What can I look at to improve economy as it seems to be low?

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Karlbar2k

Member
I Have had a chance today to go for a good long run In SWMBO's new a2. 1.4tdi 75 sport. On the same run in her old passat 130 pd with the same driving style I would have got 60. I only got 64? I know this is only on the DIS but still a valid comparison and i was expecting more.

I know all the obvious stuff as I regularly hyper mile my Octavia 4x4 (51 best ever, 40avg) so car has just had cam belt, oil and filter(pd oil) and air filter. Tyre pressure was a bit low on the fronts at 29 and 30 on the rears, so I know that will have had an effect. It's on 205/40/17's. I have a set of 15's and 16's coming soon an tyre choice will be narrower and +1-2%.

What other things do I need to start looking at? Car is standard so no obvious boost leak sounds under load (really obvious when the Octavia is having issues. Boosts to 21psi :D ).

At 87k should I be looking at cleaning the EGR and inlet manifold? Did the passat at 105k.
 
Firstly you can't trust the dis unless you have checked that it is consistent with the manual calculation over a full tank. What is your motorway cruising speed and how long was that trip? The wide 17s will also be dropping the mpg.
 
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I run 205-width tyres on 17" wheels and still invariably get in excess of 70mpg on a run. Could it be that one of your rear drum brakes is dragging?

Tom
 
I will check the heat of each rim on next run, I did have the handbrake adjusted as it was not holding on a hill
 
MikeMarsUK said:
Firstly you can't trust the dis unless you have checked that it is consistent with the manual calculation over a full tank. What is your motorway cruising speed and how long was that trip? The wide 17s will also be dropping the mpg.
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I know it is just dis vs dis but I was expecting more. On the way driving economically. Slow acceleration, 60-65 indicated on the motorway, slipstreaming when possible, overrun down hill, a bit of in gear pulsing etc and I got 63.8 on the DIS. As I said I could actually get 60+ out of the passat (bigger car with the 4cylinder pd) total trip is 80 miles so plenty of time for warm up etc
 
On the way back I zeroed the DIS and avg 70-80 normal acceleration and got 57? So not that much of a difference given the difference in driving style
 
What's your economy like when holding 60mph? Aerodynamic drag doesn't increase linearly with speed but increases as the square of speed, i.e. drag ∝ speed^2. Therefore, by calming your speed somewhat, you'll get fairly good gains in economy, as well as remaining within the law.
200 miles at 70mph takes 2 hours 51 minutes, whereas 200 miles at 60mph takes 3 hours 20 minutes. So, for the sake of 30 minutes every 200 miles, you could save a fair bit of cash.

Cheers,

Tom
 
If I remember rightly, the passat has a 6 speed box, so it will be pulling less revs in top than the A2. Engine friction is very significant and the A2's short 5th gear really doesnt help. I run 195 55 16's on the standard SE wheels which effectivly gives me 5% taller gearing. I have done a tank to tank with this tyre size and the DIS MPG is now spot on. It was over reading MPG before. I get 61MPG average, but that is trying hard, 55mph max, 2000rpm max on mixed driving.

Cheers

Andrew
 
You could:

a; fit the 1.2TDi aerodynamics add-on package - Stoke Audi parts sells it as a complete kit - front wheel arch lip spoilers, sub-frame spoiler and exhaust tunnel covers. This will give you a small reduction in drag and should improve MPG a touch.
http://www.stokeaudi-parts.co.uk/products.php?product=Audi-A2-Aero-Dynamic-Add-On-Kit

b; change the gearbox ratios in taller gears - either through the 5th gear mod (to make 5th longer), or via the new innovation kit of adding in a 6th gear (effectively giving you an overdrive 6th). Both work, but both are costly.

c; get obsessive about hypermiling and lower your maximimum speed on motorways! Free and effective!

d; try replacing the thermostat and coolant temperature sender - these are liable to failure and can have a significant impact on MPG. Just did that swap on my cousin's A2 who's MPG was down in the low 40s, they're now back up to 60MPG...

e; swap to the very lightweight, narrow OEM forged 15" alloy wheels, fit the 175 width tyres and reduce your rolling resistance for a useful MPG increase

f; crank up the tyre pressures - get them into the 40PSI region for useful MPG increase

g; try snake-oil remedies like adding 200mls of 2 stroke oil to a tank of diesel...
 
