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Where to get boost pressure reading?

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  • Where to get boost pressure reading?

    Couldn't wait any longer so I bought a Prosport 2 bar boost gauge that becomes black when powered off.

    Where on the engine do I obtain the boost pressure from?

  • #2
    A11VXL - Jon from Courtenays would be able to tell you as I didn't pay attendtion when my car was on the rollers.


    • #3
      I would prefer not having to call them, as I am not giving them any business... and they're closed till 2nd of January, anyway.

      I would assume that it connected somewhere between the throttle body and the compressor housing on the turbo
      Sure you can't see the nylon tube and grab a picture for me?


      • #4
        I'll try to see it. Might get one fitted myself actually. Have you decided wher to fit it? Wonder if I could get a A VXR style one.


        • #5
          I am placing the gauge either in the small triangular window at the A-pillar or in the empty compartment at the bottom of the center console.

          I think the best match you can get color-wise, is one that has the same black background and yellow to yellowish-white numbers (on OPC, dunno if VXR use another color scheme).

          The one I bought has 7 different colors, so hopefully one of them will resemble the yellow/yellowish-white.

          Here is a pic from their webshop:

          But it looks much better in real life... the edge is chrome not brownish as the pic shows.


          • #6
            I wish it was as (rediculous!) easy as this


            • #7
              Now if you could get it in red easy to fit a VXR badge, hmmmmm Also can you get them in psi


              • #8
                Nearly all gauge manufacturers make them in both PSI and Bar...
                Check out (lousy web site, btw)
                I paid 350 DKK ~ 30 GBP for mine.


                • #9
                  It should be the same as all the others and 'T' off the pressure regulator.


                  • #10
                    Originally posted by alex_c
                    It should be the same as all the others and 'T' off the pressure regulator.
                    What? Sorry, I didn't understand that?


                    • #11
                      Alright... got the tube running from cabin to engine now.

                      Just followed the bonnet pull. From the handle there was a rubber grommit the cable runs through, popped that one out and shoved in a hard nylon wire (which is used exactly for such occasions) and voila it re-appeared in the engine compartment exact same location as the bonnet pull.

                      Now, next problem is finding a spot to obtain the pressure.
                      I talked with alex_c and he suggested the pressure regulator, but there is only a very thin tube connected to that, so that's a no go:

                      Here's my findings on the intake manifold:

                      "A" goes to some thingy which has a sensor of some kind connected:

                      Same thingy, different angle:

                      "B" goes to some other sensor which is hard to reach.
                      "C" goes to the brake system.

                      Is the "Cut here" place the right place to connect the T-piece?
                      What about the place on the front of the engine:

                      What puzzles me, is that "A" and "B" have similar connectors on the manifold, but "C" is different?
                      Also, what is the purpose of those disc-shaped interconnectors on the tubes?


                      • #12
                        Use the connector on the first picture. You can use either end to fit the pipe too (using T piece). There is also another one on the manifold which runns to a vacum box at the rear of the manifold. Did a temp fitting to the pressure regulator one (first pic), and it worked fine. The pressure measures at normal 18psi on over boost hit 21 once and drops back to 12 then climbs to 14-15 depending on gear and acclerationrate.


                        • #13
                          It's fitted!

                          Had to remove the air intake tube that goes on top of the engine to gain access to the area where the pressure regulator resides.
                          Even with that removed, it was too tight to get the tube off the pressure regulator itself.
                          So I disconnected the opposite end of the tube (on the intake manifold) and placed the T-piece there...

                          Do I need to fear that the tubes will be blown off?
                          It seems like some of the tubes have been given some white glue-like matter.
                          I remember when I fitted a blow off on my Citroën HDi (approx 1 bar boost)... the boost pressure forced the charge tubes apart, leading to a huge black cloud behind the car
                          But that was the >60 mm charge tubes, guess that the force per square cm is larger there...?

                          Now, I just need to connect the gauge to +12V (constant) and ignition... any recommendations here?
                          There is +12V (constant) all over the place in the fuse box, but where do I easiest get ignition? I think I will go for the cigarette lighter... if I can make it in there?! :?


                          • #14
                            After spending hours and hours trying to figure out the wiring, I ended up fitting a swith to turn the gauge lights on/off. I will place it somewhere discrete... I think it's an OK solution, as the wife will be less annoyed by it when it's not lit
                            The gauge itself I temporarily mounted with straps on the round airduct (the one that can't be closed or turned). I will try to mount it in the lower corner closest to the door once I invent some bracket... :?

                            Seems the boost pressure varies a lot
                            Idle is -0.5 bar (vacuum).
                            It is possible to drive gently (AND economic, I guess) between -0.5 bar and 0 bar boost.
                            A firm foot gives 0.5 - 0.6 bar.
                            A whack to the floor gives 1.2 - 1.3 bar shortly and then settles at 0.9 bar.
                            ... and it really is different depending on gears and RPM.

                            Oh well... now it's just become more fun to drive


                            • #15
                              I think you will find that the hotter the engine becomes the slightly less boost you get when you floor it. When the engine is still not completely heat soaked the pressure will clip past the 18ps (1.2) and touch 20-21 psi, but this drops back once it settles. If you constantly give it a heavy foot the pressure drops but not much bye .5 psi. ALso what is intersting is how quickly the engine cools down.

                              Get some pics up where you fitted it. Try to get a video as I found the engine gets up to full boost very quicjkly from "0" boost. I will be using mine purely for checking all is running fine, but have fun.