A4 TDI PD115 Poor Fuel Economy

[stevebootes]

Hi all,

First post so please be gentle with me ;-)

I'm getting what I'd consider to be pretty poor fuel economy from my 2001 A4 Avant with a 115PD TDI Engine and an Auto-Tiptronic box.

My MFA Average currently says 31.2mpg.. not trusting this at all, I've worked out by hand from my fuel receipts (between full tanks) and I'm averaging around 36mpg. Fuel range on a full tank until fuel light comes on is normally around 380-400 miles. The best I've had is around 450 miles from a tank if I'm really careful on long cruises (though again, I fill up when the fuel warning comes on rather than fully empty).

I've ran various diagnostic tests with VAG-COM, including MAF sensor and Boost level checks. No problems there, no fault codes found, everything looks fine. I'm local to APS (the tuning company) so I dropped it down to them to take a look over, they couldn't find any faults with it.

The performance has always seemed a little poor to me - but then I came from a B6 S4 with full Miltek system so everything seems a little underpowered after that.

Brakes don't seem to be binding, I don't have any black smoke under load, no other obvious signs of problems. I do have what appears to be a slightly noisy aircon compressor - I can't believe that would have such a big effect on things but who knows. I have tried running with the aircon off on long journeys, which hasn't made any noticeable difference.

Am I being unrealistic for an Auto 115TDI? I previously had a TDI130 B6 A4, drove that hard and never got less than 550 miles from a tank, so I expected something similar from this car.

Any suggestions appreciated!

Steve

[neil w]

Could be the tiptronic giving lower mpg.
We have two A4 avant tdi's , one a 1996 110 tdi (5 speed manual) with 150,000 plus on the clock always averages 45 mpg (confirmed from fuel receipts).
The other a 2003 130 tdi (again a 5 speed manual) used to always give 43mpg, since the tuning box went on it now gives 49mpg around the doors and 56 plus on a run (again confirmed by fuel receipts)
The early car has a jetex panel air filter and the newer on the equivalent BMC one.
What I would say is the very often a MAF sensor signal will degrade as it wears out and not show up as a fault. the box on my later car takes this int o account and boosts and cleans upthe signal from the MAF sensor.