Compare fuel gauge - need to refuel?

Hello,

Considering my engine is still "relatively" weak (~134 hp according to the dyno, after about 2,000 km), I occasionally think about possible causes other than just the break-in period.

For example, while refueling, I noticed that the displayed average fuel consumption has been practically perfectly aligned with the amount of fuel added – a new experience for me, because, for example, with Christel's ALH Ibiza, you typically need to add about 5% more fuel than the displayed average fuel consumption would suggest.
According to the DZR (German Federal Motor Vehicle Office), the engine also has approximately 8% "excess" power (despite mostly being used for low-speed driving), which suggests that the tendency for higher-than-expected power output is largely due to "unnoticed excessive amounts of diesel being injected."

"With a colleague's Octavia with a 110 hp engine, the fuel consumption was similar (DZR value unknown), and I corrected the fuel consumption display for him through adaptation."

(My former AFN Golf didn't have a multi-function display.)

I suspect the diesel temperature sensor in my Polo: initial measurements suggest it's reporting about 8°C too low, which could potentially cause a reduced fuel injection amount.

How is it with your cars (mostly with PD engines)?
How well does the actual amount of fuel refilled match the fuel consumption reading in the medium and long term?

ulf wrote:

How is it with your cars (mostly with PD engines)? How well does the actual fuel consumption, measured over the medium and long term, match the fuel consumption indicated by the system?

Since the new STG motor was installed, the displayed fuel consumption matches the actual consumption almost 100% of the time. Before, I had a discrepancy of around 0.8 liters. It is no longer possible to adjust the display on my instrument cluster.

The usability of my AUDI depends on whether the fuel consumption display is accurate. The displayed average fuel consumption may vary by up to one liter per 100 kilometers.
The speedometer reading is more accurate when driving at a constant speed on the highway than when driving on a road with heavy traffic and frequent acceleration and braking.

"With my car's trip computer, I'm seeing a consistent discrepancy of 0.3 liters. It's overestimating my average fuel consumption – for example, it shows 4.8 liters per 100km when the actual value is 4.5." While DZR certifies an increase in performance (11%), the maximum speed (Vmax) is lacking at the top end, due to reasons (not the usual suspects...), which hopefully will be resolved soon.

With my ASV (unfortunately/fortunately? not a PD), I'm getting 3% more range than what the MFA displays. DZR has not yet been applied; I would first need to weigh the vehicle.

Regards,
mcgregg

'That's a silly question, but what does DZR mean?'

MattesTDI wrote:

That's a silly question, but what does DZR mean?

Here:
/viewtopic.php?t=3939[/url]

hi,
On the Lupo 3L, the display shows approximately 0.1 to 0.2 less than the actual value.
However, with mixtures containing approximately 50% oil, it is quite accurate.
greetings

On my Ibiza (ASZ), the deviation is approximately 0.1 - 0.2 liters per 100 km, and it's showing a lower amount than the actual consumption! It's hard to say exactly, since the display only has one decimal place.

ulf wrote:

With my Polo, I now suspect the diesel temperature sensor: initial measurements suggest it's reporting about 8°C too low at 70°C, which could potentially cause a reduced fuel injection amount.

Hello again,

For those who are still interested: The donor is working correctly.
Today, I disassembled it and measured its resistance values while immersing it in a water bath between 30°C and 90°C.
Using a VAGCOM device, one can read the temperatures in the coolant jacket with an accuracy of up to 1°C by connecting it to the diesel coolant temperature sensor connection on the engine control unit.

It's strange: when logging the temperatures, the diesel temperature is sometimes up to 30°C lower than the water temperature.
Apparently, the coolant is being flushed through the ZK (water pump) at such a rate that, when driving at a moderate pace, it only raises the engine temperature "slightly."


What also surprised me was that, several minutes after the engine was turned off, the diesel in the cylinder head should theoretically have the same temperature as the coolant.
Okay, I connected the VAGCOM diagnostic tool, selected the temperature comparison function, and manually activated the fuel pump so that it pumps one small amount of "hot" diesel from the fuel tank to the sensor.
It then dutifully displays an increasing temperature, but it stops at approximately 8°C below the water temperature. I can't get the diesel reading any higher, no matter what pulse width I use or how long I operate the pump.

That made me realize that the diesel gauge is probably showing about 8 degrees less than the actual temperature.