Jersey Posted April 4, 2004 Share Posted April 4, 2004 I'm running the DSM BOV which has a vacuum line to the manifold for a reference pressure. The problem i'm having is that at idle, she leaks a little, giving an unstable, loping idle because I run it vented to atmosphere. I'm not going to re-circulate it. I've read that they're suppose to do this due to allow air in while the turbo is acting a little restictive at this point. Question is, does the vacuum line at the top of this valve act two-fold meaning, under positive manifold, it holds pressure down on the valve to hold more boost and... under high vacuum situations, does it pull up on the valve to release it easier? If it does work like this, i'm wondering if i just put a one way valve in there to make it stop leaking at idle while still allowing it to hold boost? This might be a confusing post, sorry, but i hope i made sort of sense! lol. Quote Link to comment Share on other sites More sharing options...
Doug71zt Posted April 4, 2004 Share Posted April 4, 2004 Jersey - The one-way valve idea won't work because the BOV needs to see boost on the reference line to stay closed under boost and see vacuum when you are off the throttle in order to vent boost. Apart from crushing it to give it a little more spring pressure to stay closed at high vacuum, I think that you're hooped unless you replace it with an adjustable one or recirc it. Sorry buddy. Later - Doug Quote Link to comment Share on other sites More sharing options...
Jersey Posted April 4, 2004 Author Share Posted April 4, 2004 I thought possibly the reference line just "helps" the valve lift off it's seat under high vacuum situations and the pressure in the charge pipe when the throttle is snapped shup actually pushes the valve open. I would run the one way valve so boost pressure would apply the pressure to help hold the valve shut. Ahhh... but if the air couldn't go back toward the intake because of the one way valve, i guess it would constantly hold pressure on the BOV, even when the throttle is snapped. Hmmm... Maybe a fitting with an .022 port to release the pressure between the port of the BOV and one way valve like ya use on the Grainger/Dawes wastegate device? hmm. Thanks Doug. Just trying to see if i can figure out a way to make it work right without leaking at idle while on a wife..i mean.. budget Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 5, 2004 Share Posted April 5, 2004 I noticed that too, and yeah I was the one who posted about how they are actually designed to do that at idle, so as to allow crisper throttle response off idle by allowing air to bypass a slow spinning turbo. One solution is to crush the cap down a little, adding enough spring pressure to keep it closed at idle. I tried that and it helped, but then I decided I wanted to run recirculated anyways. It will still vent excess pressure when the throttle is closed after boosting, even though the vacuum enough would not be enough to open it, the boost building up in the pipe after the throttle closes will still be enough to push it open. The downside is that the BOV's reaction time (how quickly it vents the pressure to prevent compressor surge) will be increased (so not as effective). You are right that the boost pressure alone is enough to force the BOV open when the throttle is suddenly snapped shut... I found that out when I tried running w/o the vacuum port reference connected... it would still vent after shutting the throttle... and any other time I was on boost Best bet would be to just crush the cap down about 1-2mm or so. Well... no... better bet would be an adjustable one. You're idea for a one way valve in there to let it only see boost but no vacuum might work, if you used the same idea that is used with the grainger style boost controller. Why not try putting a small bleed hole inline after the one way valve, that way enough boost would still build up in the line to hold the BOV closed, I would think, but then when boost stopped being supplied, the pressure could bleed off thru the vent hole. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 5, 2004 Share Posted April 5, 2004 ROFL duh... okay remind me to read the whole thread next time instead of just reading the first post Sorry for just repeating that back to you dude. Quote Link to comment Share on other sites More sharing options...
