Guest jjohart Posted December 9, 2003 Share Posted December 9, 2003 I don't want to wreck my engine with the new intercooler in it, so I have to delay "turning off the boost" until I can get a mechanic to deal with what the I/C installer didn't know to DO with the Mitsu/Diamond star blow off valve. It is presently installed aft of the AFM, but he said that the large open mouth (presumed "blow off pipe") would have to be hosed somewhere also behind the AFM, or the car wouldn't run right. He said that he deals in metal piping, and didn't have a hose, or know what to run and where to put it in vis a vis the hosing/duct behind the AFM. Ditto for the vacuum outlet that is part of the DSM valve...where does it go? Quote Link to comment Share on other sites More sharing options...
yo2001 Posted December 9, 2003 Share Posted December 9, 2003 Just like your mechanic said, the BOV by the TB and vent back in front of the AFM. Quote Link to comment Share on other sites More sharing options...
240zprace Posted December 9, 2003 Share Posted December 9, 2003 mount the bov to the pipe (discharge outlet of compressor housing) the other big hole on bov, run a hose so it'll blow back into the intake after the afm. Quote Link to comment Share on other sites More sharing options...
Guest jjohart Posted December 9, 2003 Share Posted December 9, 2003 Are you sure the vacuum would go IN FRONT of the AFM? My mechanic said this would not work, that it had to be somewhere BEHIND the AFM. He did however point to a small hose that goes back in somewhere on or near the valve cover (I can't remember and I'm not looking at the car right now). He was pretty clear that things had to be plugged in AFTER the AFM? Who's right..or am I just getting confused?!?!!? Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 9, 2003 Share Posted December 9, 2003 The blowoff MUST return in the section of hose BETWEEN the AFM and the Turbocharger inlet. I replaced a section of hose with a metal pipe allowing my 1" blowoff hose to vonnect there. If it's metered by the AFM, and is not dumped back into the metered area of the air system, you get rich stumbles to beat all hell. Angle the piping so the blowoff is directed towards the turbine inlet, and ideally directed to spin the turbine in the direction it's supposed to be turning or you risk as premature compressor stall from trying to pinwheel the turbine in the reverse direction while rotating at high speed. Not good for airflow. The direction gets more important the higher the pressure you are running at. When you are blowing a 1" 15psi burst of air at the turbine, you can get a nice pre-spin for on-boost response if you engineer it all right! Lets also consider the terminology here: the H-Car crowd has popularized the name "BOV" or "Blow-Off Valve". In the dark days, when turbos were not as responsive as we have today, it was called the Compressor Bypass Valve. This implied a dual function: During non-boost operations, vacuum in the intake manifold would open this valve, allowing N/A operation to bypass the turbine allowing it to pre-spin unloaded, and allowing a bigger inlet for the off-boost airflow and better off-boost drivability. When the boost would come on, the valve would close, and when the throttles snapped shut on-boost, the spike in vacuum would open the valve, allowing the bypass of compressed air out of the intake system in front of the throttles. It really shold sound more like a big "sigh" than a BOOM or WHHOOSH! The big sound is from stuff dumping in a very inefficient manner. I think Corky Bell made a nice big bypass valve for years---it "sighed" nicely if you even lifted your foot a little bit. Compressor response in a car so equipped was much better than without, or with a "hard pop" valve. So logic would dictate that kind of valve (which is what you are talking about) would HAVE to be (dumping the pressurized air) between the AFM and Turbine Inlet as it was simply a second intake tract to the throttlebody when off-boost, and therefore would need to have metered air in it for proper ECU response. It should go both ways depending on what mode of operation the engine is operating. People have gotten into the idea that the valve is to just "dump" the excess pressure and get rid of it, but such is not the case. Quote Link to comment Share on other sites More sharing options...
Guest jjohart Posted December 9, 2003 Share Posted December 9, 2003 I am impressed at the histrionics behind blow off valves. I think they should have a more acccurate name, based on your indications of actual functioning....would it be best called a "boost gas recirculator?..pressure drop dreadlock buzz booster?..."living woman machine sigh (foreplay?), or something cruder (for the ones that "boom" on activation!?)... Ok, so demented non-sensical humor aside, what I have to ask is, what about the other hose...I mean, where's the vacuum, or smaller port supposed to hose up to? I'm having a hard time discerning that second hose's job, but I think my mechanic is ahead of me (I've forwarded these useful replies on this topic to him, but I think he's probably p.o'd b/c I'm kinda explaining to him what I hardly understand (major owner duh factor!). At least I didn't get a twin turbo thinking there's less lag because there's two of them and only one on mine! John-not totally stupid 280ZXT owner...waiting to drive off in newly I/C'd & 3 in. exhausted old "new" performance car! Quote Link to comment Share on other sites More sharing options...
