How to Eco-drive the VW PD TDI Diesel

[MeteorGray]

Yeah, the Germans knew how to make diesels make emissions. It's just that the VW group wanted to beat the world at it, even if they had to lie, cheat and steal to do it.

Unfortunately, they only managed to destroy shareholder value and, ironically, cripple the future of diesel cars in the process.

[GreenTDI]

Originally Posted by MeteorGray

It's just that the VW group wanted to beat the world at it, even if they had to lie, cheat and steal to do it.

Believe me, they were not the only car manufacturer …

But nevertheless, they build some iconic diesel engines in the present past. It all started with naturally aspirated engines in the early 70's. VW took her 1471 cc gasoline engine and simply converted into a diesel engine. The first Golf diesel was born. Besides turbo charged diesel engines, VW made naturally aspirated ones until 2008.

The most iconic TDI's are:

Distribution injection pump
1989: 2.5 TDI: 5 cylinder with 118 hp and 200 lb.ft of torque. It gave the Audi 100 a top speed of 125 MPH and an average consumption of 40 MPG.
1991: 1.9 TDI: 4 cylinder with 89 hp and 140 lb.ft. The beginning of a succesfull 20-year carreer.

High pressure fuel injector
1998: 1.9 TDI: the new technology reduces consumption phenomally. The 1.4 TDI 3 cylinder was a derivative of that one and became the first Bluemotion engine. With power outputs from 69 hp to a massive 157 hp and 243 lb.ft they left all competitor behind in terms of power, consumption and reliability.
1999 1.2 TDI: most popular 3 cylinder diesel engine. Very progressive economy wonder for that time. Especially in the futuristic Audi A2 made of aluminum. They claimed 117 MPG.
2002: 5.0 TDI: a massive 10 cylinder engine with outputs from 300 to 350 hp and an incredible 627 ft.lb of torque. This thing is truck worthy and it is found in the upper class cars like the Touareg, Pheaton
-> The largest TDI however was a 6.0 V12, only for the exclusive Audi Q7, producing an overwhelming 500 hp and 737 ft.lb.

Common Rail
2009: 1.6 TDI: new 4 cylinder engine which formed the basis for the 0.8 TDI 2-cylinder (VW XL1) and the 1.2 TDI 3-cylinder (VW Polo Bluemotion) with power outputs from 47 hp to 118 hp and a consumption up to 230 MPG for the aerodynamic XL1.
2020 2.0 TDI evo:: perhaps the last diesel engine from VW. Always in combination with a 48-volt mild hybrid system. The exhaust gas of this engine should be purer than city air.

And to remain relevant to the topic: they all need a different style of driving, especially between the different injection techniques

[COcyclist]

To achieve the best mpg there are a host of reasons why winter driving is not your friend. We discussed several reasons why a fully warmed Diesel engine is much more efficient in a previous post.

1. If you must park in sub-freezing temperatures your engine, transmission and the whole drivetrain will be cold and inefficient. Park in a heated garage if possible.

2. Cold air is more dense. It is harder to push the car through denser air.

3. Daylight hours are shorter. You may spend more hours with the headlights on. (and wipers, front and rear defrosters, the heater fan has a large current draw and in some cars heated seats-not mine). Powering the alternator to supply all these accessories hurts mpg.

4. Snow tires. In another thread I was testing smooth wheel covers for mpg and changed from winter tires to summer tires on alloy rims as part of the testing. Tire and wheel weight, tread pattern and perhaps rubber compound killed mpg. Changing to summer tires gave much better mileage change than any wheel cover change I tested.

5. Winter blend fuels may affect mpg. I do not have hard data on this.

6. Even modern diesels start harder in sub-zero temperatures. On a ski trip this past winter I had to park outside a condo for a couple of days in very cold temperatures without being able to plug in my engine heater. I needed to move the car so I attempted to start it one afternoon. It took multiple tries but it finally started reluctantly and I left it running for a while to recharge the battery and warm the engine somewhat. Idling a cold engine is certainly not good for mpg.

7. Diesel engines do not “warm up” while idling like a gasoline engine does. With no throttle plate the engine is drawing in the same amount of frigid air as the same size gasoline engine would at wide open throttle, while injecting very little fuel. Drive gently and even climb a hill if you need to get heat into the cabin.

[COcyclist]

Originally Posted by GreenTDI

The most economic way to accelerate with a small TDI: give enough throttle -> 3/4 is ideal. Never pedal to he metal, only if it's really necessary. Rev it up quickly to 2.200 rpm and upshift. Reving it above 2.500 rpm - in normal circumstances - is pointless. The 'cheapest', most effective power is concentrated between 1.500 - 2.500 rpm.

