Hypermiling videos to better fuel consumption

MikeMars

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Probably in neutral would be best. But 200,000 miles is a reasonable distance for a clutch so I doubt the wear was premature!
 

VeeDubTDI

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Thanks for all the information, Vekke and others.

Is it better to coast in neutral or with the clutch depressed only? I ask because I did have a throwout bearing failure at 325k and I did practice hypermiling by coasting down many large hills with the clutch depressed. It may have been unrelated but I did want to check to be sure.
I think 325,000 miles is a pretty good life span for any component, regardless of how you drive.
 

VeeDubTDI

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Wouldn't that be 325kkm (kilokilometers)? ;)

You're right though, I didn't notice he was from Canada. :eek:
 

Vekke

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Yes best way to coast is in neutral for the throwout bearing. If you keep the clutch pedal down the bearing is rotating all the time and bearing and clutch plate "fingers" spring tips wears down faster
 

GreyTDIowner

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Thanks all.

Yes it was in KMs and the clutch wear was OK for the amount of KMs, but the throwout bearing was shot. The dual mass flywheel was showing signs of upcoming failure so it made sense to replace it all since it was apart anyways. Also did the rear seal and main seal.

As I coasted almost exclusively with the clutch rather than neutral, I had been wondering if this may have hastened its demise. I know it was a lot of time and component wear is expected. I certainly wasn't *****ing about it, more as a consideration to prevent additional future wear on the new parts. I was curious as to whether coasting with the clutch in somehow caused extra wear somehow.

I always match revs when re-engaging the gears as well.
 
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VWJayhawk

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Is anyone else having trouble getting the videos from the first post to load? Able to get the one on the last page loaded, but not the first. Thanks!
 

MikeMars

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Justin Rizzo

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I'm currently at half a tank and at 260 miles. As far as I understand that is abysmally low for this vehicle. Sub 36mpg. Here is my typical schedule:
Mon-Fri I commute 28 miles on a highway with an average speed of 55-60mph. There are two stop lights and mild hills. A/C half the time, recirculating air the other half.
Saturdays I typically make a trip to San Antonio with my wife. There is occasionally traffic on the highway and of course city driving once we arrive. A/C the whole time.

I've been trying to break old habits from my Mazda (staying in 4th at 30mph in town with sub 1700RPM). In light of this, I've been following Vekke's hypermiling tips. I accelerate to 2400-2600RPM with 50-75% on the pedal and keep my RPM above 1700. I coast down hills in neutral if it's a reasonable distance. I maintain a smooth gradual speed up the hills. I know my lights and disregard unnecessary acceleration.

Things I have considered:

1) Cetane - This tank was filled at Valero which I now know has a 40 cetane rating. Easy fix.
2) MAF - I'm nearing 140k. I'm not lacking power. Is there a change interval on this, or do you change when it fails?
3) Injectors - Again, I'm nearing 140k. Change interval?
4) Exhaust Mani - I saw that it was sufficiently clean when TB was serviced.
5) Brake drag - I'm assuming the posts are referring to the hand brake. How do you check for this?
6) EGR/Turbo - The shop/dealer said these were replaced with OEM parts.
7) Timing - I had my whole system replaced by an endorsed tech. He showed me the TB was off from a previous "mark and pray" job and said he would restore it.
8) Next week I am replacing the fuel/oil/air filters and adding a skid plate since my splash plate is missing.
9) Malone - I'll be getting the Eco once I hit 150k and clean my ExMani.

I have to be honest, I was expecting to get 45mpg. All the 50+ stories have had me weeing my shorts in anticipation. I'm kind of bummed.

Could swapping out those filters, a higher cetane fuel, and one or two of the other variables really boost me from 35 to 45mpg?

I know fuel gauges are odd. It could be the second half of the gauge "drains" slower. I may be getting ahead of myself here. If so, I apologize. When I was topping my tank off daily (1-2 gallons) my MPG was 39.
 
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MikeMars

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It's not necessary to post in multiple threads.

Your first tank will never be representative, and partial tanks are not a reliable way to know your fuel usage since the dials are not linear.

