Just bought a 2006 T1N Free Spirit with 2.7 litre turbo diesel and 5-speed tranny. Does anybody have recommendations on max/minimum at which to shift gears? For example, it "seems right" to shift down into 4th about 2200 RPM, and then back into 5th at 3000 RPM. Any thoughts?
Welcome! I think you're pretty close. There are threads on the forum discussing this, and the experts use aftermarket instrumentation (eg. ScanGauge) that shows load percentage. I believe they've determined that the efficiency sweet spot for our 5cyl. turbo diesel is around 2700 RPM. I shift around the same numbers you're describing, drive like an old man with an egg between his foot and the gas pedal, and everything seems to work out pretty well.
We bought ours used with about 20,000 miles, at about 65,000 now. Love it, and no significant issues.
You can perhaps figure things out by ear and the seat of your pants, but nothing but a Scan Gauge II or similar OBD-II powered performance monitoring device will give you the window into your Sprinters engine management systems.
With the info from a SG II (or similar) you can see, in real time, what the most important PIDs (Parameter Identification codes) are doing.
Your engine management systems are constantly making changes to your fueling rate/ your turbo MAP/Boost pressure in response the primary and most important PID which is the % engine Load.
Actually you may want to downshift slighty sooner (2400 RPM should be about your minimum RPM when pulling hard) and carry it a little higher to around 3150-3200 RPM where your Sprinter OM-647 makes it's best power and gives you overall the best fuel economy and the best performance.
< 2400 RPM and it's lugging a little and not making much power (and probably over fueling if you have the normal almost refuses to auto downshift 5G-Tronic/NAG-1 5 speed transmission).
With the 0.83 : 1 5th gear ratio in the 5G-Tronic/NAG-1 a manual downshift only increases the RPM by ~500 RPM.
So a manual downshift down from 5th gear @ 2400 to 4th gear will push your RPM up to 2900 which is right in the most powerful/
most economical (when loaded and pulling hard) RPM range.
So the SG II will show you that you are at 100% engine load for your current RPM (99% actually as it's only a 2 digit PID).
Whenever you exceed ~75% or > Load your engine is trying to make more power, but it's maxed out on fuel flow and boost.
So, tap the shift lever to the left and you can reduce the % LOD/MAP pressure/GPH fuel flow/ and most likely the increasing
engine coolant temperature.
Without some sort of performance monitoring gauge package you will never know when you max out everything until the speed
and RPM begin to decrease.
By that time you have over fueled/possibly over boosted/ and definitely increased the coolant temp and it's a little late
to make the manual downshift as you would have to slow down and downshift twice to 3rd gear to really see a difference
in the % load value.
Hope this helps,
I like Roger's approach and agree that it is difficult to know when to downshift without some sort of feedback over and above what is provided OEM. I use a mechanical boost pressure gauge. It isn't as fancy as a performance monitor, but it works for me. I was able to put together my mechanical boost gauge very inexpensively. The performance monitor units are so inexpensive and easy to use that for most owners that makes the most sense.
More like Tinman describes, I downshift more when towing than at other times. If I see a long hill ahead I will downshift. If the boost pressure stays up at 20 psi (approx. 34 MAP) for any length of time I will downshift. I also watch the temperature gauge. Periods of seeing 215F is not unusual for my T1N when towing.
Turbos have been used for many years on many engines to increase horsepower. I don't believe that the turbo pumping more air into the engine is always a bad thing. It is part of the overall design. For that reason and some others, I am a little less aggressive with my shifting. That said, in my experience, I still believe that operator intervention is often needed with heavier loaded T1N Sprinters.
To shorten Roger and Vic's answers:
(a) buy a ScanGauge (or DashDaq or UltraGauge or use Torque on a smartphone (requires bluetooth OBD dongle))
(b) set one readout to LOD (%load), another to MPG
(d) when you notice the LOD going much above 70, downshift (note improvement in MPG )
(e) when the LOD drops below 65, consider upshifting (change in MPG will be your validation)
(f) for both (d) and (e), look at the road ahead to see if changes are needed (is the hill still going up? have we crested the ridge?)
--dick (who has to admit to occasionally forgetting to shift back to "D" after a long hill of downshifted engine braking)
p.s. extra tip: US Sprinters have a built-in upper speed limit of 82 mph (adjustable (lower) by dealer or ECM firmware change(up)).
Be aware of it when trying to pass trucks on narrow roads in Nevada....
I would also recommend getting the scan gauge II, I use mine every day. I run a small 118"wb Wagon (aka Passenger)as a daily driver and Daddy bus. I also live on a steep hill, one of the turns going onto my hill triggers my ASR (anti Skid) once or twice a week, and I'm working the turn / transition from steep to steeper in 1st gear, and playing gas pedal feather foot. I use my scan gauge II for climbing every hill, monitor on my commute and on any hwy trip. I work the power band like Sailquick (aka Roger) outlines. Got my scan gauge II on line via Auto Zone, they had a 20% off coupon deal. It is on target for a driving devise, to aid in economy.
One question, I have for all parties, on a T1N, mine is an OM612, max RPM. I do hit 3400 every once and awhile when pushing it, not always Mr feather foot.
Also, just filled up yesterday, $2.45 gallon, B5 Bio (Interstate and Killingsworth 76 station, Portland OR) good price. Ran 576.2 miles on 26.767 gallons = 21.52 mpg mixed with two beach trips, and commuting 10.5 miles each way to work.