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Old 12-20-2010, 10:06 PM   #7 (permalink)
Toe_cutter
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Join Date: Dec 2010
Location: louisiana
Posts: 27

big red - '95 ford f150 xl
90 day: 20.84 mpg (US)
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Honda may be slightly different, but, many auto makers today have totally done away with EGR valves on variable cam engines. They do this by altering the exhast valve lift and duration to keep some spent gasses in the combustion chamber, basically a built in EGR system without extra parts to break. This is good and bad. Bad because EGR always , always hurts power and fuel use, always. It is also good because EGR gasses are introduced after the MAF sensors, which means that there is unaccounted for and non combustable gasses in the combustion chamber, which hurts power and since the ex gasses dont burn on compression and ignition they dont add to engine power.
Quite a few of the performance chips for VCT engines correct the valve timing to cancel out the egr effect, usually resulting in more power and decreased fuel use.
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