Guest jjohart Posted March 2, 2004 Share Posted March 2, 2004 Hi, I've been hearing my blow off valve spritz air while I'm still on throttle at high boost=around 13psi. I know it works properly when I go off throttle. Is it possible that an old blow off valve, like this Diamond Star Mitsu, might have a weakened spring or something, so it lets off air when I'm still on throttle? John-280ZXT I/C (83) Quote Link to comment Share on other sites More sharing options...
yo2001 Posted March 2, 2004 Share Posted March 2, 2004 Crush it some it'll stop leaking. Quote Link to comment Share on other sites More sharing options...
Guest jjohart Posted March 2, 2004 Share Posted March 2, 2004 Yo, do you have anything funny, if not informational, to say?! Must be a newbie-carless former Z owner, a bit peeved, no? John Quote Link to comment Share on other sites More sharing options...
Jersey Posted March 2, 2004 Share Posted March 2, 2004 John, i have the 1G DSM BOV as well and having problems with it. Mine will hold boost, without being crushed, when boost is climbing. It seems anytime i let off the throttle lightly when there's a good load on the motor, it strats to leak a bit. Sometimes i have to let off the pedal hard and then get on the throttle to re-seat it. Glad i'm running it vented to atmosphere because i would have never known it was doing this otherwise. NOt sure if this has anything to do with your problem, just figured i'd pass it along. Here's a site with a little info - http://www.jakelatham.com/1gdsm/projects/dejon_bov/index.shtml Quote Link to comment Share on other sites More sharing options...
lifegrddude Posted March 2, 2004 Share Posted March 2, 2004 Blow offs do wear out over time, Greddy even sells replacement parts for theirs. However, what Yo was getting at is that if you crush the top of your blow off in some, it will support higher boost b/c the spring tension is increased. John 82ZXT Quote Link to comment Share on other sites More sharing options...
yo2001 Posted March 2, 2004 Share Posted March 2, 2004 Yo' date=' do you have anything funny, if not informational, to say?! Must be a newbie-carless former Z owner, a bit peeved, no? John [/quote'] it's not a joke or funny, you really put the BOV in a vise to crush it some. it'll do the samething as tighten down Greddy type-S adjustment bolt. Keeps it from leaking. Stock DSM BOV leaks FYI. Just trynig to help out man Quote Link to comment Share on other sites More sharing options...
Guest jjohart Posted March 3, 2004 Share Posted March 3, 2004 I thought it was a joke!!! Seriously, I'm crushed, though ya gotta admit, it's a bit crude to have to put a valve into a vise to get it to do waht ya waht ya waht ya want! I think I'll try to swap in another one, but it sounds like they aren't as trick as in the initial description of how to put a neato cheapo BOV in a Z project!! Then again, I still don't feel like putting $280 into a Blitz one with a funky horn sound....when will I learn to like rice?!?! John Quote Link to comment Share on other sites More sharing options...
Guest ON3GO Posted March 3, 2004 Share Posted March 3, 2004 dont knock the blitz.. its a very good unit and sounds great.. i love mine. but yes crushing the valve will help you out. i did that on my dsm's when i had the stock one on. worked fine. mike Quote Link to comment Share on other sites More sharing options...
Tony D Posted March 3, 2004 Share Posted March 3, 2004 I take it the DSM doesn't have a vacuum line to the manifold for a reference pressure. My Trust unit (bought used in 87) has somewhere around 50K miles on it, and still seats fine, though it is a manifold-referenced unit. It uses a spring pressure with manifold pressure behind it to seal under boost, and the preload on the spring determines how "hard" it lifts under lift-throttle. I have it set really light, so even a slight lift will cause a bypass back to the inlet. I would surmise that threading a fitting on the spring side of the DSM valve through the sheetmetal dome (if I am thinking of the right unit in my head ) and then using some high-stregnth epoxy putty to seat it and hold it in place would convert the DSM valve to a manifold referenced unit (much like converting N/A Mechanical Fuel Pumps in the dark days of blowthrough...) and result in some very positive seating under all boost levels---though when you lift-throttle since the spring is preset, you will have a similar popoff (harshness-wise) as a stock application. Just a thought. Quote Link to comment Share on other sites More sharing options...
yo2001 Posted March 3, 2004 Share Posted March 3, 2004 Some DSMer has done the second vaccum mod. Suppose to work well. MR2 got good BOV also. Blitz got nice sound to it. I've seen it flutter under partial throttle though. I liked Greddy type-S on Zcar, it's easy to recirculate. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted March 3, 2004 Share Posted March 3, 2004 stock 1g dsm bov does have a vacuum/boost reference line. Secondly, they are DESIGNED to leak, at least at idle. I read an interesting tidbit on this somewhere. I think in Sport Compact Car, not sure. Mitsubishi designed them to leak a little at idle, as sort of an air bypass. The thinking behind it is that, at idle, with the turbo barely moving, when throttle is suddenly opened, there is lag in the throttle response, not only because the turbo is not creating any boost, but also because at that time the turbo is actually acting as a restriction, not letting air pass freely thru it and to the now open throttle body. With full vacuum acting on the BOV, it is held slightly open, and air is actually being sucked IN thru the BOV from before the turbo, bypassing the restriction of the turbo, instead of escaping out thru the BOV as it does when it vents under boost. This is supposed to increase off idle throttle resposnse. When I read that, I promptly changed my mind about crushing down the cap on mine. This of course only applies if you are recirculating the air back into the intake... if you're gonna vent it to atmosphere then of course you want no leak at idle. Anyways, stock, uncrushed, they are supposed to be good for holding up to about 15 psi w/o leaking though when actually on the boost. If it's leaking under those conditions then yeah the spring is probably weakened and I guess you can crush down the cap a LITTLE (1 to 2mm at most) to help with that. Quote Link to comment Share on other sites More sharing options...
yo2001 Posted March 3, 2004 Share Posted March 3, 2004 300zxtt BOV/recirculate valves suppose to be design to leak under same condition to improve the throttle responce also. I have not cruched my DSM BOV yet but it'll hit 23 psi no problem. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted March 3, 2004 Share Posted March 3, 2004 yeah I mean the spring on his would have to be pretty worn. I'm thinking there must be something else wrong. Maybe something happened that is causing the valve itself inside the BOV not to seal properly? They are easy to pull off... I suggest taking it off and making sure that the valve face is in good shape and nothing is keeping it from closing all the way. You can kinda check the spring tension by hand too. On mine it takes a LOT of pressure by hand with both my thumbs to push the thing down at all. Not a very accurate way, I know! If worse comes to worse they are cheap to replace... like $50-75 on ebay but I bet you could pick up up as low as $25 or even less at a junkyard. Quote Link to comment Share on other sites More sharing options...
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