42 mpg in a TJ
- Thread starter bohuggabee
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TN_Project_Jeep
Member
You guys are relentless. Just as you should be. Carry on!
TN_Project_Jeep
Member
Literally posted that last night reflecting my thoughts as I graded essays from a final exam at the university where I work. Good chance my student and the OP in this thread are related!
I got way over 30... I think it was 34mpg, in an '11 Sienna 2GRFE 3.5 V6 multiple times, which was amazing. Typical for that minivan was about 24ish highway. It was a long straight level drive averaging about 50mph, at 11,000ft elevation, 250(?) mile round trip. Only one place in North America like that I've ever found like that. So high yet so flat. Can't remember the exact numbers it was so long ago. My theory was that it was because the air was so thin up there, there was much less drag force on the minivan, while the EFI did a great job compensating the fuel mix for altitude. No idea what really led to such great milage, but it sure was interesting.
How Toyota gets 35mpg regular sea level highway driving in the current 4th gen hybrid Sienna baffles me. I'd buy one instantly if there was a PHEV version.
Years ago I had an Audi A3 TDI and if you set the cruise at 65 in the early morning with the windows up and the ac off, I would pull 61 every single time from Tampa to Miami. (250 mi). Cooler mornings I would get 1-2 more, warmer 1-2 less. Then I finally figured out the difference was $3.89 and an additional 2 hours.
Never did that again. But it was cool to see that kind of mileage. And now I am older and giddy when I see double digits.
Higher air is thinner and produces less drag, that's the main reasons airplanes fly so high. I think the flat cruise at 50 was the bigger factor. Back when they were rationing gas the highway speed limit was set to 45 as that's where most cars get the best mileage.
It just hit me: what if the real reason behind the push for electric cars isn't to save the climate, it's so we stop buying oil from the Arabs. But they didn't want to come out and say that, kinda like they didn't want to come out and say that the "War on Terror" was about fighting violent Islamic groups. So the hawkish republicans supported the "Climate Change"(TM) leftist agenda as they saw it would advance their goals, and at little risk. They figured that if it ever came out what a crock it was people would blame the left, and help the r's gain political power.
One more thing: why 42 mpg? Is it, like, "The answer is 42." - related? Or maybe it' came from 420? Hmmm?
Anyways I picked up some clones for the garden today. The names always crack me up. I doubled up on the Tropicanna Smash Melonz.
KennethS
TJ Addict
Yep, similar to why I got 23 out of 2 consecutive tanks during easy forest road cruising at 30 MPH.
Huh? I recall it being 55 MPH.
Thought maybe that was before my time? As far back as I remember was 55mph. Could be back in 1940?
You're right. Original proposal was 50, but the national limit was 55. Some states did set it lower, as peak mileage is usually around 45 depending on the car. The national limit was repealed before I got my license.
Otto-cycle (gas) engines are terribly inefficient when lightly loaded, and this is why peak mileage speed is relatively high. Diesel engines do better because they don't have a throttle so no throttling losses. Electric suffers the least amount so they can do best where the car has the least total resistance, which is around 20mph.
If you take out the 4.0 and slap in one of these bad boys I bet you' could see 40 mpg in a TJ!
Diesel gets better mpg assuming everything else is equal because diesel has more energy per gallon than gasoline. About 14% more BTUs per gallon than gasoline.
That's a big part of it for sure, but diesels are more thermodynamically efficient and energy density of the fuel is not part of the equation. Their lack of throttling losses and higher compression ratios are the main factors.
Doubt it. Need a certain amount of Watts to push against a certain amount of air resistance. Easily calculated. For an econobox sedan or Tesla3 maybe 20-30,000 Watts at 60mph. Just guessing for a TJ probably about 55,000 Watts. Whether it's generated by one cylinder or 16 cylinders is maybe a 20% difference max, probably more like 10%, all else being equal. 16 cylinders have more internal engine drag losses mostly.... plus the energy needed to just compress air, and pull/push it past the valves.
Also why engines are measured in horsepower instead of Watts is just stupid.
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