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Old 11-19-2017, 05:49 PM   #11
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Default Re: Engine Braking a Sprinter. Does it work?

OK, I give up!
Your Sprinters may all have "engine Braking"..........Mine do not!
In the quote above, I see the important to know/operative words " engine's braking effect".
This does not indicate to me that there is any sort of an engine braking device/system/feature.
Sure I use the "engine's braking effect" to slow down all the time, but there is NO engine brake switch/lever/feature specifically designed to create negative power like in a Jacobs engine brake, or like I had in my Mitsubishi Fuso 4x4 box truck that shut off the
intake air to the engine to develop an actual engine braking mode. In the Mitsu I could flip a switch and the truck rolled free, affected
only by the negative power it took to rotate the crankshaft with no fuel to create power.
If I flipped the switch to "engine braking" I could hear the flapper valve on the intake close each time I lifted off the accelerator, and
feel the effect of true "engine braking".
Also there is another operative phrase in the above quote from the Owners Manual (mine says the same thing, I just checked it).
"you must select shift range 3, 2 or 1 in good time".
To me this means that if you want the maximum engine braking EFFECT you need to anticipate the downgrade
and do your manual shifting earlier rather than after you are already heading down the hill and gaining speed.
Works the same way for manually downshifting when going UP uphill grades.
Anticipate that your engine is going to go to 99% engine load (max sustainable power or beyond sustainable power) to get up the grade and that a manual downshift BEFORE the engine reaches it's max power and starts dropping RPM and MPH will give you better pulling power in the engines most powerful and fuel efficient RPM range (2700-3200 RPM for the OM-642 3.0 liter V6 engine/5G-Tronic-NAG-1 5 speed transmission).
Failure to be pro-active with manual shifting up or down to climb or descend road gradients will cost you in fuel and brake wear (both the pads and
the rotors).
Have it your way.....I'm done with this topic!
Roger
OBTW Just went out to my Sprinter......engine OFF... MAP Reading was 14.4 PSIA.....engine idling MAP reading was 14.3 PSIA.
The Ambient Barometric pressure at the Naval Air Station 1/2 mile from my Sprinter was 29.318 in/HG=14.4 PSIA (Altimeter).
So perhaps a very slight negative pressure @ idle engine speed, but nothing like the negative pressure stated earlier.
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2014 Sprinter 516 series (3500 DRW) 170"/4325 mm wb Hi Top Short Back
OM-651 I4 2.143 liter two stage turbo charged with 36.9 PSIA MAP Limit Valve
7 Speed 7G-Tronic, manually shiftable, automatic transmission.
Suspension Seats, Active Safety Package +, Parktronic, OEM Hitch/wiring
OEM back up camera, Bi Xenon light package, fog lamps, headlight washers.
Had 2006 T1N 3500/158|2010 NCV3 519/3500/144|2011 & 2012 NCV3 519/3500 170

Last edited by sailquik; 11-19-2017 at 09:22 PM.
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Old 11-19-2017, 06:07 PM   #12
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Default Re: Engine Braking a Sprinter. Does it work?

