RS4 B7 Stated Power claim of 420ps

[rsierra]

Nonsense. A restriction is a restriction, whether it be at the air filter, throttle, manifolds, valves, catalysts or exhausts. A build-up of debris on the valve will restrict the airflow and thus the density of the combustion mixture. For maximum power it is important that everything functions as intended. An engine's ability to breathe is hugely influenced by the inlet tract, including valve size and lift. The fact that the RS4 produces so much more oomph than the S4 is testament to how important the finer changes are - higher compession and accurate fuelling are worthless if the engine is compressing a less dense mixture. And whether valve operation is designed to improve power or efficiency they both rely on the air having as uninterupted a journey as possible.

not so...I'll do away with the 'nonsense' comments, it serves no purpose...

there is a huge difference bewteen a compressible vs non-compressible fluid...
with a filter there is no alternate path of least resistance...

what's the compression ratio difference RS4 vs S4?
12.5 vs 11 or a 13.6% difference...
does the RS4 have 14% more torque? no only 5% more...so that means the RS4's volumetric eff is LESS (it's displacement is the same) ~7%

let's look at HP 0.93 (vol eff delta) x 340 HP x 12.5/11 x 7800/6800 ~ 412 HP
very close to rated..

actually valves are designed to have a bit of restriction or backpressure, it augments expansion on the down pressure side...like an inverse nozzle...

It's been a long time since I took IC engines, but I don't ever remember learning that 13.6% bump in CR equates to a 13.6% bump in power. Nor has my real world experience shown it. I think it's more like 3%

[approved]

never been my forte, but sounds credible to me.

[ArthurPE]

It's been a long time since I took IC engines, but I don't ever remember learning that 13.6% bump in CR equates to a 13.6% bump in power. Nor has my real world experience shown it. I think it's more like 3%

torque, not power...big difference, torque is a force, power is the rate of application...
M = V x Pme/4Pi
M = moment or torque
V = displacement or volume
Pme ~ mean eff pressure ~ Cr comp ratio x Veff
4 = 4, Pi = 3.141567
Bosch Automotive Engineering Handbook...

if V is constant, then torque is directly proportional to the Cr (holding Veff ~0.9 to 1)

P = T w (w = 2 x Pi x rev/sec, angular velocity in radians)
for a given torque, power is directly proportional to engine speed...
hence F1 engines making 700+ HP at 18k rpm, with 2.4 liter
but only ~ 200 lb-ft or so of torque

[ArthurPE]

the engine will take the same amount of air with or without obstruction - Nonsense.

you would have more DP across the valve, but all that needs to happen to offset that is to crack the throttle - Nonsense.

Debris on the valves will reduce airflow and can ultimately cause valve seating problems. I find it hard to believe that Audi allowed for this at design stage, and certainly wouldn't have used such an engine as the basis for dynamometer tests.

The density of the air in the cylinder when the inlet valves close will be lower if there is less clearance at the inlet ports.

The purpose of the 'nonsense' comments are to illustrate the fact that your statements make no sense.

Incidentally, I wholeheartedly agree that a rolling road is best used for comparison purposes and not for absolute figures. Far too many variables.

there are 2 options re: nonsense, one your take, the other...
makes no sense = you do not understand?

it's a fact, physics is not subject to your opinion or beliefs...
I have studied valves for 25 years
air, steam, water, you name it...
you would have to essentially close the valve off to make a difference, and even then since the torus of the opening is >>> than the valve seat opening, it still would have little impact...period
air is compressible...

Q = Cv x sqrt(DP)
Q = volume or mass flow
Cv = valve coeficient
DP = pressure drop across the valve

doesn't matter whether it regulates air from a compressor or shyte from a sewage pump, it's all the same physics, as long as density, state, etc., are taken into consideration...and velocities are not super high...

[ArthurPE]

Q = Cv x sqrt(DP)

you may ask, but the Cv changes due to the deposits? it gets smaller, so Q does also...true

and in a static system you WOULD have less Q...but this sytem is not static like closed loop piping
you have energy being supplied by the downward moving piston (a positive displacement pump)
so although Cv may get a bit smaller, DP gets larger...the energy for the extra consumed pressure required for the drop supplied by the 'pump', net effect, 0...same Q, a state of equalibrium

think of a closed piping loop with a pump on a VFD...as you close the valve you speed up the pump, net change in flow = 0
until it's completely closed

[SimonC]

The issue of debris build-up on the valves makes no difference whatsoever and the people who build these engines are wasting their time with innovations such as multi-valves, variable lift, sand-casting, etc when an opening the size of a pin-prick would suffice.

