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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 November 23rd, 2011, 16:06   #31
Plus 3 Golfer
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I think the general rule of thumb when accelerating from a stop is to get to the tallest gear (no lugging) for the desired end speed as quick as possible (no tire spin please) and you will maximize fuel economy. Of course the desired end speed and how one does this can very considerably given traffic movement, timing of traffic lights and so forth.

Since I'm not flying airplanes but driving on surburban roads (speed limits 35 - 50 mph with traffic lights between 1/4 - 1 mile apart), I find that the best I can do (unless I'm first in line) is to keep up with the car infront of me. And I can guarantee that if I am first in line and try to time the next light by coasting so I don't have to brake, half a dozen cars will speed by me and cut infront only to have me brake for them or completely stop for the next light.

It's simple not practicable in normal driving to try to follow a % of throttle application or specific rpm shift points for each gear to accomplish the above.

Last edited by Plus 3 Golfer; November 23rd, 2011 at 16:10.
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Old November 23rd, 2011, 18:10   #32
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These videos really have helped me.
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Old November 23rd, 2011, 18:44   #33
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Quote:
Originally Posted by Plus 3 Golfer View Post
It's simple not practicable in normal driving to try to follow a % of throttle application or specific rpm shift points for each gear to accomplish the above.
Elegantly stated. In real life, with traffic and unpredictability, hypermiling becomes an art.
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Old November 24th, 2011, 09:05   #34
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I am sure road & traffic conditions play into all of this- seemingly the smallest about of throttle required to obtain required speed is most efficient.

Aircraft typically stay at fuel throttle until a safe altitude is obtained (Altitude is your best friend in departure)

Throttle is then reduced at safe altitude then set at a rate of climb that burns the least throttle.
Like auto, much depends on conditions (and traffic control instruction).
Airline industry has performed much research and trial to ascertain the most fuel efficiency.
Does this relate to a TDI? I don't know.
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Old November 24th, 2011, 09:17   #35
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Quote:
Originally Posted by Vekke View Post
General rules:
- accelerate fast with full throttle to posted speed limit
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Old November 24th, 2011, 12:38   #36
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So for me next trip Ill be going through the long and steep hills of West Virginia... how should I go about going up and down the hills? Good throttle up Im assuming but should I coast down hill or just let off the throttle in 6th gear and have no consumption at all?
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Old November 24th, 2011, 13:14   #37
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Uphills
For very long hills climb up in 6th gear at heavy load, try to keep rpm around 1800-2000 if possible. But don`t accelerate more speed in the uphill, you can lose little speed on the uphill section if the downhill starts right after and its also steep. If you come slower speed to the highest point your speed wont get so high in the downhill section. When you begin to glide in neutral.

Downhills
For downhill its better to go in neutral if you have manual and the balls to do it speed wise. In Finland the hills are not so long and deep to be a big problem but in the states they can be. If road is straight and there are no other cars I would not mind if speeds would rise even to 120 MPH, You using the potential energy you get from the diesel. If you start to press the brakes or otherwise slow down you will lose fuel. Again you have to decide what is wise for safety and so on but more speed is good for your fueleconomy

engine brake or neutral depends:
- from traffic
- grade
- speed limits and do you want to follow them
- your aero
- Your avg speed goal (even if your speeds will slow down in some long hill the difference to your avg speed is minimal. So glide the whole hill in neutral and right before the end of the hill accelerate again to your drive speed. That will give best fuel consumtion.
- fuel consumtion goals (more gliding in neutral better figures)
- few other factors

On long downhills if you know that you have to use engine brake in some point of the hill or even worse the regular brakes its more wise to start the glide in engine brake from the start, as soon as you know that you are happy with the speed drop on the top of the hill. It slows you down but save fuel.

Its very difficult to say what will work on all people and various TDI`s you will just have to test and practice your skills. At highest level of hypermiling it really becomes an art and you only learn it by driving and testing what works best on your car.

