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TDI Fuel Economy Discussions about increasing the fuel economy of your TDI engine. Non TDI related postings will be moved or removed.

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Old February 7th, 2012, 15:30   #16
WYnWest
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oops wrong spot sorry.

Last edited by WYnWest; February 7th, 2012 at 15:46. Reason: wrong thread
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Old February 7th, 2012, 15:55   #17
allana13
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That is handy information Mike.

I was under the impression drive the TDI between 1500 and 2000 rpm to achive max economy.

BTW how did you manage to get 72 avg MPG on your Audi A2 ?
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Old February 7th, 2012, 21:44   #18
lilspoon
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Do they make guage pods to monitor boost and fuel pressure for these cars?
Just switched from cummins diesels over to the tdi and have been reading around this site for two days. Alot for me to learn as a pick up my 2004 jetta in two weeks.
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Old February 8th, 2012, 00:36   #19
MikeMars
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Quote:
Originally Posted by allana13 View Post
That is handy information Mike.
I was under the impression drive the TDI between 1500 and 2000 rpm to achive max economy.
BTW how did you manage to get 72 avg MPG on your Audi A2 ?

'Reasonably frequently' is very different from 'always' :-) They can mean virtually the opposite things in terms of the overall time spent at different RPMs. The point is that you need to hit all parts of the rev range SOMETIMES. It doesn't mean that you have to keep the revs high all the time, or even for a significant fraction of time.

I keep the revs low most of the time, which can mean near 1000 in a 30 zone. But it hits 2100 (=60mph) or so every day on the highway part of my journey (70%) which is enough to keep the car decoked, and once in a while I thrash it anyway (push it all the way up to the red line at 100% throttle. But that might be once in one or two months, not even once per tank).

The A2 is relatively low geared compared to my old Passat. I used to have to red-line it more frequently (once every one or two tanks) to keep it decoked, simply because I was usually under 2000 when I was highway cruising. However, when I started pulse&glide instead of steady driving, that was enough to blow the cobwebs out on it's own.

Regarding my average MPG of 72mpg, if you notice that's UK mpg not US mpg. In US terms that's about 61 or so. It's a fairly easy target on the A2 (you'll see back-to-back 75mpg tanks during summer in my fuelly log).

It was very much harder reaching 70+ MPGuk on the Passat, although I did manage it back-to-back several times with a great deal of hypermiling effort.

I don't bother with the hypermiling on the A2. Both cars had basically the same engine (PD TDI), but the A2 has 3 cylinders & the Passat had 4, and a massive difference in weight due to the aluminium body of the A2. Hence 25% less engine resistance on the A2, versus longer glide time on the Passat due to the greater momentum. Overall the benefit of P&G is less now, whereas it was vital on the Passat.
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Audi A2 TDi 1.4*, 6M/0.588, mild aero mods, 103hp remap (* 3 pot version of 1.9PD)
Y2000 Passat TDi 115 PD RETIRED, M5, Best 75MPGuk, usually 60-70. 900m clubx7. 1000 mile clubx3.
VW Fuel saving tips

Last edited by MikeMars; February 8th, 2012 at 00:58.
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Old February 8th, 2012, 04:40   #20
whitevanman
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Quote:
Originally Posted by Sevenjays View Post
Slowing down a bit has helped me. I was at 38mpg going 72mph. Slowed to 68 or 69 and I'm above 40mpg now. I just started setting the cruise to 65mph. We'll see what that does. I would really like to average 45mpg. I'm putting most of the other suggestions into practice already.

Thanks for the thread and ideas.

BTW, at 25,000 miles a year and $4.00 a gallon fuel, 1 mpg increase is about $55/year savings. Hmmm, $200 every 100,000 miles is almost the parts kit for my timing belt change!
40mpg is terrible for a 1.9 tdi.
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Old February 8th, 2012, 09:29   #21
allana13
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Quote:
Originally Posted by whitevanman View Post
40mpg is terrible for a 1.9 tdi.
Thats what i get as well.

I am based in the UK though
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Old February 8th, 2012, 10:16   #22
JettersTDI
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Quote:
Originally Posted by MikeMars View Post
'Reasonably frequently' is very different from 'always' :-) They can mean virtually the opposite things in terms of the overall time spent at different RPMs. The point is that you need to hit all parts of the rev range SOMETIMES. It doesn't mean that you have to keep the revs high all the time, or even for a significant fraction of time.

I keep the revs low most of the time, which can mean near 1000 in a 30 zone. But it hits 2100 (=60mph) or so every day on the highway part of my journey (70%) which is enough to keep the car decoked, and once in a while I thrash it anyway (push it all the way up to the red line at 100% throttle. But that might be once in one or two months, not even once per tank).

The A2 is relatively low geared compared to my old Passat. I used to have to red-line it more frequently (once every one or two tanks) to keep it decoked, simply because I was usually under 2000 when I was highway cruising. However, when I started pulse&glide instead of steady driving, that was enough to blow the cobwebs out on it's own.

