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lajeneson
07-20-2019, 11:36 PM
Many thanks to all contributors here, my 2006 with 135k is on its third tranny, and it appears to me that the cause has been poor installers. I am on my 4th year with Vinnie and from here on its DIY as it will be with me until one of us depart. It is a motorhome. Did Volvos from 60s till Ford takeover so I appreciate the efforts of this group to "get it right." Got a great deal on the AB200 thanks to you all. So the question is, per a scan gauge 2, at idle 650rpm, with boost less than 1.0, why would my scan gauge indicate that my engine load is from 33 to 38 percent. Theoretically I should never get out of 4th gear. You need to show no mercy if my ignorance is obvious.

autostaretx
07-21-2019, 01:56 AM
The Load is an ersatz calculated value based upon the amount of fuel the Sprinter *could* be using for the current state of the engine (let's say RPM). So if it was spinning faster, you'd have more LOaD range remaining.

This page "explains" it ... note that Diesel is calculated differently than gasoline.
http://obdcon.sourceforge.net/2010/06/about-pid-calculated-load-value/

From that page: (CLV=Calculated Load Value)

The OBD regulations previously defined CLV as:
(current airflow / peak airflow @sea level) * (BARO @ sea level / BARO) * 100%

Various manufacturers have implemented this calculation in a variety of ways. The following definition, although a little more restrictive, will standardise and improve the accuracy the calculation

LOAD_PCT = [current airflow] / [(peak airflow at WOT@STP as a function of rpm) * (BARO/29.92) * SQRT(298/(AAT+273))]

Where:
STP = Standard Temperature and Pressure = 25 C, 29.92 in Hg BARO, SQRT = square root,
WOT = wide open throttle,
AAT = Ambient Air Temperature and is in C

BUT:
Compression ignition engines (diesels) shall support this PID using fuel flow in place of airflow for the above calculations.
So that turns the first equation: (current airflow / peak airflow @sea level) * (BARO @ sea level / BARO) * 100%

into: (current FUELflow / peak FUELflow @sealevel) * (BARO @ sea level / BARO) * 100%

So i read that as 33% LOAD means you're just using 33% of the fuel you could be using at that speed (rpm).
(and if you're significantly above sealevel, the LOD percentage will increase ... less air to support fuel burn).

Since the amount of fuel the Sprinter will squirt is limited by the amount of air it's ingesting, idling at 650 is nowhere near the airflow (hence increased fuel usage at the 14 to 1 air/fuel mass ratio) you could be using at 4000 rpm with the turbo going full blast.

Let's see: 2.7 liters times 650rpm/2= 877 liters per minute of uncompressed air. (divide by 2 since it's a four-stroke engine)
At 4000 rpm: 2.7 liters * 4000/2= 5400 liters per minute thus 6.15 times the flow. Uncompressed.
Turn on the turbo to (let's say) 2x boost (15 psi boost, 30 psi MAP) and you'll double that airflow.
12.3 times the air, thus potentially 12.3 times the fuel consumption (and power).

As you'll find when driving with the gauge, "100%" in 5th gear is not the same "feeling" as 100% in 4th.
(leading to the advice of downshifting when the load exceeds 70% ... your MPG will improve)

You can see your load fluctuate by turning on headlights, or by shifting between Drive and Neutral while stopped.

--dick (33% sounds high for neutral (at least near sea level). Watch (in a ScanGauge) GPH as well)

Mike DZ
07-21-2019, 01:58 AM
From the SG II manual : "LOD This is a percentage of the maximum power available currently being generated. In some vehicles it is the maximum available at the present RPM"

If in the Sprinter it is the second condition (available at present RPM), 33 to 38 % makes sense at idle. At least this how I interpret LOD for my vehicle.

billintomahawk
07-21-2019, 05:21 AM
I've been driving for the last 10 days in the mountains of New Mexico and Colorado.
Lots of climbing through hair pin turns at 15-25 mph.
My camper conversion is fairly light, I didn't have a scan gauge but I do have a temp gauge on the transmission oil return line.

Even on very long climbs I never saw the engine coolant or transmission oil temp over 205F(96C).

I ran the rpm's at 2300 and shifted to maintain that.

It seemed the best way for ascending?
I do have the Green Diesel Engineering tune.

20 mpg.

bill in tomahawk

lajeneson
07-21-2019, 04:52 PM
I'm working on getting a broad enough understanding of diesel combustion/output to restore my confidence in the transmissions functionality. Transmissions are expensive and fortunately for me SilverStar warranty has kept the Sprinter financially viable. Living just outside of the Smokies NP area, I listen to motor, watch load, travel light and spend on lot of time on the shift paddle between 2 and 4. Trying to get to the bottom of my trans problem by firstly eliminating driver error thanks for the clarifications. :shifty

Bobnoxious
07-21-2019, 06:23 PM
Wouldn't the 33-38 percent LOD represent the load required to overcome, engine and transmission friction (for lack of better word) to maintain idle???

Question: When the accelerator pedal is released, LOD goes to zero, why?

autostaretx
07-21-2019, 06:56 PM
Wouldn't the 33-38 percent LOD represent the load required to overcome, engine and transmission friction (for lack of better word) to maintain idle???
Yup.

Question: When the accelerator pedal is released, LOD goes to zero, why?
... watch the GPH or MPG ... both will show that fuel flow stops until certain circumstances occur.
(GPH to zero, MPG to 9999 (or however your gadget says "infinite")

If you're driving on the road, lifting your foot ceases fuel flow until the engine RPM drops below 1000 rpm, then it resumes. (probably also true in neutral, i haven't played with that).

--dick

Midwestdrifter
07-21-2019, 08:59 PM
Becuase the engine can't build any boost at idle. The load% represents the max available fueling for the current operating conditions. If it was near 100% at idle, you would be unable to get the engine above idle. Once the engine gets to about 1200rpm the boost builds rapidly, so the available power rises quickly.

Bobnoxious
07-21-2019, 09:02 PM
Yup.

... watch the GPH or MPG ... both will show that fuel flow stops until certain circumstances occur.
(GPH to zero, MPG to 9999 (or however your gadget says "infinite")

If you're driving on the road, lifting your foot ceases fuel flow until the engine RPM drops below 1000 rpm, then it resumes. (probably also true in neutral, i haven't played with that).

--dick

That confirms what I have read. In fact, Scan Gauge asks certain questions related to Fuel cut off.

Nautamaran
07-22-2019, 03:16 AM
When my cold-side turbo hose blew last week and I spent time in no-turbo limp mode, my LOD display went to 100% - max fuel for the condition - even though the engine was making about half its normal available power.

At idle LOD is about 33% in “D” with a/c running; 25% in N or P with a/c off.

-dave