Note also that in small grades your eyes lies is it downhill or uphill. For that purposes you can use navigator which shows heigth from sealevel etc.
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Old November 24th, 2011, 13:49   #38
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Awesome info once again Vekke! Ill try this next weekend on my trip and report my results! My last trip I averaged 50.8 US mpg and was pretty happy about that, even with boosting for break in period.
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Old November 25th, 2011, 05:53   #39
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Is the picture angle good or did you like more the headrest position like on the previous videos? Now its on the reverse mirror...
Is this quality good enough? It takes 3 hours to upload that long video with that quality. With full hd it takes over 60 hours and you have to start from the begin many times due to errors...

http://www.youtube.com/watch?v=1fZ8j...el_video_title
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Old November 27th, 2011, 09:24   #40
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I've been practicing these hypermiling techniques for the past few days in the TDI... Average MFA readings have gone from 45 MPG to between 55 and 62 MPG for 30 - 40 mile trips including cold starts. I suspect that the MFA readout is optimistic, but the point remains that I have significantly improved my average fuel economy.

The two biggest changes have been coasting in neutral and looking farther ahead in traffic so as to avoid using the brakes. I've also been trying to find trucks and stick with them as much as possible.

I will be tuning the ScanGauge over the next few tanks to get a more accurate fuel economy reading.
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Old November 29th, 2011, 04:49   #41
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At least in my Cordoba 1.9 TDI the scangauge was not able to show correct figures when using P&G technigue I had to recalibrate it. My lupos onboard fuel gauge is correct with all technigues.

Good to hear that you have seen positive effects. The hardest thing is to start testing and trying various technigues. Only one tank should be enough to see positive effects.

On highway if you are not in a hurry best way is to stay behind slower big vehicle and wait for that big catch come sby you. By catch I mean bigger car that has much bigger frontal area and it is driving faster. Even better if the car/bus or truck is also very long.

What is the speedlimit to buses in the US?
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Last edited by Vekke; November 29th, 2011 at 04:53.
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Old November 29th, 2011, 06:48   #42
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Generally, the speed limit of large trucks in the US is the same as autos. There are some freeways and interstate highways that do lower the speed limit for trucks by about 5 mph. I have driven extensively in the US and have found that most trucks travel within a few mph of the speed limit. Buses and autos tend to travel faster than the speed limit.

Buses are few and far between on the interstate highways. In fact on my recent 4500 mile road trip, I don't recall seeing any buses other than school buses. Trucks are like flys, they are everywhere. So, one can generally always find and follow trucks at right around the speed limits.

When I do draft trucks, my MFD mpg jumps up about 10% -15%. Again, the problem I have in drafting trucks is that they are traveling just to slow for me. A 5 mph difference in speed over a 1000 mile of driving in a day is over 1 hour of driving. Saving 2-3 gallons of fuel or so in 1000 miles (say $8 - $12) is not worth 1 hour of extra time driving.
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Old November 29th, 2011, 12:30   #43
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I dont usually have the patience too, but if big trucks are driving the same speeds it makes it whole lot easier to practice hypermiling techigues at high speeds on the motorway. In Finland the trucks drive at least 25% slower on the summer. In winter there is not so much places to go by because roads are only two lanes (one in each direction so you have to drive behind the trucks sometimes very long times.

Always remember even it is more fuel efficient to be between two trucks dont do it. Slow down so much that the truck will pass you, and be last in the line.

I calculate it also so how much I value my freetime is usually more than what I can possibly save in fuel on the lupo. Ofcourse there is the speed ticket chance when going +10-20 mph over the speedlimit but again you have to make your own calculations. How often do you get those tickets and how big are they.
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Old November 29th, 2011, 12:54   #44
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Drafting behind a truck puts you at risk of a chipped or broken windshield. Also, in the summer months, stick your hand out the open window and see if any debris is being kicked up, sandblasting your finish.

It may not matter to you, but it does to me. I'll take the mpg hit to stay in clean air, and I have plenty of opportunity to draft on my commute.
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Old November 29th, 2011, 14:39   #45
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Trucks here are either limited to 60mph, 100kph, or 50mph (depending on various things), probably the same as Finland I guess.

Quote:
Drafting behind a truck puts you at risk of a chipped or broken windshield
...
I stay a safe distance behind. The advantage is not so much drafting (only a very slight effect when you're 2 or 3 seconds behind), but in that other traffic is happy that you're going the same speed as the truck, whereas if you're on your own, then the other traffic sometimes becomes impatient.

Quote:
... sandblasting your finish.
Another difference due to location - there's far too much rain here to allow the roads to become sandy! It's very obvious when you are travelling, older cars look very different in the USA compared to over here. Sunbaked + sandblasted versus mud-covered & dented. I've never ever seen those plastic nose-guard protector thingies over here (I don't remember what they're called).
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