1.9 TDI PD: Fuel Consumption Problems

Hello.

ich hab da mal eine kleine Frage zum Verbrauch von den Fahrzeugen in unserem Firmenfuhrpark. We have:

- Passat 3BG Variant Trendline, 1.9 TDI, 131 hp, 6-speed manual transmission.
- Passat 3BG Variant Trendline, 1.9 TDI, 131 hp, 6-speed manual transmission.
- Passat 3BG Variant Highline 1.9 TDI 131 hp - with Tiptronic transmission.

Now, the vehicles are exhibiting very strange fuel consumption rates. They are all loaded in the same way, or not loaded at all. The fuel tank capacity is the same for all. They are all using the same winter tires and were tested by the same driver, with the same driving profile, on the same route.

The first Passat has been showing an average fuel consumption of 5.9 liters per 100 kilometers on the MFA 2 display for a long time. The second one is showing around 7.4 liters, and the Highline with Tiptronic is showing 7.1 liters per 100 kilometers.
In all cases, the fault memory is clear, and the measured values are plausible.
The question is, why is the consumption so high for 2 of these boxes?
The second trendline indicates a fuel consumption of 7.7 liters per 100 kilometers at speeds of 140-160 km/h, while the Highline model achieves approximately 7.0 liters per 100 kilometers at the same speeds on the highway.
The first one achieves a fuel consumption of 6 liters per 100 kilometers.

I don't find 7L/100km to be particularly economical for a 1.9 TDI. I personally own an Audi A6 C4 2.5 TDI Quattro with 140PS (138hp) that has been tuned to 175PS (173hp), and it has been running between 6.8 - 7.2L/100km since I've owned it. However, mine has all-wheel drive, is 300kg heavier, has 600cc more displacement, and one more cylinder.
That gives me reason to believe that something isn't right with those two 1.9 engines.
The question is only what.

Are there any factors that can significantly increase fuel consumption in a 1.9-liter TDI engine? Has anyone had any experience with this?
Especially when it comes to fuel prices, a car like that should be relatively inexpensive to run .

Perhaps someone can give me the crucial tip I need.

Thank you in advance, and have a nice Sunday.

Because the ones with the high fuel consumption have a hole in one of the turbocharger boost hoses?

Hi.

Okay, so far, the charge air system is fine for everyone. Everything is sealed, nothing is whistling. Everyone is still using the original mass airflow sensor (in the Highline, it only measures a maximum of 800mg/h, in every gear at full throttle and high RPMs - a new one has been ordered).
The boost pressure closely follows the target values. There is a slight overshoot at 1900 rpm in all vehicles.

I want to start looking for a job at the AGR tomorrow.
The vehicles initially covered almost exclusively city driving for the first 150,000 kilometers. Only in the last approximately 30,000 kilometers have they been driven on longer distances.
I definitely want to take the intake manifold off and clean it to remove the carbon buildup.

But does it really matter that much?
The timing belts have been replaced for all 3 recently at a VW service center!

There were numerous engine control units (ECUs) and software versions for the 130PS engine. Are all of these versions the SAME? The reason for this was the different configurations, for example, with PDE, 550, and 520 models, etc.

Furthermore, different weights, wheel/tire combinations (including tire pressure), payload capacities, and equipment options are significant factors. Therefore, you can never truly compare two cars. The driver also plays a role, including driving style, acceleration behavior (right foot), etc.

I have not taken into account the control units and software versions in this case.
I can only tell you that all the vehicles are from the year 2004.

The tires on all three are good Bridgestone Blizzak LM32 tires. The tire pressure is also okay.
'People are always looking at that. The boss emphasizes the importance of maintaining it.'
The weights should all be nearly identical.
More than a small tool kit can fit in most vehicles. The Highline model is an exception, as its trunk is often completely full. However, even with the full trunk, it still achieves a lower fuel consumption than the Trendline model, despite having a Tiptronic transmission!
To rule out the possibility that the problem was with the driver, the cars were already swapped between drivers.
For the Passat, which is inherently more fuel-efficient, to achieve the fuel consumption figures of the 2.0 or 3.0 liter models, you would have to drive it quite aggressively.

If you drive like an old man, setting the cruise control to 90 km/h, you can achieve a fuel consumption of around 5.5 liters per 100 km. Even the first generation Trendline can achieve that. However, at 130 km/h with cruise control on the route Frankfurt -> Hannover -> Frankfurt, the fuel consumption is closer to 7 liters per 100 km.
That's really strange. Because the fuel consumption figures are higher than the fuel consumption of my 2.5 TDI (R5) Avant Quattro on this route!
Is such high consumption variability only due to the software? Our boss should have kept the 3B with the AFN engine instead. It always used 5-6 liters per 100km .

To the best of my knowledge, the codes 019KD and 019GQ were in use in 2004.

The weights should all be nearly identical.

It can't be. An automatic transmission is always different from a manual transmission . And to be able to make clear and more accurate calculations, you would have to weigh the cars. And then you would have to drive standard laps (with the same driver/driving profile). Just the weather, wind, and track can easily account for a difference of 1 liter depending on the driver.

