Guest George89 Posted January 31, 2012 Share Posted January 31, 2012 Hi i my 2nd turbo doesnt kick in, It makes a loud screaming noise at 4K RPM. I have used a boost leak tester and can hear my bov leaking i think. Now i took the bov out of the car and tried putting it under water and blowing from the line the plenum is connecting to and yes its leaking badly. Now the question is as i don't exactly know how they work should they be releasing air from that line? I attached a picture to try and show what i mean Quote Link to comment Share on other sites More sharing options...
Lude Posted January 31, 2012 Share Posted January 31, 2012 not sure if this makes any difference, but the part you have as blow in, is the vacuum, which doesnt get air blown in, it gets air sucked out.... Quote Link to comment Share on other sites More sharing options...
chrispot Posted January 31, 2012 Share Posted January 31, 2012 (edited) Hi i my 2nd turbo doesnt kick in, It makes a loud screaming noise at 4K RPM. I have used a boost leak tester and can hear my bov leaking i think. Now i took the bov out of the car and tried putting it under water and blowing from the line the plenum is connecting to and yes its leaking badly. Now the question is as i don't exactly know how they work should they be releasing air from that line? I attached a picture to try and show what i mean i have the same dump valve and inside is a piston with no seal around it so i would have thought it would leak slightly, the pipe shown in your diagram receives boost pressure and vacume at different times, when its boosting it receives boost pressure helping to keep shut the valve as soon as you release the throttle there will be a vacume developed in the plenum chamber which then sends a vacume to that pipe which raise the dump valve, also the dump valve has still got boost pressure acting on the valve which will also push the valve open, if you look at the link that i have posted you will notice a valve below the words No1 turbocharger this is a dump valve. regarding your problem i dont think your dump valve is at fault. hope this helps regards chris. http://www.max-boost.co.uk/max-boost/supra/boosting_the_beast.htm Edited February 1, 2012 by chrispot forgot to post link (see edit history) Quote Link to comment Share on other sites More sharing options...
Guest George89 Posted January 31, 2012 Share Posted January 31, 2012 Yes but in the manifold the air would be pressurised e.g 1.2 bar. Wouldn't that leak out of the dumb valve? as when i blow hard in to it, it leaks slightly and the valve is shut I know their is a leak as i can't go above 0.5/0.6 bar and a screaming noise when i hit 2nd turbo. Quote Link to comment Share on other sites More sharing options...
Scott Posted January 31, 2012 Share Posted January 31, 2012 Yeah that's leaking mate. When you blow in there it should seal shut. it's only when there is a vacuum in the line (when you let off the throttle) that the line should actuate to allow pressurised air through the other port. For the moment I would either put the stock BOV on if you have it, or block off all 3 ports and run without one till you get sorted out. Quote Link to comment Share on other sites More sharing options...
Guest George89 Posted January 31, 2012 Share Posted January 31, 2012 Yeah that's leaking mate. When you blow in there it should seal shut. it's only when there is a vacuum in the line (when you let off the throttle) that the line should actuate to allow pressurised air through the other port. For the moment I would either put the stock BOV on if you have it, or block off all 3 ports and run without one till you get sorted out. The car has had a boost problem for about 4 months but its parked up for the winter so i aint in a rush in fixing it. It was just bugging me i needed to find the problem so i bought a boost tester and pressurized all the lines and could here air coming out the bov even tho the valve is shut. Thank you for your help guys Quote Link to comment Share on other sites More sharing options...
chrispot Posted February 1, 2012 Share Posted February 1, 2012 Yes but in the manifold the air would be pressurised e.g 1.2 bar. Wouldn't that leak out of the dumb valve? as when i blow hard in to it, it leaks slightly and the valve is shut I know their is a leak as i can't go above 0.5/0.6 bar and a screaming noise when i hit 2nd turbo. as you said leaks slightly, i would have thought that not enough air could get through that to cause it to have low boost at hi revs, to me it seems like it has to pass a lot of air though a small pipe when the turbos are putting out so much air, yes boost pressure would be less, what you could do is block this pipe and see if you get more boost, or do as scott m said remove it and block off all pipes. you said there is a screaming noise when above 4k, if the dump valve was leaking and making this noise it would do it at lower revs, as the car would still get good boost below 4k, to me it sounds like there is problem when the second turbo is operating, might be worth checking the the turbo is ok and not touching the sides and making the noise? Quote Link to comment Share on other sites More sharing options...
