Winterbagoal
2018 Winnebago Navion 24V on a 2017 Cab Chassis
Yes, but is it any more accurate than our "dinky" ones?
What should the RPM's be at 70 mph
- Thread starter Michiganmike
- Start date
sailquik
Well-known member
Winterbagoal;
Actually all Sprinter fuel gauges are reasonably accurate, once you figure out the
idiosyncrasies of how they work, but yes the NCV3 fuel gauges are pretty accurate.
The low fuel light is at 25% of fuel left in the tank (NCV3) and that leaves you with
25 liters in a 100 liter tank (6.6043 US Gallons).
But the environmental/terrain/driving factors that affect fuel mileage cause the # of miles
you can go on that 25 liters (6.6043 US Gallons) to vary significantly.
Headwinds can drop your MPG by as much as 25% (depends somewhat on the speed you
choose to drive) so if you are getting 23 mpg=151.9 miles.
If you are getting 19 mpg (pretty common for moderately loaded NCV3 3.0 liter V6/5 speeds)
you can only go 125.5 miles.
If you have a heavily loaded Sprinter or a Sprinter Based RV that's only getting 15 mpg the
distance you can travel after the low fuel light is only 99 miles.
So, the large variation is probably not "inaccuracy" in your fuel gauge but rather the current
MPG you are getting.
Caveat here: Do NOT use the above mileage figures because running a CRD turbodiesel out of
fuel can have serious consequences with fuel systems components.
Hope this helps,
Roger
Actually all Sprinter fuel gauges are reasonably accurate, once you figure out the
idiosyncrasies of how they work, but yes the NCV3 fuel gauges are pretty accurate.
The low fuel light is at 25% of fuel left in the tank (NCV3) and that leaves you with
25 liters in a 100 liter tank (6.6043 US Gallons).
But the environmental/terrain/driving factors that affect fuel mileage cause the # of miles
you can go on that 25 liters (6.6043 US Gallons) to vary significantly.
Headwinds can drop your MPG by as much as 25% (depends somewhat on the speed you
choose to drive) so if you are getting 23 mpg=151.9 miles.
If you are getting 19 mpg (pretty common for moderately loaded NCV3 3.0 liter V6/5 speeds)
you can only go 125.5 miles.
If you have a heavily loaded Sprinter or a Sprinter Based RV that's only getting 15 mpg the
distance you can travel after the low fuel light is only 99 miles.
So, the large variation is probably not "inaccuracy" in your fuel gauge but rather the current
MPG you are getting.
Caveat here: Do NOT use the above mileage figures because running a CRD turbodiesel out of
fuel can have serious consequences with fuel systems components.
Hope this helps,
Roger
Hello.
2012 Mercedes Sprinter 2500 EXT
5G-Tronic/NAG-1 transmission, stock tire size.
Winterbagoal
2018 Winnebago Navion 24V on a 2017 Cab Chassis
Roger; The "T1N/NCV3 fuel gauge accuracy" comment was intended as facetious, per the emoticon I added to it. Others have commented, yea and nay, about the perceived inaccuracy of the low fuel warning, and I was vaguely referencing that discussion with my comment. Apparently, too vaguely.
sailquik
Well-known member
Michganmike
According to some older calculations I have, your Sprinter OM-642 3.0 liter V6 Engine should be turning 2800 RPM
@ 70 mph in 5th gear (Overdrive) with your 4.182 rear differential ration and 215-85R16 tires.
If you downshift to 4th gear (1:1 ratio) your RPM would increase to ~3300 RPM.
Roger
According to some older calculations I have, your Sprinter OM-642 3.0 liter V6 Engine should be turning 2800 RPM
@ 70 mph in 5th gear (Overdrive) with your 4.182 rear differential ration and 215-85R16 tires.
If you downshift to 4th gear (1:1 ratio) your RPM would increase to ~3300 RPM.
Roger
sailquik
Well-known member
ISS,
Your OEM Build Data Card has been downloaded from the MB Int'l Vehicles Database.
I'd be glad to send it to you if you give me a valid email address to send to.
Click on "sailquik" at the top left corner of this box.
Open the drop down and click on "send email to sailquik"!
I have the VIN # and all I need is a return email address.
Unfortunately the Sprinter-Source server is not robust enough to allow me
to send you multi-page .pdf file.
Regards,
Roger
Your OEM Build Data Card has been downloaded from the MB Int'l Vehicles Database.
I'd be glad to send it to you if you give me a valid email address to send to.
Click on "sailquik" at the top left corner of this box.
Open the drop down and click on "send email to sailquik"!
I have the VIN # and all I need is a return email address.
Unfortunately the Sprinter-Source server is not robust enough to allow me
to send you multi-page .pdf file.
Regards,
Roger
Email sent
sailquik
Well-known member
ISS/All:
Check out this very long thread from several years back on this very subject.
https://sprinter-source.com/forum/showthread.php?t=24859&highlight=rpm+calculations&page=5
It goes on for 48 posts, and the calculations (and calculation spreadsheets) are in there.
The things you need to know to get the best possible accuracy/result:
1/ Tire revolutions per mile (this is available on Tire Rack and the various tire manufacturer's websites).
2/ Your rear differential ratio.
3/ Your final drive ratio (considering that 5th gear is 0.83:1 overdrive) (must be subtracted from your rear differential ratio).
4/ The 5% torque converter slip (it does not lock up 1:1 in 5G-Tronic/NAG-1 transmissions)!
