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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 March 5th, 2012, 20:22   #46
vlad0401
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Quote:
Originally Posted by oilhammer View Post
I try and keep the RPMs over 2500 during warmup. That keeps the afterglow OFF. The plugs cycle on and off at 2500 RPM, or in the case of the 2002+ cars, the control unit duty cycles them up at 2500 RPM. In either case, that constant on/off of the plugs is what shortens their life. And of course never let it sit and idle after a cold start.

I'm lucky, because I have my car covered in the morning, so no scraping ice or anything, it is backed in its spot. I literally start up, drive off, 1-2-3-4 and I am doing 60. Hold 60 in 4th (above 2500 RPM) for that first couple miles on two-lane black top until I merge on to the interstate... then hammer down and into 5th and 80+ for 40 minutes. Probably why my cars last so long. They get up to temp very quickly, and are mostly hwy miles.
why is it bad to let a car sit after a cold start? i assume that means under 32 degrees Fahrenheit. i let me car sit for 5-15 mins before i go to school every monday-friday temp is usually below 32 every morning for the past 2 months
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Old March 6th, 2012, 01:56   #47
MikeMars
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Originally Posted by vlad0401 View Post
why is it bad to let a car sit after a cold start? i assume that means under 32 degrees Fahrenheit. i let me car sit for 5-15 mins before i go to school every monday-friday temp is usually below 32 every morning for the past 2 months
a) Idling does not really help a diesel engine to warm up. You need to be driving around to use enough fuel to warm up the engine.

b) While the engine is running cold, the oil is not very fluid, & hence you get extra engine wear.

c) What is to stop someone walking up to your car & just taking it? If this happens in the UK, the insurance company will just laugh at you & refuse to pay out.

d) It's illegal in some areas (I have no idea whether that applies to your area).


Why not invest in a block heater, and pre-heat the coolant before starting?
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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; March 6th, 2012 at 01:59.
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Old March 6th, 2012, 03:50   #48
allana13
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Hi Mike,

The Block heater is something I havenít heard of before. What is it, where does it fit, how much does it cost and how does it help in increasing fuel efficiency.

Many thanks for your help in advance. Much appreciated as I have increased my fuel economy using the tips you mentioned.





Quote:
Originally Posted by MikeMars View Post
a) Idling does not really help a diesel engine to warm up. You need to be driving around to use enough fuel to warm up the engine.
b) While the engine is running cold, the oil is not very fluid, & hence you get extra engine wear.
c) What is to stop someone walking up to your car & just taking it? If this happens in the UK, the insurance company will just laugh at you & refuse to pay out.
d) It's illegal in some areas (I have no idea whether that applies to your area).
Why not invest in a block heater, and pre-heat the coolant before starting?
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Old March 6th, 2012, 07:16   #49
MikeMars
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Well, they're not really needed here in the UK (not cold enough), but if I understand correctly, it's basically a glow-plug which screws into the sump. You plug it into the mains on a timer so that it starts to heat up 2 hours before you are due to start in the morning.

They will help the fuel efficiency, because the engine is less efficient when cold, and the block heater pre-heats the engine.


This looks like a useful thread about them:
http://forums.tdiclub.com/showthread.php?t=315072
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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; March 6th, 2012 at 07:19.
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Old March 6th, 2012, 07:44   #50
Padrino
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Originally Posted by MikeMars View Post
Well, they're not really needed here in the UK (not cold enough), but if I understand correctly, it's basically a glow-plug which screws into the sump. You plug it into the mains on a timer so that it starts to heat up 2 hours before you are due to start in the morning.

They will help the fuel efficiency, because the engine is less efficient when cold, and the block heater pre-heats the engine.


This looks like a useful thread about them:
http://forums.tdiclub.com/showthread.php?t=315072
As usual Mike boy is better than search function.
How you manage to keep a tap on everything here Mike?
Your posting are always very informative but I just don't have that much time to go and search for every bid of info, looks like you have some "secret" system
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Old March 7th, 2012, 06:34   #51
MikeMars
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All I did was search for 'block heater' ... :-)
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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 March 29th, 2012, 09:03   #52
vdubtdi11
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My TDI is 2011 with just over 5k on it and I usually get about 47 on the highway at about 65. The car LOVES the 40-50 mph range where it can easily achieve mid 60's+.(too bad there is nowhere that one can drive for hours at 45mph..) In the beginning, I was mainly driving on the highway. Its just recently that I have started driving in town with it more where I usually drive my truck and I find that if I drive carefully and allow my torque to do its job to get me up to speed, my trips have resulted in the low to mid 40s! One trip, (when there was no traffic) I got 47.6 for an 11 mile suburban trip! Once the car gets up over 70 mph, the fuel economy can drop as low as 39!

