AlphaOBD and DTE correction for 51 gal Tank Mod

[6thGenMariner]

I thought I'd update my progress so far. I've had the 52 gallon Titan installed for about 6 weeks now and have run a couple of tanks through it. I filled up today and decided to give AlfaOBD a try.
I changed "VehConfig 3: Fuel Capacity (36-290L)" from 117 to 194 Liters. No other changes were made. DTE increased to 883 miles and the gauge stayed on Full. I'll run through this tank and see how the gauge responds, but I'm going to take the win on the DTE.
View attachment 524427View attachment 524428

I’ve got the 52 gal Titan that came on my new to me truck. The capacity was already changed so when the tank is full it’ll show the 800 +/- DTE. The problem is same as you state that the top 10+ gallons is above Full. This causes the whole scale to skew. It’ll read 800 miles until I burn off 10-15 gallons and then finally the needle and the DTE start dropping but by then it should be reading 600 and not 799. The DTE will work its way back to correct by the end of the tank so it’s useless information for 45 gallons of driving.

Someone else posted this setting that popped up in AlfaObd

Fuel Tank 1 Calibration, Full Datum for Fuel Voltage 1: 0

Fuel Tank 1 Calibration, 3/4 datum for Fuel Voltage 1:0.000

Fuel Tank 1 Calibration, 1/2 datum for Fuel Voltage 1:0.000

Fuel Tank 1 Calibration, 1/4 datum for Fuel Voltage 1:0.000

Fuel Tank 1 Calibration, LFW datum for Fuel Voltage 1:0.000

Fuel Tank 1 Calibration, Empty datum for Fuel Voltage 1:0.000


I’m waiting on my bypass cable and will try to scale the tank starting from when the gauge is at its mechanical max and accurate gallons reading down to empty. So it’ll be set for something like 40 gallons. At least it’ll be accurate for the 40 gallons remaining instead of accurate for the last 4 gallons remaining.

 

[RedSRT4Me]

I'm about to try this myself on my '22 2500 CCSB (but my expectations are very low). I installed the Titan 52 gallon tank last weekend.

On my first fill-up with the Titan installed I used HPTuners to read the fuel level sending unit voltage as I filled, taking readings every 5 gallons at the pump. At 40 gallons the sending unit voltage stopped changing. I believe it is at it's mechanical limit at that point. The Titan tank is significantly taller than the factory tank and the sending unit just isn't designed for that extra height.

I made this chart up to show the sending unit voltage as I filled and compare gauge readings to actual fuel level. Tank geometry really screws with the readings. Between 15-20 gallons gauge goes from 5/16 to 5/8 of a tank.

View attachment 521886

I would assume that this will be the same (or close) for anyone going from the 31 to 52 gallon tank. This picture shows the two tanks side by side, you can see how deep the sending unit is recessed in the new tank. I don't know of any way to make the gauge read correctly, all the programming in the world can't change the physical limitations of the sending unit.

View attachment 521887

At first I thought the voltage would have to be re-scaled however it appears as long as the sensor can read below .61 then additional values need to be input for 40+ gallons.

If that is not possible then the fuel level sensor would have to be rescaled.

 

[EveryoneIsAnother]

I’ve got the 52 gal Titan that came on my new to me truck. The capacity was already changed so when the tank is full it’ll show the 800 +/- DTE. The problem is same as you state that the top 10+ gallons is above Full. This causes the whole scale to skew. It’ll read 800 miles until I burn off 10-15 gallons and then finally the needle and the DTE start dropping but by then it should be reading 600 and not 799. The DTE will work its way back to correct by the end of the tank so it’s useless information for 45 gallons of driving.

Someone else posted this setting that popped up in AlfaObd

Fuel Tank 1 Calibration, Full Datum for Fuel Voltage 1: 0

Fuel Tank 1 Calibration, 3/4 datum for Fuel Voltage 1:0.000

Fuel Tank 1 Calibration, 1/2 datum for Fuel Voltage 1:0.000

Fuel Tank 1 Calibration, 1/4 datum for Fuel Voltage 1:0.000

Fuel Tank 1 Calibration, LFW datum for Fuel Voltage 1:0.000

Fuel Tank 1 Calibration, Empty datum for Fuel Voltage 1:0.000


I’m waiting on my bypass cable and will try to scale the tank starting from when the gauge is at its mechanical max and accurate gallons reading down to empty. So it’ll be set for something like 40 gallons. At least it’ll be accurate for the 40 gallons remaining instead of accurate for the last 4 gallons remaining.

