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'06 sprinter
02-20-2011, 12:17 PM
i have a '10 on the highway say i set the cruise control to 75 and hit a few hills the mph will keep dropping without downshifting, if i step on the gas it will downshift and hold the lower gear till the cruising speed is back to 75 and then upshift. it will not do this with cruise control on down to 60mph i havent let it slow down any more than that because even 75 is way to slow to be driving on the highways by me. is this somekind of programming issue or is this normal? i have a 3500 high roof thats loaded

mean_in_green
02-20-2011, 12:28 PM
What engine / body variant is it and what final drive ratio does it have? What's your kerbweight?

"...because even 75 is way to slow..."

If it's big body with modest power and your kerbweight is high it could just be that's as fast as it goes.

Reads as though you like to "make good progress"?

Don't take it the wrong way but a big loaded van can get messy pretty quickly should things take a turn for the unexpected. ESP is good but it can't overcome the laws of physics or driver error.

'06 sprinter
02-20-2011, 01:04 PM
2010 us sprinter 145" high roof 3500. the van has no problem getting back up to 75 once it down shifts i just seams the cruise control will never downshift out of 5th gear on the highway no matter how much it slows down from 75

sailquik
02-20-2011, 03:54 PM
Hi '06 Sprinter;
You are possibly doing some harm to your Sprinter by letting it "lug down" in 5th gear overdrive.
If you had a ScanGauge II and set it to read the % of engine Load (LOD on the SGII) you could watch as the following occurs using your scenario.
1/ On a flat road (no headwinds) you speedometer would read 75 mph (with the OEM/stock 2010 tires ...Continental Vanco 4 Season 215/85R16..). Your ScanGauge II Speed would be 2-3 mph slower (say 72 mph) and your actual GPS "speed over the ground") would be 72 mph.
At this speed on a flat road with no headwinds the LOD reading on the SGII will be in the 55-62% range. Add headwinds and it can go up to 70%.
2/ As you start up a grade (even a very slight 1-2% gradient) the % of Load (LOD) reading will increase as long as you stay in 5th gear (Overdrive 0.83:1 ratio) and will very quickly increase to 99% (the max a 2 digit readout can show).
So, now you are running your OM-642 V6 3.0 liter Bluetech Sprinter as hard as it can pull.
Your Manifold Absolute Pressure (MAP on the SGII) will be maxed out at 35+ PSIA!
You Engine Control Module (ECM) will have increased the fuel pressure and injector duration to the absolute maximum.
Your engine is completely maxed out, and due to the gradient, and cruise control, the entire drive train will stay at maximum power/minimum fuel economy/maximum potential for the engine to harm itself.
The engine coolant temperature will increase until the big viscous clutch fan kicks on (reducing the horsepower available at the back axle by some small percentage as it takes some power to turn that fan and pull significantly more air through the radiator).
The transmission temperature will increase as the coolant temp rises (there is a "cooling coil" the the bottom of your coolant radiator that keeps the trans. temp similar to the coolant temp.)
Engine RPM at the start of this increase (72 mph on your speedometer) will be around 3000-3200 rpm ( I have a 2010 3500 MB Sprinter so I will check the next time I'm on a road where I can go 75 mph)!
3/ If you disengage your cruise control, and really "floorboard" your accelerator pedal, the transmission may downshift to 4th gear (1:1 ratio through the transmission...so no longer in "overdrive").
When your transmission downshifts to 4th gear your RPMS will increase by 500 RPM +-50 RPM.
4/ If you leave your cruise control engaged, the % of Load (LOD) will stay maxed out at 99% and your engine/transmission/rear axle will be doing all they can do (maxed out power/max load on the transmission/max load on the rear axle) for as long as you continue to climb any gradient. You will be getting the minimum possible fuel mileage!
5/ Your only option in this situation is to manually downshift to 4th gear to reduce the % LOD.
As long as your tachometer reads < 3500 RPM, you are safe in simply tapping the shift lever to the left (toward your right leg in a LH driver position USA vehicle) and manually shifting the
trans. down to 4th gear.
NOTE: You cannot overrev the engine as the ECM and Transmission Control Module (TCM) will not allow you to downshift if it's going to over rev the engine (beyond 4000 RPM in your NCV3 OM-642).
6/ Maximum horsepower in your 2010 NCV3 occurs at 3800 RPM (according to the owners manual and most specification I have seen.

So, get a Scan Gauge II ($130-$160 @ Amazon or Pep Boys) and you can begin to control the %of Load (LOD) and manage your engine and transmission Load to increase your fuel mileage significantly and decrease the amount of time you are "hammering" the drive train at 99% (maxed out).
You will begin to see that the SGII can pay for itself pretty quickly with diesel fuel at nearly $3.50 gallon.