Guest jjohart Posted December 9, 2003 Share Posted December 9, 2003 BTW, Corky Bell in person is anything but a sigh..he's a real non-stop talker, so much that for $35 membership, you get to talk to him about whatever you want-mechanically speaking (see CarTec/Bell Engineering web site). Does that mean the Mitsubishi blow off valve is a popper, and his old unit was a quiet one? Maybe we ought to rate various ones by their sound profile...I don't think this site is up for sound files yet, though@! Thanks again! Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted December 10, 2003 Share Posted December 10, 2003 I use that same DSM recirculation valve, plumbed back after the MAF, angled towards the turbo inlet just as suggested above. I can't even hear it, which is good. The vacuum signal is from the intake manifold. As soon as you close the throttle, you get a vacuum in the manifold and it opens the valve, dumping the boost. I personally cannot tell if it helps with the lag on shifting - if I want to go fast, I don't let off the throttle. The one thing it is for sure good for is preserving your turbo. If you are surging it all the time, eventually you will break it. Quote Link to comment Share on other sites More sharing options...
Guest jjohart Posted December 10, 2003 Share Posted December 10, 2003 The last part, as much as for me, is what the actual material is that I/my mechanic hook up to the vacuum/intake manifold, specifically...does it require a metal pipe to hook up (being that the work is being done by "Custom Tubes" in Woburn, MA, whom I extend extreme confidence in, as long as I show up every week or so to clarify exactly what that is (like I'm Hellen Keller trying to say "wa-uhh!" to describe the many vivid tips and techs that I've heard on this site!). He's already gotten the point from previous replies as to how to use a 1' in. pipe out to AFM zone from the DSM blow off valve big plug/outlet (in my brain, it looks like an outdoor water spigot). What I have to be absolutely clear in my mind in order to bring it to anyone's attention (I.e installer) is what material, and exactly where on the intake manifold that vacuum line should go. I apologize for redundancy, and the fear that I may have already rec'd the appropriate reply in posts previous, but I guess I need it rubbed in again, in as un-technical language as possible (which itself is oxymoronic-me-being that this is a technical forum!)..what pipe size and exact placement needs to happen to get this BOV working from that vacuum end? Hey, I may show up tomorrow and the installer may have already instinctually have tied up both ends (his track car is a Buick Grand Nat'l, apparently, and he has already alluded as to how little diffence a turbo flange makes to a 3" exhaust unrestricted...better than the Turbo guide under this list, which totally disses the stock flange, unless I'm mistaken!)! Just trying to cover every base, which is impossible with an obsessive old car/better than new performance attitude, but hey, that's the point of this list, right...when stock won't cut it...even if I never understand STOCK to begin with...in particular, the reasoning in Japan circa 1983 why they didn't make intercoolers an option, as did Volvo on my 83 242, which had tons of on power torque, but was a Belgian assembled P-O-S!! Cheers John Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 10, 2003 Share Posted December 10, 2003 Anything that will hold the pressure and temperatures involved will work. I prefer the valve to be flange mounted, and teh blowoff line to the pre-turbine area to be a flexible hose. For years I used heater hose (good to 60psi and 250+ degrees) on that downstream section. Sparco makes some nice high-temp silicone stuff you could use now... Barring heater hose! For the small signal line to the top of the valve, stiff fuel injection line is what I used (1/4" was the connection size on my valve) and later changed to Stainless steel braided because I got it cheap (like FREE)... The DSM I believe is mounted on the OE Application by all flexible hoses, right? That would make mounting easy if space is tight, as you could run flexibles to wherever you had to place the valve. I have another CART style valve I am working on for a plenum style manifold over six throttle plates. It is a pain to duct that one as it's a 360 degree discharge. For that, I probably will have to bite the bullet, and let everyone hear it when I shift! Quote Link to comment Share on other sites More sharing options...
Jersey Posted December 10, 2003 Share Posted December 10, 2003 DSM BOV's are mounted on a flange welded to the stock pipe. I made a flange and welded it to the IC pipe right before the TB. Little nipple just goes to an open port off the intake manifold. I used the DSM boot between my AFM and T3 because it's shorter which gives you room to route an intake out through the rad support and because it has the 1.5" (?) "blow off" inlet already built in. Also, the inlet is actually angled toward the T3 as Tony was mentioning. Here's a pic. Probably can't see much but worth a shot. Kinda like... where's Waldo? I know, i know.. it's a disaster in my engine bay. No flames. Winters here in NJ.... Quote Link to comment Share on other sites More sharing options...
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