Valves- carboning up

[ArthurPE]

it sounds as if it were you who were pulled from the teat too soon...
angry and insulting without variance
sure sign of insecurity, lighten up...please

if a car were down 70HP as you claim the 3k-8k test would be well over 9 sec...big difference...

I haven't been electrocuted, but I can tell you everything you want to know about electricity...

my comments are based on ~30 years of experience and engineering involving combustion engines...I know this pales in comparison to paying someone to screw my engine up and a couple of pictures, but It'll have to do

P_G and Arthur, do you guys need a cuddle, seriously, why are you so precious.

P_G - maybe I've left some details out this time, but when I say the car had no power above 6000rpm, then the valves were clean, and then the car had power, how difficult can this be to understand. Let me try to explain it again. The manifold was taken off on a Friday afternoon, cleaned all day Saturday, and put back on Sunday. The car then felt like a "Turbo Boost" after about 5500.

So, the questions is, am I argueing with someone that has done this procedure? Do you have pictures/video? I've now been in another car that doesn't have a "Turbo Boost" after 6000, and a bore scope shows carbon (no engine and EPC). So, that's two, and I have no doubt as soon as it's cleaned it will go hard again.

So again, just so everyone else knows, have you actually done this, or are your comments just opinion?

Regarding the 3000-8000rpm run, 8 sec thing, I can't get my head around how this can be accurate (just so Arthur doesn't get upset, I'm not having a go at him, it's a genuine question). How long does it take to go from 6000-8000 in the test? I'm concerend that most cars feel the same between about 3000-6000 so any time difference is going to be higher in the rev range. So, a 0.2 sec difference, and assuming in the higher rpm range, this would be huge.

Free cuddles for all

>-- ' ' ---<

[2manytoys]

Guys, all I'm saying is that it may be worth testing this for yourself rather than relying on what should happen.

Being an Engineer, you should want to test this in real life (I'm an Engineer in Electronic's and what the book says is not always how it works in real life, it's called heat/resitance and eddy currents to name just a few). Anyway, I digress, we'll end up getting into a "mine is bigger then yours discussion".

So can you please do the real life test, otherwise, please at least tell people it's an opinion and you haven't tested this yourself when you claim carbon doesn't cause problems. That's all I ask.

Mal.

[northernpar]

Mal, I too am an Electronics Engineer although have spent the biggest part of my career in control systems however, without wishing to get into any 'mine is bigger than yours discussion' I haven't a clue what your reference to heat/resistance and eddy currents is about!? These are all electrical first principles and fully covered in any books I have studied. As Scottie would say "Ye canna beat the laws o' physics Captain".

Now in terms of your particular issues. It may be that you did have a problem with your breather/oil recovery system which caused excessive carbon build-up which in turn caused valve issues. I wouldn't even attempt to dispute that as I wasn't there and don't know enough of the detail.

I agree with your points on testing but this is problematic as there are a number of issues that could cause the power losses that you experienced both mechanical and control related. From reading the posts and assuming that the excessive carbon deposits/valve issues were the problem then surely this would affect power delivery over the full range not just above 6k RPM? In that case a 3k-8k timed road run in 3rd should show significant time difference from an engine not suffering from excessive carbon deposits/valve issues?

As I've stated on other posts I have certainly felt a loss of power above 5k RPM although this has been intermittent and judged only on the basis of my 'ass dyno'. I'm completely confident that if I looked in the intake manifold I'd find carbon build-up as this seems to be an unwanted feature of this engines operation however the fact that the loss of power isn't constant I'm looking at some of the other control components that coudl also cause a similar loss of power scenario. I'm not saying it definately is due to this but I'd prefer to test these before I resort to taking the manifold off for a clean.

When digging about into this I found an interesting TSB from Audi relating to a potential vacuum leak from a connection under the intake manifold. For Audi to release this would indicate that this particular problem has occured more times than they would like. To resolve this the intake manifold needs to be removed. Now, I'm not saying that this is what happended to you but the removal and refitting of the intake manifold for cleaning could inadvertently cure this leak through the simple action of removing and refitting this connection. I guess what I'm saying is that due to the complexity of the system it will always be difficult to pinpoint the exact cause unless all other influences are also verified at the same time.

[2manytoys]

I understand what you are saying, but all this was checked by Audi prior to pointing toward carbon buildup. In fact, a lot of time was spent in the vacuum/flaps area, as I agree, it's common. Just so you know, carbon was the last on the list, not first in my case. We even checked the cats for blockage thinking it may have caused the pinging. Also coils and plugs were check (plugs changed).

Regarding your point about removing the manifold fixed a possible leak, there were no engine or EPC lights at the time. When Audi "cleaned" the valves the first time the surge at 6k rpm was back (although small). When Gosford European Car Services fully cleaned the valves the power was amazing. I highly doubt the vacuum pipes were bumped twice and the second time it fixed it even better than the first. I also don't think air volume takes that much power away, I'd say it's more to do with retarding timing (but still a combination).

I'd like to think it's something other than excessive carbon, but the facts so far are pointing to that (given it's very simple to test).

[2manytoys]

Hey, I found this secret video of Audi discussing the carbon buildup

http://www.inspiredobjective.com/Audi/

[sonny]

Hey, I found this secret video of Audi discussing the carbon buildup

http://www.inspiredobjective.com/Audi/

[Terry1948]

Northernpar you are right that most of us find that our car performance does seem to change but as you say this is subjective. All week I drive a pickup and a truck at the weekends I get the RS out and it feels very fast, sometimes I travel to Germany to see family after 4-5 hours of autobahn it dose not seem as fast. There is a lot of snake oil out there a lot of this found in the motor industry and the hifi industry I Know because I have paid the price(sucker). Some problems are solved by coincidence. I do understand twomanytoys point of view valves cleaned power restored it is how he sees it. I had a problem with a gearbox the experts who have always been spot on were convinced it was shaft at fault common problem they said but infact it was just a electrical connection. My advice is to try the cheap and simple stuff first and work your way too the expensive stuff to cure a problem.