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I have some 15" pepper pots coming and have been looking at what size tyres to get. I also have a set of 16's coming which were going to have 205/50/16 but I am now thinking 185 instead

I know there are mods for improving economy but I am more concerned if there is anything wrong as I was expecting more from it.

The passat was a 5 Speed 130 pd
 
Karlbar2k said:
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I know there are mods for improving economy but I am more concerned if there is anything wrong as I was expecting more from it.

The passat was a 5 Speed 130 pd
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If you were pulse-&-gliding the Passat, they do P&G better than the A2 because they have more momentum (A2 is too light :))

I still have doubts about the DIS figure. It is meaningless unless you have compared a DIS tank figure with the manually calculated figure. If they match, then it is reasonable to start considering trip figures.


Karlbar2k said:
It does seem to take a bit longer to warm up than the passat used to?
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Does it go smoothly to 90 & stay there or does it jump around a bit? The temperature senders are notorious for going wrong.

How many miles/minutes does it take to heat up? Mine's usually around 4 miles / 12 minutes in the current summer weather. If it takes a lot longer than that, then it is probably the thermostat.
 
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I have done trip from cold dropping my daughter to work which is five miles away and I know that it is still not warm to 90 on the way back. However with a failed thermostat the temp would not stabilise at 90 on a run, it would drop when moving due to increased cooling effect and rise when in traffic?

I will have to test again when the 15's are on and see the difference they make. Thinking about 185/60/15?

What are the gains like from the aero mod kit that was mentioned?

I also know from experience that a remap will improve mpg (when driven sensibly of course) so this will be on the list if she wants to keep it as well.
 
Karlbar2k said:
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What are the gains like from the aero mod kit that was mentioned?

...
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Maybe an mpg or two at motorway speeds, no difference at town driving speeds of course. It all depends on the peak cruising speed (the slower you go, the less significant aerodynamic drag is).
 
Car seems to have adapted slightly as a 50 mile run yesterday resulted in 71 at 60ish. Can't wait to get some centre caps for the pepper pots and some tyres and see what a difference they make. Looks like mikes size of 175/65/15 will be the tyre of choice.
 
dan_b said:
You could:

d; try replacing the thermostat and coolant temperature sender - these are liable to failure and can have a significant impact on MPG. Just did that swap on my cousin's A2 who's MPG was down in the low 40s, they're now back up to 60MPG...

f; crank up the tyre pressures - get them into the 40PSI region for useful MPG increase
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dan_b, were the thermostat and coolant temperature sender showing fault codes?

What are the cons of running the tyres at these high pressures; if there aren't any, why doesn't the manufacturer recommend them?

Thanks, Andrew
 
ennio said:
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What are the cons of running the tyres at these high pressures; if there aren't any, why doesn't the manufacturer recommend them?
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Slightly reduced grip (although cornering is improved), but mostly it's harshness. You really get to feel the texture of the road surface...

Cheapo tyres will wear in the centre if the pressure is high (good quality ones won't). Audi have to recommend a pressure that will work with both. Currently I'm on 45psi front, 47 rear.
 
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ennio said:
dan_b, were the thermostat and coolant temperature sender showing fault codes?

What are the cons of running the tyres at these high pressures; if there aren't any, why doesn't the manufacturer recommend them?

Thanks, Andrew
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No error codes I just noticed a decline in economy and eventually that the car was taking a long tines to warm up. I'm running my tyres at 42 psi.
 
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