A piston dragging air (ie hugely variable density) into a cylinder at high speed with a limited amount of time to do the job will not be affected by a partial blockage at the entrace.

And, mathematically, a bumblebee (and a Boeing 747?) can't fly.

[ArthurPE]

The issue of debris build-up on the valves makes no difference whatsoever and the people who build these engines are wasting their time with innovations such as multi-valves, variable lift, sand-casting, etc when an opening the size of a pin-prick would suffice.

A piston dragging air (ie hugely variable density) into a cylinder at high speed with a limited amount of time to do the job will not be affected by a partial blockage at the entrace.

And, mathematically, a bumblebee (and a Boeing 747?) can't fly.

not true...with the math and physics of 100 years it could not be understood, neither could computers until Boolean math was developed in 1930's, iirc, and we do have programming code now...

rest assured that bee flight can be mathematically simulated (as can a helo) or 747..it's a fancy wives tale

http://www.straightdope.com/columns/rea ... ees-to-fly
You think this is on a par with quantum mechanics? The basic principles of bumblebee flight, and insect flight generally, have been pretty well understood for many years. Somehow, though, the idea that bees "violate aerodynamic theory" got embedded in folklore.

it is not a 'blockage' the term is 'partially occluded'

[SimonC]

I do not believe that an excessive build-up of debris on the inlet valves of this engine will have no effect on engine performance when the throttle is wide open and the engine is operating at maximum speed. My initial post in this thread was to question a post stating otherwise. The engine is attempting to draw the same volume of air through a smaller opening in the same amount of time. This will result in a slightly higher load on the engine and a slight reduction in the density of the air at the point when the cylinder is sealed.

The interweb is littered with information and maths proving both sides of this debate.

Maths in engineering requires testing because there is too much to consider, otherwise Toyota wouldn't be where they are now. Without the specific data, dimensions, flow-rates, etc which I'm sure only the boffins at Audi have access to these sums cannot be completed - they're just formulae, theory and presumption.

It is widely known that improving the ability of a naturally aspirated engine to breathe through subtle reductions in flow restrictions around the valves improves engine performance and I'm sure the people at Cosworth or any other such company would consider the removal of these deposits as essential for high flow at high engine speed.

I don't wish to malign an excellent car any more, I'd just like to see the manufacturer accept and eliminate this issue. And that's not going to happen if the owners are led to believe that the issue is irrelevant.

[Sims]

...
I don't wish to malign an excellent car..., I'd just like to see the manufacturer accept and eliminate this issue. And that's not going to happen if the owners are led to believe that the issue is irrelevant.

Good summary.

This is common sense, observation & actual experience - engineering degree optional but can get in the way because of vested interests.

[Sims]

again, another diatrabe of insults and personal attacks...
be a man, and just say it, instead of using your mouth like a whore...

and choads who live in glass houses shouldn't throw stones...reread YOUR posts, you'll see what I'm talking about...

I have you pegged as 'the guy' who sees faults in others, but is convinced he is perfect...

I stand by my comments, a bunch of whiners complaining about a non-issue...

lol, talk about opening ones horizons, you acknowledge you know nothing about the subject, yet you take a position...ponder that...
you 'read it on the internet'

so you're anti-American too?
what a loser

that's like me saying brits are a bunch of pussies and would be goose-stepping if not for us...it's hyperbole, like you accuse me of, yet you are the one doing it...
two faced hypocrite...it's you who should take a deep breath and reflect upon your actions (that does not work for those without conscience or who are perfect)

With the engineering skill you have, you have failed to convince other engineers, those who are not intimidated by you and those with common sense.

However, you have convinced me about this - that your conduct is threatening; abusive; harassing; vulgar; obscene; offensive; objectionable as anyone who reads your posts will confirm. To use words like whore, choads, loser, whiner etc devalues any contribution you do make. Does anyone here know what choad means?

I am not the 1st on these forums to suffer your insults, and I am sure your trait will forever remain whereas the carbon build up issue will not.

Have a good day.

[BlingBling]

ok, let me catch my breath....
between my last post and this one...
I removed the manifold
took pics
reinstalled
whew!

