DPF vent

[brad]

Two lessons learnt (and which should be told both potential and new purchasers of TDIs with DPF):

1. lots of short trips clog the system - build in a regular longer trip. Or DPF fitted TDIs are wrong for city living.

which makes no sense as (earlier suggested) European/UK city traffic is twice as congested as Sydney/Melbourne.

[K1W1]

which makes no sense as (earlier suggested) European/UK city traffic is twice as congested as Sydney/Melbourne.

Having thought about that a bit more I wonder is the quality of our diesel is the issue. AFAIK even our clean diesel isn't as good as what they get in Europe so perhaps the problem lies with what gets put in the tank.

[Inego]

I'm thinking fuel may be the contributor. Where I purchase is Mobil supplied, so I might try Shell or BP to see if it makes a difference? Most of the running during the week is my wife to work in the morning (5ish km, with traffic lights plus school and childcare drop-offs), then home including a school pickup in the PM. We venture further afield on the weekend, but clearly not far enough regularly

[Transporter]

Try using the diesel fuel additives. I use Moreys Diesel Smoke Killer with every tank full and every 7500km I put WURTH Common Rail Diesel Additive in the tank. Our Touareg is driven mainly in the city traffic and we never saw DPF warning light. There is also LIQUI MOLY (it is an oil company) diesel additive in the Super Cheap Auto.

[K1W1]

Most of the running during the week is my wife to work in the morning (5ish km, with traffic lights plus school and childcare drop-offs), then home including a school pickup in the PM

There is one of your problems.
My car doesn't even get up to operating temp in 5km. Maybe your wife will start having to go the long way around.

[Ocy_RS_TDi_Kombi]

We had a Pajero previously and it also had problems with the DPF and short trips. At 1 stage it ended up with the engine light on too.

The dealers solution was longish run with a bit of foot to the floor action and 20 minutes later no probs.

[bobski]

We had a Pajero previously and it also had problems with the DPF and short trips. At 1 stage it ended up with the engine light on too.

The dealers solution was longish run with a bit of foot to the floor action and 20 minutes later no probs.

hehe, I believe that is called an "apprentice service and tune"... The old quip was thats how they'd tune Ferarris because the owners were too worried to sink the welly.

Would be nice for the manufacturers or even the service dept to tell you about it though. You'd think it'd be a common enough occurance for them to want to avoid trips in under warranty.

[gregozedobe]

which makes no sense as (earlier suggested) European/UK city traffic is twice as congested as Sydney/Melbourne.

I think you will find that until very recently most euro diesels weren't fitted with a DPF. Same here in Oz, the 103Kw PD TDI engine wasn't fitted with a DPF, but the 125Kw version was (and straight away had DPF clogging issues if driven only in heavy traffic).

hehe, I believe that is called an "apprentice service and tune"... The old quip was thats how they'd tune Ferarris because the owners were too worried to sink the welly.

Not so fast, bobski (no I mean it, literally). There is a big difference between the "italian tune" of the 70's and what is required to efficiently regenerate a modern VAG TDI engine's DPF.

For an "italian tune" the problem was a build up of deposits on the spark plugs and in the combustion chambers. The solution was to drive at high revs and lots of throttle to blast all the crap out so the engine runs properly afterwards.

A partially blocked DPF is a very different scenario, and to do a proper DPF regeneration requires a distinctly different technique, as flogging a TDI engine will actually produce MORE soot and make it harder for the regeneration to complete. The details are in your owner's manual (yes, that boring thing that hardly anyone reads).

IIRC it goes something like this : Drive with the engine revs steady at around 2,000 rpm, on a light, constant acclerator pedal (ie not high revs, not flat to the floor) for around 20 minutes or so. So this can only be done in light, flowing traffic, preferably on a highway or freeway. It is perfectly OK to use 3rd or 4th gear so that the road speed doesn't get you booked for speeding.

So DPF regeneration driving is nothing like some people seem to think (and definitely not an excuse to flog the crap out of your engine, in fact quite the opposite).

Would be nice for the manufacturers or even the service dept to tell you about it though. You'd think it'd be a common enough occurance for them to want to avoid trips in under warranty.

There seems to be several factors :

Most people only talk to a salesperson before they buy their car. The salesperson (and the dealer and the manufacturer) has a real incentive NOT to tell you anything that may dissuade you from buying the car they are trying to sell you.

Some salespeople simply don't have the product knowledge to be able to tell a prospective customer all the information they need to know to make an informed buying decision.

Some service desk jockeys are only interested in making their life easy, not in going the hard yards to really help the customer (I refuse to deal with service people who have that sort of attitude).

Some customers don't read the owner's manual (or if they do,they don't seem able to absorb the info it contains).


It is just as well we have forums like this where people can find out the real facts

[Transporter]

Yeah,
Gregozedobe you nailed it, the gentle driving doesn't lead to DPF blocking, abrupt driving and unnecessary accelerating in the city does. Hence my 23 Y old daughter drives the Touareg like old grandma and there is no problem with the DPF however I take it once a month to blow out the cobwebs out of the exhaust, making sure that the vanes in the turbo don't seize.

[bobski]

So DPF regeneration driving is nothing like some people seem to think (and definitely not an excuse to flog the crap out of your engine, in fact quite the opposite).

Its a good thing I bought the petrol then I think I might have run into this problem myself.

Out of interest, does the manual talk about the best way to drive the TDI if you are going to be in stop/start traffic all the time? I figure its got as much to do with driving style as the nature of the journeys. I mean, 20 minutes at a constant speed every month or so flies in the face of the fuel economy benefits (probably not much, but still).

Most people only talk to a salesperson before they buy their car. The salesperson (and the dealer and the manufacturer) has a real incentive NOT to tell you anything that may dissuade you from buying the car they are trying to sell you.

I'm wondering how the Mazda dealers are going with the CX-7 diesel in this regard. I've read that topping up their filter system adds considerably to servicing costs. Don't mention the war?

It is just as well we have forums like this where people can find out the real facts

Too right, and if it wasn't for all the happy Skoda owners here, I'd have put my money down on something far less special (ie, a mazda 6 or accord euro)

[woofy]

Mazda are about to bring out the sheep pee thing, not sure if that negates the need for the DPF, but yep they have had the DPF in their diesels since day dot and I've never heard of them getting this clogged.

[Inego]

The details are in your owner's manual (yes, that boring thing that hardly anyone reads).

You're quite right - on P200 of the Octavia manual, in the third sentence of the third para (in significantly smaller type than the first two paras) it does say "To assist this procedure [ie. DPF regen.] we recommend not to drive regularly over short distances".

The are couple of other more prominent references to what the warning lights mean, but this is the first, and as far as I can see only, ref. to how to avoid the warning lights coming on.....

I'm pleased that this was highlighted to me.

Kent

PS. I'm not as annoyed about this as I may have been. I still love the car, but it niggles that the downsides of the DPF for mainly city drivers don't seem to be highlighted.

PPS. I thought Fairfax's Scout review today was a little harsh (3/5) given that they've given the X-Trail 4/5 in the past, and disliked it in their mini review today

[Jake02]

PPS. I thought Fairfax's Scout review today was a little harsh (3/5) given that they've given the X-Trail 4/5 in the past, and disliked it in their mini review today

As did I, but read the actual review and it's much more positive. Maybe the 3/5 was a mistake? As you said, even the X-Tail got 4/5, and they hated it in the 'She says/he says' part. In the review on the Jetta, one of the competitors was the Octavia 1.8TSI and on paper it got 3/5 but online it got 4/5 so perhaps it is a misprint. I'll do some more research on this...