diesel consumption again............

[keir1163]

chaps,
this is now frustrating me as i cannt work out if the car is running efficeintly so i would appreciate input.
Now running around on short journeys i sort of accepted 27.9mpg average (ipk)..........but i went to cornwall and back. At the end of the down leg the computer upped its average to 31mpg. Now on the way back i did a brim to brim fill. Driving was approx 50miles faffin around cornwall and 365 miles home.
On the way back i did hit traffic. Now a brim fill showed i had actaully averaged 38mpg yet my IPK showed 32.8mpg..........
i know the brim fill is the best way but would memebers still say my car is poor on consumption ?........i just need to know if i should be looking at doing something (i have ordered a tuning box)

any ideas

[Mintee]

Originally Posted by keir1163

i just need to know if i should be looking at doing something (i have ordered a tuning box)

any ideas

Change your air filter and PCV, clean the EGR. You might as well change your fuel and oil filters while you are at it and use 5w/40 fully synth oil. Check your tyre pressures (and that the brakes are not dragging)

But what 'tuning box' have you ordered? A faulty MAF can cause fuel consumption issues but for resolving issues with them anything other than one of Rover Ron's Synergy boxes is dubious at best.

And do a search for setting the trip computer, I recall there is a thread somewhere about how to adjust it so that you get a reading closer to your actual fuel consumption. Worth remembering the trip computer is just a computer - and 'garbage in equals garbage out'. There is no point in believing an instrument that is not error corrected.

[keir1163]

Hiya,
yep done all the filters....and all the basics.
MAF appears to be working fine but i cleaned it anyway. I bypassed the EGR......
i just feel 38 is too low and its even worse when i faff around locally!

[HarryM1BYT]

Originally Posted by keir1163

Hiya,
yep done all the filters....and all the basics.
MAF appears to be working fine but i cleaned it anyway. I bypassed the EGR......
i just feel 38 is too low and its even worse when i faff around locally!

There seems to be a large discrepency between the IPK figure and the brim to brim - are you resetting the IPK when you do the brim?

Either way, your mpg figures are terrible compared to mine, so I can only repeat again what you seem to have already done. Your touring run should have produced nearer 50mpg if a manual. EGR, PCV, MAF - air filter and driving style.

The Synergy (if that is what you meant) will not fix other issues, sort those out first - then you might see some small improvement with the Synergy.

[Mintee]

Originally Posted by keir1163

Hiya,
yep done all the filters....and all the basics.

Recently?

Originally Posted by keir1163

MAF appears to be working fine but i cleaned it anyway.

Cleaned it and it made no difference? Could it have been faulty to start with?

Originally Posted by keir1163

I bypassed the EGR......

With what?

Originally Posted by keir1163

i just feel 38 is too low and its even worse when i faff around locally!

Is your thermostat working properly? What does your guage read when up to temperature? Do you use your air conditioning a lot?

FWIW I have been getting an average of 43.6mpg - with a best of 50.5 and a worst of 36.1 - and yes I am dull enough to have kept a spreadsheet of my consumption for the past year. The consumption improved after I serviced it fully just after buying it. This dropped again in the cold in the winter but rose in the summer (I put this down to the thermostat not working - still not changed....) Note - the majority of this has been with the Synergy set to '10' and a Pierberg MAF - but I did not notice a significent change in fuel consumption with it. I presume because my MAF was in fact knackered when I got the car. As a whole the car goes much better now than when I bought it and it seemed to be OK. Also I know my fan is on the way out and so I don't use the air con much at all.

[keir1163]

Hiya,
appreciate the advive.
Yes filters done in last 1000miles....remind me about the PCV?
i donnt reset every time
ironically if i stand the car at Idle the heater blows coldish....when its running its as hot as i would expect?

[Dave***t]

Originally Posted by keir1163

Yes filters done in last 1000miles....remind me about the PCV?
i donnt reset every time

I get particularly poor mpg because of the way I drive to work (all very urban, a lot of traffic and with a heavy right foot because I'm usually late!), but when I had my diesel ZT even I was getting better than you seem to be getting. Long term average (nearly all urban) was 33ish, distance driving a lot higher.

PCV - small filter unit near the top of the rear of the engine, should really have been a service item on the diesels, has now been superceded by a fit-and-forget version from BMW.

Surely if you don't reset every time, you're logically inevitably going to get a different figure from the brim calculation, because the IPK will be showing an average since it was last reset rather than a figure for the tank in question?

Seems likely that your thermostat is suspect - a mildly faulty one will be preventing the engine getting up to optimum temperature and therefore hurting mpg.

[Frank Incensed]

Originally Posted by Mintee

I have been getting an average of 43.6mpg - with a best of 50.5 and a worst of 36.1 - and yes I am dull enough to have kept a spreadsheet of my consumption for the past year

I've been keeping a spreadsheet too, for the 5 months I've had the car. I've changed the air filter, the PCV, the MAF and cleaned the EGR. Consumption has changed little, no matter what my driving style. it's always 28 - 30 urban and 30 - 35 touring. Best ever brim to brim was 34.5.
The thermostat is now the only common suspect left (coolant temperature in the low to mid 80s), but I'm beginning to doubt whether running at 90C - 92C is going to get me the manufacturer's stated average of 40ish combined and the high 40s on a run. There's got to be some other factor. What about the injectors? Anybody changed them and noticed an improvement in consumption?

[sof007]

Originally Posted by Frank Incensed

I've been keeping a spreadsheet too, for the 5 months I've had the car. I've changed the air filter, the PCV, the MAF and cleaned the EGR. Consumption has changed little, no matter what my driving style. it's always 28 - 30 urban and 30 - 35 touring. Best ever brim to brim was 34.5.
The thermostat is now the only common suspect left (coolant temperature in the low to mid 80s), but I'm beginning to doubt whether running at 90C - 92C is going to get me the manufacturer's stated average of 40ish combined and the high 40s on a run. There's got to be some other factor. What about the injectors? Anybody changed them and noticed an improvement in consumption?

I forgot to mention that I used an STP injector cleaner additive and it did seem to make a difference but i'm not sure how much as I upgraded a few bits and pieces during the same brim to brim run.