So... Fuel Consumption woes

[Diagro]

hey

So... Yea on to the subject of Fuel consumption.

My 172 Was drinking petrol to the sum of 1 Tank to 100 Miles before it had new belts and dephaser fitted... Which was MENTAL!

Since its been repaired and serviced it so far has done: 233 Miles and has Just over 1 Bar of fuel left.

Lets break this down some what to get a better idea what I'm getting at.
1 Tank = 50L
50L = 11 Uk Gallons

My MPG counter is reading 35MPG, and is always reading above this which is fine if it were TRUE!

Lets divide the 11 Gallons into 8 (for the 8 fuel bars)
11/8 = 1.375

Now lets remove 1.5 of those bars

1.375/2 = 0.6875
1.375 + 0.6875 = 2.0625
11 - 2.625 = 8.9375

So in theory i have used 8.9375 over 233 miles.
233 / 8.9375 = 26.0699

We come to a sum of 26.0699MPG from all the above.. which is 9MPG shy on my current average.
But a massive 16MPG more then what I was getting before work was carried out.

if it was 35mpg then it should have covered 312.812 miles lol

What I don't understand is where is the 9MPG going? Why am I getting such bad economy from this engine? I have been driving it like an old man since I put the 99ron fuel in...

Anyone got any idea on what to check ? Its going to SRS for heating repairs on friday and would be good to have a list of things for them to quickly check

 

[hipwell]

front lambda sensor can cause poor economy.

but at the end of the day, youve bought a 2 litre hot hatch, its never going to yield amazing mpg. In my old 182 if i sat at about 65 on the motorway i could just about get 42mpg according to the dash.

going to work and back which was 3 mile each way on non motorway driving like mi nan i would still only get about 29mpg

 

[Amos91]

I wouldn't trust the gauge to be a decent way of calculating fuel economy - it moves with changing driving styles!

Go fill your car up to the first click at the pump, after driving it around fill it up again to the first click. Note how many litres of fuel you have used & mileage covered - this will be much more accurate.

 

[Diagro]

front lambda sensor can cause poor economy.

but at the end of the day, youve bought a 2 litre hot hatch, its never going to yield amazing mpg. In my old 182 if i sat at about 65 on the motorway i could just about get 42mpg according to the dash.

going to work and back which was 3 mile each way on non motorway driving like mi nan i would still only get about 29mpg

Ok will add that sensor to the list.

Yes i understand that its a 2L engine and its uber cool and all that jazz, But my commute is 40 miles a day which a good 15 miles of that is on the A46 and M69 which is fast flowing traffic. Yea one or two days was stop start for a good couple of hours but i turned the engine off for most of it.

The Mpg counter is so far out its silly ha

 

[Diagro]

I wouldn't trust the gauge to be a decent way of calculating fuel economy.

Go fill your car up to the first click at the pump, after driving it around fill it up again to the first click. Note how many litres of fuel you have used & mileage covered - this will be much more accurate.

Nice idea. Pay day is friday so will fill her up and then take a trip down to Coventry for some shopping with the wife. Then on way back will fill her up again and see how much was used.

 

[Coops Mk1]

that's bad, I commute 12 miles each way a day in the 182, averages 39mpg on the clock and pretty much exactly that when I work it out too.

so as above, lambda pre cat would be my first port of call and then reset the clocks

 

[tonyd106]

I average 38 mpg and I don't really hang round. Being sensible I usually see over 40 mpg, but I'm not to bothered about the mpg anymore.

I don't fill the tank up unless I go on long journeys but when ever I do I always get over 400 miles to a tank which imo is brilliant for a hot hatch.

I do 200 miles a week in mine and I usually have enough fuel to have a weekend blast and that's from putting £40 in.

 

[Diagro]

that's bad, I commute 12 miles each way a day in the 182, averages 39mpg on the clock and pretty much exactly that when I work it out too.

so as above, lambda pre cat would be my first port of call and then reset the clocks

I just called the garage, they said they will plug the car into their computer and have a look at all the data. And if need be replace the sensor and see what happens. Its going in friday for the heating issue anyway so two birds one stone

I average 38 mpg and I don't really hang round. Being sensible I usually see over 40 mpg, but I'm not to bothered about the mpg anymore.

I don't fill the tank up unless I go on long journeys but when ever I do I always get over 400 miles to a tank which imo is brilliant for a hot hatch.

I do 200 miles a week in mine and I usually have enough fuel to have a weekend blast and that's from putting £40 in.

Yea my commute is also 200miles a week, I would love to get at least 9 days out of a tank before needing to fill up like you are!

 

[Rob]

Rather than faffing about with all these crazy equations.. do the following and then come back with an answer....

Fill the car right up... reset the trip counter, use it for a day or two and then go back the petrol station, check trip counter, fill up.

Divide figure in simple actual maths equation, get result.

 

[Diagro]

Rather than faffing about with all these crazy equations.. do the following and then come back with an answer....

Fill the car right up... reset the trip counter, use it for a day or two and then go back the petrol station, check trip counter, fill up.

Divide figure in simple actual maths equation, get result.

Will do Rob.

Also if it is the sensor will this one be a good one to use? (just looking at all my options)
http://www.ebay.co.uk/itm/Renault-C...niversal-/130636091187?_trksid=p2054897.l4275

 

[Amos91]

Rather than faffing about with all these crazy equations.. do the following and then come back with an answer....

Fill the car right up... reset the trip counter, use it for a day or two and then go back the petrol station, check trip counter, fill up.

Divide figure in simple actual maths equation, get result.

Echoooo

 

[Nick_Leeds]

Will do Rob.

