volvo v40 18i chemical engine exhaust smell

[shimon340]

hi there

I've been doing some further research into GDI problems and it seems petrochemical companies also began looking at the problem (patents filed by Exxon and Texaco etc).

It seems the coking is caused by a few things.

First, the lean burn mode produces higher levels of NOx which also requires a different NOx reducing catalyst due to the higher oxygen levels in the exhaust during lean mode. Unfortunately, the higher levels of sulphur is European fuels (as certainly used to be but now are somewhat reduced- may not be a low as Japanese fuel though) meant this catalyst would be poised and ineffective. Therefore mitsubishi couldnt use this catalyst here and therefore had to run the euro engines richer than the japanese counterparts to reduce NOx and allow a less susceptible to sulphur poisoning catalyst to be used.

secondly, judging by the petrochemical companies research and patents in the area of fuel composition, it seems that is also responsible for the coking of the engine. euro fuel being sufficiently different to Japanese. (swedish fuel is different again, they have their own standards).

It is somewhat problematic for an engine to require a specific fuel different to the standard already available in the market. Not sure how VW/Audi got round this problem for their FSI engine. Renault used higher EGR levels to achieve lean burn. Interesting to see what solution volvo/ford/mazda come up with (or already have as these engines are close to launch now) for their new lean burn units.

I hear Ford also looked at different oil additives to help the problem. This isnt so challenging for the marketplace given that diesels with DPFs also require different oils to avoid poisoning the DPF with components from oil additives.

so, it seems the higher sulphur levels in euro fuel and different composition is to blame. I wonder how the Swedes go on with this engine given that their fuel is low is aromatics.

[shimon340]

...also

the coking problem only occurs due to use of the lean burn mode. Low load and low engine speed operate in lean burn.

So, high revs and driving "enthusiastically" would change the combustion mode to stoichiometric ie non lean burn and would therefore presumably get the engine out of problematic lean burn mode and also help burn off the soot?

[YouNeek]

Originally Posted by shimon340

...also

the coking problem only occurs due to use of the lean burn mode. Low load and low engine speed operate in lean burn.

So, high revs and driving "enthusiastically" would change the combustion mode to stoichiometric ie non lean burn and would therefore presumably get the engine out of problematic lean burn mode and also help burn off the soot?

This has occurred to me lately. Used to try and drive the GDI economically, even on short trips - now I try to keep the revs up.

For those not aware, you can set the trip computer to show current MPG. If there's an "E" in front of the MPG figure, you're in lean burn mode. So if the "E" appears, drop a gear.

Also, a high rev blast down the motorway seems to do wonders for the engine.

[shimon340]

shame though as reducing use of lean mode defeats the reason for having the GDI engine

[birdwood]

i had a strange smell from my exhaust as well
it was a sulphur eggy smell i was told it was the cat sooting up and what was needing was a damm good run

[DavidMarron]

I try to thrash the car whenever it's warm enough as I do far too few miles to justify a GDi. Having bought one it's too late and it's my own fault.

I'd be interested in how much publicity there was about the GDi being for motorway runs when it was new, as the previous owner to me was a mum who did the school run, not a rep.