Advice needed: Performance/Fuel Economy for T1N 2005 Sprinter

jousterde1

2005 Sprinter Owner
While my 2005 T1N Sprinter now has no mechanical issues (thanks to this forum contributors for advice) my fuel economy does not seem right...

-- Using OBDII tool i see fuel economy at about 11MPG average, empty, state highway driving in TX (mostly 70MPH). Why would it be this low? I have seen feedback from other owners showing as much as 27MPG.

-- Another thing that worries me is is that the van may not be shifting to OD (5th gear in the NAG1 tranny). Engine runs at 3000RPM while driving 70MPH, flat road, empty - that seems too high. I was always told: best not to run diesel engines over 2500RPM for long periods of time. How to tell if it is shifting to OD?
 

220629

Well-known member
While my 2005 T1N Sprinter now has no mechanical issues (thanks to this forum contributors for advice) my fuel economy does not seem right...

-- Using OBDII tool i see fuel economy at about 11MPG average, empty, state highway driving in TX (mostly 70MPH). Why would it be this low? I have seen feedback from other owners showing as much as 27MPG.

-- Another thing that worries me is is that the van may not be shifting to OD (5th gear in the NAG1 tranny). Engine runs at 3000RPM while driving 70MPH, flat road, empty - that seems too high. I was always told: best not to run diesel engines over 2500RPM for long periods of time. How to tell if it is shifting to OD?
OBDII mpg is sometimes hard to calibrate.

It would be good to know what your boost pressures are. You may be in LHM.

The rpm at a given speed depends upon your differential ratio.

My seat of the pants experience with my T1N's is that they will run all day and more at 3000 rpm. Fuel economy is better back in the lower 2000 rpm area though.

I've only seen 27 mpg on my way from Florida City to Marathon FL. Flat and lower speed limits. My mpg driving to Florida from Niagara Falls NY typically ranges 22 - 24 mpg 60 - 70 mph with mountains having an effect.

vic
 
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Cheyenne

UK 2004 T1N 313CDi
-- Using OBDII tool i see fuel economy at about 11MPG average...
OBD tools cannot measure fuel economy, they can only ever estimate it based on a lot of other factors, eg Engine Load, throttle position, Speed, etc, etc. The only way to get an accurate figure is tankful to tankful by brimming the tank.

-- Another thing that worries me is is that the van may not be shifting to OD (5th gear in the NAG1 tranny). Engine runs at 3000RPM while driving 70MPH,
What diff ratio do you have? If you do not know send a PM to 'Sailquik' and ask him to pull your Datacard for you, this will tell you everything about your Sprinter. You can then calculate revs/mile for your tyre size and work gear ratio out from there.

Finally a question, if you knock the gearshifter into 'Manual' does the display on the dash show which gear you are currently in? I only ask as I have a Manual shift gearbox! Or if you get a decent scanner, eg Autel MD802, you can display current gear in live data.

Keith.
 

autostaretx

Erratic Member
What OBDII scanner do you have?
I have a ScanGauge, and it takes a number (at least 3, up to 10) of "fill the tank, tell the ScanGauge how much you bought" cycles to calibrate the fuel usage properly.

I actually *get* (using the manual tank-to-tank method) 16 to 20 mpg in-city, and about 24 mpg highway (long trips)

i have kept paper records of all the fuel that's gone into the tank... the "life average" fuel usage is about 22.5 mpg.
(reflecting the percentage of in-city/highway/mountain roads driving).

I wrote an Excel spreadsheet to cover my 15" wheels' RPM-to-speed regime:

geartable.jpg

Here's the spreadsheet, you can change it to match your tires' rev-per-mile and your rear end ratio:
View attachment gears.zip

On my Sprinter, 3000 rpm in 5th gear would be 76 mph (not per the dashboard, but per the ScanGauge, which is *accurate*)
If i was stuck in 4th, 3000 rpm would only be 63 mph.

--dick
 

jousterde1

2005 Sprinter Owner
Thanks guys. Great advice.

OBDII tool I used is one from Amazon (no name brand) that uses Bluetooth and smartphone. Wasn't expecting accuracy to-the-mile but not that bad. Will use the "fill up and do the math" method :)
BTW, if you buy one of these don't leave it plugged in if the van isn't in use for a few weeks - drains battery significantly.

The display always shows "D" - its automatic transmission in this van. But, looking at geartable from Dick's post I think my dash gauge is bad. The speed is at ~70MPH, not ~63 while at 3000RPM.

The spreadsheet looks awesome - thanks for sharing. Will use it.
 

surlyoldbill

Well-known member
11MPG is about half the average you should be getting. After doing the math with a fill up, if you ARE getting the expected 22-24mpg, then some settings are wrong on the OBD reader. If you've been getting over 500 miles per fill up, you're probably getting the MPG you should. I could sometimes go over 650 miles between fill ups.
 

ECU

2006 T1n 118 Sprinter
Are you dripping fuel out on to the street? You can count the shifts in the transmission. If I have my foot in it, I think mine will stay in 4th well in to sixty.
Also there are a two different rear end ratios. information is in your vin number as to this stuff.
 

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