Towing RPM

Aqua Puttana

Poly - Thread Finder
I did a couple searches and didn't find anything regarding this, but searches are a crap shoot for me sometimes.

I've towed my boat a couple times now. About 2800# all up. It tows fine with the Sprinter. I find that the engine seems happiest around 2100 to 2400 rpm with the additional load, but seems to lug a bit below 2000. Not a hard and fast rule, though it generally applies. I figure using the gearbox within reason to keep rpm's up is not a bad thing. Have others found this true while towing or am I feeling things wrong because this is my first diesel?
 

Don Horner

2012 Unity IB
I tow several different rigs, from a pontoon boat to a car to a tandem axle trailer with a diesel tractor tractor to a closed cargo trailer to a hydraulic dump trailer loaded with mulch. The weights vary from 2000 to 5000 lbs. I let the transmission do it's own thing. I find it takes a little longer, and a delicate touch on the throttle pedal, to get it to settle into 5th gear. For me, that's usually around 55 mph and somewhere between 200 and 2100 rpm. If I go slower, it tends to shift down on it's own. I don't let it lug -- if it doesn't shift down, I pop it into 4th if the RPMs drop below 2000. However, I have only had to do that rarely.

It's a drastic difference between it and my previous highway hauler, which was a Ford WindStar, rated to pull a trailer up to 3000 lbs. It had an overdrive tranny, and I made the mistake of pulling my 6' x 12 closed cargo trailer in overdrive, at highway speeds. After about 4 hours, the tranny overheated and I almost lost it -- I managed to get some proper fluid in it as soon as I noticed it smoking. After that, I always towed with the overdrive locked out, which correspondingly dropped my fuel mileage to about 10 mpg when towing.

The Sprinter does drop to somewhere between 17 mpg and 19 mpg, depending on what I am towing -- my highway mileage when not towing tends to be in the 23-25 mpg range, and city driving produces about 20-21 mpg. The towing mileage doesn't vary much between city and highway -- it seems to be very sensitive to the amount of weight it is pulling.
 

Aqua Puttana

Poly - Thread Finder
Thanks for the reply and info.
I tow several different rigs, from a pontoon boat to a car to a tandem axle trailer with a diesel tractor tractor to a closed cargo trailer to a hydraulic dump trailer loaded with mulch. The weights vary from 2000 to 5000 lbs. I let the transmission do it's own thing. I find it takes a little longer, and a delicate touch on the throttle pedal, to get it to settle into 5th gear. For me, that's usually around 55 mph and somewhere between 200 and 2100 rpm. If I go slower, it tends to shift down on it's own. I don't let it lug -- if it doesn't shift down, I pop it into 4th if the RPMs drop below 2000. However, I have only had to do that rarely.

It's a drastic difference between it and my previous highway hauler, which was a Ford WindStar, rated to pull a trailer up to 3000 lbs. It had an overdrive tranny, and I made the mistake of pulling my 6' x 12 closed cargo trailer in overdrive, at highway speeds. After about 4 hours, the tranny overheated and I almost lost it -- I managed to get some proper fluid in it as soon as I noticed it smoking. After that, I always towed with the overdrive locked out, which correspondingly dropped my fuel mileage to about 10 mpg when towing.

The Sprinter does drop to somewhere between 17 mpg and 19 mpg, depending on what I am towing -- my highway mileage when not towing tends to be in the 23-25 mpg range, and city driving produces about 20-21 mpg. The towing mileage doesn't vary much between city and highway -- it seems to be very sensitive to the amount of weight it is pulling.
 

Aqua Puttana

Poly - Thread Finder
I figured this additional info from http://www.sprinter-source.com/forum/showthread.php?t=4535 would be better here to find if searching. Hope this helps.

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Sailquik,
I agree with what you're saying, but I haven't invested in a Scangage II.

I posted this a while ago

http://www.sprinter-source.com/forum...ead.php?t=3547

It didn't generate much discussion, but I did get a good response from one person with more experience than I have. Towing my 2800#'s or so I don't find the tranny shifts down soon enough for my liking.

I personally think the USA/Canada RV conversion Sprinters may see some of the toughest service of any Sprinters around. They are generally just so loaded with doo-dads. I also think many RV'ers (not just Sprinter RV'ers) treat/drive their vehicles more like daily drivers than the heavily loaded vehicles they are. Daily driver people don't usually watch a temperature gauge and slow down if it rises. That doesn't help the situation.