Also if it is the sensor will this one be a good one to use? (just looking at all my options)
http://www.ebay.co.uk/itm/Renault-C...niversal-/130636091187?_trksid=p2054897.l4275

You are better off with the genuine Bosch one.

 

[Diagro]

You are better off with the genuine Bosch one.

thanks Nick from leeds. I will have a look for that one and Buy one to replace mine anyway, Looking at all the cars history there is no mention of it ever being replaced so its due one.

 

[Steven103]

The fuel gauge is so far out its silly ha

EFA.

Fuel gauges are notoriously inaccurate and non-linear. Fun fact time ...

Trip computers generally use injector pulse width to calculate fuel used (the ECU knows how long it has asked each injector to be open for, it knows an approximate mass flow rate for that injector and an approximate density of fuel) which is much better but still not perfect.

The reason the trip computer is always slightly off is because the ECU has no way of knowing how the long the injector is actually open for, nor does it know the exact flow rate (flow rate depends on cylinder pressure which is obviously constantly changing) nor does it know the exact density (changes with temperature, fuel composition etc).

This is why F1 & LMP1 use separate fuel flow sensors (to enforce the fuel economy regulations) which do not work off of the ECU, injectors or fuel tank.

Also if it is the sensor will this one be a good one to use? (just looking at all my options)
http://www.ebay.co.uk/itm/Renault-C...niversal-/130636091187?_trksid=p2054897.l4275

Plenty of threads will say use OEM (Renault or Bosch - same thing different box) only but tbh I don't know if people have actually had issues with cheap ebay sensors.

IIRC MarcR used to be able to get hold of these for circa £45 ish which was the cheapest price around at the time.

 

[bozothenutter]

I have been getting an average MPG of 28.41 (with a max of 32.52)....but that is with a remapped car and a heavy right foot.
lambda's are all ok

 

[Diagro]

I have been getting an average MPG of 28.41 (with a max of 32.52)....but that is with a remapped car and a heavy right foot.
lambda's are all ok

What map? I am looking at getting the Ron98 man soon. Also my right foot is light

 

[bozothenutter]

Custom map mate, as I run an RS2 intake.......the sound it makes must be what gives me the heavy right foot

 

[Diagro]

And your still getting better MPG then me hahhaa

 

[MartinR]

Timing.

 

[Diagro]

Timing.

I will ask them to check it. Although his sons have Clio Sports and he does those so i kind athink he knows what he is doing when it comes to the belts. But will ask him anyway

 

[Diagro]

http://www.ebay.co.uk/itm/121152481986?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

have got one of these on the way.

The Timing is fine according to the garage who did the work. And did a test and i did 0-60 in around 7Seconds. So its fair to say its correct?

Anyway, Will fit this lambda Sensor and do two full tanks and see where im at

 

[Amos91]

Did you try just accurately working it out in the first place so see the true average?

 

[Andyman]

Lambda is common for bad economy so that's a good place to start. If this doesn't help maybe go to recommended tuning company to check your fueling / emissions.

 

[Diagro]

I did.
Worked out at 26mpg which is too low for how I drive.

 

[Rubicon_]

I don't understand why people buy these cars then complain about fuel economy.

Buy a diesel.

 

[Diagro]

I don't understand why people buy these cars then complain about fuel economy.

Buy a diesel.

Im not complaining about it. I would like it to at least give me the advertised MPG.
If it's not then something is wrong and needs to be fixed.
And that's what I'm doing

 

[Snake182]

Im not complaining about it. I would like it to at least give me the advertised MPG.
If it's not then something is wrong and needs to be fixed.
And that's what I'm doing

I had this exact same issue, was always 25-26 mpg no matter how light on the throttle I was.
I fitted a new bosch pre-cat lambda sensor as mine wasn't switching voltages properly and
now I am getting 29-30 mpg with normal /odd blast driving,

I get 32-33mpg if I drive carefully around town which is brilliant considering its engine size and power.

 

[Diagro]

I had this exact same issue, was always 25-26 mpg no matter how light on the throttle I was.
I fitted a new bosch pre-cat lambda sensor as mine wasn't switching voltages properly and
now I am getting 29-30 mpg with normal /odd blast driving,

I get 32-33mpg if I drive carefully around town which is brilliant considering its engine size and power.

This is the sort of thing i like to read, I hope for at least 6MPG increase and any more will be a bonus!

 

[Snake182]

This is the sort of thing i like to read, I hope for at least 6MPG increase and any more will be a bonus!

yeah, they are very common for unexplained poor fuel consumption (on most cars infact).
Make sure you change the lambda before the cat as this one is the one that controls the fuelling.
The one after the cat just monitors the catalytic converter is doing its job by checking the emission's exiting the cat and has no control over the fuelling at all.

 

[sum-dj]

I get around 32mpg. I drive 6.9 miles to work and same back home. 50mph roads. Use about £20 in fuel. Same as I used in my 1.2 Clio!! Used to have to blast the tits off that tho to do 50mph.

 

[Diagro]

yeah, they are very common for unexplained poor fuel consumption (on most cars infact).
Make sure you change the lambda before the cat as this one is the one that controls the fuelling.
The one after the cat just monitors the catalytic converter is doing its job by checking the emission's exiting the cat and has no control over the fuelling at all.

Yup, Its the Precat one I bought (although though they were the same). Hopefully its going to work.

I get around 32mpg. I drive 6.9 miles to work and same back home. 50mph roads. Use about £20 in fuel. Same as I used in my 1.2 Clio!! Used to have to blast the tits off that tho to do 50mph.

My Commute its 21Miles there and the same back, Car SAYS I'm doing 35MPG Average But when i work it out at the pump its doing between 23 and 26Mpg, So for me there is an issue.