Destiny2002

Back when I kept track of my fuel economy, I also kept track of the number of bars left. I compared this to the difference between the fuel tank capacity and the number of gallons added.

I found the fuel gage to be very linear

I found an old post where I posted the equation...

#gallons left = 0.5667*bars + 2.0844

MarkS2K

So Destiny, you're basically saying that the "reserve" in this car is 2.084 gallons. That's when all the bars are gone and the fuel light turns on.

Destiny2002

It could be interpreted that way. Of course, most of my fill-ups were somewhere in the center of the range, so give or take a few tenths of a gallon for being on the end of the data grouping.

twohoos

Mine's very linear, except under racetrack conditions. I wait for zero bars before filling up, and typically put in 10.5-11 gallons.

Destiny2002

Two bars per gallon, good rule of thumb. Don't be surprised if you first bar goes away quickly, typical of all fuel gages. And it's hard to really fill it all the way unless you are on the right slope.

Wael El-Dasher

I think the real issue is the elevated location of the fuel tank, compared to other cars I have owned and to those in my fleet, the S2000's is the most affected by slopes. I assumed immediately that fuel slosh is going to be a problem so I run with a full tank when I autocross the car.

If the fuel tank was located lower, such where the tool kit is, then this wouldn't be as severe of a problem. But then Honda probably wanted to locate the fuel tank within the wheel base so as not to affect the handling characteristic as fuel level varies. Invariably someone at Honda had to make the call to place it where it is. Obviously there is a limit on how low they can place the tank as there are mechanical clearances (drive shaft, diff, rear cross member) and safety considerations in the advent of crashes.

I recall most of my Mercs had the fuel tank behind the rear seat's back, which make running wiring a bit tricky at times (MB always left extra unused grommets thankfully), but they were not as bad the S2000's. Perhaps the problem is made more apparent due to the need for more frequent fills-ups given the anemic fuel capacity.

cheers

W

tmorrow

My last 3 bars are only good for 8 to 20 miles. It is annoying. But, I had to drive 6 miles on ZERO bars and made it...I guess the reserve is at least a gallon. I'm averaging 18.9 MPG with mostly city driving and a daily sprint to triple digits.

WhiteS2k

But there are only 18 or 19 bars. So at 2/gallon, that would mean that the fuel gauge only indicates 9-10 gallons of fuel when the actual capacity is 13 gallons. For our international friends, I'm sorry to be so "imperialistic" with the gallons, maybe the fuel gauge is really calibrated in terms of liters

Anyway, after all this time, I still find the fuel gauge of my S2000 to be very non-linear, the first "half-tank" goes slowly, and the second "half-tank" goes very quickly.

Destiny2002

Well, here is my full data before blowing off keeping fuel economy records:

#bars at fill-up... theoretical gasoline in tank before adding (Rated capacity minus amount of fuel added)

20...13.2 (original fill-up)
14...10.3 (added 2.9 gallons, 13.2-2.9=10.3)
10...7.4
10...7.4
12...9.3
13...9.5
10...7.9
11...8.2
3...3.6

Do what you want with the data. Excel spits out a trend line with the equation:

Gals left = 0.575*Bars + 1.97, R^2 = .989

But it would take a lot more data to statistically analyze this, especially since the number of bars could indicate a range of .5 gallons (resolution).

Here's a good way to theorize what the linearity should be. A fill-up of 13.2 gallons capacity is 20 bars. Let's say when you have 0 bars you have 2.2 gallons left. Therefore, your slope of gallons per bars is 11/20= .55 gallons per bar. Therefore your equation would be:

Gals left = 0.55*Bars + 2.2

Then this chart would represent what you should see if the gasoline gage is linear:

20... 13.20
19... 12.65
18... 12.10
17... 11.55
16... 11.00
15... 10.45
14... 9.90
13... 9.35
12... 8.80
11... 8.25
10... 7.70
9... 7.15
8... 6.60
7... 6.05
6... 5.50
5... 4.95
4... 4.40
3... 3.85
2... 3.30
1... 2.75
0... 2.20 (or less)

S2KTerpNut

Great stats and analysis!