Computer?

[Archive]

Just finished fueling my truck. The computer read:
489. 4 miles
16. 4 mpg
2 miles to empty

odometer read 489. 4
tank took 28. 88 gal
calculated mileage from above: 16. 95

Yeah, there is a difference in the mpg from the computer to the calculated mpg, but this ignores completely the 5. 12 gallons, or what is available of it. I don't get it.



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2001 2500 SLT, QC,4X4, AUTO, 3. 54, White/Agate, Camper Special, Trailer Tow w/ Trailer Tow Mirrors, Snow Plow Package, Westin nerf bars, K&N air filter, Rhino lined, clearance lights, fog lights.

 

[Archive]

I think I read in the owners manual that the computer calculated MPG is based on the last 30 gallons of fuel through the system and that the distance to empty is calculated on the last (can't remember the #) miles you have driven and the consumption over those miles. I don't have my truck here at work so I can not look it up.
I have driven past the empty mark on my Dad's 92 Diesel a couple of times, when you hit empty you still had 100 miles to go. I always fill up my 2001 before then to be safe.
Hope I helped.

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01 2500 SLT+ QC LWB 4x4 Auto 3. 54 rear end Forrest Green Sport with all options avail
DC Nerf Bars, DC Grill Gard, DC mud flaps, Line-X bed liner and Leer 160XL Topper
Power Edge equiped. SPA Boost/EGT Gauge on work bench, Injectors, transmission mods and Pyscotty air in planning stages.
Waiting on EGT install to decide on 4" Exhaust.
See My Truck

Dads truck: 98. 5 3500 SLT QC LWB 4x4
Brother Truck: 92 W250 SLT CC LWB 4x4 (Dads old truck)

See 5 Diesels and a Gasser
Winter fun: 2000 Skidoo Summit 700

 

[Archive]

I'm not sure what you mean when you say the computer "ignores" the 5 gallons when calculating mpg. If you're really talking about the mpg, then of course you WANT it to ignore the fuel you DIDN'T burn. And your "computer" mpg wasn't too far from your "calculated mpg. Thus, I take it your biggest concern is more about the fact that the "distance to empty feature read 2 miles when you really could have driven over 75 miles before running out.
I can't prove this, but here's my theory:
#1 Running out of fuel is a BIG BIG deal in a diesel - you don't just put a gallon in the tank and start driving again. Your system may even require the services of a mechanic to get your truck running again.
#2 Fuel gauges are NOT high precision instruments.
#3 Too many people are willing to drive until the needle is on or slightly below empty.
Put these three facts together, and basically what you have is Dodge making a decision to intentionally "fool" you into getting fuel before you run out. If they tried to hit the # exactly, then the law of averages says 50% of the people who run to E would make it to the diesel pump, and the other 50% would run out of fuel on the highway. Guess what? Having 50% of the customers hopping mad because of a minor gauge inaccuracy is unacceptable to Dodge. They would rather have 100% of their customers saying "gee the gauge isn't very accurate" (no big deal) than risk having 50% of their customers so mad they might buy a Ford Powerstroke the next time around!

 

[Archive]

I meant that it appears to ignore the 5 gallons left in the tank. I agree with your theory - I guess they don't trust the average driver.

As this is my second diesel - I also own a f*** PSD - I know that I don't want to run out of fuel myself. Why the PSD? In '94 I needed a diesel immediately to use with a piece of equipment that runs off an engine-driven hydraulic pump, and it was the only one available to me. After 87,000 road miles and an additional 3000 hours of engine time, I cringe every time I start it - will this be the time it fails?.

 

[Archive]

I believe the DTE computer number is based on voltage input from the fuel level sensor to the fuel gage. So, unlike a system where a flow meter is used to gage actual consumption, it provides an approximate figure, based on the float level in the tank.

What I'd like to know is if there is any way to re-calibrate the number for a larger capacity fuel tank? Been thinkin' about doing that. Would be nice to be able to go a couple of weeks without filling up or being able to shop for the best price in a region.


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-Adam
adam_farnham@yahoo.com
'01 2500 ETH DEE, 4wd, 3. 54 X-spin rear, black, with lighting, camper special, snow plow, trailer tow pkgs, SLT group, Walker Airsep and brake controller