"new" 2015: Is lack of power due to fix?

But why do that? The engine is likely delivering a higher BSFC than it would be at slightly higher revs for the same load.

flargabarg said:

But why do that? The engine is likely delivering a higher BSFC than it would be at slightly higher revs for the same load.

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Find a torque vs. RPM curve that has constant BSFC curves mapped on it. Running at the highest gear at the lowest RPM will put your operation in the lowest fuel consumption. This is true generally on any engine, though I'm sure there are specific cases where this is not so.

Typically, it's thought that 800 - 1000 feet-per-minute average piston velocity will give you the best fuel efficiency. Though that's a highly generalized statement, it's fairly universal.

This will also greatly extend the life of engine components.

-- Nicole

Different strokes for different folks I guess. I remember my dad telling me as a kid that the worst thing I could do when operating the diesel tractors (other than flip them over) was to lug them way down in the powerband.

turbobrick240 said:

Different strokes for different folks I guess. I remember my dad telling me as a kid that the worst thing I could do when operating the diesel tractors (other than flip them over) was to lug them way down in the powerband.

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How many diesel engines have you seen destroyed from this type of operation?

Why would the manufacturer of the engines, who have the ability to tailor rail pressure put out by the pump, allow the pump to supply rail pressure in any zone of the operation of the engine to cause the engine to become damaged by operation in this range?

The governor that you used on the engine as a boy selected an engine speed that the governor was to try to maintain utilizing a torque droop to do so. Why would the manufacturer have selected such a controller if the operator could select an engine speed that would be unsafe for the engine's operation, with the manufacturer knowing full well that the governor would provide full load at that engine speed?

The answer is, he wouldn't. The manufacturer would reduce the pressure the pump could put out at that engine speed at max fueling to ensure that the engine would operate in a safe condition.

Diesel engines are not like gasoline engines. You have to be careful with lugging a gasoline engine, particularly at low engine speeds, for fear of runaway detonation or other thermal damage, and/or too high of bearing loading which could cause damage. Diesel engines do not have any such concerns with detonation and their 50-100% larger bearing diameter sizing than similar gasoline engines ensures that the relative bearing velocities will provide full boundary lubrication with no harm to the bearings, even if highly loaded (high cylinder pressures).

-- Nicole

I think the big difference is operating RPMs and "load" on the engine.

IMO riding on the low end governor isn't bad on flat ground in 2nd or 3rd maintaining a constant speed, but if I were to ask it to pick up the pace with any sort of gusto, I'd wince as she labored up to speed.

As for the fixed 2015, the powers there, it just moved to a different pedal location.

Yeah, the load and gear are huge factors. I can feel and hear a distinct change in nvh below about 1500 rpm under load in the upper gears. I could really hear the unhappiness of the engine being bogged down much better when it was straight piped.

I'm with Nicole on this. For low load steady operation, these cars will be most efficient at the lower end of the RPM range, and they will produce enough power to maintain speed and accelerator slowly, yes, even in 5th and 6th gears. Running all the time at 1800 to 2200 RPMs is just wasting fuel IMHO. If you need to accelerate at a moments notice, sure keep it up there. But for just cruising at below highway speed, you want to be in the highest gear possible. The shift indicator even tells you to shift up around 1500 RPM if you are going constant speed on flat ground and not in 6th gear. And as already mentioned, if you need to accelerate, you shift down a gear or 2. Lugging occurs when you mash the throttle at really low RPMs, not during steady speed driving at low RPMs.

To each their own. I will say that my golf gives better fe at 55 mph in 5th gear/1800 rpm vs. 6th gear @ 1500 rpm.

Yep, definitely dont drive @ 1500 RPM. Toward 1800 much better

I'm going to go with the highest gear possible at any speed will result in the best cruising mpg.
1500 rpm in a diesel is just fine.
I had my TSI at 1500 rpm, top gear, going up an incline at 45mph with 3 adults in it. Never lugged, car never told me to downshift.
The DSGs will hit 5th at 35mph in town! No worries.

I pretty much guarantee you'll never hear any tdi guru recommend cruising around at <1500 rpm in high gear.

turbobrick240 said:

I pretty much guarantee you'll never hear any tdi guru recommend cruising around at <1500 rpm in high gear.

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You really don't have a choice. At highway speeds, you're going to be running at least 1800 rpm (on a 2-liter), unless the 6MT is geared significantly taller than the DSG.

Miss_Athanatos said:

Why would the manufacturer of the engines, who have the ability to tailor rail pressure put out by the pump, allow the pump to supply rail pressure in any zone of the operation of the engine to cause the engine to become damaged by operation in this range?

-- Nicole

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I feel bad for your turbo

Miss_Athanatos said:

Find a torque vs. RPM curve that has constant BSFC curves mapped on it. Running at the highest gear at the lowest RPM will put your operation in the lowest fuel consumption. This is true generally on any engine, though I'm sure there are specific cases where this is not so.

Typically, it's thought that 800 - 1000 feet-per-minute average piston velocity will give you the best fuel efficiency. Though that's a highly generalized statement, it's fairly universal.

This will also greatly extend the life of engine components.

-- Nicole

Click to expand...

Really? I thought it was worse for a diesel to lug that to wind.
EDIT: Just read the rest of the posts. Maybe i was told wrong?