Your Sprinter will last longer and have fewer "issues" with the emissions control equipment.
Your Sprinter will run cooler if you use manual downshifting to keep the LOD down to levels that keep the engine from spending a lot of time at MAXED OUT!
I have suggested to Daimler Vans USA LLC at the highest levels that they consider putting some sort of % of Load readout in these vans as OEM because without some indication of % engine Load, you can "hammer" your Sprinter at absolutely maxed out for long periods of time and never realize you are doing so.
The trans. does not always downshift when you floorboard the accelerator, and it for sure won't downshift itself (automatically) when in cruise control if the grade slowly increases.
A very fast and steep uphill grade will sometimes cause the trans. to downshift (this will surprise you if you aren't expecting it) while in cruise control, but on gradual grades, the engine will max out, the RPMs will drop (so will your speed) until the road flattens out or you "proactively" perform a MANUAL downshift.
Hope this helps,
Roger

itsnaturesway
02-20-2011, 06:09 PM
I always thought you needed to be a rpm miser to increase fuel mileage. I use an Autel gauge in my van, it is a cheap alternative to a scanguage ii.
Will monitor LOD % and see if I can improve mpg using your method.

sailquik
02-20-2011, 07:20 PM
Hi itsnaturesway,
On larger, older diesels (not turbo charged and not electronically controlled) keeping the RPMs
down was for sure the most economical.
With modern small displacement common rail turbo diesels, with everything tied to the ECM "sensing" the % of engine LOD, I'm finding this is no longer the case.
If you can keep the LOD < 60% (or at least 8-10% reduction in LOD) by running higher RPM
I'm finding that I get better mileage, more power, and I'm pretty sure the strain on the drive train is reduced significantly.
I'm finding that in stop and go driving, doing my own manual shifting @ 3000-3200 RPMs can
get me 1-2.5 mpg better mileage (19.5-20.5 mpg) vs letting the TCM make all the shifts at
2400 RPM (17.5-18.5 mpg).
What no one seems to realize, is that when LOD increases, the ECM sees this increase, and tells the turbo actuator to change the variable vane setting to increase the MAP (turbo boost)
and at the same time it increases the amount of fuel to each electronic injector by increasing the duration of each injection cycle.
So, more boost to make more power, and more fuel going in to keep the most efficient and cleanest combustion.
None of this is really controlled by the acellerator pedal when you are in cruise control.
It all happens without the driver realizing anything has changed (maybe the sound of the
engine at higher revs, or the sound of the engine beginning to struggle to maintain speed
as LOD increases).
Same thing can happen when you are "cruising" along trying to maintain a steady speed but
controlling the engine with the accelerator.
If you make no change in the accelerator pedal sensor, but the LOD increases, the boost and amount of fuel can go right up to 100% max HP with no change in the throttle pedal sensor that tells the ECM what speed you want.
I think this results in lots of turbo/fuel/emission systems problems because the engine is not
being allowed to rev up into it's most efficient power mode.
Change the gear ratio with a manual downshift, and everything settles back at least 10-15%.
This reduces both boost and fuel metering.
Each of our vans may be slightly different and the overall max. efficiency equation will change if you add weight, tow a trailer, run into headwinds..... anything that will increase the LOD that the ECM responds to.
It's up to the driver to determine when to downshift, as the MB engineers seem to have really
missed this somehow.
Try it, I can almost guarantee that you will see better fuel mileage and efficiency while reducing the strain on the drive train which will reduce the potential for problems related to running the engine at less than it's most efficient RPM range based on LOD.
Hope this helps,
Roger

slowstride
02-20-2011, 07:56 PM
Using the scangauge set on LOD and MPG, I was surprised to see how 'efficient' 4th gear was for open road use in our Sprinter RV.

5th gear often caused the engine to 'bog down' and the LOD to go to 99 (max). Changing down yields immediate results.

Without the scangauge I had no idea of the load I was putting on the engine. As previously pointed out, the LOD can max out with no change in the throttle position sensor. I also found max load can on quite quickly, with the throttle barely depressed, more a problem of under-revving than over-revving.

