Long journeys clear out carbon deposits?
Discussion
Chris32345 said:
Depends on where about on the back of the vales not as there's nothing to prevent build up
Unless running something like methanol Injection
He seemed to be suggesting that it worked due to one or more of: prolonged heat and/or high airflow and/or high exhaust flow and/or valves being open long enough to collect traces of fuel from the combustion chamber which helped loosen deposits.Unless running something like methanol Injection
Yes unavoidable, unless you vent the engine to the atmosphere and possibly delete EGR. I don't think a DI engine management will be happy and throw up fault codes and go into limp home mode. I would like to try water injection to see if this would attenuate the situation. A sad feature of modern low emission petrol engine motoring.
motco said:
An RS4 in my family just had a walnut shell decarbonisation to remove the build-up. Surely not needed if a long run would do it?
I've heard of this on R8 engines - are they prone to it more so than others?Also - did it make a noted improvement afterwards? - I can't image its a cheap job!
In days gone by I've done DIY head de-cokes and re-seated valves - which I liked to believe make a slight difference, although I'm talking 110hp engines at best!
On many engines with DI, you can remove the inlet manifold and associated stuff and actually physically pick the carbon/oil/gunk deposits out by hand. If you are inventive with your scraping tools and suitable solvent, you can get everything back close to normal. Cheaper than a £500 walnut shell blast.
You will definitely feel the difference on the average 50k mile engine. A cheap endoscope - I got mine from an eBay charity shop for £5.90 and boy, it is a superb tool, with a lighted camera and crisp images - linked to your phone and a minimal amount of dismantling will allow you to see if further work is needed.
Then just spend a Sunday afternoon manually decoking the inlet ports and valves. See it as part of a major service job. Or buy an older car and spend your free time chasing rust. I have :-)
You will definitely feel the difference on the average 50k mile engine. A cheap endoscope - I got mine from an eBay charity shop for £5.90 and boy, it is a superb tool, with a lighted camera and crisp images - linked to your phone and a minimal amount of dismantling will allow you to see if further work is needed.
Then just spend a Sunday afternoon manually decoking the inlet ports and valves. See it as part of a major service job. Or buy an older car and spend your free time chasing rust. I have :-)
Cold said:
As a related side note, a diesel car will initiate a regen of the DPF on a long motorway journey.
Not necessarily. The old advice of 'just thrash it for a few miles on a motorway' to keep a DPF sweet is mostly nonsense. It's true that higher exhaust temperatures can lead to some passive regeneration (that is the soot load burning off of it's own accord without the ECU actively assisting the regen process). However at motorway speeds you're typically in top gear and so the RPM and exhaust temperatures are fairly low. Most diesel engines won't start an active regeneration cycle until certain parameters are met, however opportune it may be the for the driver. It's usually triggered by the DPF pressure sensor returning a signal to indicate that a certain point of loading has been reached (that is, an accumulation of certain amount of soot is now trapped). Then the car will check over the rest of the operating parameters and begin an active regen cycle where diesel is injected on the exhaust stroke to superheat the DPF. If you watch the process happening in real time you'll see the exhaust temperatures skyrocket whilst it's ongoing.
As for DI inlet valve coking in a petrol, no, running the car hard won't do anything for it. Get a good old fashioned port injection and enjoy a quiet idle and clean valves instead.
Steamer said:
motco said:
An RS4 in my family just had a walnut shell decarbonisation to remove the build-up. Surely not needed if a long run would do it?
I've heard of this on R8 engines - are they prone to it more so than others?Also - did it make a noted improvement afterwards? - I can't image its a cheap job!
In days gone by I've done DIY head de-cokes and re-seated valves - which I liked to believe make a slight difference, although I'm talking 110hp engines at best!
RVB said:
I was chatting to someone today who knows a lot about cars and they insisted that carbon buildup in direct injection engines (petrol or diesel) will gradually clear itself during long journeys.
Is that true?
Nothing will clean up all the carbon etc....except for someone actually cleaning all the carbon.Is that true?
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