P38A mpg p38 2.5dse

My mpg says 22.3 or 23.2 all the time regardless of motorway or b roads...I've got 20wheels stormers on ...I'm trying to get at least 30 mpg ...would a remapping get me this figure..and smaller wheels

I never bettered 25 odd mpg in my DSE.....

Remapping for economy will reduce engine output as Diesel output is a function of fuel input as air charge is constant.

To increase economy, reduce fuel input.....to increase power, increase fuel input.....simple principle....

Obviously there are factors that influence efficiency, like air filter cleanliness, blocked or gummed up EGR/Intercooler/induction hoses and manifold, blocked exhausts, Viscous Fan constantly running, tyre pressures, driving style etc etc....

johnnysensi said:

My mpg says 22.3 or 23.2 all the time regardless of motorway or b roads...I've got 20wheels stormers on ...I'm trying to get at least 30 mpg ...would a remapping get me this figure..and smaller wheels

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What size tyres do you have on your 20" wheels? MPG depends on how the car is driven and the roads it is driven on and how far each trip is. On a decent M way run i get 32/34 MPG mine is chipped. Normally around town up hill down dale 20/22 MPG. But if i gun it around town stop start short runs it will drop below 20 MPG. If you have it chipped and drive like a nun you may see a slight improvement because of the chips more linear MAP. If you use the extra power and torque you WILL use more fuel.

27-28 mpg with mine never seems to alter much. Not chipped.

I get similar to wammers and mine is chipped. Im on 255 55 19's
I do alot of bimbling along country lanes at a constant speed. Definetely notice the difference when popping around cities etc. Seems to plummet!

No matter if I drive like miss daisy or boot it ...never changes ...275 40 20 ...I think ..there low profile tyres ...can drive different ways and stays same mpg ...confused loool

275 is quite a contact patch....rolling resistance I think is your enemy....

johnnysensi said:

No matter if I drive like miss daisy or boot it ...never changes ...275 40 20 ...I think ..there low profile tyres ...can drive different ways and stays same mpg ...confused loool

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Do you reset the computer when you fill up?

Rolling radius of your tyres is wrong. With 275/40/20 at an indicated 60 MPH you are only doing 57.2 MPH that will effect the computer calculations. 45s would be nearer giving at 60 indicate 59.4MPH

Also, the computer may well not be accurate. Mine does a couple of miles more mpg than the trip computer indicates.

Thanking you ..

Try brimming the tank a few times and work it out from there. Mine does over 30mpg on motorways doing 70 mph. If you go much higher, 20mph say for theoretical purposes, it will start to suck fuel fast. Similarly, towns will kill it.

I'm showing 25.8 at the mo, lot of round town, have had 32.2 on a run (70 and a bit more on motorway/ A roads). Chipped by Superchip.

tomcat59alan said:

I'm showing 25.8 at the mo, lot of round town, have had 32.2 on a run (70 and a bit more on motorway/ A roads). Chipped by Superchip.

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Have you compared the displayed mpg with the actual? I thought I'd read that chipped cars tend to over calculate the mpg because there is more fuel going in that the car expects?

The OPs car has tyres on his 20" wheels that send the wrong information back to the ECU. Speed is calculated as a mile = 8000 pulses from the ABS sensors. If the wheel and tyre have a smaller rolling radius it turns quicker for any given road speed and the 8000 pulses occur sooner. At an indicated 60 MPH the actual road speed is only 57.2 MPH. The fuel calculation is done by comparing fuel used and miles travelled. So if he put a gallon of fuel in and drove at an indicated 60 MPH for one hour then ran out of fuel. Theoretically his MPG should be 60. Were in actual fact he has only travelled 57.2 miles not 60. So he is only getting 57.2 MPG. This discrepancy cocks up the fuel computer. Just as it would if you had larger rolling radius wheels and tyres because they turn slower you would be going faster than indicated. Plus with smaller rolling radius's he is adding 2.8 more miles to his overall mileage than he needs to every 60 miles. You can't get that back.