In my opinion, the whole thing is a pointless endeavor.

You didn't understand...
Despite the automatic transmission being heavier, having a fully loaded trunk, and being an automatic (which typically consumes more fuel), it still uses less fuel than the Trendline manual transmission, which lacks features like the navigation system, leather upholstery, and a trailer hitch.
As I mentioned, it needs more than my 2.5 Quattro, which already weighs 300 kg more according to the registration papers.
We're not talking about differences of just 0.2 - 0.3 liters per 100km; we're talking about differences of up to 2 liters per 100km, which is a significant amount!

2L... that's how much fuel a Lupo 3L uses for 66 kilometers.

I absolutely understand.

Only you are comparing apples and oranges. An accurate statement, or any statement at all, requires technical equality. The driver must be the same. The driving profile must be the same. The weather must be the same. The route must be the same. The weights must be the same. The engine control units, including the software version, must be the same. The technical condition must be the same (this includes wear and tear, etc.). And so on. This is not the case here, so the results will always be different due to the principle. Here, 0.1 liters, there, 0.1 liters. The engine coolant or its flow is slightly dirty - 0.01 liters.

Ultimately, they are always different. And technically, they can't be made any better. Cars are just as diverse as people are.

That can't be right. An automatic is always different from a manual . To be able to make clear and more accurate calculations, you would have to weigh the cars. And then drive standard laps (with the same driver/driving profile). Just the weather, wind, and track can easily account for a difference of 1 liter, depending on the driver.

In my opinion, the whole thing is a pointless exercise .

Okay, so you're saying that even two identical cars, technically sound, with the same equipment, and carrying the same load (although one might have a tow hitch), can still have a difference of 2 liters per 100 kilometers in fuel consumption.
Especially when dealing with 2 or 3 cars that travel the same routes (sometimes in a convoy).

And it is also normal, in your opinion, that a 1.9 TDI engine in a Passat consumes more fuel than a heavier Audi A6 Quattro with 175 horsepower and full equipment...

Very interesting .

I drove the Passat myself, on the route I regularly drive twice a week. When I go up north and back, I can already see that I need more [fuel/power/something else] than I do with my Audi, and that just can't be right.
But you probably see it differently, right?

The Audi MFA displays are, on average, off by over 1 liter. Furthermore, the CW values, weights, and software calibrations are completely different.

If you believe that everything is the same, that everything must be technically okay, that all driving routes, temperatures, weather conditions, etc., are identical, then, conversely, the consumption must also be identical.

Then, all the factors that influence consumption are eliminated, and everything written here becomes irrelevant.


(sometimes in a column).

Drafting/convoy driving reduces what? And has an influence on what?

'I'm glad my Audi doesn't have an MFA (Multi Function Display), so I have to carefully calculate the fuel consumption at the gas pump.'
'And if my A6 C4 with a 63-liter diesel tank only manages 900km, while the 1.9 TDI in the Trendline only does 800km, then I know something is wrong!'


Regarding the lane, the car following behind was traveling at 7.1, while the car in front was going at 5.9.
I'm not stupid!

Okay. Then it's as I said. EVERYTHING is the same, everything is OK.

Wow, what a mess!
As Mulle already said: if all the conditions are the same, the same amount of energy must be consumed for the same performance. If there are differences, then they can be attributed to any of the factors that influence consumption. It seems you yourself have doubts that the technology works equally well in all cases or is in good condition (you mentioned the mass airflow sensor and intake manifold). Keep investigating and let us know what you find.
Or would you like to read that your Audi is the more economical option compared to VWs?
My 74 kW (leather interior, without trailer hitch, 195 tires in winter, 205 tires in summer) has been consuming 6.4 liters per 100 km (approximately 38.1 mpg) for a healthy mix of long and short distances (no short trips, etc.) over a distance of about 130,000 km (80,000 miles), and the intake manifold has remained perfectly clean, surprisingly without any soot buildup.
Otherwise, take a look at the "Spritmonitor" website to see what other people are getting for fuel consumption... I think even a 96 kW 3BG starts at around 5.x liters per 100 kilometers.
haithamina

Good evening...

Certainly, my concern isn't that my Audi needs less maintenance.
The differences in consumption figures among the Passats seem strange to me, especially since they all have the same engine.

Let's take a closer look at the technical aspects. But things like tire pressure or a stuck handbrake, I can rule those out for now.

Then, first clarify everything that has already been said.

- Leak tightness of the LD line.
-Are all the brakes completely free, is there no dragging, are the wheel bearings in good condition, is the underbody protection present and not damaged?
-Software versions and hardware are truly identical.
-...

That reminds me...

Last week, there were some minor issues with the Highline during the inspection.
Initially, the problem was the engine temperature, which consistently stayed below 80°C despite giving it full throttle for 10 minutes after driving 20 kilometers and letting it idle. Then, the measurement had to be repeated five times because the full-throttle readings at 5000 RPM were consistently too high.

I didn't even think about that when I wrote the original post here.