Driving by scangauge has been an education.

talkinghorse43
02-20-2011, 07:59 PM
i have a '10 on the highway say i set the cruise control to 75 and hit a few hills the mph will keep dropping without downshifting, if i step on the gas it will downshift and hold the lower gear till the cruising speed is back to 75 and then upshift. it will not do this with cruise control on down to 60mph i havent let it slow down any more than that because even 75 is way to slow to be driving on the highways by me. is this somekind of programming issue or is this normal? i have a 3500 high roof thats loaded


Mine doesn't act that way and the tranny is the same, so I'd say something is wrong. I'd have someone with the right technology look for faults.

sailquik
02-20-2011, 10:06 PM
Hi talkinghorse43,
Having upgraded from a 2006 Dodge T1N 3500 Sprinter (158"wb) to the 2010 Mercedes
NCV3 (144"wb short back) there is a huge difference in how each "system" responds
to the throttle positioner and manual vs TCM downshifting.
I'm reasonably sure there was some difference (probably not as significant or noticeable)
between your 2002 Sprinter and the 2006 3500 I had.
The new NCV3 is very different.
Lot's more available power, much larger tires, perhaps a little lighter in weight.
My '06 easily settled down below 60% LOD in a flat road/no wind situation.
Add weight, or the 4.5k lb trailer and getting down to < 60% LOD in overdrive was
nearly impossible, but downshft to 4th and get the revs up to 2800-3200 and it would
cruise all day at 52-60% LOD.
With the OM-642 V6, I almost never see < 60% LOD in overdrive!
By downshifting, I can cruise along @ 3,000 rpm (62 mph) with the load hovering in the
53-60% range.
The OM-642 NCV3 responds to +- LOD % very differently from the OM-647 and earlier I5
engines.
My OM-647 '06 T1N provided max horsepower @ 3,250 RPM.
The new OM-642 NCV3 puts out max. horsepower @ 3,800 RPM and it will rev to 4,000 RPM
in a hearbeat.
There is a major difference between the Bluetec 2010 and later Sprinters and the earlier
inline models.
Roger

'06 sprinter
02-21-2011, 12:32 AM
That is my point I have never driven a car where cruise control where it lugs overdrive usually the car is overanxious to downshift to the lowest gear possible and accelerate as quick as possible to get to target speed. I know it's bad to lug the motor that's the reason for my post it's not like I have a vehicle from the 70's and a ancient cruise control system

talkinghorse43
02-21-2011, 01:05 AM
That is my point I have never driven a car where cruise control where it lugs overdrive usually the car is overanxious to downshift to the lowest gear possible and accelerate as quick as possible to get to target speed. I know it's bad to lug the motor that's the reason for my post it's not like I have a vehicle from the 70's and a ancient cruise control system

Cruise control is an automatic speed control system. If you have to intervene manually to get it back to the desired speed, then something is wrong.

Aqua Puttana
02-21-2011, 01:18 AM
I've had cruise control systems which were patient to wait for a while if they lost an mph or two on inclines. I've had others that panicked and immediately downshifted, racing the engine if they lost as little as what seemed a 1/2 mph. I don't think they can be perfect in all load, road condition situations.

FWIW. I basically agree with Roger in that for the most part my Sprinter cruise control is reluctant to downshift when it seems to me the engine is lugging a bit. I often downshift manually on inclines to keep the rpm's up.

As an aside, I've had my Sprinter cruise control downshift to slow down to set speed when going down an incline. Kinda surprised me the first time, but pleasantly given the number of police I've seen manning radar guns. I like that feature. YMMV. vic

talkinghorse43
02-21-2011, 01:29 AM
I've had cruise control systems which were patient to wait for a while if they lost an mph or two on inclines. I've had others that panicked and immediately downshifted, racing the engine if they lost as little as what seemed a 1/2 mph. I don't think they can be perfect in all load, road condition situations.

The OP is complaining about drifting down to 60 from 75 - that's 15 mph.

Aqua Puttana
02-21-2011, 01:54 AM
The OP is complaining about drifting down to 60 from 75 - that's 15 mph.
Apparently my attention span is working just as well as his cruise control.

Too bad I don't have a "Thanks :doh: " button for posts. Then again, I'd probably wear it out in short order. :rolleyes: vic

