Re: Automotive News: Turbocharger Fans Owe Saab a Thank You - Saab General Bulletin Board - Saabnet.com
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Re: Automotive News: Turbocharger Fans Owe Saab a Thank You
Posted by Dean (more from Dean) on Thu, 29 Oct 2015 07:43:24
In Reply to: Automotive News: Turbocharger Fans Owe Saab a Thank You, Scott Paterson [Profile/Gallery]
, Wed, 28 Oct 2015 13:30:18
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" Saab engineers also developed a method to prevent ignition knock by automatically lowering the boost while the engine is under load"
That is simplistic.
That is really not right with T5-T7 engines. Under high boost levels the AF mixture is made rich* [fat] and ignition advance is reduced. If, with DI systems, there is still a threat of knocking, the boost is reduced. That used to be by manipulation of the wastegate, but later utilized motorized throttle control which allowed for more and faster control. All of this also adapts to changing temperatures, barometric pressure, combustion chamber temperatures, plug conditions and fuel quality.
* The fuel pressure regulator is connected to intake manifold pressure and fuel pressure is increased on boost and decreased on negative manifold pressures. With a rich mixture, the O2 sensors are not able to work well and the T5 engine was open loop and rich under boost and a black sooty tail pipe was normal. The T7 with MAF sensor probably took out some of the excess fat.
I am sure that others could outline these features better that I.
posted by 108.207.118...
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