Quote:
Originally Posted by sailquik View Post
OK, I give up!
Your Sprinters may all have "engine Braking"..........Mine do not!
In the quote above, I see the important to know/operative words " engine's braking effect".
This does not indicate to me that there is any sort of an engine braking feature.
Sure I use the "engine's braking effect" to slow down all the time, but there is NO engine brake switch/lever/feature specifically
designed to create negative power like in a Jacobs engine brake, or like I had in my Mitsubishi Fuso 4x4 box truck that shut off the
intake air to the engine to develop an actual engine braking mode. In the Mitsu I could flip a switch and the truck rolled free, affected
only by the negative power it took to rotate the crankshaft with no fuel to create power.
If I flipped the switch to "engine braking" I could hear the flapper valve on the intake close each time I lifted off the accelerator, and
feel the effect of true "engine braking".
Also there is another operative phrase in the above quote from the Owners Manual (mine says the same thing, I just checked it).
"you must select shift range 3, 2 or 1 in good time".
To me this means that if you want the maximum engine braking EFFECT you need to anticipate the downgrade
and do your manual shifting earlier rather than after you are already heading down the hill and gaining speed.
Works the same way for manually downshifting when going UP uphill grades.
Anticipate that your engine is going to go to 99% engine load to get up the grade and that a manual downshift BEFORE the
engine reaches it's max power and starts dropping RPM and MPH will give you better pulling power in the engines most powerful and fuel efficient
RPM range (2700-3200 RPM for the OM-642 3.0 liter V6 engine/5G-Tronic-NAG-1 5 speed transmission).
Failure to be pro-active with manual shifting up or down to climb or descend road gradients will cost you in fuel and brake wear (both the pads and
the rotors).
Have it your way.....I'm done with this topic!
Roger
OBTW Just went out to my Sprinter......engine OFF... MAP Reading was 14.4 PSIA.....engine idling MAP reading was 14.3 PSIA.
The Ambient Barometric pressure at the Naval Air Station 1/2 mile from my Sprinter was 29.318 in/HG=14.4 PSIA (Altimeter).
So perhaps a very slight negative pressure @ idle engine speed, but nothing like the negative pressure stated earlier.
You're the only one I've ever come across that considers all "engine braking" to indicate that there is a jake brake, or some change in internal dynamics for the purpose of braking. Engine braking for passenger vehicles has always meant using the engine as a brake. AKA- leveraging the internal resistance of the motor to slow you down. You've posted this idea that Sprinters don't engine brake enough that it's been referenced multiple times on this forum. I'm guessing by the OP, as well.
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Old 11-19-2017, 06:12 PM   #13
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Default Re: Engine Braking a Sprinter. Does it work?

The classic high vacuum situation, draws lots of oil into the cylinder via worn valve guides. My BMW 2002 never used much oil, but on decel/compression braking would suck large amounts of oil through the guides, leading to big clouds of smoke upon acceleration.


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Old 11-19-2017, 06:53 PM   #14
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Default Re: Engine Braking a Sprinter. Does it work?

Quote:
Originally Posted by Aqua Puttana View Post
... I don't believe that long time periods of no fuel/no power engine braking are good for any engine.
...

vic
In my mind there is a big difference between an engine turning rpm's under power and an engine floating at high(er) rpm's being used to help slow down the vehicle. (Note that I avoided the term engine engine braking.) Under power the fuel is being injected into the cylinder, compression is produced by an explosion, etc. The resulting operation/stresses are different power vs float.

There was a thread here where an engine suffered piston damage. Prior to that failure the engine was used with a lower gear, with engine speed up near 4000 rpm on a long grade to slow down the truck. I believe the long term engine braking operation contributed to that failure.

I have no data. Drive as you feel appropriate.

vic
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Last edited by Aqua Puttana; 11-19-2017 at 07:25 PM.
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Old 11-19-2017, 07:32 PM   #15
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Default Re: Engine Braking a Sprinter. Does it work?

I always thought that this was a major difference for using engine as a brake between gas and diesel, perhaps is no longer valid with diesel pollution system, as well as a key factor for a diesel engine economy. I use the engine to slow down going downhill and it works sufficiently.

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Old 11-19-2017, 09:42 PM   #16
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Default Re: Engine Braking a Sprinter. Does it work?