sailquik
02-21-2011, 02:40 AM
All,
The Cruise Control in Sprinters seems very reluctant to downshift.
However, the exact same thing happens if you are not in cruise control
and you encounter an uphill grade.
The "expected" auto downshift, to get the Sprinter in the correct gear to
efficiently go up that grade seems to take forever.
Sometimes it never will downshift until you've gone over the crest of grade and then it just
reduces the LOD as the grade flattens out and the speed will come back up to what
you were doing prior to the hill.
Only problem with this is that the entire time you are pulling up that hill the LOD is maxed
at 99%... the MAP is maxed at 35+ PSIA.... the ECM has opened up the injection cycle to
max so you are force feeding fuel to the engine.... some of this doesnt burn too well as
the revs are not in an effcient range for the grade/load you are pulling.
So, if the grade goes on for 10 minutes, you are running your Sprinter at max everything
for 10 minutes. This is more than likely not very good for the engine and transmission.
Both the engine and transmission will begin to overheat in a few minutes.
Only thing you can do is downshift MANUALLY!
Don't even need to take it out of cruise control. Just tap the shift lever to the left and
it will drop down one gear.
If it's still lugging along at < 2500 RPM, tap it again to go down to 3rd gear and get the
engine turning up in the most efficient RPM range (2800-3250 for T1N Sprinters.... 3000-3800
for NCV3 Sprinters).
It may not be what we think our Sprinters have been engineered to do, but it is what it is
and the only thing you can do is manually downshift.
I've asked dealers and Sprinter technicians about this and no one has a suggested fix.
They say it will downshift if it really needs to do so.
I say I'm hurting it some by waiting way to long to relieve the strain, so when it feels like my
Sprinter is lugging or not happy, I downshift it and it responds very happily every time.
Temps drop, speed comes back up, everything settles out at 10-15% reduced load, MAP reduces 10-12 PSIA, and fuel useage on the scanGauge II (both MPG and GPH) gets significantly better as the injectors are now putting a normal and efficient amount of fuel.
It's the way these vehicles have been engineered, and it's not something the dealers and technicans can do anything to change.
Maybe some of the tuners can change the program some, but I'm unwilling to have my Sprinter "chipped" until well past warranty.
Roger

talkinghorse43
02-21-2011, 02:35 PM
The Cruise Control in Sprinters seems very reluctant to downshift.

Mine must be unusual, because it readily downshifts. After observing its operation over many miles, it seems to me it will downshift the moment it determines that the power available will not be able to drive the road speed to the setpoint. Actually, it doesn't drive it exactly to the setpoint (when climbing hills) as it seems to accept a ~2 mph lower approach as OK. But, I've learned to accept that single imperfection. My wife doesn't drive often, but when she does, she's not as forgiving and is continually raising (uphill) and lowering (downhill) the setpoint for perfection.

'06 sprinter
02-22-2011, 11:54 PM
i know lugging the motor is bad thats why i downshift it manually while going up hills with the cruise control on...my question was if this was normal for the sprinter computer to allow lugging and not downshifting automatically.

Aqua Puttana
02-23-2011, 02:33 AM
...my question was if this was normal for the sprinter computer to allow lugging and not downshifting automatically.

Sorry, I must not have been clear when I replied earlier. My 2004 does not shift down as soon as I think it should. So in my opinion "the Sprinter computer allows lugging and not downshifting automatically", if you're looking for opinion. Apparently TH43 thinks his shifts when it should.

When my 2004 loses a couple miles per hour on an incline I know the turbo is wide open and the engine is working hard so I've learned to downshift before I know that happens. Many people just put the cruise control on and let it do its thing with no problems at all. There are definitely differences in thinking about when it should shift down. vic

sailquik
02-23-2011, 04:17 AM
Hi '06 Sprinter,
Is it normal for Sprinters to "lug down" to below the max. torque RPM spec.?
Well, somone a MB seems to think this is a good idea.
But, the number of blown turbo hoses and turbo hose seals, perhaps some
of the DPF issues, some overheating etc. seems to the the result of
letting an engine that makes great power (for it's relatively small 3.0 liter
displacement) wind down from 2800-3800 (where it's quite efficient and
very peppy for it's size) to <2500 RPMs where it is straining at full bore
(Max. MAP/turbo boost) (Max. fuel flow with the injectors pumping in
every bit of fuel possible).
For a minute or two, or 1/2 a mile or so.... probably not doing too much
damage.
To take on one of the big long grades over the mountains?...... No way!
Just leaving it in cruise control in 5th gear overdrive?....That's crazy,
or a driver who neither understands nor cares about the drive train
in their Sprinter. All of the aforementioned "issues" seem to happen
most often to drivers who believe the salesman and dealers that it's
OK to put a Sprinter in Drive (D); let it shift to 5th gear Overdrive
and push the throttle pedal to the floor. This cannot be good for the
machine!
It may make sense to the MB engineers, and it may be a way to keep the
emissions lower (I'm very doubtful on this), but I'm not going to run my 3.0 V6 this way.
My 2010 has an odd resonance right at 2400 RPM (supposedly max. torque) in 5th gear overdrive.
This resonance drives me a little nuts, so I run faster or downshift manually.
Unfortunately it's right around 60 MPH which is the legal speed on some to the
roads I travel most often.
Roger