Pictures of my inlet ports....

[2manytoys]

Yep, volume I get, but what about air direction/flow pattern. There seems to be a lot of focus on this (given the engine design, plus you should see the shape of the pistons). It seems Audi went to a lot of effort in getting this right. Wouldn't carbon mess this up?

So what could happen assuming its majorly messed up given some carbon is pretty bad? Poor fuel economy?

[Sims]

..
So what could happen assuming its majorly messed up given some carbon is pretty bad? Poor fuel economy?

This is what has been posted elsewhere:

What is “Carbon build-upâ€

[2manytoys]

Yep. Is it that the fuel doesn't burn correctly. The reason I ask is that when my car was at it's peak "crapola" black smoke would come out the exhaust when I gave it a hit. So would unburnt fuel/lean cause knock, and so the engine management adds more fuel too (that helps reduce knock too doesn't it?). Does anyone know if the timing is pulled back and/or more fuel is added?

[ArthurPE]

but in the case of the RS4
no power loss, at most 1-2%
does not impact timing

[ArthurPE]

The purpose of the intake runner flaps is both to make the airflow more turbulent and to direct it to one or both valves. This helps create a small "pocket" of air:fuel mixture in the vicinity of the spark plug that has a sufficiently fuel content to ignite even with a very weak air:fuel ratio taking the cylinder as a whole.

Since the airflow is not equal across the whole inlet area, especially when the intake runner flaps are operated, carbon in places where there is minimal airflow will have little effect on the volume of air entering the cylinder - and hence little effect on power.

It's important to remember that with this engine intake airflow is not laminar, and the fuel mixture is not homogeneous.

what he said...
at low rpm's the velocity is not high enough for good mixing

[2manytoys]

I think the point is that a heap of people already know that some how carbon does cause power loss, seriously, there are people on almost every Audi related website that have had their carbon cleaned. Audi are cleaning the valves to fix the problems too.

Anyway, I was asking a serious question, if timing is pulled, does the ECU also add more fuel to help reduce knock, or is it just timing? My other thought was that the car needs "X" amount of fuel for "X" power, but now that the timing has been pulled back it's running rich?

PS: Arthur, do you get advertising fees from Audi for each post like the one two posts up? You need a signature at the bottom of each of your posts: Disclaimer: Audi pays me/my company $300,000pa and I'm a Direct Injection Consultant with many big customers that wouldn't like me to confirm carbon is a problem (just using information you have said/posted as the truth)

[silverRS4]

2manytoys-

Fueling has its own target values (the targets being air-fuel ratios) and correction capabilities. Ignition timing has its own target values and correction capabilities. The tables of target values are dependant upon load% and RPM in both cases. I will stop calling them strictly closed-loop, but they both are capable of practically instantaneous correction. Fueling is not directly dependant upon ignition timing and vice versa. So to answer your question, no, fueling is not used to control knock directly, but the target air-fuel ratios for higher loads are richer than low-load targets. So in that sense, the fuel ratio is as good as it can be. If the engine still knocks, it is a knock correction loop, fuel grade, or engine problem.

[2manytoys]

Ok, so if the fuel target is load and RPM (yep I get that from looking at MoTeC type ECU's for the race car) then if the timing is pulled would the car run rich? I'm just trying to explain all the black smoke when my car was carboned up. The weird thing was that the Dyno showed 13:1 almost completely flat (even when the timimg was pulled and the power was flat)

[ArthurPE]

I never said I worked for Audi as the truth, the one time I said it was in jest and in response to being attacked and my position diminished because you and others said I worked for Audi...so in summary, you are full of crap...

I have stated at least 10 times, and once again, I do not work for Audi...
I have no business relationship with Audi (other than buying a car)

I do spec DI engines for use, they are called 'diesels'

deposits do not cost power (<2%)
they do not alter timing
they do not cause (detonation, pre-ig or mis-fires) pick one, they are used interchangably around here, lol

the fuel mixtrue is continuously adjusted in 2 ways, much like timing
an ideal value from a map, primarily from the AFM and throttle position
a trimmed valued (actually + and - in this case) by the O2 sensor...

I think the point is that a heap of people already know that some how carbon does cause power loss, seriously, there are people on almost every Audi related website that have had their carbon cleaned. Audi are cleaning the valves to fix the problems too.

Anyway, I was asking a serious question, if timing is pulled, does the ECU also add more fuel to help reduce knock, or is it just timing? My other thought was that the car needs "X" amount of fuel for "X" power, but now that the timing has been pulled back it's running rich?

PS: Arthur, do you get advertising fees from Audi for each post like the one two posts up? You need a signature at the bottom of each of your posts: Disclaimer: Audi pays me/my company $300,000pa and I'm a Direct Injection Consultant with many big customers that wouldn't like me to confirm carbon is a problem (just using information you have said/posted as the truth)

[ArthurPE]

sims, a question:
say you have water in a pipe under pressure at >247 psi, and at a temp of 400F
what happens if you open a valve to atm?
what comes out?
water?

