fuel computer

[bill196510]

what does the fuel computer use for calculations. when i accelerate it goes down to 17mpg. any slight push on throttle sends economy right down. does it use maf.
its so poor on fuel its scary.
cheers
bill

[CitroJim]

Depends on the vehicle Bill. Which one do you have?

But generally they work on information supplied from the engine ECU which has a pretty good handle on fuel flow rates and vehicle speed and so on...

[SaabC5]

Just drive down hills Bill, i can get 999mpg downhill, thats pretty good for a 2.2.

[bill196510]

oh yeah lol citroen c5 2.2 hdi 2003
going to map out dpf and egr soon.
can dpf and egr have big affect on mpg

[wideboyno1]

It all depends on who you talk to.Can only speak on my experience but my '53' 2.2 gives me around an extra 70-80 miles per full tank now.Had the dpf took out a while back,engine ecu remapped and egr blanked off.

So in my case it was well worth it,especially with the increase in useable power when needed.Only downside is the very slight increase in smoke out the back but really nothing to worry about.

HTH

[bill196510]

so i don't need to map out egr then

[wideboyno1]

Don't think it's strictly necessary but have heard talk about it before.If it helps i do get the occasional 'Anti-Polution Fault' pop up and Lexia diagnoses it as a flow problem with the egr.It's apparently actually caused by one of the sensors supplying info to the egr so not sure whether it would be better to map it out completely but the place that did mine didn't seem to think so.
Good luck with it anyway,wish i was brave enough to have done my own.

[bill196510]

I use memoscan u480 £14 including delivery, when it goes in limp mode, quick scan and delete, less than 1 minute, back to normal, lol. Scanned 2001 c5 aswell, it scans anything done a few fords and rovers, thought need lixia if diesel and older than 2004, but this works a treat, lol. Saves 30 a trip to garage, can reset limp anytime, carry it in car:P:D:D:D

[Peter.N.]

My 2.2 will descend into single figures if I push it hard, unlike the 2.0. which doesn't often go below 20 mpg.

Peter

[bill196510]

Sounds like an 80's petrol auto mpg, I had a vw santana 1.9 5clnder auto, 125 mph did at least 25mpg but 18 if pushed, lol.
Vw tdi never gets poor mpg no matter wat u do to it

[citroenxm]

The 2.2 hdi in early cars is not known for being great on fuel anyway.. 40tops... driving carefully ..

[JohnD]

When I set off on a journey pulling my caravan, with the cold engine and mostly uphill to reach the M25, my fuel computer is usually showing about 9 miles per gallon for the first few miles. It isn't until I can get into 6th gear that the consumption figure gradually creeps around to 30ish.

Incidentally I've had my particle filter removed and although the engine is a bit more lively, fuel consumption hasn't changed hardly at all.

[bill196510]

When I first got car about 3 months ago, did 47.9mpg going to cleethorpes over humber bridge, 257 miles, lots traffic, steady run taking daughter to work, 32 miles round trip, 26 being motorway at 60 mph, 50.1mpg, now same run, 31mpg, would blocked egr and dpf affect mpg this much, lost abit of power aswell.

[Peter.N.]

I have never had a good fuel consumption from my 2.2. When I first had it I managed 49 mpg at a steady 60 mph on the motorway but it normally averages about 40 mpg and I drive with a glass slipper, my 2.0. C5 on the other hand did over 60 mpg whan I drove it back from Wales after buying it. I very occasionally see reports of 50 mpg or more for the 2.2 but the vast majority of owners giving poor consumption figures with auto's showing less than 30 mpg in town.

The 2.2 is a nicer car to drive than the 2.0. but I can't live with that fuel consumption so it has to go. If anyone knows how to improve it I would be very interested to know, I have cleaned the MAF and EGR, I even tried a tuning box, it went like a scalded cat but the fuel consumption remained the same.

Peter

[bill196510]

Mine 9.4 round town lol.