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Discussion Starter · #2 ·
What I meant to say about this car before I pressed the wrong button was that when I changed the air filter a month ago the indicated MPG fell from circa 31.2 to 28.1 and is still falling slowly.
Replacing the filter involved a certain amount of pipework disconnection around what I think is referred to as the hooter valve. Could it be that I have upset this device ?
Driving style does not seem to make a big difference. Can anyone help please ?
 

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Hmm, About a month ago the temperature around here (the South East) dropped from a higher than normal point to damn chilly, frosty mornings etc.
If you're doing short journeys frequently then the operation of the fuel injections' fuel enrichment (like having the choke on ) will cause the MPG to fall by this amount.
If your journeys are much longer there might be a problem but I don't think it's likely.
 

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Discussion Starter · #4 ·
Thanks for that cdcarlsson..I'm begining to think that my engine is not getting up to optimum temp during the winter. I bought the car in March 2001 and it was indicating 31 MPG but the previous owner was a motor way cruiser. I've noticed elsewhere on this board discussion on typical engine temp readings...I've only been paying attention to this in the last few days and it's not shifting above the seven o'clock position at the moment ! 6 miles to work 6 miles back, ambient temp -3 to +3 maybe not a good tome to judge ? indicated MPG now down to 27.8
 

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I had a similar experience when I got mine from a guy who used it for long motorway journeys. As it's an average figure, it takes a while to arrive at the real driving conditions of the new ownership.

If you want an immediate and accurate mpg, you should reset it and then what it records is only you and not the aggregate of your new data and the previous owner's numbers.
 

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I've noticed similar myself. I've seen postings with people saying they get an average of 30 - 31 mpg, I don't do a great deal of motorway driving and I'm lucky to get 24 mpg half the time.

Neil
 

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There was a thread on this a while back. For the record I have a 1992 9000 CSE 2.3 turbo, 5sp, and I return an easy 34 mpg at a steady cruise controlled and thoruoghly illeagal 80 mph between Bristol and Blackpool on the motorway. In and around Bristol the worst yet is 25.7 mpg.
 

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Don't forget that cold air burns better then warm air. So forgetting about extra alternator load, you ought to get better fuel consumption in winter - especially tiptoeing round slippery roads!
 

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I get similar figures to Zaphod in my 2.3 1990 non turbo - I got 34.5 on my run back home last saturday using country roads and the M6/M5. Round town its about 24 mpg - but because of the cold air I think I'm getting better acceleration as it leads to a larger volume of O2 in the cylinder.

Steve
 

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Sorry to disagree Liam, but cold air doesn't 'burn better' it's just denser which allows (slightly) more of the air fuel mixture into the cylinder on each stroke. This in turn creates more energy on combustion. As the engine management senses the volume of air entering the inlet with the help of the Air Mass Meter it gives the correct amount of fuel for the amount of air present so it will not be more economical.
I still stand by my earlier statement about the fuel enrichment having an adverse effect on fuel economy on anything but the longest journeys, even then it still has an effect but it will be masked by the large following mileage.
Nick.
 

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OK, so 'burn better' was a simplification. However, seeing as you're producing more power for any given throttle opening, you ought to be using less fuel to maintain the same speed?
 

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Yes, for any given throttle opening I think you will be getting more power when the inlet temperature is lower, but...
As I stated the Air Mass Meter senses the greater amount of air and gives the engine more fuel to go with the greater amount of air, so economy is just the same. QED.
By the way, if the engine wasn't given the extra fuel, it would be running lean, the most undisirable situation there is, especially in a turbo car.
Nick.
 

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34 MPG ?? Shrewsbury to Norwich, at night ....mostly motorway and dual carriageway at 65-70mph and I get 41.2MPG.(ish)

Or is my 1987 9000 Turbo using its little computer to tell me little porkies ?? (actually, from cash spent for litres used, I don't think it is )
 

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Tried and tested on my 2.3iCSE over the past 17,000 miles is average of 31.2 mpg doing mainly a 70 mile round trip on open roads, one way clear of traffic at 65 mph the other way the typical 40 mph crawl. It used to go up to about 35 mpg in the summer but seems worse now, perhaps I'm giving the heated seats too much stick. Still a Fiesta with 45mpg wouldn't be half as good. Worth it if you ask me, sod the MPG.
AB
 

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My brothers 2.3 FPT gives mpgs in the 40's and hes done measurements using full tanks of fuel and its correct... so maybe the turbo gives the boost when it really is needed and pushes up the mpg

Steve
 
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