406oc.co.uk

Hi,
I'm on my first full tank of diesel in a 2.2HDi SE estate- really nice car so far, 100k, 2003, mechanic owned, has had a clutch, cambelt, steering rack, tyres, brakes all round, FSH etc etc. MPG seems alarmingly low though- around 30 for short trips, 34 on a run according to the onboard computer. Range is coming up as around 300 now, and i've covered 99 so far which would be 400 to a full tank! Eeks! It does have an after market k and n air filter, and will need oil and filter in 3 months. Should i change the k and n back to a standard air box to improve this? Does anything else come out when a K and N goes in? Airflow meter for example? Anyone have any other pointers? Our old 90bhp 2.0HDi estate was still achieving 48 average so i need to get this better or it will be a bit of a false economy upgrading the car!

a remap and de-fap should see it get abit better but the 90 are abit more economical than the 2.2

There have been a few stories of aftermarket air filters (especially oiled ones) destroying the MAF sensor, which would cause lower MPG due to overfuelling. It doesn't usually flag a DTC or EML though.

The only way to check really is to get hold of a known working MAF.

check to see if it has a tuning box plugged in to injectors if it has it just pumps extra fuel into to gain minimal power increase

Definitely bin any tuning box. They're rubbish.

The consensus on the standard air filter seems to me to be that it's big enough.

If you need a MAF then this Auto Sensors place seem pretty good. Some people on the coupe club say that they don't expect a MAF to last more than 10 years. Our approach here is 'if it aint broke...'.

Is your trip computer accurate? Mine is out by about 12mpg compared to brim filling, but I've never seen another so bad.

Is your FAP blocked? Definitely get a de-FAP!

Have you got any fault codes logged?

EGR or air doser sticking open?

Thanks folks. I'll take a look to see if any other tuning add ons are present. Thinking of buying and fitting this:
http://www.ebay.co.uk/itm/PEUGEOT-406-C ... 69d&_uhb=1
and have it serviced at a peugeot specialist in the hope it will improve- service indicator is at 1500 until a service, so as it is a new car to me i'll get it done now and see what's what. No fault codes logged or any warning lights- a full compliment is there at ignition.
Just travelled 30 rural miles and my range has improved to 370, i know the onboard trip computer isn't gospel.
thanks

Hi & welcome to the forum.

650 - 700 miles to a full tank is about right. I would definitely go back to the std filter.

Does it still have the FAP, (dpf)?

Just done some maths with a brim to brim tank,mostly up & down the M5 for work(80 on the cruise) & a bit of running around & i`ve managed nearly 47mpg.Pretty much what my computer tells me.Thats with a 2003 hdi 110 se estate 177k miles,remapped to 140 ish with a oiled k&n filter on it since 60k odd miles.

Yes the DPF is still there. I'll buy that standard filter box with the MAF in it and have it serviced. Fingers crossed. Is £40 reasonable for the box and sensor?
Thanks

Suggest you seriously think about getting rid of the FAP, mainly to avoid future expense. It definitely wastes some fuel every regen cycle and maybe a little bit all the time.

Thanks. Back to standard air box, service, defap and a remap then! I presume you have done the same? What did it cost for the removal of the dpf and a remap?

This whole issue of messing around with cone filters interests me. Are there any properly documented trials on this? I have a sneaky suspision that all they do is to make money for the people making them.
Not least of which being can it be good to be using hot air from behind the rad?

rupesmcd wrote:Thanks. Back to standard air box, service, defap and a remap then! I presume you have done the same? What did it cost for the removal of the dpf and a remap?

Not a lot - I've PMed you some details.

Busman wrote:This whole issue of messing around with cone filters interests me. Are there any properly documented trials on this? I have a sneaky suspision that all they do is to make money for the people making them.
Not least of which being can it be good to be using hot air from behind the rad?

I'm sure you're right. Might have made a difference in years gone by when cars were less well sorted.
If the standard airbox can handle the air demands of a v6 at maximum revs, or a remapped 2.2 HDi at 1.5 bar boost, it's not going to struggle too much with any other 406.

I did 500 miles this week, all on the M27 and in rush hour traffic, with only the occasional ' get off my back bumper ' blast when some german car is tailgating me, but not for long. Not because of my great acceleration but more because they didn't want to be covered in black oily smoke....
Imagine my surprise when my high mileage 2.2Hdi with de-cat, de-fap and 180 remapped 7 seat estate showed this It shows 400 as I refueled after the first 100 miles and reset the counter.
Happy days, even my Hdi90 was only getting 55mpg on a run and that was driving as if I was a cautious pensioner.