Last edited by vdubtdi11; March 29th, 2012 at 09:14.
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Old March 29th, 2012, 09:20   #53
vdubtdi11
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BTW, is it possible for my new car to be making black smoke when I floor it? Has there been time for soot build up? My friend said he saw black smoke when I did that but I didn't see any. I do baby the car 99% of the time but I still feel like after then 3000 highway miles, that that shouldn't be a problem. Also, when Oilhammer said to drive with spirit to clear out the engine and help the turbo and intake, would normal 75mph on the highway be sufficient?
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Old March 29th, 2012, 10:00   #54
MikeMars
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...drive with spirit to clear out the engine and help the turbo and intake, would normal 75mph on the highway be sufficient?
It does sound like you are coked up.

Drop down to 4th and do the 75mph for a minute or two (preferably when going uphill). Do this once per tank or two and that should be enough.
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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
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Old March 29th, 2012, 14:17   #55
kay.DIESLpwr
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Quote:
a) Idling does not really help a diesel engine to warm up. You need to be driving around to use enough fuel to warm up the engine.

b) While the engine is running cold, the oil is not very fluid, & hence you get extra engine wear.

c) What is to stop someone walking up to your car & just taking it? If this happens in the UK, the insurance company will just laugh at you & refuse to pay out.

d) It's illegal in some areas (I have no idea whether that applies to your area).


Why not invest in a block heater, and pre-heat the coolant before starting?
hey Mike, im new here and i just got accptd today actually and what you said in A) is actually let the car run after a cold start?
and about using neutral while in gear(for automatic), isnt that bad for your engine? and i also read that coasting in neutral eats gas than coasting in gear.
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Old March 29th, 2012, 16:46   #56
MikeMars
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Originally Posted by kay.DIESLpwr View Post
hey Mike, im new here and i just got accptd today actually and what you said in A) is actually let the car run after a cold start?
and about using neutral while in gear(for automatic), isnt that bad for your engine? and i also read that coasting in neutral eats gas than coasting in gear.
Answering via phone so please excuse terse reply.

Do NOT idle to warm up. Get in the car and drive without waiting for it to warm up.

When I refer to neutral it is always in the context of a manual gearbox. I have never owned a car with a slushbox and know little about them because few people use them in this country.

Neutral vs. in gear ... This is a complex situation, and both techniques should be used in the right circumstance. If you want to slow down via engine breaking then in gear is best since that uses zero fuel. However if you want to roll without wasting kinetic energy on the level or downhill then neutral is best over 35mph or so.
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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; March 29th, 2012 at 16:50.
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Old March 29th, 2012, 19:19   #57
kay.DIESLpwr
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Quote:
Originally Posted by MikeMars View Post
Answering via phone so please excuse terse reply.

Do NOT idle to warm up. Get in the car and drive without waiting for it to warm up.

When I refer to neutral it is always in the context of a manual gearbox. I have never owned a car with a slushbox and know little about them because few people use them in this country.

Neutral vs. in gear ... This is a complex situation, and both techniques should be used in the right circumstance. If you want to slow down via engine breaking then in gear is best since that uses zero fuel. However if you want to roll without wasting kinetic energy on the level or downhill then neutral is best over 35mph or so.
oh so just run the car right away after cold start then? but when i or my dad drive it, we hear this weird sound in the engine. is that ok? i mean its been like this since we got it. so whenever it happens, we just stop on the curb and wait 1-3 mins then runs fine again.

hmm, well i use to always use neutral when im going down a hill at 40+mph and i read a post somewhere and stopped it right away and in this forums, i kept reading that neutral is fine(i know they are talking about manual trans) but im kind of confused now though..

Last edited by kay.DIESLpwr; March 30th, 2012 at 02:31.
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Old March 30th, 2012, 02:05   #58
allana13
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Achived 70.4mpg with BP ultimate diesel cruising at 60MPH for a distance of 45miles on the motorway

Well chuffed.
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Old March 30th, 2012, 02:50   #59
MikeMars
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Quote:
Originally Posted by allana13 View Post
Achived 70.4mpg with BP ultimate diesel cruising at 60MPH for a distance of 45miles on the motorway

Well chuffed.
Good work, congratulations on that. The next target is to see if you can beat your 'high score' on the full tank :-)


Your 70mpg(imp) / 60 mph fits the forum's '120 rule' perfectly (after converting to us gal).
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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
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Old March 30th, 2012, 04:14   #60
allana13
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Thanks Mike,

I am hoping with a service that should improve the MPG.

But yes the key to high MPG i felt was driving at 60mph

The moment I went to 70mph it drops down.
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