[2manytoys]

ok, so now we are getting somewhere. Your experiance is with Diesels only. Ok, yeah, carbon may not be a problem because they only rev out to 4-5000 rpm. Funny that the RS4 doesn't suffer any problems until higher in the rev range hey? Probably the rev range you lack experiance in.

I looked at a Diesel (Direct Injection) with 280,000km on it (in my mates workshop). Guess what. It was clogged by Carbon Buildup. It was everywhere and probably reduced the circumference by half (maybe more). The owner has been complaining about poor performance. Guess what... once it was cleaned up the performance come back.

So I wonder how much the RS4 has to reduce until it suffers from a powerloss at the top end. 5% blocked, 10%.. surely you can make some numbers up. What about 50% or 70%, or will you still mislead people and say even 90% blocked there will be no power loss.

[ArthurPE]

I didn't say only diesels...gasoline, propane and natrual gas...
diesels usually run at 1800 rpm (or less) for prime mover applications
the physics and thermo are the same, only the timing/rate of events changes...

again:
no power loss (<2%)
it does not affect timing, that is physically impossible...absurd

even at 50% blockage (1/2 of lift) it would not impede airflow
(the valve opening area is 1/2 as much area as the torus, lift x opening, and is the limiting factor)
the max I've seem in pics is 10% or so...and it's limited at that by by the increased air velocity scouring them, it's reached its limit...
just becasue you "can't do the math" do not state lies that I am 'making up' the numbers...if you had the ability you would prove me wrong, you don't, so sit back and learn...

you are the only person misleading people by telling them it costs power, 20% or so...in fact you posted a graph saying yours lost 70-80HP, I told you it was flaps, low and behold, it was flaps...and yet you still say 'deposits', BS

ok, so now we are getting somewhere. Your experiance is with Diesels only. Ok, yeah, carbon may not be a problem because they only rev out to 4-5000 rpm. Funny that the RS4 doesn't suffer any problems until higher in the rev range hey? Probably the rev range you lack experiance in.

I looked at a Diesel (Direct Injection) with 280,000km on it (in my mates workshop). Guess what. It was clogged by Carbon Buildup. It was everywhere and probably reduced the circumference by half (maybe more). The owner has been complaining about poor performance. Guess what... once it was cleaned up the performance come back.

So I wonder how much the RS4 has to reduce until it suffers from a powerloss at the top end. 5% blocked, 10%.. surely you can make some numbers up. What about 50% or 70%, or will you still mislead people and say even 90% blocked there will be no power loss.

[2manytoys]

Below is my graph. You see the flat line? This is probably caused by timing not restriction in air flow per se.

Here is my graph:


Here were my valves (after Audi "cleaned" them), still bad.


This is what they looked like after a proper cleaning:


My intake runner flaps were never a problem during this. This was tested many times (and you've read that from me many times too). The entire manifold was replaced about 10,000km after all of this due to an unrelated problem. Did you want me to make that bold, so again it sinks in and maybe this time you'll stop mis-quoting me and stop misleading people for your own gain?

[ArthurPE]

that was then, and is now, caused by malfunctioning intake flaps...

deposits can't <beep> timing on a DI engine, it is physically impossible...
what mechanism would cause it?
the mixture is not affected so detonation can't be the cause?
what physically causes it? what are the mechanics?

eg: port injection possible cause...
fuel gets absorbed by the valve deposits, mixture goes lean and it causes poor mixing, prone to detonation, and possibly pre-ignition...

give me a detailed explanation of the mechanism in a DI engine...
I've shown that the fuel basically explodes out of the nozzle since it is > vapor state, held in check only by pressure which is relieved, instantaneously changes state to vapor and completely fills the cylinder, top that off with the piston squishing and swirling the mixture, and it can't be 'mixed poorly'...

so PLEASE give me the mechanism that leads to detonation and spark <beep>...and why do not all RS4 engines respond like yours since they ALL have deposits?

oem wheel power ~330, yours ~260, ~20% loss
prorated to the crank 420 to 330...no way deposits (or supposed deposit related timing <beep>) cost 90 HP...no way

Below is my graph. You see the flat line? This is probably caused by timing not restriction in air flow per se.

Here is my graph:

Here were my valves (after Audi "cleaned" them), still bad.

This is what they looked like after a proper cleaning:

My intake runner flaps were never a problem during this. This was tested many times (and you've read that from me many times too). The entire manifold was replaced about 10,000km after all of this due to an unrelated problem. Did you want me to make that bold, so again it sinks in and maybe this time you'll stop mis-quoting me and stop misleading people for your own gain?

[2manytoys]

So now you are assuming the peak number from this dyno is accurate??? I thought you said they were not accurate so how do YOU know what the actual loss is??

Anyway, again, it's the shape of the curve. Many people have produced a similar graph, and many people have shown the curve returns to a normal curve once cleaned.

I think your inexperiance is showing that you don't know why it happens either. The difference between you and I is that I simply show the impact and results where as you mislead people by inexperiance and denial.

At least to the good people that read this forum, Audi have realised it's a problem and are cleaning it under warranty. Hats off to Audi for addressing this problem.