Scott Posted February 1, 2012 Share Posted February 1, 2012 as you said leaks slightly, i would have thought that not enough air could get through that to cause it to have low boost at hi revs, to me it seems like it has to pass a lot of air though a small pipe when the turbos are putting out so much air, yes boost pressure would be less, what you could do is block this pipe and see if you get more boost, or do as scott m said remove it and block off all pipes. you said there is a screaming noise when above 4k, if the dump valve was leaking and making this noise it would do it at lower revs, as the car would still get good boost below 4k, to me it sounds like there is problem when the second turbo is operating, might be worth checking the the turbo is ok and not touching the sides and making the noise? You would be amazed at how little a boost leak has a massive effect on the boost levels. If you can blow (with your mouth) through a leaking area then the turbos will happily dump all their pressure through that hole. Quote Link to comment Share on other sites More sharing options...
Guest George89 Posted February 1, 2012 Share Posted February 1, 2012 You would be amazed at how little a boost leak has a massive effect on the boost levels. If you can blow (with your mouth) through a leaking area then the turbos will happily dump all their pressure through that hole. Exactly, i am guessing i can probaly produce 2-3 psi with my mouth and manage to make it leak, with 15PSI the whole would be even bigger. (It makes sense as the BOV is designed to make a loud sound and its leaking from that area hence the loud screaming noise. I know the turbo aint blown as it was and i changed it. Since i changed the turbo i stayed on stock boost never raised it. (Plus when it was blown all pressure would be released with the 2nd turbo engages) Quote Link to comment Share on other sites More sharing options...
chrispot Posted February 1, 2012 Share Posted February 1, 2012 Exactly, i am guessing i can probaly produce 2-3 psi with my mouth and manage to make it leak, with 15PSI the whole would be even bigger. (It makes sense as the BOV is designed to make a loud sound and its leaking from that area hence the loud screaming noise. I know the turbo aint blown as it was and i changed it. Since i changed the turbo i stayed on stock boost never raised it. (Plus when it was blown all pressure would be released with the 2nd turbo engages) I bow down to scott m having more experience and knowledge in this area about the boost leaking through a small hole causing a massive boost loss. in your orignal post you said it makes a noise at 4k, does it make a noise at lower revs? and have you had it boost to 1.2bar since you have put in another no2 turbo?. as you said when the second turbo went, all the boost was lost when the inlet control valve opened up, was the turbo seized?. so if the dump valve is making all the noise it would be very easy to put right, it would bug me not knowing, do as scott m said remove dump valve and block pipes up. please keep us informed to what the cure was as anyone searching the site my see this and it gives them the possible answer to there problem. hope you get it sorted regards chris Quote Link to comment Share on other sites More sharing options...
Guest George89 Posted February 1, 2012 Share Posted February 1, 2012 Well a small update, As i said before i got a boost leak tester, i have sealed the air inlet and used an air compressor to pump air in to the whole system, Before it wouldn't hold any pressure. I removed the BOV and blocked the holes and now it holds pressure and can't here anything else leaking. I put the bov back on tried again and sprayed water on the BOV and can see it bubbling when i turn the compressor on. I can't unfortunatly drive the car at the moment due to it been SORN off road and its parked on a drive way which took me 2 hours to get up their due to the car being so low i needed to use pieces of woods to keep raising the front up. When i get the car back on road i will test it and let you guys know on this thread. thank you for your help. P.S. The BOV leaks at 1psi off pressure nevermind 0.8bar-1.2bar The car doesn't scream under 4k rpm but it doesnt have the same responds or power from the first turbo as it used too. When 2nd turbo kicks in it raises by 0.1 bar (0.6bar) but won't go higher. Quote Link to comment Share on other sites More sharing options...
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