Regarding my average MPG of 72mpg, if you notice that's UK mpg not US mpg. In US terms that's about 61 or so. It's a fairly easy target on the A2 (you'll see back-to-back 75mpg tanks during summer in my fuelly log).

It was very much harder reaching 70+ MPGuk on the Passat, although I did manage it back-to-back several times with a great deal of hypermiling effort.

I don't bother with the hypermiling on the A2. Both cars had basically the same engine (PD TDI), but the A2 has 3 cylinders & the Passat had 4, and a massive difference in weight due to the aluminium body of the A2. Hence 25% less engine resistance on the A2, versus longer glide time on the Passat due to the greater momentum. Overall the benefit of P&G is less now, whereas it was vital on the Passat.
That's impressive fuel economy.

But according to this guy, driving the TDi to get the best possible mpg is NOT fun, which means driving slower or at the posted limit.

Quote:
Originally Posted by Conrad -JSW View Post
PLEASE do not drive below the speed limit! Some folks like to get where they're going in a reasonable amount of time. If you wanted to drive like that you should have bought a Prius. Driving should be fun and if you're driving like an old woman while you have one eye on the MFD trying to maximize your MPG, you're not having fun and neither are the people in the line of cars behind you.
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Old February 8th, 2012, 11:03   #23
MikeMars
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Originally Posted by JettersTDI View Post
...
But according to this guy, driving the TDi to get the best possible mpg is NOT fun, which means driving slower or at the posted limit.
Hmm, well, different people find different things fun. I like to try to beat my own mpg 'high scores'.

And his comments don't really match up with reality - why on earth would there need to be a queue behind someone on a multilane road with european-style lane rules? It's easy to handle traffic with wildly different speeds if the lane discipline rules are written with that in mind (overtaking lanes are for overtaking, not absent-mindedly cruising). If people have passed their test, they should be capable of these simple driving tasks such as when to change lane & how to use an overtaking lane.
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Audi A2 TDi 1.4*, 6M/0.588, mild aero mods, 103hp remap (* 3 pot version of 1.9PD)
Y2000 Passat TDi 115 PD RETIRED, M5, Best 75MPGuk, usually 60-70. 900m clubx7. 1000 mile clubx3.
VW Fuel saving tips

Last edited by MikeMars; February 8th, 2012 at 11:07.
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Old February 8th, 2012, 12:59   #24
allana13
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Mike can you please provide some tips

I have a MK4 Golf Estate 130 Bhp TDI

The max i have achived it 54mpg
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Old February 8th, 2012, 13:05   #25
whitevanman
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Quote:
Originally Posted by allana13 View Post
Thats what i get as well.

I am based in the UK though
Im based in the uk too. is it auto? what engine is it
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Old February 8th, 2012, 13:09   #26
whitevanman
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Quote:
Originally Posted by allana13 View Post
Mike can you please provide some tips

I have a MK4 Golf Estate 130 Bhp TDI

The max i have achived it 54mpg
Well I can start. service the car, flush the coolant do all the coolant sensors,thermostat and fuel system cleaner.

you should be getting at least 47 mpg after this
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Old February 8th, 2012, 14:09   #27
allana13
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Hi

Its a 6 Speed Manual 1.9 TDi 130 BHP engine Golf Estate
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Old February 8th, 2012, 16:21   #28
MikeMars
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I tried to write a detailed reply via my phone but it was lost. So I hope you forgive this short one.

Read the vw leaflet in my signature, it covers 90% of it, I will add more to this post tomorrow when I am able to.
__________________

Audi A2 TDi 1.4*, 6M/0.588, mild aero mods, 103hp remap (* 3 pot version of 1.9PD)
Y2000 Passat TDi 115 PD RETIRED, M5, Best 75MPGuk, usually 60-70. 900m clubx7. 1000 mile clubx3.
VW Fuel saving tips
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Old February 9th, 2012, 01:22   #29
allana13
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Thanks Mike
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Old February 9th, 2012, 05:14   #30
MikeMars
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I'm at a proper computer now :-) This is an adapted version of something I posted on a different forum:


Note that since the weather is now subzero, the good tanks from summer are unlikely to be repeated until next may or so when the temperatures recover.

Here's the full list of techniques I use - the really important ones are in bold.