yo2001 Posted April 5, 2004 Share Posted April 5, 2004 http://www.dejontool.web.aplus.net/dsm-misc.htm checkout the middle of page. There is a mod. BOV and leak stop kit Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 5, 2004 Share Posted April 5, 2004 ah that is cool. just got home from work so kinda too tired to really understand the mumbo jumbo behind what that kit does but it definately sounds cool. Jersey - dont you run into problems with your BOV vented? Besides idle, I mean, aren't you running super rich between shifts? When I had mine vented it would bog really badly between shifts and a puff of black smoke from the exhaust every time, also it would bog and feel really badly any time I was decelerating in gear, and I mean ANY deceleration even just letting off the pedal a little, if there was vacuum at all it would run really rich. Just wondering how you're getting around that. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 5, 2004 Share Posted April 5, 2004 One thing I wanted to ask, about crushing the cap on these BOV's, do you guys think it makes any noticeable difference on turbo spoolup, after shifting? I mean one point of the BOV is to keep pressure from backing up into the turbo (THE point, actually ) which slows down the spinning... by crushing the cap and tightening the spring, it takes more pressure to open, and probably closes sooner, letting more pressure get back to the turbo, and slowing down more than if it were uncrushed, right? I've been having second thoughts ever since crushing mine and have been considering picking up another one from ebay, seeing as the prices seem to have come down quite a bit. Now that I'm running recirculated there is no point in it being crushed really, and I'm definately never going to run the kind of boost levels that necessitate crushing it otherwise... just dont know if it's hurting spool between shifts, or if it is enough to worry about. Quote Link to comment Share on other sites More sharing options...
lifegrddude Posted April 6, 2004 Share Posted April 6, 2004 You're right about the crushed caps being a little slower to respond to venting, but that's the tradeoff you get for having a blowoff valve that can handle higher pressure. The response time will be slower, but your valve won't leak and you won't lose boost pressure when you crank up the psi. If you're not pushing too much air, I wouldn't worry about it. John 82ZXT Quote Link to comment Share on other sites More sharing options...
fl327 Posted April 6, 2004 Share Posted April 6, 2004 Having an open atmosphere dump does cause a small surge, doesnt effect running of car at all IME. The factory bovs all have their drawbacks, especially running a valve made to recirc as a open one. Ive seen dsms do it for years now, and im not sure how they do it. My buddy also runs one DSM type open on a z car (halteched) and its fine for him as well. You can try crushing it but yes it will react slower to it and sometimes they dont work at all. Blitz and greddy as well as a bunch other companies make BOVs that will bolt right in place of that dsm valve, and really give off the whoosh whoosh. I dont notice any difference venting mine out vs. recirculating the air on my car, with the t3 it makes boost instantaneously after the shift, 12psi after 12psi with no kind of wait. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 7, 2004 Share Posted April 7, 2004 I DEFINATELY notice a huge difference if I vent mine... car runs like crap. I wish I hadn't crushed the cap down.... As it stands my boost DEFINATELY doesn't come back on instantly after every shift... but I think this is mostly due to my 2.5" crushbent exhaust creating backpressure and slowing it down. It has to build back up to full boost, which I really don't like. It only takes a split second but it's still noticeable and makes it feel like a bog after every shift. Just another one of those things on my long to do list to get fixed. But I do wonder if crushing the cap down is contributing to that as well. I might take a vice grips and try to 'uncrush' it a little. Quote Link to comment Share on other sites More sharing options...
fl327 Posted April 7, 2004 Share Posted April 7, 2004 My car wont even run with a dsm or saab style bov un recirculated, unless i keep reving it up. With the jpipe i got some of the fastest boost response ever, and when I intercooled the car i was kinda bummed I lost that big kick in the pants the small turbo gives with the jpipe, but response in the powerband was a lot better and didnt lag out between shifts. I do run a pretty nice 3" exh, stock dp though Quote Link to comment Share on other sites More sharing options...
Jersey Posted April 7, 2004 Author Share Posted April 7, 2004 Hey guys. Sorry it's taken me so long to reply to my own post. Yo, or anyone, do you know what or where that little port in the bottom of the DSM BOV does/goes to? I know the top port is above the valve and presses down on it during positive manifold pressure and also helps lift it off it's seat during vacuum situations, just don't know what that bottom one is for? I dont have any problems running it open to the atmosphere. I may get a puff of smoke between shifts because i'm sure it turns rich for the moment but i never really noticed or cared since it doesn't bog or effect performance as you say it does in your case. It helps performance in my case as it seems to do in FL327's - no re-spooling required. Whatever boost psi i'm pushing at the end of a gear, it's back at the same pressure in the next gear. I'm also running a 45deg DP and 3" exhaust which may be why your having to re-spool 525. Let that thing BREATH! lol. Thanks for the info and ideas guys. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 7, 2004 Share Posted April 7, 2004 I dont think open or recirculated would effect spool at all, in general or between shifts... or does it? You guys are all running good exhausts, I'm sure that's why you're turbos maintain boost between shifts while mine does not... I know dude trust me I want to do a proper exhaust... one thing at a time. Jersey about that bottom port, not sure what it's for, but in the link Yo listed with the modded BOV's, they use that port somehow to do what you were asking about... basically to make the thing not leak under vacuum but still do what it's meant to do on boost. You should check out that link if you havent already. Quote Link to comment Share on other sites More sharing options...
