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2001 Saab 9-3 Aero strange exhaust valve bending?

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  • #634543
    hemmyhemmy
    Participant

      I have a very very strange problem with my Saab 9-3 Aero. I will try to explain…

      Engine is 2.0 turbo 16V, stock 205 Hp, it has the following mods done:

      -Stage 2 tune to 260 Hp/380Nm (this map is on the car for about 2+ years now.)
      Stock boost is 0,8 bar, now it is on 1,1 bar.
      -3″ custom downpipe with stock cat modified to 3″ (this DP is on the car for about a year)
      -Forge diverter valve + silicone vacuum hoses(1 year on the car)
      -Intake muffler removed

      Well the problem that first happended about 2 months ago is that car bends a single exhaust valve…

      First time it happened:

      I floored it in first gear and shifted to second at around 4000-4500 rpm range…As soon as i shifted to second i heard a noise and the car started to run on 3 cylinders. We took everything apart and there was only one bent valve on cyl number 2. That valve was replaced + hydraulic lifter.

      At that time it was also checked that timming chain is OK, tensoiner is OK, camshafts are OK, timming is spot on, head was never lowered…

      Engine was put back togheter and i drove it for about two months but never really floored it properly since because i had a strange feeling it would happen again…

      Well two weeks ago i wanted to show a friend how a saab goes and guess what! In third gear at around 5000-5500 rpm range the same noise happned and car once again ran on 3 cylinders!

      Engine was taken apart AGAIN and this time its one bent exhaust valve on cyl number 3…

      I am clueless… Only thing i can think off are weak valve springs or only a single weak spring that was mixed by my mechanic and put on cly 3 this time…

      I ordered a set of valve springs and i just sent one new and one old(taken from bent valve) to testing to see if there is any difference in tension between them.

      There are no harder or stronger valve springs for these cars on the market, they use stock springs in racing aplication saabs that have a redline at 7000 rpm or more… Stock redline is around 6200 rpm, i never ever run it to the redline because boost droops rapidly after 5000 rpm and it pulls better if you just shift it in the next gear. I ve been with this car on the track two times before and had no problems with it at that time and same mods.

      Any suggestions, ideas? I can’t find similiar problem anywhere on the net, no mechanic i ask have a clue or heard of anything like this…

      Thanks.

    Viewing 8 replies - 1 through 8 (of 8 total)
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    • #634628
      college mancollege man
      Moderator

        I think your theory of weak springs is a good theory. I would think
        if it was timing you would destroy more valves.

        #634690
        george gonzalezgeorge gonzalez
        Participant

          You may have too much boost, they didn’t limit it to 0.8 for no good reason. If your exhaust valves overheat they could bind in the stem area and that would be bad.

          Also if it happens on just one cylinder you may have a lean fuel condition in that cylinder that leads to higher than normal temperatures in there. Try swapping injectors between 2 and 4. if your next bent valve is in cylinder 4 you have some circumstantial evidence that it’s the injector.

          #634698
          hemmyhemmy
          Participant

            First time it happened on cyl number 2, second time on cyl number 3…So its not a cyl related.

            Also there are no signs of overheating.

            Here are the photos of bent valves:

            1. time cyl 2:

            2. time cyl 3:

            Also it can’t be too much boost because people run much more than 1.1 bar on these turbos and engines…Up to 1.3 bar on stock TD04 turbo… Later saab engines 2.3 that are the same as 2.0 just longer stroke. Head and valves are the same came at 260 Hp stock from the factory.

            I run this map for more than 2 years and the problems started about 2 months ago.

            #634873
            george gonzalezgeorge gonzalez
            Participant

              Okay, so much for my wild guesses. About the only other explanation is that somehow the valve is down when the piston is going up. So it’s either sticking real hard (unlikely), or the cam follower gets wedged (also unlikely, but….) or the cam somehow gets out of position for part of a revolution and then fixes itself. I suppose it’s theoretically possible for the belt to jump up on the pulley edge for part of a rev, or a belt-tensioner to get weak, so at high revs and high valve loading the valve timing slips back. Nothing else comes to mind.

              #635022
              BillBill
              Participant

                I would say weak valve springs but is you tachometer accurate?

                #638826
                hemmyhemmy
                Participant

                  Case solved. Also it was the same valve bent two times! A little flip up by my mechanic who counted them wrong and i didn’t double check him :S It was on cyl number 3 both times :pinch:

                  Reason was the valve spring washer, here is the video:

                  [video width=550 height=309 type=youtube]D2vK7KEkoyg[/video]

                  Also meanwhile i also sent the old and new valve springs for testing…There was only 0,5 kg difference in tension between 13 years old springs and new ones.

                  #638832
                  college mancollege man
                  Moderator

                    Glad you caught it. New replacements installed?

                    #638834
                    hemmyhemmy
                    Participant

                      Yes, all new springs, all new washers and collets.

                      I hope i am done for a while.

                    Viewing 8 replies - 1 through 8 (of 8 total)
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