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Discussion Starter #1 (Edited)
OK, I now have multiple fillups at all levels except zero bars. A couple of people have reached zero bars and reported filling between 15.3 and 15.6 gallons. The reported fuel tank capacity of a 2017 (and 2018) Giulia is 15.3 U.S. gallons or 58 liters, and the reserve is 2.3 U.S. gallons or 9 liters. 9 liters is actually 2.37755 U.S. gallons, and 58 liters is 15.322 U.S. gallons. It's not really clear why Alfa rounded the way they did on the "reserve", but it is very clear that the "reserve" IS included in the normal fuel level measurement. It will also become clear below, there is no useful indicator that you have entered the so called "reserve" section of your fuel tank. The normal 2 bars remaining happens at about 2.9 U.S. gallons to empty and the orange fuel pump happens at about 1.8 U.S. gallons.

The following data is applicable to my vehicle only, but seems to generally match what other owners experience. The method was refueling as soon as practical after observing the fuel gauge drop a bar. Mileage was noted at the time the bar dropped off and at the time the refueling was done. This way, the first mileage, divided by the seond served as a proxy measurement to compensate for the fuel used to reach the gas station (e.g. at 260.0 miles today, the fourth bar dropped off...I pulled into the gas station and filled up at 261.4 miles...my calculated correction factor is 0.9946442). With that data, the fuel pumped is multiplied by the correction factor, which yields the estimated fuel used to fill to the point where the bar dropped off (e.g. 0.9946442 x 10.740 = 10.682478).

The problem with the above method is the inherent spread on the autoshutoff of differing fuel pumps and the inaccuracy of the correction factor. To combat this, I discarded any fillup with a correction factor smaller than 0.98, which equates to .028 gallons on a fillup at 1 bar. Additionally, I simply selected the first gas station to fillup at. After multiple fillup data was acquired, I targeted additional fillups at levels where the standard deviation between the calculated fills was over 0.2 U.S. gallons. Outlying calculated figures were discarded, which somewhat fits the data, but also corrects for autoshutoff variability. No attempt was made to correct for fuel temperature.

So, what did I find out, that the Giulia has a very Italian gas gauge (U.S. gallons and liters rounded to one decimal point, the stated U.S. gallon capacity used for calculations):

Full/8 Bars is defaulted as 15.3 U.S. gallons or 58 liters
7 bars indicated remaining 12.3 U.S. gallons or 46.6 liters
6 bars indicated remaining 10.6 U.S. gallons or 40.1 liters
5 bars indicated remaining 8.9 U.S. gallons or 33.7 liters
4 bars indicated remaining 6.6 U.S. gallons or 25 liters
3 bars indicated remaining 4.8 U.S. gallons or 18.2 liters
2 bars indicated remaining 2.9 U.S. gallons or 11 liters
Orange gas light illuminates 1.8 U.S. gallons or 6.8 liters remaining
1 bar indicated remaining 1.4 U.S. gallons or 5.3 liters, gas gauge turns red

Notes:
-The most confusing part is the 3 U.S. gallons/11.4 liters 8th bar.
-The 5th bar is almost as bad, at 2.3 U.S gallons/8.7 liters worth.
-The 7th, 6th and 4th bars are all 1.7 U.S. gallons/6.4 liters.
-The 3rd bar is 1.9 U.S. gallons/7.2 liters and the 2nd bar is around 1.6 U.S. gallons/6.1 liters.
-The 1st bar is a pitiful 1.4 U.S. gallons/5.3 liters.
-A half tank indicated is really about 40% left.
-The last indicated "quarter" of the tank is more like 18-19% of the tank left.
 

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Wow, thank you for sharing this. This sounds INSANE to me that the gauge is on a gradual scale instead of being linear. I won't be surprised if many people run out of gas accidently not realizing that they were already under a quarter tank at 2/8 bars.
 

