Diesel engines...

[pcn1]

I read on the net the other day (some ford site about Mondeo 2.2 diesels that the wife has) that because of the tall 6th gear, motorway speeds are run with very low engine rpm.
However this can cause problems because the diesel engines do need a time at higher rpm to help keep them clean of internal deposits.

Would you agree with that statement ?

[camel_landy]

No.

• Modern engine management systems mean the engines are running cleaner, therefore you do not get the deposits you previously would.
• You go through periods of higher engine speeds, getting up to those motorway cruising speeds and as part of the 'urban cycle'.

M

[skene]

Absolutely, diesels need a high rev from time to time to blow them out for multiple reasons. Two main ones I can think are the EGR valves and the DPFs

If driven like miss daisy, the egr valve will gum up the inlet manifold resulting in reduced power and in some cases damage to swirl flaps etc. often can mean a new inlet manifold which can be ££££.

DPFs also need blown out from time to time mainly to get the temperature up inside the core and to burn the deposits off.

[normalbloke]

skene said:

Absolutely, diesels need a high rev from time to time to blow them out for multiple reasons. Two main ones I can think are the EGR valves and the DPFs

If driven like miss daisy, the egr valve will gum up the inlet manifold resulting in reduced power and in some cases damage to swirl flaps etc. often can mean a new inlet manifold which can be ££££.

DPFs also need blown out from time to time mainly to get the temperature up inside the core and to burn the deposits off.

Agreed mostly. However, the EGR valve in most VWs will clog regardless of your driving style. Not only the valve, but also the whole inlet plenum and manifold can suffer after a relatively short period of time. Another thing tha can suffer, are the vanes in the VNT compressors. These will eventually clog and throw a check light. The VW stealership will always try and flog you a £1200 urbo for that little pleasure!

[A.J.M]

As said, diesel's still benefit from a old fashioned "Italian tune up" every now and again.

EGR valves will fail regardless, blank if you can, some engine's cant be blanked as they throw a warning light on.
I know my engine will throw out some smoke clouds if i floor it after a period of gentle driving.

[camel_landy]

It it worth mentioning the low-revving truck & bus engines at this point? You know, the ones that clock up intergalactic mileage and spend most of their day plugging up & down motorways.

M

[Truckosaurus]

I suspect that pottering around town a couple of miles at a time where the engine/DPF/EGR/etc. never gets properly hot will be 'worse' than cruising for a decent length of time along the motorway in 6th gear.

[Bibbs]

I used to potter about in my old Surf and it'd soot up badly.

Used to wait until you had the typical 'Audi tailgater' and then I'd put the foot to the floor.

It would cog down 2 gears, the revs would jump to 4k .. and a big black cloud would appear.

Wouldn't go any faster though.

My MOT man used to ask me to drive it hard to the test, as it made it cleaner for the emissions afterwards.

[wheedler]

I drive my diesel like I would drive a petrol and in 120k I was meant to have two turbos gone according to my friends when in fact I had no issues what so ever. I was told by some that if I continue to drive like I do the turbo will give way, that was 60k ago. Funnily enough my car is a vw with a egr and dpf, so no I don't agree what has been said about vw imo

I do want to give the egr a clean once the weather gets a bit warmer

[abbotsmike]

wheedler said:

I drive my diesel like I would drive a petrol and in 120k I was meant to have two turbos gone according to my friends when in fact I had no issues what so ever. I was told by some that if I continue to drive like I do the turbo will give way, that was 60k ago. Funnily enough my car is a vw with a egr and dpf, so no I don't agree what has been said about vw imo

I do want to give the egr a clean once the weather gets a bit warmer

I had my PD130 Ibiza MOT'd the other day, and they said it was cleaner than any car they could remember seeing, despite being a diesel. I drive it properly too! No DPF on mine though, and it's done 60k, 10k of which have been mine. I also never see it smoke, except on the odd occasion I'm forced to run it on supermarket fuel.

[Trevoready]

Hi I am new to this site but have seen it before linked from various car sites. I was checking forums this morning to see if anyone could help me work out my VW problem & decided to join up. So if anyone can help me with the following it would be deeply appreciated. My VW is a 02 Caddy, and since i have had it ( a little under a year )it seems as though its about to cut out on idle (but never does). Also when changing through the gears on a normal run it seems to stutter in between 1500-2000 revs .Once above 2000 its fine ???? Also it has on occasion decided to come to a stand still just after accelerating off. When it does this it likes to bellow smoke out and refuse to move for a few minutes til its cleared its throat. It will then carry on as normal . I have mentioned the three problems as i am not sure if they are linked. Like I said any help would be very much appreciated.My mechanic tells me he has blown out the EGR valve thinking this could be the problem , but it still persists.