C5 2.2 fuel consumption - again!

[Peter.N.]

I am begining to become attached to my 2.2 C5 and although I am still looking for a 2.0 at the right price, this one seems reliable and fault free - at the moment, so I am wondering if there is anything I can check/do to improve the mpg. The very best I can get with my glass slipper driving is 49.6 whereas I have had 67.3 out of my 406 which is quite a difference. I have read of others getting in excess of 50 mpg from there's, if they can do that I should with my style of driving be able to do better.

I have so far fitted a tuning box which makes it go like the clappers (on rare occaisions) but has not changed the fuel consumption at all, I have also checked the mainfold flap valves which seem to be working OK, I have no warning lights only a 'low fuel additive' warning, which it isn't as I have topped it up but can't get my Lexia to work to reset it. Does anyone have any suggestions?

Peter

[Citroenmad]

I was talking to a guy with a 2.2 manual C5 the other day, he is on here actually but not a frequent poster, who said he can get over 60MPG from his on a run. It sounds as though he drives for economy, which must explain some of it. However as you do too, Peter, it can only be something slight amiss with your example.

I also know someone with a 2.2 auto and they are getting less than 30 on average and at best 37 on a run. I have had a look at it on my Lexia and nothing strikes me as a problem. The only thing I can see is it has recently had a new but cheap MAF. The owner is going to swap this for a genuine one and see if things improve. Having had a similar problem with a 2.0 110 C5 which was cured by fitting a genuine MAF, I fully believe this is the problem. So check yours has an original Citroen part.

As you know, a binding brake, underinflated tyre, tracking out of alignment etc all add to the drag. Have you checked the handbrake is not binding on? Its a common C5 problem.

[Lighty]

all of the above is great advice, tyre quality is also relevant.
Personally I think removing the DPF would give the best results, as this is just never going to help fuel consumption, I would expect an immediate 3 or 4 mpg, even more if its blocked or restricted in any way,

[red_dwarfers]

Maybe you could buy some magnets to put on your fuel lines

Once I'm back from the ICCCR and Scotland shall I pop over with my Lexia? I'd be interested to have another look at yours while I'm there. I should be back from around the 21st.

[Citroenmad]

Here is a thought which might disprove my MAF theory on your car. To me the MAF on the 2.0 110 and 2.2 look identical (they might well not be internally) on the outside and will fit either car. Since you get good economy from your 2.0HDi 406 I would try swapping the MAF from one to the other and see how that goes. It might take a good few miles to notice the difference, but its a very easy way to rule it out.

[Peter.N.]

Thanks for your replies and suggestions, I might well try swapping MAFs and see if it makes any difference. I can immediately see the difference in fuel consumption between the two when I go from here to Axminster as I frequently do, there is a three mile stretch of the B3165 which is fairly level, drive on it at a steady 50 mph in the 406 and its showing 60-70 mpg, on the C5 about 40-50, so any improvement would become instantly apparant.

I was getting 50+ on a run from my XMs, better than this super efficient Hdi engine! There is no lack of performance from it especially with the tuning chip, put you foot down and it pins you into the seat, nice but to expensive. I used to run the XMs with soft tyres deliberately to improve the ride but could still get 50+ mpg.

I will look into this MAF business and keep you posted.

Peter

[Citroenmad]

I will look into this MAF business and keep you posted.

Peter

Its certainly worth a try

[jgra1]

500 miles at the weekend, all with as light a foot as I could get away with.. while trying to keep to 70.. all motorway

46mph average, and about the same for fuel :O

I couldn't do much better from my 110 C5 2.0.. all driving without shoes too! ...

oddly, i returned not far off this figure when I drove my V6 406 coupe a few years ago !...

[Citroenmad]

Was that in a 2.2 jgra1?

I get just a shade over 50mpg on average from my 2.0HDi 138 C5, not hanging about too much but I do a good few motorway miles and long runs. On a really good trip taking it fairly easy, never below the limits, it will do nearer 60mpg. Big car comforts and enough power yet with the day to day running costs of a shoebox.

[jgra1]

Chris sorry that is my 2.0 C5.. (my new one) ....

hmmm
John

[triumphtoledo]

Citromad, if your c5 II 2.0 HDI is anything like mine, the computer MPG read out is 5-8% out. Mine achieves a real 42-48mpg normally.

R

[Citroenmad]

Citromad, if your c5 II 2.0 HDI is anything like mine, the computer MPG read out is 5-8% out. Mine achieves a real 42-48mpg normally.

R

I have checked mine quite regularily and find it is as near as makes no difference spot on, give or take 1mpg. Our C5II 2.0HDi does overread slightly, by about 2mpg usually. I have no idea why there is a difference between cars. Our 2002 C5 HDi underreads by about 3mpg.

[Peter.N.]

Right, as we were going to Trago Mills this afternoon, a round trip of about 100 miles I decided it would be a good time to swap the MAFs over, had a good look at them both and the seemed identical - until I got them out that was, the 406 one has a smaller diameter, so I put it back, other than that they are the same.

While I had the C5 one out I decided to try giving it a clean, the most volatile liquid I have here is Easystart, it has the added bonus of making you feel relaxed so I gave it a good spray, I didn't really expect any improvement but I was wrong, the best average consumption at a steady 60 mph I have had so far was 49.6, today it was 53.3 for the round trip, not a spectacular improvement and still about 10 mpg worse than the 406, but at least its something.

Where do I go from here?

Peter

[SaabC5]

Peter try some Wynns EGR3 down the pipe to the EGR valve and also the other side of the pipe into the inlet manifold. Its about £8 from eBay and certainly livened up my 2.2 and gave better fuel economy into the bargain.

Andy

[Peter.N.]

Thanks Andy, I will look into that. I don't want it livening up, its lively enough, I don't mind unlivelying it if it will improve the consumption.

Peter