26k miles, never cleaned

This is a joke post right? In the 10 minutes between your posts you managed to remove, inspect and re-install the intake manifold.......! That truly defies all logic and physics

Also, I have seen that picture posted on another forum by a member who actually had their valves cleaned after a build up. It will come to me soon which one

[rsierra]

Arthur, Why do engine tuners spend endless hours on a flowbench trying to extract the most flow from a cylinder head?

Also you insist that you have proven that carbon build up has no effect on performance. I have read your posts here and on on other sites and yet to see any conclusive evidence that supports your claim. Maybe you can summarize the data that supports your claim. I am talking real world performance data not theory.

The other thing I am trying to understand is your motivation. You are clearly obsessed with defending Audi, and even mention that it would be very difficult to win a lawsuit against them.

Are you working for Audi in some way?

[SR71]

Correct.

Arthur keeps confusing his terms.

All we've had from him is basic math. Yet his idea about what is really going in inside the inlet is as good as anybody elses.

If, on the other hand, he was saying, my math suggests "X", and I have measured "X", then his theory would have been proved by observation

One of the only people who has had a go at anything constructive is London RS4 in this thread: http://www.audizine.com/forum/showthrea ... p-Clean-Up

He had a go at developing a CFD model of the flow and concluded, as Arthur reported, that, if his model was correct, deposition of a depth much below 4mm would not affect the flow into the cylinder.

However, again, the model is really useless unless it is validated against measured data.

Au contraire, on the observational side, many of us on here have measured the maximum mass flow rate our engines record, and seen the difference that cleaning the inlet/valves makes.

That is fact.

Anyone who knows anything about mathematical modelling would know this. One of the major problems with my PhD (which happened to be in Unsteady Aerodynamics) was that validating the nonlinear indicial response model I developed was almost as difficult as developing the bloody thing in the first place. Whatever, it took 4 years and wasn't done on the back of an envelope.

I have no idea of many of the assumptions the aforementioned physicist made, but I suspect that one of the problems, would have been the way the deposition was modelled.

What I do know is the RS4 Study Guide says:

Different Features of the
High-revving Engine

To match the higher engine power output and RPM, the
following cylinder head components were modified:

Intake ports are charge optimized (based on larger
cross-sections)

Intake valves are chrome-plated hollow stem valves
(for weight reduction)

Valve springs are made of a material with higher
tensile strength and also have higher spring force

To meet the higher fuel requirements, the injectors are
designed for higher flow rates.

Roller rocker arms are more robustly designed, with
peened rollers for higher strength

Camshafts have different timings and larger opening
lengths

Intake valve opening angle 230 crank angle degrees

Exhaust valve opening angle 220 crank angle degrees

The lifters were adapted from the 3.2L V6 engine found
in the TT and A3. They have a larger ball stroke which,
in the course of testing, proved advantageous for the
high-revving engine (with regard to the inflation of the
hydraulic valve clearance compensation element).

The cylinder head has a modified water jacket which
circulates coolant to the area between the intake port
and the injector, thereby reducing the temperatures in
the cylinder head combustion chamber plate.

Due to a modified camshaft drive reduction ratio, the
camshaft adjuster has 25 teeth for the chain drive, as
opposed to 30 teeth in the basic engine.

By simple analogy then, if the enlarged intake ports on the RS4 are reduced in size by carbon deposition back towards the size of the non high-revving engine, flow suffers.

[SR71]

Just to remind ourselves of what we're potentially looking at:

[ArthurPE]

OK, I get the gist of this now:

I present detailed explanations with back-up of my opinions, you post pictures and anecdotal and personal character attacks...
by that logic, since I can't see the curvature of the earth, it must be flat...
and those who disagree must be 'inquisitoned'

We should only present 1 side, and that is yours, I am 'wrong', you are 'right'...that leads to healthy discussion

I have NOTHING to gain and will not benefit from my position, while the other side wants to sell you something to fix, imo, a non-existent 'problem'

I'm a svengali or pied piper leading the clueless down the primrose path...and this one irks me most because it implies you believe the other members are stupid and will not do their due diligence/research and draw their own conclusions...they are clueless...but on the other hand they should buy your position without reservation because you are 'right'...hmmmmm

as far as failing to convince other engineers, I believe they do not have the tools to comprehend the system, and they obviously believe the same of me...it's called 'disagreement', it's 'healthy' and promotes 'understanding and increased knowledge'

it is not an issue because it does not reduce the volume Q or air aspirated...period