How do cars know how much fuel is in the tank?
- Thread starter Skeeter
- Start date
I've always wondered in this modern age of technologically advanced cars, why there isn't a flow/flowrate meter in the filler neck. That way ECU knows the amount in, and can work out the amount used by injector flow rates and firing pattern. It "could" be exact, whereas at present (or at least in every car I've driven) they aren't particularly accurate at all.
Once again I read one of your posts and think "WTF?"
Are you on a one man mission to spam every thread with a useless response?
Once again I read one of your posts and think "WTF?"
Are you on a one man mission to spam every thread with a useless response?
well i find that a little harsh
check through my posts and you will see that i have been helping folks.
well it is programmed into the ecu.
amount of fuel in the tank.
size of tank.
and how heavy or light you are with your foot.
check through my posts and you will see that i have been helping folks.
well it is programmed into the ecu.
amount of fuel in the tank.
size of tank.
and how heavy or light you are with your foot.
Last edited:
Associate
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Float moves what is pretty much a variable resistor. Usually quite crude; I recommend everyone runs the car dry atleast once with a jerrycan of petrol in the boot, so you know exactly how far you can go when range=0
(note: Diesel drivers should not do this)
(note: Diesel drivers should not do this)
![[TW]Fox](/data/man-of-honor/2009.png){kind=avatar}
The ECU knows how many litres are left and it also knows, on average, how much fuel its using. It can then calculate the expected range from this. You can often see a lot of this raw data yourself if you have the right interface/software
It would surprisingly hard to measure flow at the filler neck, compared to just measuring the level.
Yeah, but the pump flow meters are quite expensive to get the required accuracy, but yeah there's nothing stopping the pump communicating that info the car afterwards though.Not sure how? The pump dispensing it manages fine. Heck, if measuring it as it enters the car is that hard, pumps and cars could be fitted with NFC
Not sure of the point, normal float gauges work fine.
The range feature on my car is bloody useless though, put a full tank in and it comes up with some pie in the sky figure of 450-500 miles, it will actually do about 390 before running out. It also cuts off to zero when there's still quite a bit left.
The range feature on my car is bloody useless though, put a full tank in and it comes up with some pie in the sky figure of 450-500 miles, it will actually do about 390 before running out. It also cuts off to zero when there's still quite a bit left.
And get ready for a bill. Run the tank to empty and all the dirt and crap from the bottom of the tank will get dragged up into the fuel filter or worse. If you're not bright enough to put enough fuel in for as journey you shouldn't be behind the wheel.
Why do you need to know "exactly" how many mile you can do on a tank. There are so many variables. Driver, traffic, weather, even temp.
I find driving straight from the petrol station to another petrol station is the best approach, you can never be too careful.
How does dirt get into the tank then?
Associate
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or why does it suck this magical dirt up only when empty?
bullit
bullit
You're kidding me. Have you ever emptied an old patrol tank?? Do you think the fuel doesn't contain dirt grime and even water? You should see the sludge at the bottom of the average patrol station storage tank.
Cut an old fuel filter in half as and see how clean it is. Plus there's a clue, most modern cars will have one or more filters to keep the dirt out. And modern fuel injection systems like clean fuel.
Don't get me wrong I can see where you're coming from, wanting to know what the tank actually holds but running a tank to empty is potentially asking for trouble.
Sorry didn't mean to sound grumpy.
Because dirt and grime tend to be solids so collect at the bottom of the tank. When you're running on the dregs, the chances of sucking them up increases. The fuel pick up is normally at the bottom of the tank.