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Insane yes, until you think about how the sender may interact with the fill level. Most are on an arc afaik, and what we see in the quasi-logarithmic bar graph on the dash may actually be a good hint as to how the values will skew. My 360 bar graph is similar and only has 9 bars so you have to think in thirds. :D Anyone have more info on the sender-float arrangement?
 

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I had my gas gauge turn to 1 bar and I freaked out trying to find the nearest gas station (top tier gas only), luckily it was a Shell and was only 1 mile away. I filled up 14.7 gallons.
 
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Using a different, much faster technique I came up with somewhat different numbers:

Starting from 3 bars showing I filled slowing until the number of bars increased and noted the number of gallons added. This yielded

All values in gallons to fill.
4 bars reference 0
5 bars 2.016 (delta = 2.016) (AlfaCrisis 1.8 gallons)
6 bars 3.566 (delta = 1.550) (AlfaCrisis 2.3 gallons)
7 bars 5.307 (delta = 1.741) (AlfaCrisis 1.7 gallons)
8 bars 7.044 (delta = 1.737) (AlfaCrisis 1.7 gallons)
full 9.547 (delta = 2.503) (Alfa Crisis 3.0 gallons)

Partway into 3 bars the total fill was 11.375 gallons, for approximately 4 gallons left. It took 1.8 gallons to indicate 4 bars so I apparently would have had 2 bars indicated if I had driven a short distance more. This indicates a roughly 1 gallon offset relative to AlfaCrisis's car.

This method of measuring the fill amount is faster than it sounds. It is easy to see the fuel gauge from the filler. Then once the first bar is reached by very slow filling, add 1.5 gallons quickly before slowly filling to the next bar. There may be some hysteresis that could cause filling versus draining readings to be different. However, the test is done with one pump at one time, making the measurement self-consistent.
 

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Discussion Starter #6
As I noted, lockem, I’m not claiming to represent all Giulia’s, just mine, as your readings represent yours. What I’d find useful is data from anyone else on their fill ups at say 2, 4 and 6 bars remaining. That being said, your numbers are close to mine with one bigger excursion (6 bars) and do seem to show a wonkiness to them. I considered your method, but given the interactions I’ve seen with the gauge, it concerned me. For instance, I have shutdown on 5 bars and restarted to see 6 bars again, and have that continue for 10 miles before falling to 5 bars again. I have also shutdown with 4 bars and restarted the next morning with 3 bars. The behavior of the senders and gauge seems a bit erratic, thus my preference for multiple readings.

That being said, if I can find a safe way to try that method (might get you shot around here, delaying people and all), I might try adding 1/10 of a gallon at a time and checking the numbers.
 
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Yeah, it's misleading. But, it's better now after my last update than when I first got my Giulia back in May 2017. It originally showed half-tank yet I could add 10 gallons. Showing half-tank still isn't 7.5 gallons, but it's a lot closer than it had been.
 

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Resurrecting this old thread:

Using OBD2AA, torque, AA, my phone, and an OBD to bluetooth adapter I can get the fuel sensor readout on a gauge on the infotainment system. This presents % fuel fill in fine increments (the increments are about 1.4% I think) so that it is possible to get a better idea about what is going on. I only made a few quick readings after filling up at the Wa She Shu Chevron station where they have no evaporative emissions capture on the reservation, I do not know if that makes a difference to the max fill that goes in the tank:

1) It stays pegged at 100% until I burn through about 1.5 to 1.8 gallons. This seems consistent with other people's observation that "the reserve" is at the top of the tank instead of the bottom like it is on most other cars.

2) The number of bars on the instrument panel display is ceil((fuel%/100) *8). That is, at 87.5% it drops to 7 bars, at 75% it drops to 6 bars, etc. Thus, as I pointed out before, the gauge display of 7 bars means that you have between 6 and 7 bars worth of fuel remaining.

3) The rate at which the fuel % reading drops appears to be somewhat faster than what I would expect. I expect that the reading will change by 1/(15.3-1.8) = 7.4% per gallon, but my eyeball estimate is that it changes 8-9% per gallon. I may try monitoring the readout while filling up to get something more meaningful.

