Supporting Member betoney Posted July 21, 2018 Supporting Member Share Posted July 21, 2018 I just got back from a road trip into Northern California where it was pretty d@mn hot, my air temp sensor was constantly reading 107-111 and coolant temperature read 199-209 while moving. I noticed a drastic increase in average fuel economy on every tank of fuel, I reset the average with every fill up and it was always averaging a low of 49 and one tank as high as 54mpg. At sea level in a cooler climate in Washington, each fill up usually reads 42-46mpg. We were almost always 10-15 above the speed limit riding twisties, fast sweepers, lots of passing zones, climbing grades. We were always between 4-5,000 ft elevation. So the questions are, does high temperature or higher elevation add to increased economy? Is there something in California gas to meet EPA regulations? Shouldn't the ECU and O2 sensor monitor and balance the AFR to remain constant regardless of temperature or elevation? Thanks guys ***2015 Candy Red FJ-09*** Link to comment Share on other sites More sharing options...
phpaul Posted July 21, 2018 Share Posted July 21, 2018 DISCLAIMER: I have precisely ZERO facts to back my views on this subject. However, I never let that keep me from having an opinion... I suspect that if anything, increased altitude should reduce mileage due to decreased efficiency. I'd be more likely to suspect a better fuel blend is behind the improvement. Did you do the math to determine actual fuel mileage or go by the instrument readings? I've always found them to be more than a little optimistic. Link to comment Share on other sites More sharing options...
suitedsevens Posted July 21, 2018 Share Posted July 21, 2018 Likely elevation more than anything I suppose. I get close to 50mpg and I pretty much only ride above 6,000 feet. The only time I've ridden my fj at sea level so far I was blown away how much power it had. I didn't know it was capable of a wheelie with traction control on, that was a bit of a surprise. '17 electric white fj - oem heated grips - oem hard side bags - heated corbin saddle - mra touring screen - motodynamic tail light - baja designs led turn signals - yoshimura full exhaust/fender eliminator - k-tech razor r rear shock/front fork kit - evotech radiator guard - mt-09 adventure pegs - pazzo shorty levers - stainless bar end weights '19 Husky fe501 - cut off a few things and fixed the fueling Link to comment Share on other sites More sharing options...
vijay Posted July 21, 2018 Share Posted July 21, 2018 Altitude has always increased mileage markedly in Fuel Injected systems. The computer automatically limits fuel to account for the less airfllow through the system. Result ... higher mileage, less power. Link to comment Share on other sites More sharing options...
Supporting Member betoney Posted July 21, 2018 Author Supporting Member Share Posted July 21, 2018 Did you do the math to determine actual fuel mileage or go by the instrument readings? I've always found them to be more than a little optimistic. I have done the math before and find that the gauge readout is always 2-3mpg higher than real world results. For this trip I was strictly using the "average fuel" readout, where I normally see 42-46mpg per tank, in California where the temps were well over 100, I was routinely seeing 50 or higher with constant "spirited" riding. ***2015 Candy Red FJ-09*** Link to comment Share on other sites More sharing options...
phpaul Posted July 21, 2018 Share Posted July 21, 2018 Altitude has always increased mileage markedly in Fuel Injected systems. The computer automatically limits fuel to account for the less airfllow through the system. Result ... higher mileage, less power. That makes sense, now that you mention it. Thanks. Link to comment Share on other sites More sharing options...
skipperT Posted July 21, 2018 Share Posted July 21, 2018 Altitude has always increased mileage markedly in Fuel Injected systems. The computer automatically limits fuel to account for the less airfllow through the system. Result ... higher mileage, less power. That makes sense, now that you mention it. Thanks. Ok but remember it’s NOT due to less air flowing through the system. I believe it’s because the air DENSITY is lower. There’s less oxygen in the air the higher you go. So the fuel injector duration is shortened. Modern FI systems will usually retard the timing as well to cope with altitude, I believe. -Skip Link to comment Share on other sites More sharing options...
vijay Posted July 22, 2018 Share Posted July 22, 2018 That makes sense, now that you mention it. Thanks.Ok but remember it’s NOT due to less air flowing through the system. I believe it’s because the air DENSITY is lower. There’s less oxygen in the air the higher you go. So the fuel injector duration is shortened. Modern FI systems will usually retard the timing as well to cope with altitude, I believe. -Skip Skip: Sir you are indeed correct. I improperly shortened my explanation by just assuming that people would understand that with less density their would be less oxygen flowing across the sensors. And as has been so often quoted to me by long since deceased parents: You know what assume means .... I've been trying to follow my family's ongoing request: when someone asks you the time don't tell them how the different clocks works!! Seriously, thank you for correcting me. Link to comment Share on other sites More sharing options...
skipperT Posted July 22, 2018 Share Posted July 22, 2018 Oh sorry, I actually wasn’t trying to correct you... more just to clarify. Hard to convey intention via typing sometimes. Cheers! -S Link to comment Share on other sites More sharing options...
leonardlloyd Posted July 22, 2018 Share Posted July 22, 2018 All correct except that no need for inboard computer to retard spark at high altitudes. Will tolerate some advance to recover some of lost power. Link to comment Share on other sites More sharing options...
vijay Posted July 23, 2018 Share Posted July 23, 2018 Oh sorry, I actually wasn’t trying to correct you... more just to clarify. Hard to convey intention via typing sometimes. Cheers! -S Truly ... I don't mind being corrected at all. I was wrong and you were right. Both factually and in correcting my shorthand response. BTW .... I don't really have a handle on why we seem to get better gas mileage when it gets hot outside. My assumption has been the change by the refineries to a different mix. But I actually have no real clue. Link to comment Share on other sites More sharing options...
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