It is always about money, but sizing and turbo efficiency are important factors too. With the HP being increase beyond 185, the limits of the T25 were probably getting painfully obvious. See my other LONG post in this thread for my thinking about the T25's limitations. And after 5 or 6 years, there would have been advances in turbo chargers to take advantage of too. And what turbo charger manufacturer would not compete on price to supply Saab which has been producing turbo charge vehicles for over 25 years? The Mitsu model might have presented a turbo sizing sweet spot too.

But with the VTN turbos coming on with the new 2003 models, the variable geometry turbine trim really turns the whole sizing issue on its head as these turbos have much broader efficiency curves. This is definately not about money. The VTN turbos are not cheaper! They allow for fast turbo spin up from idle and much better efficiencies at high CFM's. A waste gate type turbo can't do that! Did you know that a VTN turbo has no wastegate? It is about time that Saab intro'd this turbo technology. It has been around for quite a while now. Don't think that you can adjust the VTN actuatator rod! With some known implementations, to get the low RPM boost, the turbos are dancing on the edge of severe compressor surge. Some VTN's, not re-adjusted, on vehicles with other engine performance mods have grenaded. Operation at higher altitudes seems to make this more of a risk.

posted by 65.68.10...

• Why did Saab switch from Garrett to Mitsubishi on Aero?, J, Sun, 15 Sep 2002 14:34:49
  • Re: Why did Saab switch from Garrett to Mitsubishi on Aero?, sean, Sun, 15 Sep 2002 19:54:24
  • Re: Why did Saab switch from Garrett to Mitsubishi on Aero?, StanleyB, Sun, 15 Sep 2002 15:41:52
    • There is always more to it than money... long, Dean, Sun, 15 Sep 2002 19:09:36 <-- Viewing This Message
      • I meant fuel economy. >, StanleyB, Mon, 16 Sep 2002 08:30:08
        • Re: I meant fuel economy. >, Dean, Mon, 16 Sep 2002 09:19:01
          • Dean, can you explain VTN? Also..., Richard P., Tue, 17 Sep 2002 08:54:54
            • Re: Dean, can you explain VTN? Also..., Dean, Wed, 18 Sep 2002 09:37:00
  • the TD04 is better than the T25, nickR, Sun, 15 Sep 2002 14:53:03
    • Not "better" but capable of higher boost, Alex, Sun, 15 Sep 2002 17:11:08
      • TD04 laggier than T3?, gorper, Mon, 16 Sep 2002 01:59:43
        • Re: TD04 laggier than T3?, Alex, Tue, 17 Sep 2002 10:28:05
      • T3 Aero?, Kevin K , Sun, 15 Sep 2002 21:20:13
        • T25 = T3 45-trim (same thing) n/m, Alex, Tue, 17 Sep 2002 10:26:39
          • Actually come to think of it... might be a 50-trim n/m, Alex, Tue, 17 Sep 2002 10:33:57
      • Re: Not "better" but capable of higher boost, Roger Wilco, Sun, 15 Sep 2002 20:55:57
      • thanks ... I won't give out the site to search engines, J, Sun, 15 Sep 2002 18:49:26
      • Technically true but..., nickR, Sun, 15 Sep 2002 17:33:08
        • Yeah, true =), Alex, Tue, 17 Sep 2002 10:33:00
    • ... capable of producing higher boost?, J, Sun, 15 Sep 2002 14:55:49
      • Re: ... capable of producing higher boost?, Dean, Mon, 16 Sep 2002 09:28:08
      • Three good sources for understanding Turbocharger, Talladega900, Sun, 15 Sep 2002 17:00:57
        • The T25 is undersized to cover up for... LONG, Dean, Sun, 15 Sep 2002 18:50:01
          • Still unsure about something.., SteveW, Mon, 16 Sep 2002 00:19:50
            • Re: Still unsure about something.., Dean, Mon, 16 Sep 2002 09:36:48
          • VNT for 2003 diesel only ? n/m, Kevin K , Sun, 15 Sep 2002 21:26:58
        • Woah ... they have *books* about this stuff? :-), J, Sun, 15 Sep 2002 18:43:40
          • Re: Woah ... they have *books* about this stuff? :-), Dean, Sun, 15 Sep 2002 18:52:10
            • Re: Woah ... they have *books* about this stuff? :-), J, Sun, 15 Sep 2002 18:56:23
              • more links too!, Dean, Sun, 15 Sep 2002 19:12:42

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