C5 2.2HDi poor economy

andybsmith · Post by **andybsmith** » 15 Nov 2009, 23:49

Hi I have a 53 plate c5 2.2 HDi exclusive with an auto box my fuel economy is lousy about 22 mpg around town and about 42 mpg on the motorway, is this normal? The car has plenty of power although it suffers from slight turbolag when cold any ideas guys coz its costing me an arm and leg in diesel

lolingram · Post by **lolingram** » 16 Nov 2009, 07:58

Hi I have a 53 plate c5 2.2 HDi exclusive with an auto box my fuel economy is lousy about 22 mpg around town and about 42 mpg on the motorway, is this normal? The car has plenty of power although it suffers from slight turbolag when cold any ideas guys coz its costing me an arm and leg in diesel

Sounds about right to me - the around town figure means you are in 2/3rd gear for much of the time. 'Around town' can be very different at times.

HDI · Post by **HDI** » 16 Nov 2009, 10:00

Any other symptoms , like black smoke from the exhaust at any time ?

den169 · Post by **den169** » 16 Nov 2009, 13:54

Sounds bad to me.My 2.0 hdi estate does 42+ local and i live right at the top of the pennines so hills everywhere.At 70mph 50+.No chance of me buying a 2.2 then.

Trainman · Post by **Trainman** » 16 Nov 2009, 14:22

Hi Andy,

Unfortunately that is about the norm, the killer is the 4 speed auto box, having had the same vehicle (but the S2) on a 55, I actually get better economy from the C6 than I did from the C5 because of the 6 speed auto box

regards

lexi · Post by **lexi** » 16 Nov 2009, 15:06

It`s only when an Auto box locks up on the torque converter that it becomes as fuel efficient as a manual box. This is usually something that happens on overdrive mode. Older type autos are murder on fuel in traffic.

HDI · Post by **HDI** » 16 Nov 2009, 16:00

But 22mpg urban ??!!

Post by **CitroJim** » 16 Nov 2009, 16:55

HDI wrote:But 22mpg urban ??!!

It does seem low. My experience with the V6 is that the TC locks up quite enthusiastically and not only in top gear. I believe it'll lock from second upwards and it happens pretty quickly. Certainly I get better than 22mpg from the V6 around town..

Maybe the lock-up clutch is the problem or else there is a problem with the stator in the TC.

Easy way to tell if the TC is locked and that's to accelerate and see how the tacho needle responds. If flies up briefly with little apparent increase in road speed, the TC is unlocked. If it behaves like a manual car (i.e. the speedo follows the tacho in a linear fashion) then it is locked.

You can usually tell when the TC locks as you'll see a small decrease in revs.

What autobox does the 2.2HDi have? I'd be amazed if it were not auto-adaptive and cleverer than the V6 4HP20.

wheeler · Post by **wheeler** » 16 Nov 2009, 17:48

I belive the 2.2 HDi & the V6 use the 4HP20, all other models use the AL4.

cachaciero · Post by **cachaciero** » 16 Nov 2009, 19:27

2.2 HDi has the 4HP20 which does seem in my experience to often be in a lower gear than I would expect. However I suspect that the gear logic will be to keep it in a gear which ensures the TC is locked up. Having said all that I have not been able to improve the fuel consumption by driving it "manually"

My consumption is 40 ish on a long haul motorway and 29 on town and town and country route. In fact on one particular journey I do regularly which starts in town followed by 15 miles country B road and then finishes in town the consumption can be anywhere between 24 and 32 mpg. If town traffic is light at both ends then we are at the higher end. If the traffic is heavy at the start and lighter at the end then the consumption will be heavier than if the start traffic conditions are light and the end is heavy. I put this down to the engine management system which jumps through hoops to get the engine hot quickly including loading the alternator with close on a kilowatt of load used to heat the water quicker all this uses fuel, cold start and running in my experience eats fuel on this engine.

The only known defect on mine is a small leak on the intercooler which I don't think has a significant affect.

If the swirl valve system is not working correctly then this will make a difference to fuel consumpton below about 2500 rpm i.e increase consumption by maybe as much as 4mpg.

cachaciero

lexi · Post by **lexi** » 16 Nov 2009, 20:52

Interesting that 4HP 20 has lock up on more than one gear. The Puter must do that. On my last auto I had to put a switch fed through relay into auto box ECU. This let me lock up in 3rd and overdrive(4th).

Like Jim says you drop around 300 revs when you locked . You had to unlock before coming to a halt OR ENGINE STALLED. Ist generation ECUs. That was a Jatco.

Sympathy anyway mate. Nobody buys a diesel for 22mpg although it is the total yearly mpg that counts? Thing is guys . These new cars are heavy and heavy car with auto in town aint good.

I think I read that new Mini is heavier than old Zephyr V6

Post by **CitroJim** » 16 Nov 2009, 21:02

I believe the 4HP20 I have here as a spares donor is out a 2.2 as when I came to use the output/intermediate and diff gears from it in a V6 4HP20, the gearing did seem somewhat lower and has caused all kinds of trouble but that's another story...

The algorithms for the 2.2 diesel must be quite different. The V6 version, when it's got its super economy map selected, is very keen to keep in the highest gear possible and to get up to it quickly. It will happily change up into 3rd at 30mph with the engine doing barely 1500rpm and if you drift down to 30mph as you enter a speed limit it'll stay in 4th for a good while.

Andy, you haven't got it stuck in sport mode by any chance?

DickieG · Post by **DickieG** » 16 Nov 2009, 22:36

22mpg urban

what is it about the 2.2 that makes it so uneconomical compared with a 3.0 V6 petrol? Surely there must be something wrong with a diesel producing such low figures.

The HPi engines are also best left alone by all accounts which goes some way to explaining why there are so many of them for sale, so with a C5 you either go 2.0 HDi for economy or for more performance a 3.0 V6

andybsmith · Post by **andybsmith** » 16 Nov 2009, 23:43

Having flicked in between auto and sequential modes it does seem to hold 2nd gear for too long so I suppose that I'll just have to run around town using the sequential box and save the auto for motorways. It will happily pul 3rd at 1500 30 ish but in auto mode it will stop in 2nd until about 38 ish, thanks for the advice guys, hindsight before the act would be a marvellous thing lol.

DickieG · Post by **DickieG** » 17 Nov 2009, 07:54

Bearing the above in mind it may be the case that the gearbox requires re-initiallising or having a software update in order for it to select the correct gear for the speed (either a dealer or a friendly FCF member with a Lexia may be able to help you out with this).

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C5 2.2HDi poor economy

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