Flame away if anyone chooses, but I said "many" and it is totally just my biased very subjective opinion. Hope this doesn't hurt.
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Hi Aqua Puttana,
I saw your prevoous thread a while back, but I wasn't "up to speed" enough on the Sprinter and
the ScanGage at that time.
The reason I asked this question was to alert anyone with a Sprinter that's carrying any sort of load
that they probably have no idea how hard they are working (perhaps straining is a better term) their Sprinter
if they don't have a ScanGage II or something similar to give them "the rest of the story".
I think you are correct, they drive it just like a car....and figure the DC/MB engineers have it all figured
out. The GAVW on my '06 3500 SHC 158" WB high roof is 9,990lbs.
Unfortunately, putting a heavy RV body on a Sprinter and then filling it with all the "goodies" some
folks need to go "RV'ing" probalby puts the GVW well above what the engineers had in mind.
Add a trailer over about 1500# GVW (or a trailer that creates a lot of wind resistance like mine) and
you can very quickly find the engine at near 100% load quite a bit of the time.
This is OK, if you have an understanding of small Turbodiesels...and get something like a ScanGage II so you can
tell what the loading is, what the temps (various places with sensors) are, and you can take steps to
drive your Sprinter more economically and lighten up on the drive train whenever possible.
You are running your Sprinter in the 2100-2400 rpm range pulling your 2800 lb. boat (is that the weight
of just the boat or is that GVW of the board and trailer?).....Right?.
My cargo trailer weighs about 1k lbs. more and I've found that I can drop the LOD (% engine loading) by
10 to 15% with a big improvement in fuel comsumption (12.5 mpg vs 15-17 mpg) by shifting down into
a lower gear at 2400 rpm.
I do not (unless I'm not towing or it's an emergency and I don't have time to shift down) stomp the accellerator
pedal to have the auto trans drop down a gear.
I shift it down manually @ 2400 RPM in top gear, and the engine revs to about 3200 rpm in 4th gear.
This drops the (LOD) by as much as 15% and raises the MPG from < 5 to 10-12 mpg.
I have my ScanGage II set to read:
Upper LH= Speed (MPH) Upper RH= LOD (% engine loading ....0-99%)
Lower LH= RPM (Engine Speed) Lower RH= MPG (constantly changes as you apply more or less accelerator)
With these readings, I can monitor what the engine is doing and where to downshift/upshift to get the least
engine load and the max. fuel mileage.

There are quite a few other parameters you can monitor, but these seem to work the best for me.
I've checked the Speed readout wth as many as 3 GPS units running at the same time and the ScanGage "MPH"
readout is right on with the GPS (the ScanGage II reads only full 1 mph changes, the GPS units all read to 1/10 mph).
This corrects the 2-3 mph "error" that DC built into the Sprinter to keep you from getting a ticket.

My guess would be that if you put in a ScanGage II you would find that you are running at or near
99% at anything below 2400 RPM when towing your boat.
Also without the LOD reading, you let the Sprinter shift up itself, but nearly any time you accellerate
(even slowly from a stop sign or red light) you will find that you push the accelerator much too far down
and the LOD goes to 99% (the Max it can read) and stays at 99% until the van gets fully up to speed.
You are wasting alot of fuel this way.
I have found that by easing off the accellerator at around 85-90% load I get up to speed just as fast
(sometimes faster as the van upshifts at a lower RPM when the LOD is < 90%) but uses far less
fuel.
No, I do not have any interest in the manufacture/sales/promotion of the ScanGage II!
If they sell 1 million ScanGages, or 2 Scangages my cost was still about $125.00 and my profit
(other than savings on fuel and maintenance) is zilch/zero.
I just feel that it's a Sprinter driver's "best friend" as it allows you to keep everything in a
range that gives you the best performance...the best economy....and the best longevity.
My guess is that most Sprinter drivers without a ScanGage II (or something similar) are wasting
enough fuel that the addition of a ScanGage will allow them to recover the $125 cost in 6 months
to a year while at the same time "teaching them" more efficient and less damaging (to the Sprinter Drive
train) driving habits.
Roger
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Sailquik,
It seems you've been learning quite a bit watching the Scangage II. Not being a gadget person I wasn't inclined to spend the money to replace my generic code reader, but maybe it should go on my Christmas wish list.

Glad to hear that you think my "feel" of the Sprinter shifting while towing is not far off base. (My Grandfather's quip was, "I met a really intelligent guy the other day, he agreed with most everything I said.")

My J/22 sailboat class weight is 858 kg (about 1890#) with 13 kg corrector weight. I've always figured about 900# for trailer and gear not allowed in the class weight. All up boat/trailer may really be closer to 3000#. Generally 2 or 3 people travel in the van, some tools, spare race and camping stuff for staying at the regatta. Let's say 1200# in the van. Total trailer and stuff probably 4200#. Maybe even more, the weight added when you camp or travel goes up pretty quickly.

Do you have 15 or 16 inch wheels? My 2004 Low roof runs 16". That will effect your RPM comments if someone applies your suggestions.

Thanks for the detailed input and reply. vic
 
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