a track. The MAP is not the only sensor reading that would be necessary, however. You'd really want to look at the shaft speed of the turbo. Not only do you have a larger volume of air available - the turbocharger is already sitting at a higher shaft speed when the throttle is cracked. Given a turbocharger with a shaft speed sensor, I could log this through the ECU. Unfortunately, I don't have one lying around the shop. If you'd like to buy a rally potato for testing, they've got one built right into the compressor housing.

Quote:
Originally Posted by ride5000 View Post
Since my car is off the road for repair and refreshing I cannot finish my testing, but based on everything I've observed first hand the ONLY time a bov must never be open at all is during WOT. (naturally if you are maf fueling there are other constraints, but they are eliminated with a recirc.)
Bypassing air at part-throttle = less air entering the cylinders at part-throttle = lower part-throttle torque. Yeah, you don't *need* to have the BOV shut at part-throttle for the engine to run, but you'd be leaving performance on the table. I really don't know how you could possibly dispute that...

Also, remember when you said the following on page 16?

Quote:
Originally Posted by ride5000 View Post
the jdm is most certainly not partially open at idle vacuum.
You now you're saying that even if it was, it doesn't matter? Did you ever stick a camera down there and look, as I suggested?

Quote:
Originally Posted by ride5000 View Post
As I asked earlier, let's take your "explanation" to a logical conclusion: why not run no valve at all? Quirt Crawford suggested this for years. Surely if the stiffer spring is better for "performance" then an infinitely stiff spring is best? If an infinitely stiff spring isn't best, then what is the breakpoint at which it becomes a hindrance to "performance?"
Again - I am not advocating a black/white extreme solution but rather a compromise in reliability/performance. The 'no valve' situation may have merit, and was in fact used on WRC cars and many GpN cars (only when regional/club ruling may have allowed this - FIA rules did not). The WRC example is difficult to analyze due to the unique ALS which may have made this a necessity.

Given the stock options (the topic of this thread), I'd say the breakpoint in performance/reliability, for me, is using a modified late-model USDM valve when holding 24+ PSI is needed. At levels below this, I would use the late-model USDM valve (unmodified).

You clearly prefer the JDM valve, though I'm still not sure of your opinion on the theory of operation due to you taking both positions in a single post.

Last edited by mrsaturn7085; 04-06-2016 at 12:11 PM.
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Old 04-06-2016, 03:38 PM   #415
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So Ill probably keep an eye open for a "factory modded" early Jdm sti bypass valve.

But, as I am searching, I will likely buy another stock Us bpv and do this mod to it, but which do I want? The "E marked" Sti bpv, or the non "E marked" bpv like the stock bpv on my usdm 2005 Wrx?
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Old 04-06-2016, 05:22 PM   #416
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Quote:
Originally Posted by 4eat05 View Post
So Ill probably keep an eye open for a "factory modded" early Jdm sti bypass valve.

But, as I am searching, I will likely buy another stock Us bpv and do this mod to it, but which do I want? The "E marked" Sti bpv, or the non "E marked" bpv like the stock bpv on my usdm 2005 Wrx?
As far as I have been told, the STi BPV has been known to hold more boost pressure. Generally speaking, I for one, would expect this seeing that their turbo is moving more air stock. Also, after a set point, the STi and WRX shared BPVs. I don't know necessarily how true this is as I have only worked with the JDM valve and the USDM BPV.

With what you have, even a WRX BPV modified will be sufficient.

Like I have stated and what I've understood from this thread and personal experimentation: this mod is ultimately for higher boost pressure without going aftermarket. Every other caveat or feature is secondary.

Ride5000, I'm not trying to cause a stir or otherwise, just trying to share my experiences. There is a video that is floating around here or YouTube where someone pressure tests the factory plastic valve, an aftermarket valve and a modded plastic valve all back to back showing PSI.

http://legacygt.com/forums/showthrea...-197583p3.html

I don't know if this will add to the discussion or not but I found it very informative and was one of the reasons why I explored the mod even after getting the JDM valve.

-Randy
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Old 04-06-2016, 06:40 PM   #417
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Quote:
Originally Posted by 4eat05 View Post
So Ill probably keep an eye open for a "factory modded" early Jdm sti bypass valve.

But, as I am searching, I will likely buy another stock Us bpv and do this mod to it, but which do I want? The "E marked" Sti bpv, or the non "E marked" bpv like the stock bpv on my usdm 2005 Wrx?
The E-marked valve is the one to get.
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Old 04-06-2016, 09:38 PM   #418
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So the later "E marked" Jdm and "E marked" usdm have stiffer springs than the earlier Jdm and non "E marked" usdm valves? Would the non "E marked" usdm springs be firmer than the earlier Jdm valve, but not as stiff as the later "E marked" valves?

If one is firmer than the "factory modded" Jdm Sti valve, but less stiff than the usdm "E" valve, thats probably the one I want.
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Old 04-07-2016, 07:14 AM   #419
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Okay. For the last time: ANY valve is stiffer than the earlier JDM BPV. It is done by function and how the ports are referenced.

Easiest test:

You can push the spring in with little to no effort with your thumbs on a JDM valve.

ANY USDM valve:

Requires more than a concerted effort to compress the spring.

Why?

On the later JDM and USDM this is what seals the BPV shut until enough pressure blows it off. This was done as a safety net by engineers at FHI much smarter than you and I to keep from blowing **** up.

What does the mod do?