There are reports now that for newer cars the behavior is completely different, with a large reserve at the bottom of the range.

https://www.giuliaforums.com/forum/778-alfa-romeo-giulia-issues-problems/44346-fuel-gauge-problem.html
 

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Returning from my trip last weekend, I had 1 bar of fuel remaining on the gauge and the orange fuel pump light was not on until the car was started again, it took 12.9 gallons to fill up at that point. 2017 model.
 

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Resurrecting this old thread:

Using OBD2AA, torque, AA, my phone, and an OBD to bluetooth adapter I can get the fuel sensor readout on a gauge on the infotainment system. This presents % fuel fill in fine increments (the increments are about 1.4% I think) so that it is possible to get a better idea about what is going on. I only made a few quick readings after filling up at the Wa She Shu Chevron station where they have no evaporative emissions capture on the reservation, I do not know if that makes a difference to the max fill that goes in the tank:

1) It stays pegged at 100% until I burn through about 1.5 to 1.8 gallons. This seems consistent with other people's observation that "the reserve" is at the top of the tank instead of the bottom like it is on most other cars.

2) The number of bars on the instrument panel display is ceil((fuel%/100) *8). That is, at 87.5% it drops to 7 bars, at 75% it drops to 6 bars, etc. Thus, as I pointed out before, the gauge display of 7 bars means that you have between 6 and 7 bars worth of fuel remaining.

3) The rate at which the fuel % reading drops appears to be somewhat faster than what I would expect. I expect that the reading will change by 1/(15.3-1.8) = 7.4% per gallon, but my eyeball estimate is that it changes 8-9% per gallon. I may try monitoring the readout while filling up to get something more meaningful.

There are reports now that for newer cars the behavior is completely different, with a large reserve at the bottom of the range.

https://www.giuliaforums.com/forum/778-alfa-romeo-giulia-issues-problems/44346-fuel-gauge-problem.html
Did you find that each bar was an even percentage of 100? I thought the consensus was that while each bar should be 12.5%, the top bar is 20% and the last is 8%
 

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for me 1bar means 50mi which adds to 400mi i never reach :D:D:D:D:D
 

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Did you find that each bar was an even percentage of 100? I thought the consensus was that while each bar should be 12.5%, the top bar is 20% and the last is 8%
I think you are confusing measured percentage fill of the fuel tank versus the percentage fill read out from the tank sensor.

The dashboard readout appears to simply be ceil(tank sensor * 8)

The tank sensor appears to not accurately translate the amount of fuel in the tank to a percentage. Did somebody say its a Bosch part?
It reads 100% well after 1 gallon is burned off, but drops below 100% before 2 gallons are burned off. It subsequently appears to drop faster while on the top of its range than fuel is taken out of the tank. I'll get a better reading after I burn more and fill up.

Feel free to replicate my results. It would be very interesting to see if there is a lot of variability between tank sensors. If you have an Android phone and AA on your car the rest of the bits are only about $20.
 

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I think you are confusing measured percentage fill of the fuel tank versus the percentage fill read out from the tank sensor.

The dashboard readout appears to simply be ceil(tank sensor * 8)

The tank sensor appears to not accurately translate the amount of fuel in the tank to a percentage. Did somebody say its a Bosch part?
It reads 100% well after 1 gallon is burned off, but drops below 100% before 2 gallons are burned off. It subsequently appears to drop faster while on the top of its range than fuel is taken out of the tank. I'll get a better reading after I burn more and fill up.

Feel free to replicate my results. It would be very interesting to see if there is a lot of variability between tank sensors. If you have an Android phone and AA on your car the rest of the bits are only about $20.
I'm only talking about the gauge. I know that the top 4 bars take up way more then half of the fuel. I wish they would have made it linear.

I have an iPhone so no means to do any proper testing unfortunately.

Are you saying that even with an app that measures precisely, it's still not accurate?
 

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I'm only talking about the gauge. I know that the top 4 bars take up way more then half of the fuel. I wish they would have made it linear.