Turn off the A/C compressor if your climate is bearable without it (try parking in the shade instead if you can. Open windows are OK at low speed but a bad idea >40mph). Note that it will impact your MPG, and particularly during slow / city driving.

I let my RPMs drop right down to 1400 or so if there is little/no load such as when driving slowly on the flat (obviously if you need power you need to change down first).

Brake drag - feel your hubs after a long drive. The fronts should be warm (but not hot), but the rears should be cold. But it is far too early to be worrying about mpg if you are only part way through your first tank - see how your second tank looks before changing anything.
 

Justin Rizzo

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It's not necessary to post in multiple threads.

Your first tank will never be representative, and partial tanks are not a reliable way to know your fuel usage since the dials are not linear.

Turn off the A/C compressor if your climate is bearable without it (try parking in the shade instead if you can. Open windows are OK at low speed but a bad idea >40mph). Note that it will impact your MPG, and particularly during slow / city driving.

I let my RPMs drop right down to 1400 or so if there is little/no load such as when driving slowly on the flat (obviously if you need power you need to change down first).

Brake drag - feel your hubs after a long drive. The fronts should be warm (but not hot), but the rears should be cold. But it is far too early to be worrying about mpg if you are only part way through your first tank - see how your second tank looks before changing anything.
I double posted because I wanted to hear from Vekke as well.

Thanks for the tips. I'm from Texas, and I have to run A/C on my way to work at 3pm. It's just too hot. I thought I might have been getting ahead of myself, I'll come back once I have finished the tank and started again with a higher cetane fuel.
 

VeeDubTDI

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Justin, are you sure that your car is getting up to temperature? Often times the dash gauge will still go up to the mid position, but due to the gauge's buffer, you don't notice that the engine isn't actually getting up to temperature and the result is poor fuel economy.
 

Justin Rizzo

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Justin, are you sure that your car is getting up to temperature? Often times the dash gauge will still go up to the mid position, but due to the gauge's buffer, you don't notice that the engine isn't actually getting up to temperature and the result is poor fuel economy.
This is interesting. I haven't read about this. As you say, my gauge reads a consistent 190 after the car has been running for few minutes. How else would I check for an accurate reading? Scanguage II?

Currently I'm at 5/16th of a tank and 400 miles. If the gauge drops at the same rate that it has been, I'll be lucky to hit 500 miles which would put me at 35mpg.

I think once I change my filters and fill up with a higher cetane fuel I will use the car only to commute to work to eliminate the city driving variable. Even with the mild hills and A/C I don't see why I shouldn't get at least 40.
 
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MikeMars

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... How else would I check for an accurate reading? Scanguage II?
Yes. (VDCS/VagCom, or ultragauge, will also work ...). But I still think it is too early to be considering this stuff.

Currently I'm at 5/16th of a tank and 400 miles. If the gauge drops at the same rate that it has been, I'll be lucky to hit 500 miles which would put me at 35mpg. ...
The gauge is not linear so you cannot make this extrapolation. Did you fill up the tank yourself originally, or was it the seller?

... I will use the car only to commute to work to eliminate the city driving variable. ...
You didn't mention any city driving earlier (apart from the San Antonio trips each Sat). How much other short trip / stop-go driving do you do? TDIs don't like short trips or stop/go. How many miles is the San Antonio trip?
 
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Justin Rizzo

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I have been considering a SGII since I got the car. It would be nice to have. I found one on Craigslist in San Antonio for $90. Need to sell something to pay for this.

I'm taking your earlier advice regarding the gauge, but I'm still documenting this tank for reference once I use a higher cetane.