* The single most important thing is to keep your motorway cruising speed down to reduce aero drag. I usually stick to 60mph (often I am pulse&gliding between 55 and 60 where traffic, terrain & wind direction permits).
* Make sure the car is in good condition (the correct oil, clean filters, brakes not binding, etc).
* Tyres @ high pressure - I use 44/46 psi, but keep an eye on the centre wear since cheapo tyres will bulge & wear unevenly if at this pressure. Good tyres can handle the pressure fine. The tyres should never be allowed to drop below their proper pressure.
* Climate control & heater off unless absolutely essential (e.g., if it is near freezing you should have the heater on). But turn on the climate control briefly once per tank, after the engine has fully warmed up. This keeps the seals good.
* Keep windows shut above 35mph (not really relevant at the moment since they wouldn't be open in the first place!!!)
* Keep RPM low (but only when engine load is also low). When I'm going at a steady 30 on the flat I'm in 5th at around 1000 rpm. If you need to slow down / speed up / go up an incline you will need to drop a gear or two otherwise you will be overloading ('lugging') the engine. As stated elsewhere you will also need to thrash the car sometimes in order to clean out the coke. Also be aware that low-rpm/high-load will stress your clutch & transmission, so don't forget to change down using the throttle.
* Be aware of wind speed & direction and change your cruising speed appropriately (it affects aero drag). You can go faster with a tailwind but drop your cruising speed if there is a headwind.
* Keep an eye on engine temperature, be very gentle until it was warmed up properly. This can take a long time in the winter. If you have the MFD or a scangauge you'll see that fuel efficiency is terrible until the engine is hot.
* Keep the audio off (so you can hear the engine)
* Leave lots of space between you and the car in front (so you don't need to brake unnecessarily). I'm usually about 3 seconds behind. Some people draft to get better MPG, but this is foolish - you will write off your car sooner or later if you do that.
* Be aware of what is around you at all times (including behind), again so you don't need to brake unnecessarily
* Drive with a steady engine load (allowing RPM & speed to drift)
* Coasting in neutral with engine on - I do this as part of pulse & glide, but only over 35mph or so. Once you are at 30 or below there is no advantage.
* Coasting in gear (when you need to slow down gently, for example down a hill, or towards red lights)
* Drive as if your brake pads were made of platinum :-) Every time you touch your brakes unnecessarily you waste fuel.
* Pulse & Glide (40-50mph range)
* High Speed Pulse & Glide (55-60 mph range). Always keep track of other traffic when using P&G, you don't want to irritate other drivers, and there is nothing more irritating than being stuck behind a P&Ging driver.
* Park in a high spot if you can (so when you start, gravity helps you get moving)
* Face-Out Parking so that you don't have to reverse when your engine is cold
* When it is raining, avoid the grooves in the road where the heavy vehicles have worn it out since water causes massive rolling resistance
* Use Shank's pony or a bike if your journey is short
* Avoid traffic jams, cold weather, passengers, rain, wind and driving in the dark. OK, you can't really avoid these, but be aware that they will kill your MPG.

The pulse & glide techniques only have a minimal effect on the MPG of the A2, but used to have a big effect on my old Passat. The difference is that the engine resistance of the A2 is already less due to the 3 cylinders, and also that the A2 is much lighter than the Passat (hence, the Passat would glide better because it had more momentum, and saved more fuel due to the idle making more of a difference).

Some means of knowing trip & instantaneous MPG is extremely useful. The MFD (DIS) was very useful on my old Passat. It allows you to keep track of the MPG for each journey and work out why it was good (or bad) ... for example, I used to be able to tell wind speed & direction from the effect on trip MPG as I drove.

Wheels & tyres: Avoid big rims with wide tyres, tall & narrow tyres give better MPG. Low rolling resistance (LRR) tyres also help.

In terms of mods, I have remapped, installed the 1.2TDI aerodynamic components, and scangauge. Be aware that these modifications will never repay their cost. Being realistic, it's purely for vanity not value for money. Cruise Control is OK MPG-wise on the flat, but turn it off for hills.


The other thing you need to consider is your journey - if you ever do short trips (a mile to the shops or whatever), this will really knock down your tank average. Walk or cycle instead. The car only really starts to get efficient after the engine has fully warmed up (which can be anywhere from 3 miles to 15 miles depending on the weather).

Similarly, city driving will also really push down your MPG. Every time you stop & have to get back up to speed, you are losing fuel.

If your car is new, forget all the above. You should be concentrating on running it in properly (if you always baby it while it is running in, then you will not get a good seal on the piston rings - give it a workout throughout the rev range once in a while, once it is fully up to temperature).

If you have a car with a Diesel Particulate Filter (DPF, > 2005 or so), you also have to sometimes drive it hard enough & long enough to regenerate the DPF, at least once per tank but twice is better. This is extremely important for city drivers, or drivers who only usually do short distances. Otherwise it will clag up quickly & cost you a great deal if you are in the UK or Europe. US drivers usually have it covered under manufacturer warranty so have less to worry about.
__________________

Audi A2 TDi 1.4*, 6M/0.588, mild aero mods, 103hp remap (* 3 pot version of 1.9PD)
Y2000 Passat TDi 115 PD RETIRED, M5, Best 75MPGuk, usually 60-70. 900m clubx7. 1000 mile clubx3.
VW Fuel saving tips

Last edited by MikeMars; February 9th, 2012 at 05:51.
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