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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 July 4th, 2000, 15:21   #1
Ric Woodruff
BANNED, Ric went to Coventry.
 
Join Date: Feb 1999
Default Fuel Economy Tips



How you drive:

How you drive is biggest factor affecting fuel consumption. Driving harshly, that is, accelerating and stopping hard, is the easiest thing to change. Not only does it adversely effect your mileage, but it puts you in a very high risk group. Moving you from point A to point B is about physics, it takes energy (gas) to accelerate and stop you (because you must reaccelerate to proceed again). Ever notice big rigs in the city, they pace the lights. Why do you think that is? We make a big thing about 'hitting all the lights', imagine pacing the lights so that you almost always hit them. That will have a dramatic effect on fuel economy. Lets face it, saving 25 cents on a tank of gas won't pad your retirement fund, but getting an extra 50 - 100 miles out of a tank of gas will.

Where you drive:

Its no secret that your vehicle gets better mileage on the highway than in the city. This is directly related to starting and stopping. If you can, plan your route to take advantage of the highway.

When you drive:

If starting and stopping are fuel mileage killers and you can't take advantage of choosing your route then consider when you drive. It doesn't take a rocket scientist to realize that driving in rush hour is the absolute worst time. Consider this, when your sitting at a red light, your getting 0 mpg. Seasons and weather also have an effect on consumption. Driving in rain or snow is a mileage killer. Especially snow, if you can avoid it, do it.

Engine Tune:

Common sense here. An out of tune engine can play havoc with consumption. A sticky choke, an intermittent misfire are all relatively inexpensive to correct with a very good return on investment.

Wheel Alignment

Are your roads bad, if their like they are just about everywhere else you most likely need a wheel alignment. Imagine having one of your wheels locked and skidding for 50 feet for each mile you drive. What would that do to your fuel consumption? Right.

Brakes

A dragging brake or maladjusted parking brake is not just dangerous but costly as well.

Tire Pressure & Type

Snow tires or under inflated tires are both easy and cheap to correct. Studies have been done that show almost 70% of the vehicles on the road have under inflated tires.

Options

Ask anybody with air conditioning in their vehicle what it does to fuel mileage. The same goes for optional equipment that places a heavy load on the electrical system. It takes extra energy to drive your alternator to generate that electricity, more than you think.

Vehicle Accessories

Roof or luggage racks, bug deflectors, running boards all have negative affect on mileage, Sport utility vehicles are popular now, does yours have a little air deflector to keep the rear window clean? Same thing for pick-up trucks, if you have nothing in your bed and are going on a long road trip, open your tailgate. Thats worth almost 2mpg all by itself! A better solution is a tonneau cover and leave the tailgate up!




------------------
Ric Woodruff

Braumeister von Sehr Gutem Bier
Since the Last Millennium

1998 Jetta TDI Sport
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Old July 4th, 2000, 22:29   #2
Alek
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Join Date: Apr 2000
Location: Ljubljana, Slovenia
Default Re: Fuel Economy Tips

Ric:

On the 27th June 2000 I sent you an E-mail on the rwoodruff@webinbox.com address. Today I was notified that delivery was unsuccessful.
Sorry for that.
Anyhow I can't help you with ALP. Your posting was first time I heard of it.
We'll have to communicate through forum.


Best regards,
Ales K.
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Old July 5th, 2000, 08:55   #3
SkyPup
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Default Re: Fuel Economy Tips

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Ric Woodruff:


How you drive:

How you drive is biggest factor affecting fuel consumption. Driving harshly, that is, accelerating and stopping hard, is the easiest thing to change. Not only does it adversely effect your mileage, but it puts you in a very high risk group. Moving you from point A to point B is about physics, it takes energy (gas) to accelerate and stop you (because you must reaccelerate to proceed again). Ever notice big rigs in the city, they pace the lights. Why do you think that is? We make a big thing about 'hitting all the lights', imagine pacing the lights so that you almost always hit them. That will have a dramatic effect on fuel economy. Lets face it, saving 25 cents on a tank of gas won't pad your retirement fund, but getting an extra 50 - 100 miles out of a tank of gas will.

