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beepbeep beepbeep is offline
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Join Date: Jun 2001
Location: Sweden
Posts: 5,464
Merv: whoever told you that doesn't know what he's talking about. Boost controller will keep wastegate shut until preset boost arrives, it will then abruptly open the vent in order to keep boost at preset level. As long as spring load is greater then exhaust pressure behind, there is no difference between wastegate being shut by 0.7 bar spring or wastegate being shut by 1.1 bar spring. It's being shut and that's all that matters.

On the contrary, letting the spring control the boost usually leads to non-linear boost curve. As efficiency drops towards higher mass flow, boost regulated by spring only will typically start to taper downwards.

Electronic boost controller will usually detect this and start blowing off more poressure from wastegate bell to keep boost constant.

This is a log-file for typical boost profile with spring only:


As you can see, boost goes down as turbocharger runs out of breath. If I used electronic boost controller, boost curve could be kept reasonably flat. I could lower the boost peak around 3000 RPM (that kills my gearbox) and raise top-end boost somewhat for more poke.


So for all means, do use electronic boost controller if you own one. It will also allow you to lower the boost to your base boost (controlled by the spring tension) in case you expirience knock. With high temperatures present in Australia, I found it wise to be able to do so
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Old 11-10-2006, 05:28 AM
  Pelican Parts Technical Article Directory    Reply With Quote #12 (permalink)