I have an iPhone so no means to do any proper testing unfortunately.

Are you saying that even with an app that measures precisely, it's still not accurate?
Is torque available for the iPhone? I only need AA and OBD2AA to be able to have the convenience of getting a gauge on the infotainment screen. Torque can read the fuel level and display it on your phone if you don't have a scheme to use the infotainment screen.

The app does not measure anything. It displays the value that the fuel sensor reports. I do not know if that value has been processed before it is reported to the torque app, but suspect that it is not "raw". I suspect that the raw data indicates the fuel height in the tank, but because the tank does not have a constant cross sectional area some processing is required to turn fuel height into the amount of fuel in the tank. I also do not know if there are separate sensors for the two sides of the tank or if the fuel level in the two sides of the tank are maintained equal.

IIRC, my car drops to 4 bars on the instrument panel when about 9.5 gallons have been burned.
Assuming that the sensor is linear after the first 1.8 gallons we get an estimate that the drop to 4 bars corresponds to

(15.3-1.8)*0.5 + 1.8 = 8.6 gallons burned--still not right <sigh>.
 

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I see the app I think but I don't have an OBD2 reader.

At this point I've given up on my fuel gauge and go by miles driven. I typically go 240 before filling up as I know I'm around 12 gallons by then and I'd rather play it safe
 

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Having an OBD reader and an app that can clear errors is strongly recommended for the driver of any modern car. Otherwise any intermittent anything can leave you stranded or at least severely inconvenienced.
 

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having had my Quad for about 4 months now, and read just about every post on this forum, and the warnings about running the car out for fuel, and becoming aware of the non-linear rate of fuel use on my gage, and the changing "miles to empty", (which I suspect is based on the projected use of fuel over some real-time use at the moment) I refuel when my car is nearing half full on the gage.

There are manufacturers cautions about running a DI car out of gas. Besides I like to get out and stretch my legs, maybe get something to drink on any trip.

All the best... NV
 

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Unlike my wife, and seemingly other posters here, I don't tempt fate. I fill up at between 1/2 and 1/4 full, in any car. Why wait? Bad weather, rushing to get somewhere, any number of factors may cause a delay for stopping for a fill-up when the tank is really low -- may as well replenish earlier. Same amount of fuel, you are just buying it earlier at a lower fill volume.

BTW, almost every car takes longer for the fuel gauge indicator to drop from full, as opposed to ongoing drop during continued fuel usage. This is because at full, the fuel level in the tank is "higher" than the actual highest limit of the fuel level float, or whatever sensing device is used to send data to the gauge. It's not about "reserve", it's just how things work.
 

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Unlike my wife, and seemingly other posters here, I don't tempt fate. I fill up at between 1/2 and 1/4 full, in any car. Why wait? Bad weather, rushing to get somewhere, any number of factors may cause a delay for stopping for a fill-up when the tank is really low -- may as well replenish earlier. Same amount of fuel, you are just buying it earlier at a lower fill volume.

BTW, almost every car takes longer for the fuel gauge indicator to drop from full, as opposed to ongoing drop during continued fuel usage. This is because at full, the fuel level in the tank is "higher" than the actual highest limit of the fuel level float, or whatever sensing device is used to send data to the gauge. It's not about "reserve", it's just how things work.
Why wait? It takes time and I don't like wasting time. I also drive in areas where gas stations are few and far between so I often need to ask "can I make it to the next station or do I need to buy $5/gallon gas in Bridgeport, Ca?"

Giulia does not have fuel float(s). She has electronic sensors.
Giulia also has a complex shape fuel tank and evidence has it that there is no compensation for the shape of the tank.

I made some measurements of the fuel sensor output while I added 1/2 gallon at a time to the car and got very confusing results. I'll process the measurements later but one thing that was really obvious is that the output has a considerable amount of hysteresis as I had to add quite a bit of gas before the reading changed at all. I presume the hysteresis is there to mask apparent fuel level changes when the car is on a slope or accelerating.
 
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