Is the 1.6TD BOV adjustable? - page 1 - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.

• Is the 1.6TD BOV adjustable? by VWRacer on 28 May, 2004 19:50
• I noticed that there is a screw in the top of the BOV. Does anyone know if it is for preloading the spring? It would be very convenient if we could just "dial in" the desired boost...
• #1 by n_tensetuning on 28 May, 2004 20:32
• that's what i've been wanting to know as well.... i tried messing with mine back and forth just a tad.... didn't notice any change...... still running 10psi
  
  i thought i had read somewhere that it only adjust .7psi +/-  anyone?
  
  
  it would be nice to just dial it in from there.... afterall it is a pressure regulating valve
  
  
  d
• #2 by DVST8R on 28 May, 2004 20:47
• From what I remember that screw is only a cap, but you can then remove the spring and change it out for a stiffer one I would asume. This may be completely wrong, but it seems like I read that on a post long ago on the old hostboard site.
  
  Now that I think about it if that was the case then you should be able to just stack washers or some other spacer in there untill the spring is preloaded to the point you want, assuming there is enough space for this and the spring has enough travel.  :?:
  
  If this is the case you could get the best of both worlds as far as boost control, you could have a gated boost controler, with this as a way to control creep, and sudden extra air pressure.
  
  If some one doesn't beat me to it when the wife gets home I will open it up and see what I can see.
• #3 by Dr. Diesel on 29 May, 2004 06:13
• Even if you do this, your turbo is still spinning at/beyond full speed. Better to block off the BOV and control boost at the turbo.
• #4 by DieselsRcool on 29 May, 2004 10:11
• The screw in the bov has a spring under it holding down a clapper. When the pressure rises enough it lifts the clapper. Simple! To raise pressure, change to stiffer spring. Or, to block, replace spring with a sawn off 1/4" bolt. Clapper no move.  
• #5 by VWRacer on 29 May, 2004 10:26
• I'm really getting a lot out of this thread, and am really enjoying it, so thanks to all who have made inputs!
  
  After Dr Diesel's comments last night I took the BOV off and snapped a couple of pics, which I share here for those who are iterested but not inclined to tear up their engine...
  
  I've labelled just about everything, so it should be pretty much self-explanitory.
  
  
  
  And here is the BOV with a brake cleaner can cap inserted. The idea is to prevent the BOV releasing air pressure from the intake manifold.
  
  
  
  Then I took the car for a test drive... :twisted:
  
  Surprise! The engine still hit a max of 12 psi. :?
  
  What's up with that? I am pretty certain that the cap is effectively blocking off the BOV, so at this point I'm scratching my head. And yes, I did a post-test tear down to ensure the cap hadn't moved, melted or otherwise failed.
  
  I guess the next step is to make a real block-off plate to test.
  
  Cheers! Stan
• #6 by DVST8R on 29 May, 2004 10:48
• You don't want ot block off your pcv or you will blow the seals in you car or at very least have oil shoot out your dip stick hole (actually saw that once :shock: ) what I found works well as a catch can is a 1L oil bottle, as the tube that used to return it to the intake is almost exatcly the same size so you just slide the bottle in and titen it up with the same hose clamp. THen you cut out the flat section on the top of the bottle, and Shazam you have a cheap effective catch can.
• #7 by DVST8R on 29 May, 2004 10:52
• Oh, by the way thanks Stan for the break down
  
  Dr. D, I had advocated using a manual boost controler inconjunction with the BOV to control compresser surgess, as well as boost creep commonly found with gated type controllers.
• #8 by VWRacer on 29 May, 2004 10:55
• I should have specified that I am venting the PCV to the atmosphere while conducting these tests. Not to worry, the hose is not blocked!
  
  I did, however, plug the line to the compressor's intake hose to prevent unfiltered air entering the turbo. (Blue plug in the photos above.)
  
  [Edited for clarity.]
• #9 by Dr. Diesel on 29 May, 2004 12:17
• Stan, that is most definitely a suprise.
  In my early diesel tuning days, I had maxed out a wastegate bleed valve, only to get 12 psi. As soon as I plugged the pop-off valve's outlet line, it jumped to 27. I suppose it's possible that your inj. pump's setting is anemic enough to limit boost to that level, though it seems unlikely. I think you said that the wastegate is disconnected. If it's a garrett, there are two lines going to the wastegate. Are they both disconnected? Perhaps the wastegate valve is getting blown open by the exhaust pressure...  I wonder what would happen if you routed boost pressure to the wastegate line that normally senses pressure at the compressor inlet? would that act to help keep the wastegate valve closed?
• #10 by fspGTD on 29 May, 2004 12:31
• Stan - when the BOV opens, the effect is very noticeable.  Once opened, it will stay open continuously, bleeding off large quantities of air until boost pressure drops quite low, and at that point it will finally close.  The resulting drop in performance when this happens is very noticeable - it is not a smooth boost pressure regulation effect like a wastegate gives.
  
  If you did wastegate modifications but you haven't turned up your fuel level any bit from stock, I would guess that is what is limiting how much boost pressure you are getting.
  
