How to Eco-drive the VW PD TDI Diesel

[GreenTDI]

Originally Posted by COcyclist

We have discussed DFCO and engine braking in previous posts and I was doing a lot of that. I also was trying to conserve momentum through the corners so I would have less acceleration losses coming out of the corners. Carry momentum as much as you can do safely.

+1
I always apply those techniques. On the BC I can clearly see when fuel is being injected again, and that's around 900 rpm. A modern TDI has very little braking power, even at high rpm's, so the car can coast in gear for a very long time. In my case it will maintain speed on light descents and even accelerate at a percentage of 5%. When engine braking is really required, the air conditioning does the job.

[cRiPpLe_rOoStEr]

Originally Posted by GreenTDI

When engine braking is really required, the air conditioning does the job.

Even though turning the AC on might suffice, sometimes an exhaust brake such as the ones fitted to large trucks is desirable. Reminds me of a Suzuki Vitara repowered with a Volkswagen EA827 1.6D that an uncle of mine used to own.

[pete c]

Excellent thread.

I came in here shortly after buying my '11JSW 6 MT about a year and a half ago and there really wasn't a whole lot here about them.

I have a year and a half now with it and here are my observations.

MPG- 42-44 has been typical, with largely hiway driving. I find the onboard computer to be a tad dishonest. Real mpg seems to be about 10% less than what it is telling me.

I've never done an entire tank where I was trying to eek out every bit of efficiency I could, but for 40-50 mile drives, I can get indicated mileage into the low 50s with a bit of effort. So, real mpg would be 46-48, maybe.

I have seen reports of deleted CJAAs getting well into the 50s. No plans on doing it yet.

So far, mine has been good, knock on wood. I attribute this to regular 3-4th gear floggings. 3rd gear 75 mph on ramp pulls don't do mpg numbers much good, but they seem to keep the dpf happy. And as long as there is any chance of taking advantage of VW's extended warranty they were forced into as part of the buy-back solution, I will be doing no deletes.

On the topic of EOCing, I am considering it for a few reasons.

1. There is some efficiency gains. Not as much as a gasser, for sure, but something.

2. When it is in DFCO, I wonder if all that cool air moving through the cat and dpf have an effect on them? Do they cool off much? Does idling cool them or contribute to them clogging?

I don't know. I do know that driving them for economy all the time does lead to DPF issues. I have a friend that had one. His wife drove it, primarily and he told me ended up getting rid of it because of DPF headaches, which he attributed to the wife's conservative driving.

So, my thought is that perhaps it is best to just shut the damn thing down during extended coasting opportunities.

Of course, I would be cognizant of things like turbo temp. I would not do it shortly after a hard pull and when I did do it, I would likely give it a good 5-10 seconds of idling or better yet DFCO before shutting down.

Does scanguage give turbo temps? Would be a nice thing to know.

Odds are I won't do this, but I am giving it some thought.

[pete c]

As for the rationality of buying a tdi today, if I had a crystal ball and could see the drop in fuel costs brought on by CV, I likely would have just bought a gasser.

Modern gassers aren't as efficient as a tdi, but they have closed the gap.

When RUG was 3.25 and Diesel 3.75, there was a small advantage to diesel, but it was negligible.

Today with RUG around 2.00 and Diesel at 2.60, RUG wins....all day long.

But, of course, it's not all about $$$$$. There is something to be said for that intoxicating torque kick in the back on long uphill pulls!!! 4th gear 100 mph (or close to it) pulls put a smile on my face every time!

[MeteorGray]

I bought a Mazda3 2.0 gas automatic because I could get it for around $20K and the fuel mileage was rated at 41mpg highway. So, I gave away a few mpgs for a cheaper-to-buy purchase price compared with the VW TDI.

So far, I'm driving the Mazda at a fuel cost of about 5.5 cents per mile without a problem. My overall fuel mileage is almost 45 mpg. I don't do hypermiling, but the car is driven mostly on long-and-steady highway trips.

I've look at the economics, and I believe I'm ahead driving the Mazda versus a TDI.

The price differential between RUG and diesel, plus the complexities of emissions controls on the diesel, are hard to ignore.

[COcyclist]

Originally Posted by pete c

On the topic of EOCing, I am considering it for a few reasons.

1. There is some efficiency gains. Not as much as a gasser, for sure, but something.

2. When it is in DFCO, I wonder if all that cool air moving through the cat and dpf have an effect on them? Do they cool off much? Does idling cool them or contribute to them clogging?

I don't know. I do know that driving them for economy all the time does lead to DPF issues. I have a friend that had one. His wife drove it, primarily and he told me ended up getting rid of it because of DPF headaches, which he attributed to the wife's conservative driving.

So, my thought is that perhaps it is best to just shut the damn thing down during extended coasting opportunities.

Of course, I would be cognizant of things like turbo temp. I would not do it shortly after a hard pull and when I did do it, I would likely give it a good 5-10 seconds of idling or better yet DFCO before shutting down.

Does scanguage give turbo temps? Would be a nice thing to know.

Odds are I won't do this, but I am giving it some thought.

I do not have a DPF so I cannot speak to that concerning the TDI. VW has done a lot with EGR to keep NOX emissions down in the newer TDIs so there may be a throttle plate that closes to pull in more EGR. IMHO your engine should not create much soot in the DPF at idle because the computer injects only enough fuel to maintain 900 RPM.

I find that if I can coast, it is usually for a minute or less. If I am on a longer hill I pick up too much speed to coast, therefore I am using engine braking. The loss of power brakes and steering and possible steering lock and wear from using the key switch make me very reluctant to use EOC. I suspect any gains from EOC would be minuscule.

On my car, the ScanGuage will not read turbo or exhaust temperature. I read somewhere that you can double your intake temperature reading to get a rough idea of how hot your turbo is running. In my experience, on long Colorado climbs the intake temperatures rise steadily so there may be some truth to that.

[cRiPpLe_rOoStEr]

Originally Posted by MeteorGray

The price differential between RUG and diesel, plus the complexities of emissions controls on the diesel, are hard to ignore.

I am a die-hard Diesel enthusiast, but I must confess sometimes the complexity of all the newer emissions hardware makes me look at the most recent Diesel engine generations with a grain of salt. The prevalence of manual transmissions in the Diesel versions of some cars, with hybridization increasing market share of automatics even in Europe while also narrowing the fuel consumption gap between gasser and Diesel, is also a strong argument against Diesel for most new car buyers.

[COcyclist]

Quick update. I did an intake cleaning on my TDI last summer at 120,000 miles. I probably should have done it sooner but it is a bit of a messy job. Good News? The TDI intake manifold comes apart so you can really get in there and clean it out. The Bad News? It was full of surprisingly large "diesel boogers", almost walnut sized. I used a cardboard box, gasket scrapers and screwdrivers, parts brushes and brake cleaner to clean it out.

It seems to run much better. There is hardly any soot in the rear view mirror on hard pulls. I am driving faster than in my hard-core hypermiler days and the mpg has not really fallen off. The Golf TDI is a powerful, sporty car that can still return Prius-like mpg.