OK, one last shot at this.
Gasoline engines provide engine braking because when you lift off the accelerator you reduce the air and fuel flow to the engine, and the speed of the vehicle is reduced by the drag of the engine making very little power.
But none of them have an engine brake....not a system....not feature.....not a device.... and all literature/adverts never suggest
that there is any "engine braking".
Conversely, diesel engines are normally categorized by those that offer an engine braking system (either OEM or something purchased in the
aftermarket which turns a non engine braking engine into an engine equipped with an engine braking system) and those diesel
engines that do not offer any specific device or system that develops negative power to act as an "Engine Brake system" feature.
MB/FL/Dodge Sprinters, with OM-612/OM-647/OM-642 5 cylinder and V6 engines fall into the second category.
There is nothing in the literature/adverts/etc on these Common Rail Diesel (CRD) Garrett Turbocharger's VNT (Variable Nozzle Technology)
engines that suggests that they offer any sort of engine braking device/system/ feature.
The Operators Manual suggests that there is some engine braking EFFECT.....but nowhere does it state that there is an engine braking system/
feature or device that can be added to provide positive engine braking beyond the existing engine braking effect.
If you want/need auxiliary braking (in addition to the the 4 wheel ABS equipped disc brakes that work pretty well, you can get a
Telma Retarder system that attaches to the driveshaft and generates a lot of electrical current which bleeds off as heat when the retarder is
engaged.
If Sprinters had some sort of engine braking system.....i"m pretty sure there would be NO Telma Retarders.
Yes, this is semantics, but how often here on this forum has someone gone off the rails about some feature/device/system in Sprinters and all the
newbies (who don't yet know any better) run out buy a Sprinter based on that feature/device/system only to find that it either does not exist at all,
cannot be imported into the USA (or other countries with emissions standards) or can only be special ordered in certain geographic regions.
In order to be CRYSTAL CLEAR.....I continue to hold the opinion that Sprinters do not have any actual engine braking feature/device/system.
If I take my foot off the accelerator does my Sprinter slow down due to the engine no longer producing any power because there is no fuel
to burn or boost pressure from the turbocharger to force air into the engine.....why yes, it does, but this is NOT an engine brake system
that specifically develops negative power to slow the vehicle.
Roger
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2014 Sprinter 516 series (3500 DRW) 170"/4325 mm wb Hi Top Short Back
OM-651 I4 2.143 liter two stage turbo charged with 36.9 PSIA MAP Limit Valve
7 Speed 7G-Tronic, manually shiftable, automatic transmission.
Suspension Seats, Active Safety Package +, Parktronic, OEM Hitch/wiring
OEM back up camera, Bi Xenon light package, fog lamps, headlight washers.
Had 2006 T1N 3500/158|2010 NCV3 519/3500/144|2011 & 2012 NCV3 519/3500 170

Last edited by sailquik; 11-19-2017 at 10:03 PM.
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Old 11-19-2017, 10:32 PM   #17
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Default Re: Engine Braking a Sprinter. Does it work?

Roger,
Keeping with your logic.

There is no engine braking system.

Downshifting every Sprinter transmission does cause the engine to be more efficient at slowing the vehicle... for whatever reasons.

Quote:
Originally Posted by sailquik View Post
...
Yes, this is semantics, but how often here on this forum has someone gone off the rails about some feature/device/system in Sprinters
...
Often when you explain about operating a Sprinter and using a performance monitor device (eg. - ScangaugeII) you make it sound like downshifting a Sprinter has no braking effect.

Quote:
Originally Posted by sailquik View Post
ptgman,
...
If you manually downshift (within the range the TCM programming will allow), you simply spin the engine faster.
There is no engine braking beyond what ever it takes to spin the engine, making no power (either positive (with fuel) or negative (no fuel).
There is no change in the camshaft timing (like big trucks with Jacobs Brake systems that make huge amounts of "negative"/braking power by injecting the fuel much earlier before the pistons reach TDC causing the engine to develop significant engine braking negative horsepower.
Sprinters have no such feature....they make power when you add fuel (with the accelerator) and they spin freely, making no power when you lift off the accelerator.
...
Roger
That could be confusing to a newbie.


So.

Quote:
Originally Posted by sailquik View Post
In order to be CRYSTAL CLEAR.....
Even without an added/designed engine braking system, downshifting a Sprinter transmission on a long downhill grade will help to slow the truck and will help to avoid overheating the brakes.

This is almost as good as an oil thread.

vic
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16 ounces of unnecessary prevention can be worth a pound of manure.

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Old 11-19-2017, 11:04 PM   #18
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Default Re: Engine Braking a Sprinter. Does it work?

OK..........we need a test. anyone live on or near a big long hill ?

Test run 1

Run down the hill coasting in neutral...........note the speed at 10 second intervals. might take some BALLS not to brake depending on the hill.

