datman Posted July 2, 2007 Share Posted July 2, 2007 As I am about to finish my l28 ET project I've been looking into choices for dump (BOV) valves. It seems if you want high boost you need a strong spring which in turn will put extra load on the trubo before venting..the whole setup seems a bit basic considering todays technology. I was think of controlling a BOV using a solenoid which could be linked to a throttle switch or even to Megsquirt. Another idea would be to place another throttle body in front of the compressor and have it slightly offset to the main TB causing a vacuum and keeping the compressor wheel spinning, I know thisis possible as it was used in F1 racing years ago, I just wondered if anyone here had tried to make it work? I think the turbo must have carbon seals to stop it drawing oil although this could be worked around by routing the oil drian into a catch tank which would be at the same pressure as the inlet. what do you guys think? Quote Link to comment Share on other sites More sharing options...
mario_82_ZXT Posted July 2, 2007 Share Posted July 2, 2007 Most BOVs are held closed by boost pressure on both sides plus the spring keeping it shut. They open as soon as there is vacuum on one side and enough boost on the other to overcome the spring tension. I was under the impression that if your IC piping etc were done right, the pressure difference would be minimal and not require such a strong spring. Random thoughts, Mario Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted July 2, 2007 Share Posted July 2, 2007 A lot of the diesel turbo guys are using a "turbo guard" made by bully dog. It is basically microprocessor controlled BOV and takes input from your TPS and other places. I have been thinking about getting one and adapting it to a turbo L6 aplication. Quote Link to comment Share on other sites More sharing options...
datman Posted July 2, 2007 Author Share Posted July 2, 2007 Mario, yes you're right that's what should happen but it's most likely the very expensive BOV's that actually do just that. Thanks for the info Olderthanme, http://www.jegs.com/webapp/wcs/stores/servlet/product_10001_12052_761991_-1_11283 Little expensive though. Looks like a regular BOV but with a solenoid fitted. Should be fairly easy to make something like that. I'll try the regular BOV, then I'll try a homemade electronic Bov and post my results. Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted July 2, 2007 Share Posted July 2, 2007 You can get a lightly used one from one of the diesel forums for about half price. BTW the OE DSM BOV that I have only has one port on it for a pressure line. Probably just a spring and a diaphragm. You could get a cheap Ebay BOV and cut off the top to mount a solenoid. ~Dan~ Quote Link to comment Share on other sites More sharing options...
datman Posted July 2, 2007 Author Share Posted July 2, 2007 Yes that's what I was thinking, I have a cheap collins style BOV....looks like a small cylinder with a piston and a spring holding the piston down, the spring is so stiff and the amount of vacuum pullingon the piston is not enough to lift it without a fair amount of pressure acting on the underside. I've been looking at Gas valves used on heating systems, they seem to have fast acting solenoids that will do the trick maybe triggered by a vacuum operated switch or just from a basic throttle position micro switch. Quote Link to comment Share on other sites More sharing options...
Clifton Posted July 2, 2007 Share Posted July 2, 2007 You don't need a stiff spring for high boost. I wouldn't try making it too complicated. Quote Link to comment Share on other sites More sharing options...
datman Posted July 2, 2007 Author Share Posted July 2, 2007 Yes I agree, maybe it just needs a soft spring with a larger hose connection on the top to keep the pressure the same on each side. I still want to mess with an electric valve though just for my own amusement Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted July 9, 2007 Share Posted July 9, 2007 formula one and older WRC cars use to use this setup... Keep in mind they are NOT allowed to use a blow off valve according to the FIA. They are allowed a Pop off Valve to prevent overboosting. Soo.. you would NOT be running a BOV in this setup Quote Link to comment Share on other sites More sharing options...
datman Posted July 9, 2007 Author Share Posted July 9, 2007 No i realise a BOV wouldn't be needed if a pre turbo throttle was used, actually my brother tried it on his race car at the weekend, unfortunately his garrett BB turbo didn't have a carbon seal...lots of oil in the IC..not good. Quote Link to comment Share on other sites More sharing options...
datman Posted July 10, 2007 Author Share Posted July 10, 2007 Here is a reply from a well respected Turbo dealer. OK here's the deal: Turbochargers come with 2 different designs of seals on the compressor side, "dynamic seal" and "carbon seal". Dynamic seal is nothing more than a piston ring style labyrinth type seal machined into the thrust collar on the compressor side of the turbo, where the O.D. of the ring seals against the I.D. of the compressor backplate. This is not designed to seal the oil in the bearing housing under negative pressure (vacuum in the compressor due to throttle being upstream of the turbo in a draw through system) and also doesn't seal well in systems with marginal oil drainage. A carbon seal is an actual lip seal which uses a spring backed ring of carbon in the compressor backplate which seals against the outboard side of the thrust collar, and will rarely allow any oil at all into the compressor under any conditions. Of course, for a draw-through system you need a turbo with a carbon seal. The problem is, 90 percent of OE turbo applications use the dynamic seal, so you will have a hard time finding one. You can, however, convert any Garrett T3 or T4 series turbo to carbon seal by changing these parts, but it needs to be done by an experienced turbo reman shop. Also be aware that ALL Rajay turbos have carbon sealed compressors, but you will not find one in a junkyard (except on a Corvair haha) because they are usually found in aircraft and aftermarket applications. Carbon sealed Garrett T-3s can be found on some Volvos, SVO Mustangs and Thunderbird turbo coupes, Buick Regal T-types Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted July 19, 2007 Share Posted July 19, 2007 The more vacuum you put in the compressor inlet the harder the turbo must work (which is the obvious rule that allows your intended result to come true). Honestly, I've seen "take your pick" japanese BOV's hold 30+ psi with reliable operation. What exactly are you trying to do? Go buy a 1G DSM BOV and do "crush mod" and it will hold 20 pretty easily. It'll only leak a bit if it can't handle it and you will know immediately. It's not like it will puke little hard bits into your engine. The HKS SSBOV features a more positive sealing method but it requires a bit of "lube" once in a while to stay working right. My money is on a TiAL if you must go with something nice. BTW, a nice stiff line for the BOV vac line is good (but a bit overkill; nylon braided rubber or thick silicone is fine), but a "larger hose connection" will only make the BOV respond more slowly. There are several two port BOV's out there but they rarely improve response. 1G DSM BOV's can be modified quite easily to make it a quasi two port. Quote Link to comment Share on other sites More sharing options...
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