[ArthurPE]

the hifi industry does have lots of 'snake oil', ie, $5k speaker cables! lol

a lot of the perception of decreased performance is familiarity...
when I got mine, it seemed soooo fast relative to my e46 M3, as I got some hours in, the margin decreased...
on the other hand, the power delivery in my 951 is so much different than th RS4, ite 'feels' faster under certain conditions...obvioulsy it's not...

the difference in g force between a 106 sec and a 110 sec 1/4 mile run is so minute, not even a fighter pilot could distinguish....
yet that is a 75+ HP delta...

ps: anyone else watch the f1 race...pretty good, and pretty dang early in my part of the world 05:30, lol

[victor2vt]

Hey, I found this secret video of Audi discussing the carbon buildup

http://www.inspiredobjective.com/Audi/

EXCELLENT !!!

You've got friends in high places

Got any more ??

[bfettie]

Ok Guys,time to pick your brains!!
I have noticed a considerable drop off in performance of late but not really had a chance to do much about it.To give you an idea I have tried a couple of Arthur's runs and average about 10 secs!! There is no 'vtec' at 5000rpm the epc light comes on sometimes more so when colder and it can have hesitations anywhere above 4000 rpm , still runs fine below that.All I have done so far is check the bungs I put in the vacuum pipes to the tailpipe valves which are still sound,so could it be the flaps and if so which ones ?

[northernpar]

I understand what you are saying, but all this was checked by Audi prior to pointing toward carbon buildup. In fact, a lot of time was spent in the vacuum/flaps area, as I agree, it's common. Just so you know, carbon was the last on the list, not first in my case. We even checked the cats for blockage thinking it may have caused the pinging. Also coils and plugs were check (plugs changed).

Regarding your point about removing the manifold fixed a possible leak, there were no engine or EPC lights at the time. When Audi "cleaned" the valves the first time the surge at 6k rpm was back (although small). When Gosford European Car Services fully cleaned the valves the power was amazing. I highly doubt the vacuum pipes were bumped twice and the second time it fixed it even better than the first. I also don't think air volume takes that much power away, I'd say it's more to do with retarding timing (but still a combination).

I'd like to think it's something other than excessive carbon, but the facts so far are pointing to that (given it's very simple to test).

2manytoys, as I say you may just have been extremely unlucky to have experienced this problem at an extreme level which would undoubtedly cause problems if the valves were being compromised and bits of carbon were coming loose in the intake. So in your case it is not inconceivable that carbon build up was the cause of the problems. I guess the interesting question would be why so much build up in the first place? It's also interesting that they replaced components in the breather/recovery system which is where the answer to that question could lie.

There are a number of owners on here with relatively high mileage cars who haven't suffered the same issues as you which adds further confusion to this. I don't think anyone in their right mind would dispute that carbon build-up happens and that too much will create engine/performance issues. But how much is too much? And what would constitute normal build-up? We may never know the answer to that one although it sounds that you may have come close.

[2manytoys]

Well here is a pic of my valves after 2000kms (after they were cleaned and all the power come back).



I can't be sure, but I don't think this much carbon caused any power loss. It's hard to tell and I wouldn't argue that this amount causes problems (maybe this is the point others are trying to make?). I can say that more than this though and you'll notice it.

Audi are replcing the seperator now, only because the carbon has come back so quickly. Maybe there are just a few cars out there with faulty seperators. Either way though, the carbon is an issue (if you have it as bad as I've had it).

Mal

[ArthurPE]

the oil deposits are not coming from the blow by via the seperator....

a member cleaned his valves and disconnect the seperator completely, vented to atm
the deposits were back just as above within 2k miles

another inserted a catch can in series (before) the seperator
all it caught was water, the oil was insignificant, and the seperator would have caught it...

to the guy with 10 sec runs...it is NOT deposits...has Audi checked the car?
vacuum leaks
manifold flaps
???

ALL cars will have deposits of similar degree...driving habits/fuel/etc. will cause some variation...


but the majority of the cars tested (all in my dadta base) run better than or equal to, factory spec...so a conclusion can't be drawn that deposits = loss of performance, since ALL cars have them, and very few experience performance LOSS...

[PetrolDave]

There is no 'vtec' at 5000rpm the epc light comes on sometimes more so when colder and it can have hesitations anywhere above 4000 rpm , still runs fine below that.

Sounds to me like two possible issues:

1) the flaps in the intake manifold that cause turbulent flow at low revs (and hence allow FSI mode), but open to allow full flow to both valves at higher revs may be sticking. This could explain the EPC light above 4000rpm.

2) the power flap in the air cleaner box almost certainly isn't opening, hence the lack of "VTEC" at 5000rpm.

[ArthurPE]

Sounds to me like two possible issues:

1) the flaps in the intake manifold that cause turbulent flow at low revs (and hence allow FSI mode), but open to allow full flow to both valves at higher revs may be sticking. This could explain the EPC light above 4000rpm.

2) the power flap in the air cleaner box almost certainly isn't opening, hence the lack of "VTEC" at 5000rpm.

yep, or both due to a vacuum leak...