urban consumption

[peteo48]

I havnt paid  frequent attention  to fuel consumption other than being pleased with the 65.9 mpg average  for the 2251 miles from new (which I have as trip A   ) and the 66.9 mpg over 497 miles since last  resetting trip B.   (fibometer readings, I dont bother comparing against  actual litres purchased.)

I dont think I have checked the estimated fuel  consumption display  for the last driving cycles   but may do so in future as its  a useful way of checking consumption on  a journey you have just completed  without having to reset trip meters.   The number of leaves on the little trees  dont help me much. 

To be honest I think the fibometer is OK provided you assume an exaggeration factor. Over many years with Hondas I've found knocking 4 mpg off the fibometer reading gives me a figure not that much different from the actual figures using brim to brim methods.

[Geoff_W]

My smartphone is showing signs of imminent death and the thought of getting a new one keeps me awake at night.

I switched to apple a while back as they are very easy to use - when driving I have it connected to the infotainment screen display and actually use the phone to change radio stations for me with voice control.

Rather than having to program radio stations the phone just streams them through the internet - makes it easier when I have to factory reset the infotainment unit and it loses all the settings/stations.

Been thinking of doing that myself as O2 have given me a decent offer on an i-phone. The switch to a different operating system seems a bit complex from what I've read. Having to download an App just to make the switch according to "Business Insider." ?

The app will copy across contacts/etc from your old phone but you don't have to use it as you could set them up from new on the iPhone depending on how much data you have.

The voice control using the button on the steering wheel is a great benefit - I don't have to take my hands off the wheel to set/change sat nav destination or radio station/etc.

I tried using voice control to select a radio station but it didn't understand what I was trying to do. Maybe I wasn't using the correct syntax. Worked OK for the satnav, though.

[sportse]

For me with an iPhone and Apple Music, I just say ‘play classic fm’ to Siri and it starts.

There are quite a few other live radio stations on Apple Music.

[Wonder]

Hello,
I then checked and yes the trip computer is also present in my car, I had never noticed  .
But I don't understand two things,
1) The remaining km of autonomy correspond to those indicated by the odometer, while the consumption l / 100km is different from that indicated by the odometer
2) I noticed that when the car has a full tank it indicates lower fuel consumption l / 100km than when the tank is almost empty

[Kremmen]

Known phenomenon, it can only accurately assess the current tank mpg / kpl based on current consumption.

[Wonder]

Hi, can you explain better what it means
"accurately evaluate the current mpg / kpl tank based on current consumption"
that with online translation I can not understand?
Thanks

[Kremmen]

With a full tank of fuel the car computer can only guess the range

[ColinB]

With a full tank of fuel the car computer can only guess the range

If you fill the tank to the brim when refuelling, then your first few miles/km after that will be using the fuel in the filler pipe. The tank will be pressed full until the filler pipe's empty, so the fuel level sensor in the tank won't register any change in level or fuel usage. So as far as the computer's concerned, you're covering distance without using fuel.

[Kremmen]

I don't brim it as I think there is a safety drain up there on some cars.

I always wait a few seconds after the first click while the 'bubbles' settle then trickle a bit more in till it clicks again.

[Lord Voltermore]

If you fill the tank to the brim when refuelling, then your first few miles/km after that will be using the fuel in the filler pipe. The tank will be pressed full until the filler pipe's empty, so the fuel level sensor in the tank won't register any change in level or fuel usage. So as far as the computer's concerned, you're covering distance without using fuel.

I dont think the system relies just on measuring the fuel  level from the float  in the tank.  It can give  a fuel consumption   even  if you have driven less than a mile and still using the fuel  in the filler neck.

The Jazz  tank profile is relatively  flat and shallow. Small  drops in level may be too small to measure accurately ,and will be constantly changing as fuel sloshes and surges. Modern systems normally average  tank float readings out over a period. Thats why when you fill the tank it can sometimes take a few seconds before the fuel gauge registers the change.     

   I think it also measures actual  fuel flow into the engine, or maybe just estimates it based on the engine running time and loading.      Every so often it reconciles readings ,possibly including tank level, and gives a new estimated range.

[ColinB]

If you fill the tank to the brim when refuelling, then your first few miles/km after that will be using the fuel in the filler pipe. The tank will be pressed full until the filler pipe's empty, so the fuel level sensor in the tank won't register any change in level or fuel usage. So as far as the computer's concerned, you're covering distance without using fuel.

I dont think the system relies just on measuring the fuel  level from the float  in the tank.  It can give  a fuel consumption   even  if you have driven less than a mile and still using the fuel  in the filler neck.

The Jazz  tank profile is relatively  flat and shallow. Small  drops in level may be too small to measure accurately ,and will be constantly changing as fuel sloshes and surges. Modern systems normally average  tank float readings out over a period. Thats why when you fill the tank it can sometimes take a few seconds before the fuel gauge registers the change.     

   I think it also measures actual  fuel flow into the engine, or maybe just estimates it based on the engine running time and loading.      Every so often it reconciles readings ,possibly including tank level, and gives a new estimated range.

You're right that in order to measure fuel economy, the car has to use the actual fuel flow. But Kremmen's comment was about range, and for that the car has to know how much fuel is onboard. Once the free surface is down into the tank, you can expect it to know that. But whilst fuel is still in the filler neck, the car can't know.

[embee]

I'm not particularly up to date on such details, but in my experience fuel used (for mpg indication etc) was calculated from the calibration of the injector flow vs on-time. To my knowledge no-one uses a true fuel flow meter device, but I'm happy to be shown to be wrong on that. The sum of injector on-time gave the total flow once appropriate calculations were done.

Typical port injection injectors have 3 phases of flow, the opening phase, hold, and closing. The opening and closing "ramps" mean that the flow volume is not strictly directly proportional to total on-time, the shorter the on-time (light load) the greater the departure from linear. It could also vary slightly with engine running conditions which might affect the pressure difference across the injector (rail pressure vs inlet manifold pressure), which can have dynamic influences (frequency of injections and pressure waves in the rail etc).

I never got directly involved in the algorithms for fuel used calculations for the purposes of trip computer numbers. I imagine there are some approximations used, it doesn't really need to be super accurate (and usually isn't!).

Fuel tank content calibration is another can of worms.

[Kremmen]

Most conventional cars have a cube style fuel tank so measuring the level via a float can be fairly accurate.

I know the Civic with magic seats, and probably the Jazz, have long wide thin fuel tanks under the seats so is far more difficult to assess.

[Neil Ives]

I always wait a few seconds.... while the 'bubbles' settle then trickle a bit more in...

Sounds like me peeing  :'(

[culzean]

     I think it also measures actual  fuel flow into the engine, or maybe just estimates it based on the engine running time and loading.      Every so often it reconciles readings ,possibly including tank level, and gives a new estimated range.

The normal way of measuring fuel used in a fuel injected engine is using the fuel injector 'on ' time via ECU... assuming fuel pressure to be constant then the amount of time the injector is open will give a certain volume of fuel used.  Under load or when engine cold the injectors stay open for longer...