Like the title say, why are the fuel gauges in Japanese cars so slow to update? Got thinking about this last night, after topping off my Baja's tank. My Jeep and GMs, you fill the tank, turn the key on and the gauge instantly reads full. My Mazdas, Subarus and Hondas, you put gas in and 5 minutes later the needle is still moving up. Why is that?
Dampened. So the needle doesn't bounce around when you corner, accelerate, etc. The Esprit (RIP) had no dampening. It was basically useless. Don't know what the GM's/Dodges do. Maybe they electronically dampen the signal.
My old Fiat's had bouncy fuel gages too. Going straight they would read accurate, turn a corner, stop, or just be on a bumpy road... "well... I have fuel"
Ford does this too. If you leave the key in while fueling the gauge sweep moves so slowly it takes something like half an hour to reach full. If you remove the key completely the computer has a bypass and it will jump straight to full. Kinda clever but if you forget to take the key out, very frustrating.
I find that on Japanese cars if you fill up when you are only down maybe an 8th or a quarter of a tank or so, like if you are topping off to head out of town or for the weekend, it's seems to take forever to register. If you are down half a tank or more then it pops right back up.
As far as I can tell, some use a slow sweep to prevent the needle bouncing and others use a kind of averaging.
The slow sweep will come up to the level in a few seconds after turning on the key because it gets the information immediately and starts its slow sweep to the level. The averaging ones tend to take a longer time. The data they have is zero, then full, so it keeps re-averaging by halves for a few minutes until it gets to the right level. Its first data set is 0 and 1, so it sweeps to half pretty fast, then the next data set is 1/2 and 1 so it sweeps to 3/4, then 7/8, then 15/16, then 31/32.... etc.
My F150 was pretty good at startup, but if you turned off the key, filled the tank, and then restarted, it took 5 minutes or so to register full.
It's becuase you are putting in American gallons instead of Japanese liters. American gas molocules are egg shaped whereas Japanese are elongated, thin and more densely packed together. Because of the computer initially sees less of the American gas molecules and due to the fact that the fuel float level is high the computer recognizes that the tank has been filled with American gas molecules and recalculates. Additionally because it is a Japanese computer it runs the sub routine dozens of times before it sends to the gauge, once the gauge gets the signal it runs its own sub routine dozens of times. All this takes time.
Also never never install a Chinese gauge as the friction between the Japanese pump and Chinese gauge is an age old problem known to cause the fuel tank to explode. The root of the problem is the Chinese do there calculations using ancient alien technology. This isn't a problem for American cars built after 1947 as that's when the U.S. started using alien technology. While the American alien technology is new alien technology it is capable of reading ancient alien technology.
In reply to Tom1200 :
This sounds like my sons doctoral thesis defense when three professors and he got into a discussion on the shape of nanoparticles. Sounds legit to me.
I was hoping for a punchline.
@poopshovel Using Elf/Motul fuel will fix the problem as French fuel will convert almost instantaneously............how's that?
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