Tdi With Low Mpg Average, Any Ideas?

[34laxy]

Hi folks,

 

The average MPG readout on the dashboard has currently settled around the 37.0 mpg mark. In its prime it used to achieve 44.0+ on runs along the motorway, but no longer :-(. It currently has 95K on the clock and VAGCOM reports a good match between the expected and delivered values on the Air Mass (guessing the terminology here as it was last week when I ran the dynamic test). No other faults reported on VAG COM. Replaced air filter in January and as far as I'm aware it has the original MAF sensor and Cataylitic converter.

 

Thoughts and ideas much appreciated ;-)

[gregers]

cant help im afraid,but funnily enough mine seems to be very similar to yours,i just thought either me or the missus had a heavy right foot,so i look forward to see what people suggest.

[seatkid]

1. Change engine oil for high quality fully synthetic fuel economy grade (5w30 or 0w30) meeting PD requirements of course.

 

2. Fit some decent tyres e.g. Continental Premiumcontacts instead of those Kamakazi brands.

 

3. Make sure the air pressures in the tyres are correct and at upper end of allowable range) and check you dont have any steering geometry defects

 

4. Start using Millers diesel power sport 4 additive, possibly at double dose for the first tank to clean up those injectors.

 

5. Check your rear brakes are not binding (do the discs get stinking hot?) - the handbrake actuator has a habit of sticking on.

 

6. Make sure the engine undertray is fitted!

 

7. Remove the battery lead for 2 minutes (after you remember to check you have the radio code first!) to reset all ecu parameters.

 

8. Clean the car and give it a good polish/wax - make it feel grateful......

 

9. Give it an Italian tune up or two (with Millers in the tank!)

 

10. Drive slower and treat it like you would a young virgin and after a while you will enjoy 50mpg+ as a reward!

Edited March 21, 2009 by seatkid

[davgree]

Another line of thought could be to get your injectors serviced! -yes its expensive, but the rewards could be high!

 

I had a black smoke problem recently with my Galaxy and threw some money at it trying to resolve the problem, I had one new injector and the other 3 refurbished. The report on the state of 3 injectors sent for refurbishment was that they were not atomising the derv correctly, which will reduce mpg.

 

Now my Galaxy (2004 Tdi Auto) will return about 450 miles per tank rather than the previous 380-400 miles per tank. Thats over 10% better, as I use my Galaxy as a Taxi, fuel savings will pay for refurbishment within a year.

 

I used http://www.uniteddiesel.co.uk/ who charged abut

Edited March 22, 2009 by davgree

[seatkid]

Another line of thought could be to get your injectors serviced! -yes its expensive, but the rewards could be high!

 

I had a black smoke problem recently with my Galaxy and threw some money at it trying to resolve the problem, I had one new injector and the other 3 refurbished. The report on the state of 3 injectors sent for refurbishment was that they were not atomising the derv correctly, which will reduce mpg.

 

Now my Galaxy (2004 Tdi Auto) will return about 450 miles per tank rather than the previous 380-400 miles per tank. Thats over 10% better, as I use my Galaxy as a Taxi, fuel savings will pay for refurbishment within a year.

 

I used http://www.uniteddiesel.co.uk/ who charged abut

Edited March 22, 2009 by seatkid

[gregers]

hi seatkid,just reading your smoke test results.heres mine from my mot on the 12/2/09

 

smoke reading

peak 1 =2.34 m-1

peak 2 =1.57

peak 3 =1.31

 

zero drift =0.04 PASS MAX 0.10

 

average =1.70

 

MOT TEST RESULT

turbo =1.70 m-1 PASS MAX 3.00

 

 

as i havnt a clue on what these all mean apart from being pleased it passed,and im assuming you do?how good are they in the general scheme of things.

 

and i do occasinaly carry out the italian tune ups.

Edited March 22, 2009 by gregers

[suzuki91]

my tdi 115ps galaxy is returning about 35mpg as well. the under car heater is running most times i start the car as well.

even returning from france at 85mph it did 35mpg.

[seatkid]

hi seatkid,just reading your smoke test results.heres mine from my mot on the 12/2/09

 

smoke reading

peak 1 =2.34 m-1

peak 2 =1.57

peak 3 =1.31

 

zero drift =0.04 PASS MAX 0.10

 

average =1.70

 

MOT TEST RESULT

turbo =1.70 m-1 PASS MAX 3.00

 

 

as i havnt a clue on what these all mean apart from being pleased it passed,and im assuming you do?how good are they in the general scheme of things.

 

and i do occasinaly carry out the italian tune ups.

 

I dont really know what units MOT opacity is measured in - I think its % per metre where % is the reduction in light transmission using a defined light source.

 

MOT smoke tests - as I understand - should be carried out under controlled conditions, the most important of which is that the engine is at working temperature - the oil temperature should be checked to be above 80 deg C. My experience is this is rarely the case - the temperature is usually marked n/a. However, it is difficult if not impossible to reach 80deg C oil temp from cold just by idling a Tdi engine.

 

The test consists of one or more (maximum of six), maximum engine speed runs for several seconds each, during which time a machine measures opacity.

 

The engine will be accelerated up to governed speed and the smoke density measured. Engines that emit very little smoke and achieve a meter reading of 1.5m-1 or less will pass the test after the first acceleration. However, if the test is not passed on the first acceleration a further two accelerations will be carried out. The average of the three acceleration readings will be calculated and if the reading is at or below 2.5m-1 for non-turbocharged engines or 3.0m-1 for turbocharged engines, the vehicle will pass this element of the test. However, if the average is higher, a further acceleration will be carried out, and the average of the last three readings will be calculated. This will continue up to a maximum of six accelerations. If the average of the fourth, fifth and sixth accelerations is higher than the appropriate level, the vehicle will not pass the test. In addition, vehicles may be refused a certificate if the exhaust emits excessive smoke.

 

Black smoke in the MOT test can be caused by several things.

 

Accumulation of soot in the exhaust system. (Italian tune ups usually shift this)

Poor atomisation or spray pattern due to dirty or faulty injectors or low injection pressures.

Injection timing problems.

Overfuelling and/or inadequate air intake (remaps and tuning boxes)

[smokie]

Hi all iam guessing that an "Itailian tune up" means revving the nuts off it?????

[seatkid]

Hi all iam guessing that an "Itailian tune up" means revving the nuts off it?????

Yes, but under load, full throttle, say in 3rd gear on a deserted Motorway. Only do this if you are sure your engine can stand the stress e.g. it has had its services / cambelt change etc to schedule. And dont it with a cold engine.

 

Don't break the speed limit, and have some consideration for the drivers following you - they won't appreciate what youre doing.

 

Ideally,start off and accelerate hard (max throttle) through the gears, hitting 4000rpm until 3rd gear (you might want to limit your speed at that point!) - keep it there for 30secs or more, then slow down and repeat. The idea is to try and get maximum exhaust gases flowing.

 

A quick glance in the rear view mirror will confirm how badly clogged the engine is.

Edited March 23, 2009 by seatkid