@6thGenMariner Did you ever get your DTE sorted? I just installed the new 55 gallon S&B in my 2024 Mega Cab 3500 and was considering getting the security bypass cable and AlfaOBD to adjust the fuel capacity settings. I was curious if you had any luck doing the same?

 

[bluewater360]

I too am struggling with correcting fuel gauge and DTE using ALFAOBD and SGW bypass cable and OBDLINK MX+. I have installed the s&B 60 gal tank from stock 32 gal in my 2018 ram 3500 dually. If I use the 227 litter entry tank guage goes to 1/2 full. If I leave it set for the 32 gal tank it's past full. DTE won't go past 599.

 

[EveryoneIsAnother]

@bluewater360 I've ordered my security bypass cable and will be attempting the DTE capacity update in about 2-3 weeks.

Everything I’ve read states the DTE adjustment never works if capacity is set above 194L, so I would try that number or one below it.

But here’s the critical issue: I thought about this carefully through the lens of an engineer, and I believe the most correct capacity to specify is strictly the amount of capacity that the factory fuel sensor has access to measure. In all after market tanks, that’s going to be significantly less than the tank’s full capacity. For example, a 60 gallon tank might only expose the sensor to be able to measure 46-50 gallons of liquid volume.

For example, I’m still working on the calculations, but my 55 gallon S&B tank only exposes the factory fuel sensor to about 40-45 gallons of fuel. Therefore, as soon as I get my calculations dialed in, I’ll likely try to set my capacity to around 151-177 liters. Setting this correctly would enable the DTE calculation to be linearly accurate during the range of travel of the factory sensor from Full to Empty. However, the top 8-15 gallons wouldn’t be counted because to attempt to count those unmeasurable gallons would skew the DTE count and make the range fall in a nonlinear fashion even during linear consumption.

Bottom line: set your capacity to be whatever the true sensor-measurable capacity of the tank is (in terms of what the sensor can “see”). For your tank, I would imagine that’s no more than about 189 liters or so—you’ll need to do some trial and error sleuthing over several fill-ups, and/or contact the tank manufacturer, to find the exact amount of fuel that tank exposes to the factory measurement device.

 

[18CrewDually]

@bluewater360 I've ordered my security bypass cable and will be attempting the DTE capacity update in about 2-3 weeks.

Everything I’ve read states the DTE adjustment never works if capacity is set above 194L, so I would try that number or one below it.

But here’s the critical issue: I thought about this carefully through the lens of an engineer, and I believe the most correct capacity to specify is strictly the amount of capacity that the factory fuel sensor has access to measure. In all after market tanks, that’s going to be significantly less than the tank’s full capacity. For example, a 60 gallon tank might only expose the sensor to be able to measure 46-50 gallons of liquid volume.

For example, I’m still working on the calculations, but my 55 gallon S&B tank only exposes the factory fuel sensor to about 40-45 gallons of fuel. Therefore, as soon as I get my calculations dialed in, I’ll likely try to set my capacity to around 151-177 liters. Setting this correctly would enable the DTE calculation to be linearly accurate during the range of travel of the factory sensor from Full to Empty. However, the top 8-15 gallons wouldn’t be counted because to attempt to count those unmeasurable gallons would skew the DTE count and make the range fall in a nonlinear fashion even during linear consumption.

Bottom line: set your capacity to be whatever the true sensor-measurable capacity of the tank is (in terms of what the sensor can “see”). For your tank, I would imagine that’s no more than about 189 liters or so—you’ll need to do some trial and error sleuthing over several fill-ups, and/or contact the tank manufacturer, to find the exact amount of fuel that tank exposes to the factory measurement device.

The sensor can only read and adjust for Z axis (vertical). It has no way of reporting the increased X & Y axis which is most commonly increased on aftermarket high capacity tanks. That's why S&B tells you in small print you will NOT be able to ever adjust for that.