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"Tuning" a BOV?
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10-15-2009, 02:24 AM | #1 |
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"Tuning" a BOV?
I recently picked up a TiAl BOV kit. I have been running OEM replacement Forge DVs with the yellow springs for about 25k miles and have been very satisfied with the performance, but I wanted to try something new.
I have no experience with BOVs... always thought it was cool that you could "tune" the Forge DVs with different springs depending on boost so I was stoked that you could do something similar with the TiAl BOVs. You could select a specific spring for your valve according to the engine's vacuum at idle: http://www.tialmedia.com/documents/w3_tial_bov50_sp.pdf -22 and -23 in/Hg Pink -12 Psi (-24 in/Hg ) -18 and -21 in/Hg Un-painted -11 Psi (-22 in/Hg ) -14 and -17 in/Hg White -9 Psi (-18 in/Hg ) -10 and -13 in/Hg Black -7 Psi (-14 in/Hg ) So for the N54 which idles at -20 in/Hg, the appropriate spring to use would be the unpainted spring. However, I'm confused about a few things and I haven't been able to find answers that are consistent or definitive. 1. Is the valve *supposed* to be open during idle? What about during cruise (off boost)? 2. If the N54 idles at about -20, and per the recommendations above we use the unpainted spring rated at -22, does the -22 mean that it requires -22 in/Hg of vacuum to overcome the spring and keep the valve open? Doesn't that imply the valve will remain closed during idle? (which really contradicts what I've read elsewhere that the valve is *supposed* to stay open at idle). 3. From what I've been told, most standard TiAl kits for our cars come with the white spring preinstalled, and it seems to work just fine. However, would switching to stiffer spring (unpainted) result in faster response between shifts, hold booster better, etc. (similar to changing the Forge DV springs from green to yellow)?
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10-15-2009, 07:40 AM | #2 |
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I recently picked up a TiAl BOV kit. I have been running OEM replacement Forge DVs with the yellow springs for about 25k miles and have been very satisfied with the performance, but I wanted to try something new.
I have no experience with BOVs... always thought it was cool that you could "tune" the Forge DVs with different springs depending on boost so I was stoked that you could do something similar with the TiAl BOVs. You could select a specific spring for your valve according to the engine's vacuum at idle: http://www.tialmedia.com/documents/w3_tial_bov50_sp.pdf -22 and -23 in/Hg Pink -12 Psi (-24 in/Hg ) -18 and -21 in/Hg Un-painted -11 Psi (-22 in/Hg ) -14 and -17 in/Hg White -9 Psi (-18 in/Hg ) -10 and -13 in/Hg Black -7 Psi (-14 in/Hg ) So for the N54 which idles at -20 in/Hg, the appropriate spring to use would be the unpainted spring. However, I'm confused about a few things and I haven't been able to find answers that are consistent or definitive. 1. Is the valve *supposed* to be open during idle? What about during cruise (off boost)? The N54 is not a mass air meter car so you can have the valve open or closed at Idle, however what you need to look at is that under immediate accel(WOT) the valve doesnt momentarily open as the factory diverters do under high boost. you want the lightest spring you can use as long as the valve closes under all forms of acceleration(boost) 2. If the N54 idles at about -20, and per the recommendations above we use the unpainted spring rated at -22, does the -22 mean that it requires -22 in/Hg of vacuum to overcome the spring and keep the valve open? Doesn't that imply the valve will remain closed during idle? (which really contradicts what I've read elsewhere that the valve is *supposed* to stay open at idle). Yes in theory, but in practice u need to test! 3. From what I've been told, most standard TiAl kits for our cars come with the white spring preinstalled, and it seems to work just fine. However, would switching to stiffer spring (unpainted) result in faster response between shifts, hold booster better, etc. (similar to changing the Forge DV springs from green to yellow)? Read above again, you need to test this on your car, its easiest to see on a dyno as long as the fyno loads the car as if its in a road going situation! |
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10-15-2009, 08:08 AM | #3 | |
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10-15-2009, 10:37 AM | #4 |
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interesting...i may have to look for the spring kit so i can try the unpainted one. i think i saw it somewhere for like $25.
