To start with I must say that what you are expecting is incorrect and that what you are getting is correct. A turbo operates strictly off the flow of exhaust from your engine. There are two parts to a turbocharger. One is a turbine which is driven, or spun, by the flow of exhaust gases. The other is a compressor which is connected to the turbine by a shaft. When you are putting the engine under load, i.e. accelerating, the engine is putting out more exhaust, causing the turbine to spin faster thereby spinning the compressor wheel faster as well. It is only when the compressor is being spun at high enough speeds that you will see boost conditions. Therefore when you let up on the accelerator the turbo, turbine & compressor, slow down so that the manifold pressure decreases. When everything is working correctly this will happen rapidly and you will see your boost gauge read down into the white. Also, you will only see boost under load conditions, meaning that you cannot get boost when sitting still and reving the engine.

The white band on your gauge is not base boost as you have been thinking, but is actually vacuum. The area right between the white and yellow areas is simply atmosheric pressure, or the absence of vacuum and boost. When it moves into the yellow and beyond you are then into boost. From what you have described you are certainly getting good boost.

Base boost, just to add a little possible confusion, is what you get when the wastegate is fully open and properly adjusted. I'm not entirely sure where this is indicated on the gauge, but I believe it is about midway on the yellow band.

I hope this helps solve some confusion without adding any.

Tom R.
'87 9000 Turbo
287,500 miles and still going (like a timex only more fun)

posted by 67.120.8...

• Is my turbo functioning properly or not? Confused (long, Tony O, Thu, 16 Jan 2003 05:11:19
  • Yet another way to look at it., Ari , Thu, 16 Jan 2003 13:04:45
  • Score 1 for the autobox..., Joe98, Thu, 16 Jan 2003 12:55:30
  • Re: more or less :-), Andrew , Thu, 16 Jan 2003 12:18:00
    • Re: more or less :-), Eric Law, Thu, 16 Jan 2003 13:32:58
      • Hehhh.., Andrew , Thu, 16 Jan 2003 16:36:18
  • Tony, a little course in turbos..., Trobinson9kT, Thu, 16 Jan 2003 06:42:20 <-- Viewing This Message
    • True, but..., Craig, Thu, 16 Jan 2003 19:56:31
      • Oops, Ari beat me to it. nm, Craig, Thu, 16 Jan 2003 19:58:23
    • I have finally seen the light....thanks guys, Tony O, Thu, 16 Jan 2003 14:13:10

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