Where you drive:

Its no secret that your vehicle gets better mileage on the highway than in the city. This is directly related to starting and stopping. If you can, plan your route to take advantage of the highway.

When you drive:

If starting and stopping are fuel mileage killers and you can't take advantage of choosing your route then consider when you drive. It doesn't take a rocket scientist to realize that driving in rush hour is the absolute worst time. Consider this, when your sitting at a red light, your getting 0 mpg. Seasons and weather also have an effect on consumption. Driving in rain or snow is a mileage killer. Especially snow, if you can avoid it, do it.

Engine Tune:

Common sense here. An out of tune engine can play havoc with consumption. A sticky choke, an intermittent misfire are all relatively inexpensive to correct with a very good return on investment.

Wheel Alignment

Are your roads bad, if their like they are just about everywhere else you most likely need a wheel alignment. Imagine having one of your wheels locked and skidding for 50 feet for each mile you drive. What would that do to your fuel consumption? Right.

Brakes

A dragging brake or maladjusted parking brake is not just dangerous but costly as well.

Tire Pressure & Type

Snow tires or under inflated tires are both easy and cheap to correct. Studies have been done that show almost 70% of the vehicles on the road have under inflated tires.

Options

Ask anybody with air conditioning in their vehicle what it does to fuel mileage. The same goes for optional equipment that places a heavy load on the electrical system. It takes extra energy to drive your alternator to generate that electricity, more than you think.

Vehicle Accessories

Roof or luggage racks, bug deflectors, running boards all have negative affect on mileage, Sport utility vehicles are popular now, does yours have a little air deflector to keep the rear window clean? Same thing for pick-up trucks, if you have nothing in your bed and are going on a long road trip, open your tailgate. Thats worth almost 2mpg all by itself! A better solution is a tonneau cover and leave the tailgate up!


Ric, Cut N' Paste? The least you could have done is change the word gas to diesel!


<HR></BLOCKQUOTE>

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Old July 5th, 2000, 16:06   #4
Ric Woodruff
BANNED, Ric went to Coventry.
 
Join Date: Feb 1999
Default Re: Fuel Economy Tips

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by SkyPup:
<HR></BLOCKQUOTE>

It is generic information that applies to both gas AND diesel vehicles.

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Old July 5th, 2000, 18:56   #5
ENUTPEN8
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Join Date: Jul 1999
Location: AR , USA
Default Re: Fuel Economy Tips

Gas? Choke? Snow tires? Alignment? I don't think the .50 cal. creates that much drag... Is this cosmic?? Hey, Ric, you weren't driving the '54 DeSoto in the Mobil Economy Run that year, were you?? Driveon...NickatNight

------------------
1999 green/tan MkIV Golf GLS TDI auto/lux, flaps down, K&N, Bilstein HD.
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Old July 8th, 2000, 20:08   #6
MacGyver
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Location: SW Ont, Canada
Fuel Economy: ~54mpg imp
Default Re: Fuel Economy Tips

The alternator eats 1hp to make about 22amps. I'm not going to look it up, but I remember the manual telling how much more fuel it takes to leave the rear defroster on continuously. Makes sense.
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Old July 14th, 2000, 04:30   #7
Ric Woodruff
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Join Date: Feb 1999
Default Re: Fuel Economy Tips

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by MacGyver:
The alternator eats 1hp to make about 22amps. I'm not going to look it up, but I remember the manual telling how much more fuel it takes to leave the rear defroster on continuously. Makes sense. <HR></BLOCKQUOTE>

Wow, that is a really inefficient alternator if true! 22 amps x say, 14 volts = 308 watts. 1 HP = 746 watts, so the alternator is only 41% efficient??? Doubtful.

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Old July 16th, 2000, 06:40   #8
fnj2
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Default Re: Fuel Economy Tips

I don't find the figure doubtful at all - first of all, the 1 hp figure is obviously approximate, and next and more importantly, 22 amps is only a small part load; the alternator is operating well below max efficiency.

Keep in mind also the alternator must operate over a wide rpm range, and cannot deliver max efficiency over the entire range - most likely it is best at high rpm.

