2.0 hdi very poor fuel economy pls help

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colin+teresac5
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2.0 hdi very poor fuel economy pls help

Post by colin+teresac5 »

hi i have a c5 2.0 hdi 110 auto the car is great apart from how much fuel it uses i drive steady but the is only doing 22 mpg any ideas please let ne know
den169
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Post by den169 »

Wow something wrong with that then.I have a 2003 sx estate hdi 110 and get 38 to 40 knocking about (in the pennines) and 50+ on the motorway at 70mph.
colin+teresac5
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Post by colin+teresac5 »

on the motorway it is fine and does around 50 mpg does any one know what speed the car should go into third gear mine changes at 35 mph so at 30 it is revving high any help
cachaciero
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Post by cachaciero »

colin+teresac5 wrote:on the motorway it is fine and does around 50 mpg does any one know what speed the car should go into third gear mine changes at 35 mph so at 30 it is revving high any help
I don't think it is as simple as that, not quite sure which box you have the AL4 or the 4HP20 but I believe that it is the same computer whichever mechanicals you have.
The laws that govern changing gear and lock up are quite complex depends on the speed you are doing, engine torque, whether you are accelerating or decelerating or on trailing throttle and even whether you are going uphill or downhill and what you are doing or have just done with the brakes.
Those are some of the factors the computer looks at to decide when to change gear then couple that with the fact that it is an auto adaptive system which means the box is constantly adapting itself to your driving in order to give the best gear for your particular driving style which simply put means that if the box changed gear at a given speed 10 minutes ago doesn't necessarily mean that it will change at that speed now all other things being equal.

My car has the 4HP20 and I often feel that it is in to low a gear, yet over any given route if I drive the car in manual or a mixture of manual and auto the resulting fuel consumption will often only be marginally better and sometimes worse than if I leave the box in auto.

I would say that if you have no warnings and the box appears to be working correctly in a mechanical sense i.e you can manually select all the gears and there are no apparent jerks or slippage then your fuel consumption problem is probably not the box.

What is your low end performance like in terms of acceleration? is the engine putting out a lot of smoke?. If it was my problem I would be looking at the EGR system, MAF or Turbo control.

cachaciero
2006 Toyota Prius T Spirit
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1995 XM 2.1 TD Auto SX died @ 140K
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