DanB36 said:

You really don't have a choice. At highway speeds, you're going to be running at least 1800 rpm (on a 2-liter), unless the 6MT is geared significantly taller than the DSG.

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On the '10-'14 2L tdi's the 6mt is geared much taller than the dsg. From what I've seen the '15 dsg is actually geared taller than the mt. In any case, it sounds like some folks here are using 6th gear at much less than highway speeds.

I think the heavy load coupled with low rpm can be detrimental for the engine if driven too long without downshifting. However, I agree that on a relatively flat road practice of driving with highest gear and the lowest possible rpm would produce the highest FE.

kooyajerms said:

I feel bad for your turbo

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Why would you feel bad about the turbo? It's not in operation under the conditions I described.

-- Nicole

Yawiney said:

Really? I thought it was worse for a diesel to lug that to wind.
EDIT: Just read the rest of the posts. Maybe i was told wrong?

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Most people who tell you it's bad for an engine to run in a high gear at low RPMs say so due to the detrimental effects this has on a gasoline engine. This is the ideal condition of operation for a diesel engine and where a diesel engine proves a difference from gasoline engines.

tdi54 said:

I think the heavy load coupled with low rpm can be detrimental for the engine if driven too long without downshifting. However, I agree that on a relatively flat road practice of driving with highest gear and the lowest possible rpm would produce the highest FE.

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Diesels prove themselves under heavy load at low RPMs. If it's ok to run in that condition for a short while (and by definition it is ok if the programming allows it), it's ok to run in that condition perpetually. Even though the 2.0L TDI is a high-revving diesel engine, it still has a strong diesel bottom end. You can't drive it like it's a 6.7 L CTD, but it definitely operates like a diesel nonetheless.

-- Nicole

Here's the official word from Cummins on lugging:
Cummins lugging

Miss_Athanatos said:

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That BSFC map clearly shows the engine is most efficient at nearly full load between 2000-3000 rpm.

Miss_Athanatos said:

Diesels prove themselves under heavy load at low RPMs. If it's ok to run in that condition for a short while (and by definition it is ok if the programming allows it), it's ok to run in that condition perpetually. Even though the 2.0L TDI is a high-revving diesel engine, it still has a strong diesel bottom end. You can't drive it like it's a 6.7 L CTD, but it definitely operates like a diesel nonetheless.

-- Nicole

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+1
You have some awesome Data that closely matches Everything I have been told and taught about diesel engines in the last 7 years of running HD diesel engines, and matches what I do driving my VW.

surfstar said:

I'm going to go with the highest gear possible at any speed will result in the best cruising mpg.
1500 rpm in a diesel is just fine.
I had my TSI at 1500 rpm, top gear, going up an incline at 45mph with 3 adults in it. Never lugged, car never told me to downshift.
The DSGs will hit 5th at 35mph in town! No worries.

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I'll call bull on the TSI at 1500MPH going up hill as "not lugging". The DSG in the Alltrack will easily double down shift and exceed 2500RPM just to maintain speed on the hills near my house, sure if it was in manual mode it would make it up but I'm not that sadistic.

TSI and TDI are apples and oranges.

Maybe the hills aren't as bad where you live.

turbobrick240 said:

That BSFC map clearly shows the engine is most efficient at nearly full load between 2000-3000 rpm.

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But we're not talking about full load, we're talking about light load.

VWMark said:

But we're not talking about full load, we're talking about light load.

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Fair enough. The map shows the worst efficiency is at the lightest loads. People can drive their cars however they like. I won't be lugging mine.

turbobrick240 said:

Fair enough. The map shows the worst efficiency is at the lightest loads. People can drive their cars however they like. I won't be lugging mine.

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So, if you're running 3000 RPM and the torque is at the 6 line, you're practically at the 230 BSFC line...which corresponds to practically 210 BSFC line at 1500 RPM, since you'd be at the 12 line on the torque axis.

That's pretty much the opposite of what you're saying.

-- Nicole

OhOh

Miss_Athanatos said:

So, if you're running 3000 RPM and the torque is at the 6 line, you're practically at the 230 BSFC line...which corresponds to practically 210 BSFC line at 1500 RPM, since you'd be at the 12 line on the torque axis.
That's pretty much the opposite of what you're saying.
-- Nicole

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No, that's not the opposite of what I'm saying. I for one don't run around at 3000 rpm under extremely light load. And I'm reading much closer to 219 g/kw hr for 1500 rpm at 12 bar mean effective pressure. That example corresponds to 40 hp. At 40 hp that engine is more efficient at 1800 rpm than 1400 rpm. Even if dogging around at <1500 rpm did save a penny or two, it's not worth the abuse the engine and turbo would take. And most importantly to me, I don't like sluggish throttle response.

Also, does the lugging = more soot? Maybe not the same as jamming down the throttle at low rpms but more soot than the 1800 to 2200 range?

giuseppe_b said:

Also, does the lugging = more soot? Maybe not the same as jamming down the throttle at low rpms but more soot than the 1800 to 2200 range?

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I have no idea if lugging would result in more soot, but my feeling is it would. But we are not talking about lugging here. Running these cars at steady speed around 1500 RPMs is not lugging. If you are towing a trailer and going up a big hill at 1500 RPMs, then you are lugging!