The trip to San Antonio on Saturdays is my city driving.
 

keaton

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1st set of links are broken if you will, doesn't take you directly to the videos takes you to your general page.

not sure how you are "engine braking". Diesels don't have a throttle plate or a jakebrake. throttle plate your generating a vacuum and a load (pumping losses) that work against the motor. a jake your not firing the injectors, holding the exhaust valve shut till the last second (acting like an air compressor) then opening the valve briefly to let the air out. only "engine braking" your doing is using the friction of the motor internal to help slow the car down.

and when it comes to coasting to a stop in gear vs neutral it depends on your motor, I know my PD motor does not inject fuel on off throttle in gear coasting, you can hear when the injectors are firing fuel. I can't speak for a car that has a VE IP (ALH, Z1, AUH etc)
 

Maffken

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1st set of links are broken if you will, doesn't take you directly to the videos takes you to your general page.

not sure how you are "engine braking". Diesels don't have a throttle plate or a jakebrake. throttle plate your generating a vacuum and a load (pumping losses) that work against the motor. a jake your not firing the injectors, holding the exhaust valve shut till the last second (acting like an air compressor) then opening the valve briefly to let the air out. only "engine braking" your doing is using the friction of the motor internal to help slow the car down.

and when it comes to coasting to a stop in gear vs neutral it depends on your motor, I know my PD motor does not inject fuel on off throttle in gear coasting, you can hear when the injectors are firing fuel. I can't speak for a car that has a VE IP (ALH, Z1, AUH etc)
Far as autos go my 01M 'breaks' by throwing it into a higher gear when I let off the throttle after about 25-30ft pretty consistently; must just be leaned since it was once a hilly PA car.

The DSG does a similar thing but it's really clunky since one gear is heavier than the other so I just throw it in N when I can to make it smoother.

Shifting into N will throw my ALH into idle mode, so presumably there is some fuel savings there. Same thing happens when I just lightly tap the brake, so that's usually what I do.

Diesels do have 'jakebrakes', but you won't find them on most engines our size :p.
 

keaton

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Far as autos go my 01M 'breaks' by throwing it into a higher gear when I let off the throttle after about 25-30ft pretty consistently; must just be leaned since it was once a hilly PA car.

The DSG does a similar thing but it's really clunky since one gear is heavier than the other so I just throw it in N when I can to make it smoother.

Shifting into N will throw my ALH into idle mode, so presumably there is some fuel savings there. Same thing happens when I just lightly tap the brake, so that's usually what I do.

Diesels do have 'jakebrakes', but you won't find them on most engines our size :p.
well i was implying manual transmission for turning off the injectors on off throttle. if you were really concerned about fuel econ you would not have bought a POS automatic trans. again even being in a higher gear your still not "engine braking" for the reasons stated above, unless you have and throttle plate that is closing, a jake brake, or an exhaust brake...

I know diesel do have jake brakes, I meant our engines dont have them.
 

NachtRitter

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While it may not be "engine braking" in the same sense as a gasoline engine, keeping the TDI in gear when letting off the accelerator definitely has a noticeable slowing effect vs taking it out of gear ... if it's not called "engine braking" then I'm not sure what the correct term would be for having the engine slow me down... "engine slowing"?
 

keaton

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While it may not be "engine braking" in the same sense as a gasoline engine, keeping the TDI in gear when letting off the accelerator definitely has a noticeable slowing effect vs taking it out of gear ... if it's not called "engine braking" then I'm not sure what the correct term would be for having the engine slow me down... "engine slowing"?
your just using the friction of the or the rotation & reciprocating assembly in the motor... if you could trigger the ASV to close 98% of the way then you could get some "engine braking". if you want to call the friction from the motor "engine braking" then go ahead, but i wouldn't


I have gone down a 5% or 8% grade hill with my TDI in gear and it would accelerate not slow. did the same road in my BMW in gear and the would slow down or hold speed.
 

MikeMars

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... if you want to call the friction from the motor "engine braking" then go ahead, but i wouldn't ...
Why not? Normal brakes = friction surface, so I don't see why it is unreasonable to refer to the internal friction of the engine as engine braking. The friction is coming from the engine. The effect is the same as using the brakes. Hence 'engine braking'. So what if the petrol engines have additional sources of inefficiency?
 

