Originariamente Scritto da
d3a
infatti anche nei forum stranieri sostengono che convenga nel 99% dei casi una TT RS s-tronic,che anche sulla carta è più veloce fino a 100 km/h
---------- Post added at 20.42.06 ---------- Previous post was at 20.41.27 ----------
se intendi questo problema,ecco la spiegazione da post direttamente ingegnere che lavora a Ingolstadt
"Carbon build-up"
Dear Friends,
as promised, i would like to say a word or two concerning „Carbon build-up“:
What is “Carbon build-up” and how does it come into being:
With fuel direct injection the cylinder heads and valves are no longer “washed” by fuel, which leads to a lacking “cleaning factor”. This is where the exhaust gas recirculation combined with the ventilation vapor of the crankcase ventilation and oil starts to build up. Particles of dirt and jets of water coming through the air intake path form into firmly adhering layer. This layer is taken up within the chambers of the cylinder heads and the admission valves, resulting in a rough surface, the airflow cross-sections become more narrow leading to non optimal air interlacing and cylinder charge. In total the results of “Carbon build-up” can be bad exhaust emissions, lower power output and higher consumption. In worst case the “Carbon build-up” affects the valve train. The valves can not close completely, which leads to low compression on the relevant cylinder, the fuel composition is not “fired”.
Factors that promote “Carbon build-up”:
Low quality fuel
Frequent short range driving
Preventing higher engine temps
Low RPM driving
intermittent driving
long time „not-using“
using non-specific engine oil
Audi RS 5 and „Carbon build-up“, do i have to worry?
As you might already know, the RS 5 engine ist based on the RS 4 V8 version. Main “Carbon build-up” relevant points that have been altered:
Engine production tolerance over again significant improved
Engine oil temp is increased by ~10°C
Modified piston rings
Resume:
The probability of „Carbon build-up“ within the RS 5 engine is nominal.
PS: as the RS 4 V8 was also mentioned you migh like to note, that the engines from build date CW20/2007 received a altered cylinder head with different piston rings.
Dear Friends,
for clarification: "promote" is not "cause". To cause "Carbon build-up" more than just one factor has to be achieved and this is where the "promote factors" come into play. To the best of my knowledge there are no "Carbon build-up" problems reported to the quattro GmbH for RS 4 V8 produced after the CW20/2007. Pre- CW20/2007 RS 4 V8 that had "Carbon build-up" problems leading to engine failure or compression loss have been covered with a warranty repair, new improved cylinder head. (different piston rings) Reported cars had high oil consumption, up to 1 liter on 1.000km (within range up to 0.5l every 2.000-2.500km)
If happened the principle of cause and effect varies case-by-case depending on specific parameters. (running-in procedure mishandled etc. for example)
5 cilindri turbo: RS!
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