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10-15-2009, 10:49 AM | #5 | |||
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10-15-2009, 11:11 AM | #6 | |
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I found this thread on a corvette forums: http://forums.corvetteforum.com/c5-f...ch-spring.html There's a guy there saying the valve should be open at idle. However, is the BOV sucking air in at idle? Or pushing air out? If it's pushing air out, why are people still "filtering" their DIY DV to BOV conversions? Yeah, that sounds about right... I've seen it for 25-30.
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10-15-2009, 11:37 AM | #7 | |
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10-15-2009, 11:51 AM | #8 | |
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10-15-2009, 11:59 AM | #9 | |
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The N54 is not a mass air meter car so you can have the valve open or closed at Idle, however what you need to look at is that under immediate accel(WOT) the valve doesnt momentarily open as the factory diverters do under high boost. you want the lightest spring you can use as long as the valve closes under all forms of acceleration(boost) The spring doesn't shut the BOV high vacuum and boost closes the BOV and holds it shut.
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10-15-2009, 12:03 PM | #10 | |
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http://www.kewego.com/video/iLyROoafY7i4.html
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10-15-2009, 12:28 PM | #11 | ||
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10-15-2009, 12:36 PM | #12 |
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I noticed it when I first put it in that my tial stayed shut at idle and would only open to blow off. I asked stett what springs where he putting in them and he told me the white ones. I thought so too when I first installed my ******** BOV that it would be sucking air in, but when I put my hand there it was blowing it out.
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10-15-2009, 12:47 PM | #13 |
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The N54 provides positive Boost Air at all times (open or closed) and only ever sees boost pressure from the Charge Pipe which means it's always blowing air out, so there is no need to filter the Bov. The charge pipe never sees vacuum. Having the BOV open at idle or at cruise alleviates any unnecessary stress on the turbo's or engine and improves mpg.
Without any load on the engine without the car moving, even if you rev it, all the intake will see is vacuum.........not boost. Once you're under way and the throttle body begins to open, the BOV shuts very quickly and allows the turbo's to build boost. The Synapse approach is more ideal than a spring loaded BOV in this situation as it allows it to be open when not in boost and closed when boosting. The way it should be. Last edited by Sparky66; 10-16-2009 at 10:35 AM.. |
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10-15-2009, 01:32 PM | #15 |
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It's your preference... Are you okay with it being open at idle and venting the positive pressure generated by the turbos? Or do you want it closed at idle?
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10-15-2009, 05:03 PM | #16 |
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Hey Flem, did you ever get to run your car with the white springs? If so did you notice any difference or improvement in throttle response? Discernible compressor surge?
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10-15-2009, 08:48 PM | #17 | |
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Please correct me if I'm making assumptions here. If you go on immediate accel (WOT), it seems boost in the chargepipe overcomes the spring pressure in the valve, thus opening it (I'm assuming this is the abrupt opening of the stock DVs that was described). At that moment when the throttle plate opens, is the manifold still in vacuum when this occurs (at that very moment the valve opens up)? And when the valve shuts after that (possible) abrupt opening, is there a large difference across the throttle body between manifold pressure and chargepipe/intercooler pressure? Are they pretty much equal when the manifold is in full boost (per the boost gauge)?
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10-16-2009, 09:41 AM | #18 | ||
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I have only had the tiniest bit of compressor surge with the unpainted spring. Maybe once or twice in the 6 months I have had the tial in the car. But as far as what spring you should use? It's up to you. Quote:
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10-16-2009, 10:00 AM | #19 |
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Everything I've read shows no advantage of using a BOV over DV and vice versa other than BOV's on our cars suck in unfiltered air. Correct me if I am wrong.
I personally do not like the BOV vacuum cleaner sound I associate them with and they suck in unfiltered air into the engine. |
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10-16-2009, 10:06 AM | #20 |
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I thought the same... But after Terrance and I discussed it above (I had to read a bit about it as well) the N54 makes positive pressure at idle so it actually blows air out if the BOV is open at idle
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10-16-2009, 10:27 AM | #21 |
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I'm not really worried about anything getting sucked in... the chargepipe side never sees vacuum.
What I'm still agonizing about is which spring gives the best *performance benefit*, while trying to prevent instances of compressor surge. I know that for Forge DVs, the heavier yellow springs are the way to go for tuned cars. But even with these, I've had some occasional flutter. Does anyone happen to know if the yellow springs allow the DVs to divert back to the intake at idle? In other words, do the yellow springs allow the Forge units to be open at idle/cruise?
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10-16-2009, 10:42 AM | #22 | |
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