5/ Your actual speed (from a GPS or perhaps a Scan Gauge II) as your speedometer will read a couple (to about +5) mph higher
than your actual speed.
ISS:
OK, now we know you have the middle ratio (3.923:1) of the normal ratios available in USA/CAN Sprinters.
In 5th gear you must reduce that ratio by the 0.83:1 overdrive ratio (5th gear) so actual 5th gear ratio is 3.923 x 0.83= 3.256:1.
If you want the actual 1:1 ratio (through your transmission) you would need to manually downshift to 4th gear.
I'll let you read through the previous link and make your own calculations.
Without an OBD-II device to give you accurate digital RPM (and possibly correct your speedometer) it's going to be very
difficult (and somewhat less than accurate) to assign numbers reading from analog gauges.
And, last but not least, WHY are we calculating all this? What is your desired outcome here?
If you get the Scan Gauge II, you will have all the accurate numbers, but if you really want to get the best
fuel mileage and performance from your Sprinter, set the SGII on % engine Load and drive your Sprinter in a
manner that keeps the % engine load as low as possible as much of the time as possible by manually downshifting
your transmission when needed to keep the % engine load @ < 80% as much of the time as possible.
Hope this helps,
Roger
Check out this very long thread from several years back on this very subject.
https://sprinter-source.com/forum/showthread.php?t=24859&highlight=rpm+calculations&page=5
It goes on for 48 posts, and the calculations (and calculation spreadsheets) are in there.
The things you need to know to get the best possible accuracy/result:
1/ Tire revolutions per mile (this is available on Tire Rack and the various tire manufacturer's websites).
2/ Your rear differential ratio.
3/ Your final drive ratio (considering that 5th gear is 0.83:1 overdrive) (must be subtracted from your rear differential ratio).
4/ The 5% torque converter slip (it does not lock up 1:1 in 5G-Tronic/NAG-1 transmissions)!
5/ Your actual speed (from a GPS or perhaps a Scan Gauge II) as your speedometer will read a couple (to about +5) mph higher
than your actual speed.
ISS:
OK, now we know you have the middle ratio (3.923:1) of the normal ratios available in USA/CAN Sprinters.
In 5th gear you must reduce that ratio by the 0.83:1 overdrive ratio (5th gear) so actual 5th gear ratio is 3.923 x 0.83= 3.256:1.
If you want the actual 1:1 ratio (through your transmission) you would need to manually downshift to 4th gear.
I'll let you read through the previous link and make your own calculations.
Without an OBD-II device to give you accurate digital RPM (and possibly correct your speedometer) it's going to be very
difficult (and somewhat less than accurate) to assign numbers reading from analog gauges.
And, last but not least, WHY are we calculating all this? What is your desired outcome here?
If you get the Scan Gauge II, you will have all the accurate numbers, but if you really want to get the best
fuel mileage and performance from your Sprinter, set the SGII on % engine Load and drive your Sprinter in a
manner that keeps the % engine load as low as possible as much of the time as possible by manually downshifting
your transmission when needed to keep the % engine load @ < 80% as much of the time as possible.
Hope this helps,
Roger
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that is exactly where my 2017 144 is at
Cheyenne
UK 2004 T1N 313CDi
If I read the figures as 53 mph and 2,200 rpm then the algebra is:
2,200 / 53 x 70
So at 70 mph would be approx 2,900 rpm.
But do bear in mind your speedo will likely be over reading by maybe 2 to 3 mph so can you get an accurate speed either from GPS or through CAN with something like a ScanGauge II?
Keith.
trenchmonkey
Member
Sounds like mine...in 4th gear! 2600 in 5th rolling at ~10,800lbs.
whambulance
New member
Just in case anyone finds this useful...
*edit* to be clear, being in the antipodes this is kmh, Not miles. If anyone has a 110mph sprinter, I'd like to see that!
*edit* to be clear, being in the antipodes this is kmh, Not miles. If anyone has a 110mph sprinter, I'd like to see that!
Attachments
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Winterbagoal
2018 Winnebago Navion 24V on a 2017 Cab Chassis
Results from a 2 hour freeway cruise yesterday.
60 MPH = 2200 RPM
65 MPH = 2400 RPM
70 MPH = 2600 RPM.
All results were noted on a relatively flat stretch of roadway, transmission in D, with minimal winds, at an ambient temperature of 44F. 13,000 miles on the engine & drive train. 3.0L V6 w/5 speed auto transmission. Forgot to mention the RV weighed 10,400 lbs.
Fluid temps were 214 EOT, 197 fWT, and 145 TFT for those with SGII real time gauges, for comparison.
60 MPH = 2200 RPM
65 MPH = 2400 RPM
70 MPH = 2600 RPM.
All results were noted on a relatively flat stretch of roadway, transmission in D, with minimal winds, at an ambient temperature of 44F. 13,000 miles on the engine & drive train. 3.0L V6 w/5 speed auto transmission. Forgot to mention the RV weighed 10,400 lbs.
Fluid temps were 214 EOT, 197 fWT, and 145 TFT for those with SGII real time gauges, for comparison.
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Winterbagoal
2018 Winnebago Navion 24V on a 2017 Cab Chassis
Transmission Fluid Temperature.
I added custom ScanGauge II Sprinter gauges earlier this year from info derived from this thread. It may have been one of them, as I believe/seem to recall the SGII doesn't have a generic TFT gauge.
http://www.irv2.com/forums/f280/scan-gauge-2-for-sprinter-374228.html
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D