  FYI: If you just screw the BOV adjustment in all the way in, it won't open until a little bit over 14 psi.  You can get the opening point higher yet by adding shims or a thicker spring.  (Shim is solid, and it won't open at all.)
• #11 by dieseltech on 29 May, 2004 13:17
• It sounds as though the waste gate is still functioning. and i had a simular problem on my 86 jetta td, it turned out that for emission reasons vw used a 1.50" exhaust pipe from the flange to the resonator then 2" from there on. with that setup i could get no more than 12 to 14psi.
  so when i modded the car i got an intake off of a eco diesel because it has no safety valve  and i made an electronic boost controller using a fast acting pressure switch adjustable and set it at 19psi (best power whithout smoke) and a idle up solinoid from a 88 a1 cabriolet gasser to send pressure to the wastegate when the 19psi was reached.
  the setup has been great and dead on 19 psi. if anybody wants plans on building the setup let me know i can post it.
  
  about running the turbo whithout the wastegate connected, well your nuts cause when the turbo lets go it is a bit $$$$ to fix. unless gils did a pump for ya there is no need to go above 20 psi. there is not enough fuel from a stock pump turned up a bit.  if you dont want to buy a boost conyroller you can make one with a brigs & straton fuel valve for a lawnmower. put it between the compressor out and the wastegate with a length of hose, crack it open a bit, take it for a spin and check your psi. adjust as needed
   
  just adding boost without extra fuel wont do anything except raise your egt and shorten the life of your engine.
• #12 by VWRacer on 29 May, 2004 13:38
• Thanks for adding your insights, Chris.
  
  When I took the car out I was concerned about overboosting it without any protection, so accelerated very smoothly, keeping a good eye on the boost gauge. I first got 5 psi, then 7, then 9 and finally 12 when I ran it out in 3rd after about 10 minutes of driving. I added 5-bucks worth of diesel since the fuel gauge barely rose off dead empty after engine start, then came home, working my way up on boost. I was very surprised that it wouldn't develop more boost than it did.
  
  However, now that I think about it, there are a couple other observations I should mention, in case they may be affecting my results. First, I noticed that although the engine revved quite freely, it seemed to be a bit down on seat-of-the-pants power, so I stopped and hooked up the G-Tech. It recorded just 40 max hp. Clutch...? :?
  
  Second, the engine now puts out a lot of black smoke once the boost gets above about 5 psi. It's not blue "oil smoke". It is the classic diesel looking black smoke...maybe very dark grey. Ideas?
  
  Finally, I just now took this pic. It shows the disconnected hard line to the wastegate, the compressor scroll plug and the compressor wheel. (I disassembled everything to take the pic - I don't run it this way.) Notice that the blades are pretty chewed up. Bad as it looks, I somehow doubt this is what's keeping me down at 12 psi. Any ideas?
  
  
  
  Thanks! Stan
• #13 by VWRacer on 29 May, 2004 13:45
• Quote from: "Dr. Diesel"

  Stan, that is most definitely a suprise.
  In my early diesel tuning days, I had maxed out a wastegate bleed valve, only to get 12 psi. As soon as I plugged the pop-off valve's outlet line, it jumped to 27. I suppose it's possible that your inj. pump's setting is anemic enough to limit boost to that level, though it seems unlikely. I think you said that the wastegate is disconnected. If it's a garrett, there are two lines going to the wastegate. Are they both disconnected? Perhaps the wastegate valve is getting blown open by the exhaust pressure...  I wonder what would happen if you routed boost pressure to the wastegate line that normally senses pressure at the compressor inlet? would that act to help keep the wastegate valve closed?

  
  Doc, my turbo is a k24, and I can only find one line to the wastegate. Anybody know for sure that there are two lines?
  
  I think I'm going to have to fab up a solid block-off plate to completely replace the BOV. I just don't trust that it's not somehow releasing pressure.
• #14 by VWRacer on 29 May, 2004 15:04
• Thanks for putting up with me, guys, but I've been having fun with this all day...
  
  Anyway, I took some scrap plate aluminum and made a block-off plate for the BOV. Using the stock collar-clamp I RTV'd the flange then clamped it all together to completely block off the BOV port. Here's what it looks like...
  
  
  
  Then I took it out for another test drive. Well, first thing was that I discovered that I had left the cold-start knob out last night...I wonder if that affected my results? Second, after pushing the cold-start knob in most of the smoke went away. There is still a bit at higher boost, but most of it is gone.
  
  The bottom line, though, is that there was no change in max boost. It is still hitting 12 psi and then backs off to about 11 if I just hold it in gear at max revs (the pump is pulling fuel out, isn't it?).
  
  In the photo below, one can see that there is an EGR system plumbed from the exhaust manifold to the intake. There is something at left which appears to be some sort of blow-off valve. My Bentley doesn't mention the diesel's EGR, but I wonder if this could be the source of my limited boost?
  
  
  
  I realise that I am grasping at straws here, since Dr D and DV8STR got 20-plus psi by simply blocking the BOV. Any ideas?
  
  Thanks! Stan