ayrula

Hello guys. I am hearing that AoA has extended warranties on the 3.0 tfsi and 3.2 fsi engines. Any chance this will be extended to the d3 s8s? After reading all the carbon buildup threads I am concerned as to whether I have the issue as well. I am not the original owner so I don't have anything to compare to regarding power loss. The s8 has plenty of power but does feel like 450hp especially coming from modded b7 s4 4.2

EHLO

I doubt that it will be extended to the V10 because typically there is no problem if you use high quality, correct octane gas. Having an S8 myself, I've been studying the issue for a few years now, and have heard of exactly one V10 with a problem in an S6. Perhaps the fine oil separator had failed, or the owner was repeatedly subjecting it to high revs under low load that would cause excess blow by, overloading same. I occasionally check with a Borescope down the plug hole, and there is very little buildup at over 85K on mine.

s4master1

you can not see the carbon build up thru the spark plug hole.

ayrula

I agree with s4master1. Everything I've read also confirms that this is an fsi issue period. Low quality fuel just accelerates the problem. I doubt all the rs4 owners are using cheap gas, the problem goes beyond that.

SoCalJ

Sorry, I don't quite understand what "high rev & low load", "low rev & high load" or what combination.....exactly means. What would staying in 1st gear and driving it in 4k-5k RPM be??...high rev & high load?? I just need to grasp the meaning behind the rev/load combination. If I need to modify my driving habits to prevent future carbon issues, then please explain away. Thanks.

EHLO

Ok, your example is only the second I've seen of carbon buildup on a V10.
We see the pictures, but there are also some questions;
1. What was the mileage?
2. How often was low quality fuel used?
3. Did the owner use Mobil 1 or other high quality synthetic oil, and how often was it changed?
4. Had the fine oil separator failed in some way, was it or the return feed to the crankcase blocked up by sludge, perhaps due to not following point 3?
5. Was the correct octane used, so that the variable valve timing never had to change to a point that there could be blow back of unburnt hydrocarbons into the intake manifold?

EHLO

Yes, I believe low load is when one is driving along at a steady rate at a moderate speed with the engine in the upper rev range.
High load would be acceleration through the gears, where the engine is working hard at pulling the car along.

EHLO

The valve timing is different on the RS4, in that unburnt hydrocarbons can be blown back into the intake manifold under normal driving.

I want to make it clear that I'm not defending Audi's DI design, even the most conservative valve timing and the best fine oil separator won't eliminate the problem over the lifespan of an engine.
I've read of a yet to be implemented design that has a fuel injector in the intake manifold, designed to introduce just enough fuel to keep things clean.

snagitseven

Just to clarify, the warranty extension for 3.0T and 3.2TFSI engines is for carbon buildup on the secondary air ports only, which are located inside the cylinders (an FSI design). The warranty extension does not address any carbon on the valves and cleaning of the SAPs will only be covered if the condition throws a CEL. Since fuel does not come in contact with the SAPs, gas quality is not a factor with this issue (and as a result, cleaning agents like Seafoam won't help in this particular case). Still, using Tier 1 fuel as recommended by Audi could help avoid or delay carbon buildup on the valves of any engine.

mishar

Load is power/torque.

High rev low load can be achieved in manual mode, driving in a lower gear with very little gas pedal. Unreasonable use of a Sport mode can give same results.

Low rev high load would be lots of gas pedal while keeping a higher gear. Possible only in a manual mode and just to the certain point when automatic will kick in and shift into lower gear. Of course, all of this is way more relevant with manual transmission.

Buildup in those pictures is obviously from oil.

Millage is definitely relevant.

Fuel quality is not with FSI engines.

Oil quality or changing intervals won't make any significant difference either. This is not sludge. Any oil would create same deposits if it comes in contact with a hot surface.

Oil separator is crucial, but not only factor. Oil can get there also leaking around valve studs. How much depends on a millage, age and driving habits. Abused engines, likely RS and S engines bought for the reason, work hotter and wear valve studs and seals faster. Most of oil is sucked into intake manifold under idling and engine braking.

So, no unnecessary revving or Sport mode, no long idling for heating or air conditioning purposes and no forced downshifting is all we can do in order to prevent carbon buildup. Audi and other engineers have to take care of oil separators.

Higher revving engines have a different (longer) valve timing and some blow back is present on lower rpm, but there is very little unburnt stuff, mostly carbon monoxide and it is too hot to create any deposits.

Injecting fuel to the intake valves keeps them cooler. Racing engines use fuel to cool combustion chamber and exhaust valves too. That's fire we can see from the exhaust under braking.