RS4 B7 Stated Power claim of 420ps

[johneroberts]

Firstly this thread was brought to my attention because of abusive behaviour.
Something i cannot tolerate and are against the forums rules and regulations (please read them)
I find the discussion very interesting and informative, please keep on topic and dont make it a personal attack
Afterall its supposed to fun guys, lets keep it that way
jr

[HYFR]

Guys, my car is in with Audi as i've had EPC light problems...the fault was diagnosed as

"fault code re secondary air throughput - both banks too low, checked operation of motor + valve - ok, checked piping visually as best as poss - ok, carried out basic setting of system - ok, system working correctly"

last time they changed the air box flap or something or other (sorry not mechanically minded)

they've just called saying they are going to have to remove the manifold which will take 4hrs and replace there...

Could this be linked to the carbon build up?! my car is on 70k, so if its been building up, there will be a lot there !

all under warranty of course

[Sims]

they've just called saying they are going to have to remove the manifold which will take 4hrs and replace there...

Could this be linked to the carbon build up?! my car is on 70k, so if its been building up, there will be a lot there !

all under warranty of course

DK, I suggest you ask them to take some photos for it will be good to see the insides of a high mileage ( & well driven ) car.

Hope you get it sorted soon.

[ArthurPE]

Guys, my car is in with Audi as i've had EPC light problems...the fault was diagnosed as

"fault code re secondary air throughput - both banks too low, checked operation of motor + valve - ok, checked piping visually as best as poss - ok, carried out basic setting of system - ok, system working correctly"

last time they changed the air box flap or something or other (sorry not mechanically minded)

they've just called saying they are going to have to remove the manifold which will take 4hrs and replace there...

Could this be linked to the carbon build up?! my car is on 70k, so if its been building up, there will be a lot there !

all under warranty of course

probably not...there is a TSB out for the manifold flaps and loss of power or ECL's...

your car has warranty at 70k miles? wow

did you do any of the 3-8k times runs?
if not do some before and after...

pics at 70k miles would be good, to compare them at the 6k pics and 20k pics...see if it tapers off as I suspect...

[HYFR]

your car has warranty at 70k miles? wow

Audi UK let you extend the warranty every year until you are over 100k at the point of renewal (i.e. if you renew at 99,999miles you can have a warranty at 114,999miles or even higher if you go for the unlimited mileage option

[sonny]

Interesting, will wait to see the outcome. is your car modded?

[HYFR]

not modded (except for Milltek!)

[MarkD]

".......In order for surface roughness to impact flow appreciably, the high spots must be high enough to protrude into the faster moving air toward the center. Only a very rough surface does this.


now what this would imply is bigger isn't always better, so a small reduction in area (deposits) will not have as big as impact as you might expect..."

The idea of "surface roughness" and "protrude into faster moving air" is important when you look at pictures of intake valves with a ring of carbon formed on the upper portion of the valve stem.

As we know, high turbulence is very helpful in increasing the flame speed in stratified and direct injection spark ignition engines. Generally, it is suggested to have a strong tumble motion during suction stroke with high kinetic energy because this will be later dissipated as turbulence during the compression stroke at the point of spark.

However, there is a noticeable reduction in tumble ratio as a valve opening gets smaller. By smaller, the general understanding is the valve is less than 100% open.

So, assuming the RS4's cylinder head has been optimized for air flow patterns into the cylinder (ie. the structure and pattern of the in cylinder flow field does not change much with engine speed), it would make sense that the tumble ratio would be a strong function of the intake valve lift, more so than a function of the rate at which the air flows into the cylinder.

Given all of the above, would it be fair to say that if the "opening" were further reduced by unwanted carbon build-up on the valve stem, and by "opening" I'm talking about the path that the optimized air flow follows into the cylinder, tumble ratio would decrease, which would effect the turbulence within the cylinder during compression and because this is a direct injection engine, the flame propagation rate through the cylinder?

Which, for my simple mind means that an engine might be down on power as slight carbon deposits form in the beginning, and in extreme cases of carbon deposits, have the timing pulled back because of something a sensor might think is detonation due to a poor flame front moving through a cylinder?

Or this might all be idle ramblings because I've been up for a while.

[ArthurPE]

although the engine is DI, it operates primarily in homogenous mode...meaning fuel is injected during the intake stroke, not the compression...
so the fuel is mixed prior to compression...
and mixing is augmented by the piston suction...

as long as the injector does its part (vaporized fuel droplets) I don't think it matters much, and as compression occurs the air is compressed, the fuel is not, so any random voids/poor mixing would be dimished by the volume being reduced 12.5:1, and the air voids shrinking, and the fuel volume not...

some say that is the reason for higher deposits, no lean burn mode...

I think the reason we see more deposits on the stem:
it's from the valve seal(s)
the air flow keeps it scoured at the lip...maintaining ~ the original velocity...

[ArthurPE]

something to consider:
the deposits are continuously polished by the air flow...
as the material is deposited it is 'soft' and takes time to harden, while this is happening, air flow polishes it...shapes it...
so as it hardens, it forms in a shape conduciive to the natural flow pattern...
mother nature is like that

also all directions are affected equally, if only one valve segment were impacted it might mess with the pattern, but since all are affected the same, the pattern should not change, but the velocity will increase...

first para:
From the results, it is found that the overall airflow direction at the exit of the intake valve does not change significantly with the air flow rate and intake valve opening conditions. The tumble ratio increases with increase in intake valve opening and not much affected by the change in the air flow rates. It is also found that, the variations of the velocity profiles at the two specified lines are smooth at full intake valve opening irrespective of the air flow rate.

http://www.jafmonline.net/modules/htmla ... hrough.pdf

[Sims]

I read this elsewhere, purported to be from someone at Audi. Some interesting stuff, what do you guys think?

"Carbon build-up"

What is “Carbon build-upâ€

[S2tuner]

Very interesting read!

[Dom81]

Any idea why intermittent driving and long time "not-using" are factors?

I'm not asking whether the build up signifcantly affects performance - that one's been done to death - but I'm interested in why these two contribute to build up in the first place.

My car only does 5k miles p/a as I intentionally don't take it on short runs to the shops or slow crawls across London. I would have thought that only using it for long, fast trips (with Optimax / Ultimate fuel and Titan oil change each year) would be the ideal treatment - however long the gap between each is...

What's supposedly happening when I'm not driving it?!

[sonny]

CW20/2007? Interesting.

So cars built after 2007 should see less CB in the heads?

[Sims]

CW20/2007? Interesting.

So cars built after 2007 should see less CB in the heads?

May 2007 production onwards. 20 is the week number in 2007.