Fuel Computer

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Fuel Computer

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Fuel Computer - 4/7/2007 7:23:30 PM

tcs17_tim

Posts: 22
Joined: 3/27/2007
Status: offline

Now the fuel reading in litres/100miles is annoying but has anyone else measured the accuracy of the fuel computer? I log my fuel and mileage at every fill up and compare it with the trip computer. The computer usually indicates between 8 and 10litres/100miles which equates to 45 to 55mpg. However the mpg actually achieved is usually between 39 and 42 mpg. My calculations show it as 18 - 24% out, that is very poor and next to useless.

I am happy with 40ish mpg but why is trip computer accuracy so bad?

Is this a warranty issue?

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2.0 TD (143bhp) Sport
Phantom Blue

Post #: 1

RE: Fuel Computer - 4/8/2007 3:02:29 PM

Dads_Taxi

Posts: 146
Joined: 2/4/2007
From: Cheadle, Cheshire
Status: offline

Good Grief, I just logged on to the forum to start a new topic, and you beat me to it!!

We even have the same model + colour!

Anyway, I soon learned to TOTALLY DISREGARD the fuel computer, it is optimistic in the extreme. My car has never bettered 44mpg, and that was a tedious trip when I deliberately plodded along to see if I could actually achieve what the computer claimed. On an average week's running I'm afraid I usually get about 36 mpg from a tank-full, with the computer reckoning I've averaged 45-ish. I'm impressed that you are hovering around the 40 mpg mark. My most depressing result was a fortnight of only doing the school run, with no motorway trips, and I got a wallet-walloping 32mpg.

I have just assumed that everyone suffers the same misleading figures, but would be pleased to hear from anyone who has found the fuel computer to be accurate, as that would imply that it IS possible to have it calibrated correctly.

Dave.

_____________________________

Mazda 5 2.0D Sport-Nav 2006
Phantom Blue

(in reply to tcs17_tim)

Post #: 2

RE: Fuel Computer - 4/8/2007 5:05:40 PM

tcs17_tim

Posts: 22
Joined: 3/27/2007
Status: offline

I find I get the best economy when doing the work run, about 10miles each way. A motorway run and economy drops a bit. This is opposite to all my previous cars (petrol). I put this down mainly to the heavier loads and size/shape hence worse wind resistance meaning higher speed is harder work.

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2.0 TD (143bhp) Sport
Phantom Blue

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Post #: 3

RE: Fuel Computer - 4/10/2007 10:27:24 AM

Puggit

Posts: 5
Joined: 4/10/2007
Status: offline

Hi all - another Phantom Blue 2.0 Sport (143) driver with a terrible fuel computer... Is it just us?!

I did manage to get over 500 miles out of the tank once, mainly cruising on good A roads and motorways... what mpg is that?

(in reply to tcs17_tim)

Post #: 4

RE: Fuel Computer - 4/10/2007 1:51:38 PM

traffikboy

Posts: 3
Joined: 3/14/2007
Status: offline

hey guys,
two things... first of all you could be getting numbers that are a little off because there are different gallons all over the world (imperial gallon, us gallon are two that I am aware of...) and 2nd... have any of you with your trip computers had to get "rebooted", or was there a code that you were given to "activate" your trip computer? I am in the USA with a Mazda 5.. we dont have trip computers here (at least not activated)..so if you can help us, that would be very much appreciated...

thanks,

Traffikboy

(in reply to tcs17_tim)

Post #: 5

RE: Fuel Computer - 4/10/2007 4:12:01 PM

tcs17_tim

Posts: 22
Joined: 3/27/2007
Status: offline

There was no activation required but there are 2 buttons 1 says info and 1 says clock. Pressing info takes me into trip computer and removes the clock display, pressing again changes the chosen trip feature, current mpg, average mpg, miles remaining (which seems to accelerate as fuel gets low each mile driven loses at least 2 on the miles remaining display!), average speed.

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2.0 TD (143bhp) Sport
Phantom Blue

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Post #: 6

RE: Fuel Computer - 4/10/2007 4:19:22 PM

tcs17_tim

Posts: 22
Joined: 3/27/2007
Status: offline

Puggit

500 miles from a tank (60 litres) is 8.3 miles per litre, therefore 37.8mpg. However its very unlikely you arrived at the pump with nil fuel left so you probably got 40 or more mpg. The most fuel I have ever put in was 49.5 litre when the needle was at the very bottom and if you put the same in for your 500 miles then you achieved 45.9 mpg.

To get accurate figures you need to fill up, reset trip then record mileage when you fill up next time.

_____________________________

2.0 TD (143bhp) Sport
Phantom Blue

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Post #: 7

RE: Fuel Computer - 4/10/2007 4:30:54 PM

davmal735

Posts: 41
Joined: 3/9/2007
Status: offline

Don't like to buck the trend but our trip computer has been OK. Generally 36 mpg (12 Ltrs/100) but 45 on a decent run. Perhaps running on slicks helps?

2.0 TD Sport Phantom Blue

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Post #: 8

RE: Fuel Computer - 4/11/2007 7:52:39 AM

Puggit

Posts: 5
Joined: 4/10/2007
Status: offline

I've never managed to get more then 50 litres in, when the tank guage and the computer say it's near empty - that equals 50 litres. So that was over 500 miles to about 49 litres

I know the car is specced with a 60 litre tank, but I daren't risk it - running out of diesel is an expensive game compared to running out of petrol!

(in reply to davmal735)

Post #: 9

RE: Fuel Computer - 4/12/2007 1:25:30 PM

Dads_Taxi

Posts: 146
Joined: 2/4/2007
From: Cheadle, Cheshire
Status: offline

I've just had my best-ever fuel consumption, did Wilmslow to London and back, 383 miles, used 38.3litres of diesil, which calculates to EXACTLY 10 Litres/100 miles, which is 45.4 mpg.
BUT, I forgot to zero the info computer before I left, so I didn't get to see it's imaginary figures!! Doh !

I have checked indicated consumption against actual on a previous trip though, got an actual 40.4mpg with the computer saying 47.9 mpg for the same trip, so it's 18% out, as suggested by tcs17_tim at the start of this thread.

Here's two great calculaters to help you work out your mpg from fill-up to fill-up.....

http://www.geocities.com/mpgcalc/

and http://www.cleavebooks.co.uk/scol/ccfuel.htm which works for US Gallons as well as proper imperial ones!!

Anyone asked Mazda if the computer can be re-calibrated yet?

Dave.

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Mazda 5 2.0D Sport-Nav 2006
Phantom Blue

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Post #: 10