Test run 2

run down the hill coasting in drive..............note the speed at 10 second intervals

Test run 3

Run the hill coasting but manual shifting to a lower gear ..............note the speed at 10 second intervals

report your findings .............my guess run 3 will be slower than run 1.

NOTE even a small short hill may give valid data points to conclude if engine braking exists with minimal risks. Reality even a block long gentle hill would be more than adequate. Where is myth busters when you need them ?
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Old 11-20-2017, 12:02 AM   #19
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Default Re: Engine Braking a Sprinter. Does it work?

Guys/gals;
I never said that Sprinters have NO Engine Braking EFFECT.
I use the engine braking EFFECT every day, even where there are no downhill gradients.
Lifting your foot off the accelerator pedal so the TPS (Throttle Position Sensor) sends zero (0) % to the ECM, the fuel flow (GPH) is at 0.0 GPH indicating
that no fuel is being fed to the engine by the fuel injectors/fuel injection system, and the turbocharger output (MAP in PSIA here as that's what the ECM uses) is at <~14.7 PSIA (29.921 in/HG atmospheric pressure at sea level) indicating the turbocharger is producing no increase in boost pressure into the intake manifold > the ambient local atmospheric pressure, means the engine is just spinning.
Of course there is a certain amount of rotational resistance or drag slowing down the 6,000-11,000 lb. vehicle.
This is for sure Engine Braking Effect, and we all use it every time we lift our right foot off the throttle.
But it is NOT an engine brake!....
Ever been beside a big dump truck or semi tractor when they need to slow down in a hurry...... that heavy thumping Grrrrr sound you hear is the
Jacobs Engine brake system changing the camshaft timing to produce lots of negative power to slow that heavy truck down quickly with much less
use of the wheel brakes.
Drive along side of one of the tricked out Euro Mfg. tour buses that go to the casinos sometime......they alternate between squeaks from the turbo waste gate (s) lifting to dump boost under hard acceleration to the heavy thumping Grrrr of the engine brake system producing negative acceleration (heavy deceleration actually).
These engines have engine braking, in spades. They also have "noise restrictions" in many small towns that don't want the trucks decelerating waking them up all the time.
Sprinters have a little engine brake effect when you lift off the accelerator pedal and let the TPS send a 0% indication to the ECM to shut off all the fuel and boost.
To me that's a huge difference.....so if I am asked about my Sprinter engine braking performance I have an integrity issue with saying I think the engine braking is just great when I know that there is no engine braking device/function/system, but that there is some engine braking EFFECT from spinning the engine.
If I needed additional braking, the only option available for Mercedes Common Rail Diesel Turbo engines in our Sprinters is the Telma Retarder, which is NOT an engine system, but rather an attachment to the drive train after the transmission.
Roger
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2014 Sprinter 516 series (3500 DRW) 170"/4325 mm wb Hi Top Short Back
OM-651 I4 2.143 liter two stage turbo charged with 36.9 PSIA MAP Limit Valve
7 Speed 7G-Tronic, manually shiftable, automatic transmission.
Suspension Seats, Active Safety Package +, Parktronic, OEM Hitch/wiring
OEM back up camera, Bi Xenon light package, fog lamps, headlight washers.
Had 2006 T1N 3500/158|2010 NCV3 519/3500/144|2011 & 2012 NCV3 519/3500 170

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Old 11-20-2017, 12:16 AM   #20
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Default Re: Engine Braking a Sprinter. Does it work?

I'm going to add a Solex carburetor to my T1N's just to have a throttle plate.

Quote:
Originally Posted by sailquik View Post
...
If I needed additional braking, the only option available for Mercedes Common Rail Diesel Turbo engines in our Sprinters is the Telma Retarder, which is NOT an engine system, but rather an attachment to the drive train after the transmission.
Roger
A dual purpose Telma Retarder should be fitted to every Cab Chassis commercial RV conversion. During normal slow downs the generated energy could be sent to the house battery. During times that downhill braking is needed the resistor bank could be kicked in.

Electric vehicles have that don't they?

vic
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