Jersey Posted April 7, 2004 Author Share Posted April 7, 2004 I did check the link out and understand they plug it and intersect it with another vacuum line but, i just don't know where that port goes to inside the BOV. I'll have to cut one apart to figure it out i guess. I'd like to try and cut the top off of one anyway and make it adjustable like the aftermarkets. BTW - Took my cousins 78 out 2 nights ago for it's maiden turbo voyage, running the DSM BOV, T3/T4, and on one of the high boost shifts, blew both charge pipes off the intercooler and seemed to have damaged the DSM BOV. Went out yesterday and bought the Greddy typeS BOV, strapped it on and it works perfect. Guess the aftermarket is the way to go if you've got the cash but, since i don't all the time, i like trying to figure a way to modify what i can, if i can. It's fun to me anyway. Open or recirculated i wouldn't think would effect spool any differently, in my opinion. Quote Link to comment Share on other sites More sharing options...
yo2001 Posted April 7, 2004 Share Posted April 7, 2004 Hey guys. Sorry it's taken me so long to reply to my own post. Yo' date=' or anyone, do you know what or where that little port in the bottom of the DSM BOV does/goes to? I know the top port is above the valve and presses down on it during positive manifold pressure and also helps lift it off it's seat during vacuum situations, just don't know what that bottom one is for? I dont have any problems running it open to the atmosphere. I may get a puff of smoke between shifts because i'm sure it turns rich for the moment but i never really noticed or cared since it doesn't bog or effect performance as you say it does in your case. It helps performance in my case as it seems to do in FL327's - no re-spooling required. Whatever boost psi i'm pushing at the end of a gear, it's back at the same pressure in the next gear. I'm also running a 45deg DP and 3" exhaust which may be why your having to re-spool 525. Let that thing BREATH! lol. Thanks for the info and ideas guys.[/quote'] the port on bottom does the same thing as the second nipple on Greddy type-S except it's not as effective because of the location. DSMer's are relocating that port by drill and tapping the refence line outside to boost line so it'll only see boost. Here is an info how to do it. http://www.thedodgegarage.com/turbo_bov_mod.html Quote Link to comment Share on other sites More sharing options...
Jersey Posted April 7, 2004 Author Share Posted April 7, 2004 Thanks yo. I have that site bookmarked as well but just couldn't figure where that port went up inside the BOV to. The mod on that site says that'll fix leaking above 17psi but nothing about fixing the leak at idle. The Greddy S i bought for my cousin yesterday, the little port is the one i guess you're talking about.. it just seems to connect to the "blow off" 1.5" port. I'll have to do some research on the Greddy and that little port and then maybe i'll understand the DSM port a little better if you say it acts the same. Thanks for the help. Quote Link to comment Share on other sites More sharing options...
Guest ZmeFly Posted April 8, 2004 Share Posted April 8, 2004 There are two attachments on the Greddy Bov. The top attachment is to use for vacumn reference to the manifold. The bottom attachment is meant to be left open as per what the greddy site says on installation. Quote Link to comment Share on other sites More sharing options...
Jersey Posted April 8, 2004 Author Share Posted April 8, 2004 I do have the Greddy installed and running nice, just wondering what that smaller reference port actual does, then maybe i can figure out what the small port on the bottom of ths DSM BOV does since Yo's saying they're basically the same. Do you or Yo, do you know what it's actually for? Quote Link to comment Share on other sites More sharing options...
wigenOut-S30 Posted April 8, 2004 Share Posted April 8, 2004 I have the 1st Gen DSM BOV also.. I have not installed it yet. What about plugging that small port on the bottom of the DSM Bov? by doing that wont it stop the leaking at idle and smaller boost levels? then you could crush it just abit to hold more boost.. Anyone else think of doing that or will it mess something up?? Quote Link to comment Share on other sites More sharing options...
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