| Cold intake air and power VS fuel economy [message #193687] |
Sat, 22 December 2012 11:20  |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma:
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We know that a colder intake air temp is better for maximum power, but not so sure about for maximum light part throttle mileage. Todays cars run at higher temp to try to squeeze efficiency. What I have noticed is that on my OBDII Cherokee with SFI, the instantaeous mileage highway figures are down in the winter with colder IATs. My stat and gauge confirm 195 operating temp, so it doesn't think it's cold coolant temp causing enrichment. My guess is the computer is adding some fuel to allow for the colder IAT and poorer vaporization? On my GMC I have the heat tube still connected and working to try to maintain faster warmup and less emmisions and hopefully better mileage. As we know at WOT it goes to colder oustide air anyway so it doesn't diminish max power. My crossovers are supposedly restricted (per Cinnabar standards) but not blocked. The only other thing I can put my finger on with the Jeep is that the winter blend fuels here give poorer highway mileage but don't know if that is the case or the opposite should be true. So... the question is on the GMC at light throttle cruise (maybe primaries at 30%)wouldn't the best mileage come with a constant 115 deg IAT at the carb for better vaporization allowing leaner jetting as oppose to wildly swinging IAT depending on the weather? On a hot day the ThermAc door should be wide open anyway and out of the picture.
John Lebetski
Woodstock, IL
77 Eleganza II
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