Quote:
Originally Posted by Fat Charlie
Turbos kill mpg when you get into boost.
In applications designed for higher mpg they help by giving a puny engine more punch when it's really wanted- but staying in the powerless, non-boosted state is where the savings actually are.
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Fixed your wording a little.
Anyway, I'm tired and didn't feel like responding, but thought I would because Old Tele Man, I don't know how extensive your knowledge is on forced induction engines, but you are most certainly wrong. When off-boost the effective CID does go up, but so does engine efficiency (which increases exponentially as boost builds, btw). The engine does not have to work as hard to 'ingest' the air so the engine is running at a higher efficiency. More efficiency = less throttle required to produce the same amount of power.
Just as an example, on my turbo insight, when climbing my 6% grade I used to have to use 34-38% throttle to maintain 70. Now I use 26-32% to maintain the same amount of speed. Why? I'm not producing boost and my vacuum levels are the same. It's because the engine itself is running at a higher efficiency and the extra back- pressure in the exhaust caused by the turbo restrictions is creating more torque, which again is great for efficiency.