I agree except for “Never pedal to the metal”. I occasionally do a full throttle blast in 4th or 5th to keep the turbo linkages from getting sticky and to blow the accumulated oil out of the intercooler. In my car with no DPF you can see the cloud of soot behind me in the rear view mirror. Once it is cleared out, it runs clean even on subsequent hard pulls. I’m sure full throttle pulls are not helping mileage at that time but it “feels” like the car runs better afterward.

[cRiPpLe_rOoStEr]

Originally Posted by COcyclist

Diesel engines do not “warm up” while idling like a gasoline engine does. With no throttle plate the engine is drawing in the same amount of frigid air as the same size gasoline engine would at wide open throttle, while injecting very little fuel.

Some modern ones now feature a throttle-plate, even though it's for emissions compliance instead of cold-start concerns. On a sidenote, fitting an extra glowplug to the intake elbow of some older engines is also not unheard of.

Drive gently and even climb a hill if you need to get heat into the cabin.

Got me to remember the day a friend who was not so used to Diesel engines told me quite surprised about a bus driver who kept flooring the throttle pedal right after a cold start in order to raise the temperature quicker.

[GreenTDI]

Originally Posted by COcyclist

I agree except for “Never pedal to the metal”. I occasionally do a full throttle blast in 4th or 5th to keep the turbo linkages from getting sticky and to blow the accumulated oil out to the intercooler.

True. It is better to prevent this internal pollution. Small distances are therefore also the big enemy of a diesel. I was only referring to the fact that it bad for the actual mileage, which collapses immediately.

Once every year I have the opportunity to sin on the Autobahn (sorry ecomodders, it feels like a confession)! by flooring (pushing it trough the floor) the car for at least an hour. The weeks that follow I clearly notice the difference due to a quieter running of the engine and indeed lower consumption.

[cRiPpLe_rOoStEr]

Originally Posted by GreenTDI

Once every year I have the opportunity to sin on the Autobahn (sorry ecomodders, it feels like a confession)! by flooring (pushing it trough the floor) the car for at least an hour. The weeks that follow I clearly notice the difference due to a quieter running of the engine and indeed lower consumption.

Passive regeneration of the DPF is not bad at all. Well, besides the increased fuel consumption which would involve an active DPF regeneration, with all the environmental concerns surrounding the higher amount of fuel required, even if the ECM sets a leaner AFR in order to raise the EGTs and as a consequence the NOx emissions increase a bit, that ends up being not so awful at all.

[GreenTDI]

@ cRiPpLe_rOoStEr

Indeed. Besides, it's nothing spectacular either: it feels like cruising around 110 mph at a comfortable 3.500 rpm still averaging 30 MPG. With a gasoline engine you see some other figures ...

So from time to time it is good to make the TDI work harder. Do it only with a warm engine and preferably in the middle of a long ride. This way you still have enough time to compensate for that extra consumption.

[cRiPpLe_rOoStEr]

Originally Posted by GreenTDI

Do it only with a warm engine and preferably in the middle of a long ride. This way you still have enough time to compensate for that extra consumption.

Sure. On a sidenote, makes me wonder how water injection would affect both the particulate matter buildup and the regeneration process.

[mwebb]

Originally Posted by cRiPpLe_rOoStEr

Sure. On a sidenote, makes me wonder how water injection would affect both the particulate matter buildup and the regeneration process.

watch out for thermal shock
on early VWs of the mark 4 vintage the heater on the AFR or 02 sensor does not get switched to on
until
after
the car gets to 50mph or thereabouts AND coolant temp crosses a threshold the value of which is not released to the mortals
to
avoid
thermal shock of the thimbles in the AFR / 02 sensors
on the theory that there will be no liquid h2o in the exhaust stream , it will all be in vapor state due to the heat / temperature in the exhaust

you do not want to crack the substrate in the DPF or the thimbles in the lambda sensors

so
no
you should NOT use water injection in any TDi or ever

imho

and
EGR is good
more EGR is better than less to a point and defeating a properly function ing EGR does not improve fuel economy or power as
EGR does not operate at high load anyway .

carbon buildup is mostly caused by the driver AND bad fuel
also
imho

current VW diesel tech
the opinions expressed are my own

i own 2 mark 4 golfs with BEW and 5sp
average hi 40s on both
less in colder weather
43psi on tire pressure
one has 225 45 17 continental tires
the other 205 55 16 michellin tires