The mod takes away the boost reference port on the inside facing the intercooler and uses an atmospheric port to control the valve. The spring is now redundant. It now uses differential pressure across the diaphragm to blow off. Coupled with the stiffer spring, it requires a higher initial pressure than even the JDM valve to blow off. You take away the safety net.

This is why the earlier JDM valve is much like the valve you have now. The lighter spring pressure utilizing the atmospheric referenced port gives it the same responsiveness as an unmodded USDM of ANY flavor. It just holds more boost because it uses equalizing pressure on both sides of the diaphragm versus relying on a spring holding it shut. How do I know? I have run all three.

This is where you toe the line between surge and responsiveness. If your turbo does not produce enough boost to actuate the valve to blow off, you will surge until it does.

Again:

This is done ultimately to hold more boost. More boost than even your stage 2+ setup can produce. You will have to decide ultimately what works best for your setup.

Between all of the banter, ten plus years on the topic and my rehashing of a FAQ, you should have every detail to make your decision. It can't be spoon fed any further.

So if you want something more than you have now your choices are as follows:

-Contact Japan Parts and get yourself an early BPV

-Go to any DIY store worth a damn and buy the tools necessary to mod your valve

-Search for an E valve and do what you will. Be advised that unless you get one from a dry climate, that lettering is probably gone.

-Get a spare BPV from any WRX/STi and mod that

-Find a known STi valve and run it as its known to hold more pressure. High chance that it will be for naught as it will perform the same as you have now.

Best of luck.

-Randy

Edit:

http://forums.nasioc.com/forums/show....php?t=2781057

There you go...

Last edited by tomacGTi; 04-07-2016 at 07:25 AM.
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Old 04-07-2016, 12:06 PM   #420
mrsaturn7085
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Quote:
Originally Posted by 4eat05 View Post
So the later "E marked" Jdm and "E marked" usdm have stiffer springs than the earlier Jdm and non "E marked" usdm valves? Would the non "E marked" usdm springs be firmer than the earlier Jdm valve, but not as stiff as the later "E marked" valves?

If one is firmer than the "factory modded" Jdm Sti valve, but less stiff than the usdm "E" valve, thats probably the one I want.
Find me a USDM valve that is not "E-marked"...

I believe the E-marked valve was actually installed in 2004+ in the US, so this question is irrelevant. The valve you are talking about (probably) doesn't exist.
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Old 04-08-2016, 01:16 AM   #421
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Quote:
Originally Posted by tomacGTi View Post

-Find a known STi valve and run it as its known to hold more pressure. High chance that it will be for naught as it will perform the same as you have now.

Best of luck.

-Randy
This is why I asked. If the usdm Sti bpv has a slightly stiffer spring than the usdm Wrx bpv, I would probably want the oem Wrx bpv to do this mod to. I understand the difference between the internal boost reference and external atmosphere reference valves, just trying to figure out if there is an oem bpv that has a spring stiffer than the early jdm Sti but softer than the usdm Sti (i.e. usdm Wrx)
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Old 04-08-2016, 12:36 PM   #422
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04-07 STI & 06-07 WRX = 14471AA140/141/142/143

All 2.5L engines (and 06+ JDM EJ207) use the late-model "E"-marked valve.

02-05 WRX = 14471AA120

I do not know the status of the 120 p/n valve, but it was used on the EJ205 in both the US and Japan - buy one and report back!

Early JDM EJ207 valve is 14471AA112, for reference.
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Old 04-09-2016, 11:41 AM   #423
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Quote:
Originally Posted by mrsaturn7085 View Post
Bypassing air at part-throttle = less air entering the cylinders at part-throttle = lower part-throttle torque. Yeah, you don't *need* to have the BOV shut at part-throttle for the engine to run, but you'd be leaving performance on the table. I really don't know how you could possibly dispute that...
this is a fundamental issue of the discussion.

what "performance" is left on the table during a part throttle open bov/bpv?

i have repeatedly offered that there are definite gains to be had in this common scenario by reducing drive torque requirements on the CHRA. (hopefully i don't have to describe yet again why reducing the load on the exhaust side is a universally good thing.)

so how exactly does it make "performance" sense to cause the compressor to work harder over compressing the charge just so that you can then cause a larger pressure drop downstream across a partially-opened throttle to net a given MAP?
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Old 04-12-2016, 12:40 AM   #424
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wow that sounds sketchy, but maybe it's cause i couldn't pull it off.
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Old 04-12-2016, 12:54 PM   #425
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what "performance" is left on the table during a part throttle open bov/bpv?
More air bypassed means less air entering the cylinders...

So given a specific throttle position (let's say 50%) you've got less wheel torque, right? Weaker intake charge = decreased torque output. I really shouldn't need to elaborate on this part...

The natural response to this is probably going to be 'just add more throttle'. Now you end up with a peaky throttle that feels weak until you hit 80-100% throttle. This is not due to a slow-spooling turbo, but rather the fact that you are dumping/diverting a perfectly usable part-throttle mass of air AWAY from the cylinders.

The next follow-up may be 'but wait, I've got a DBW throttle and can tune it accordingly'. Okay, that's a good band-aid, but you'll be losing throttle resolution by trying to chase a smooth throttle-torque curve. Dedicating the last 50-60% of pedal position to the upper 10-20% of throttle position would just be silly. Due to the nature of the system, this doesn't work anyhow - you can't 'tune out' a mechanically weaker spring at a part-throttle position; it just does not work.

Or, you know, you could just use a BPV that bypasses less air at a part-throttle position. Something like an E-marked, or modified E-marked OEM valve...
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