Oilerlord

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Why not? Normal brakes = friction surface, so I don't see why it is unreasonable to refer to the internal friction of the engine as engine braking. The friction is coming from the engine. The effect is the same as using the brakes. Hence 'engine braking'. So what if the petrol engines have additional sources of inefficiency?
I've also discovered that we can get "free" A/C by turning it on while coasting in gear. This stops the car faster and doesn't affect MPG. On warm days, I sometimes do that when coasting to signal lights.
 

Justin Rizzo

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I want to make sure I'm correct in understanding my research throughout these forums.

I shouldn't be shifting at 2400RPM.
I should always shift between 2800-3000 RPM and keep my RPM above 2000.

This is the most fuel efficient method of driving this car and preventing damage to the turbo and build up in the exhaust manifold.

I'm new to turbo and diesel. I'm reading the how-to's, but not necessarily understanding anything beyond that.
 
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MikeMars

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... This is the most fuel efficient method of driving this car ...
Nope.

Most fuel efficient = low RPM. The BSFC chart tells you the most efficient RPM at a given load, and the most efficient point is often when the engine is close to lugging. However, there are significant downsides to always sticking at a very low RPM, in particular it causes extra strain on the gearbox and clutch, and eventually the turbo will coke up.

But you can keep the turbo clear by giving it an Italian tune once every second tank, and you can avoid the gearbox strain by always changing down whenever you need to accelerate / go up a hill / whatever.
 
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keaton

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Why not? Normal brakes = friction surface, so I don't see why it is unreasonable to refer to the internal friction of the engine as engine braking. The friction is coming from the engine. The effect is the same as using the brakes. Hence 'engine braking'. So what if the petrol engines have additional sources of inefficiency?
totally different
normal brakes use a force to generate friction to slow the car, remember your brake pads have a slight drag on the rotor.

all petrol motors suffer from pumping losses because of the throttle body/plates. these when closed create a load that works against the motor creating "engine braking" this is a addition source of inefficiency.
pumping loss is the work needed to move the air in and out of the cylinders

http://en.wikipedia.org/wiki/Engine_braking


But you can keep the turbo clear by giving it an Italian tune once every second tank, and you can avoid the gearbox strain by always changing down whenever you need to accelerate / go up a hill / whatever.
Italian tune? you me mean peg red line?
when I 1st got my car it was very sooty on the high RPM pulls, hard launches, brake boost launches,etc, now the back of the car is pretty clean in comparison. guessing the previous owners kept the revs low and never got on it and I was blowing out all the build up.
 

keaton

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I think our Diesel engines would be considered modern...
and they state a DPF & EGR for that. I can see how the DPF would cause increased back pressure and creates a slight load that works against the engine. I don't see how EGR would do this.
It also states that that the VGT are closing the vanes in off throttle usages, which is totally wrong and bad for the turbos. The exhaust brakes are post turbo so the delta between TIP & TOP is low.

listen to big turbo VGT cars (easier to hear) you can hear the turbo spin down off throttle = open vanes = low EMP
 

Justin Rizzo

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So I'm confused. There seems to be some varying information about this.

In this thread Vekke says to accelerate full throttle and keep RPM between 1800-3000. On the first page he also says (as I understand it) to accelerate from 1700 to 2300RPM for gear shifts.

In this thread (http://forums.tdiclub.com/showpost.php?p=1987974&postcount=1) Bleachedbora says to go easy on the accelerator. He also says regarding city driving that slow constant speeds with low RPM in high gear is ideal (which would put the RPM below 1700).

Both threads are guides but I feel like they offer conflicting information. Or, I am reading them wrong.

From what I have read so far I assumed it would be wise to keep the RPM between 1700-2400 when speeding up with a max of 75% on the pedal. This would not be considered harmful to the turbo as it hits the "sweet spot" with the boost (not babying it) and keeps mild RPMs for fuel economy. From my gasser experience I assumed that it would be wise to cruise in 4th when going 30mph vs 3rd (shifting down to 3rd when the time came to accelerate).

Am I wrong?
 
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VeeDubTDI

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Justin - there is a key difference between this thread and Drivbiwire's thread. This thread is about maximum fuel efficiency and Drivbiwire's is about engine break-in without regard to fuel efficiency.
 
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