------------------
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Old July 16th, 2000, 09:01   #9
cars wanted
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Location: Rockville, Maryland U.S.A.
Fuel Economy: 65/45/38
Default Re: Fuel Economy Tips

Although I expect an alternator's AC generator to be quite efficient, I think that the rectifier diodes, (to make it DC voltage), would take a hit in maximum efficiency.
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Old July 17th, 2000, 09:42   #10
MacGyver
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Location: SW Ont, Canada
Fuel Economy: ~54mpg imp
Default Re: Fuel Economy Tips

That was an indirect quote from some car magazine I remember reading years ago.

Ric, how efficient do you expect it to be? It is afterall a mechanical device. I work with 48V telephone equipment. The modern charging equipment is 80-90 percent efficient, and it is all electronic, solid state. No moving parts. Remember the last time you touched a running alternator? Not freezing cold was it? Where do you think all that heat energy came from? Belt, pulley, bearings, magnetism, rectifier...I think 40 percent is respectable.
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Old July 17th, 2000, 11:40   #11
Powder Hound
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Location: Conkud, New Hampshiyuh, USA
Fuel Economy: pretty freakin' good.
Default Re: Fuel Economy Tips

MacGuyver,

Don't worry about Ric's pronouncements on anything. He doesn't know what he's talking about.

------------------
Always interested in steep & deep.
Ski resorts closed! Break out the cameras and fly rod ...
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Old July 17th, 2000, 18:45   #12
SpeedingAgain!
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Location: Ardfern, Argyll, Scotland
TDI(s): none
Default Re: Fuel Economy Tips

All this business about keeping the revs down and not accelerating harshly may be good for the fuel consumption.
However, it is not good for the cylinder bores, rings and ring grooves for the engine to be run on a low load all the time. Running a diesel engine on low load continually allows build up of carbon. This is exaggerated with our TDI engines with the egr valve.
You may already know this but carbon polishes the liners leading to drop in compression, it also sticks in the ring grooves eventually jamming the rings and a sticking ring will wear badly on the ring grooves on the piston and on the liner, resulting in even less compression still.
The only way to fix it is to strip it down.
Or you could simply give the engine a bit of welly every so often which will burn all the carbon off! That's my excuse any way.
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Old July 17th, 2000, 19:43   #13
jayb79
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Default Re: Fuel Economy Tips

After putting around for a couple of hours mash the pedal and let the revs come up to about 3000-3500 in a couple of gears and watch the black cloud come out the back. Poof all cleaned out.
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Old July 18th, 2000, 04:05   #14
Ric Woodruff
BANNED, Ric went to Coventry.
 
Join Date: Feb 1999
Default Re: Fuel Economy Tips

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jayb79:
After putting around for a couple of hours mash the pedal and let the revs come up to about 3000-3500 in a couple of gears and watch the black cloud come out the back. Poof all cleaned out. <HR></BLOCKQUOTE>

The black smoke is a result of build up of soot in the exhaust system, and has nothing to do with "cleaning the engine". The surface areas of the exhaust manifold, the exhaust pipe, the muffler and catalytic converter are very extensive.

If you feel better blowing out all that soot, go right ahead (I do it myself occasionally), but don't expect your engine to run any better afterwards.

The term "Italian tuneup" came from Italian sports cars that ran cold under normal driving and consequently had fouling of spark plugs. Reving high and driving hard tended to clean them, and made the engines run better. We have no spark plugs, so reving high and running hard does nothing to a diesel engine.

Ric

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Old July 20th, 2000, 11:43   #15
SkyPup
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Default Re: Fuel Economy Tips

Rics fallices notwithstanding, the TDI oxidizing catalytic convertor does not oxidize soot until it reaches and holds a temperature of 300 degrees F, which normally is a few minutes after startup, therefore the soot DOES NOT build up in the exhaust system as Ric imagines as long as the car is driven and not idled for extended periods of time.
SpeedingAgain is exactly right about the carbon build-up in the cylinder, this is why Ric's ride is burning so much oil and smoking, it the oil he's burning from the way he drives, not the soot!
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