Hello from Sofia

A6 All/ S6 All
#1

Hi guys, I’m so excited to find this forum - especially the C6 S6 V10 info dump!!! I’ve been searching for an accurate and detailed source of V10 knowledge for awhile now, but it’s hard to come by.

I’ve got an 2007 S6 I bought last year in DC and then, after a sudden relocation, took overseas to BG. I actually tried to sell it before I left, but couldn’t get a bite above $17K so I figured I just keep it an take the fuel economy hit. And now with the price of gas in Europe down to the same as last year in DC, I feel great about it! Here are some pics I took for the listing:

http://imgur.com/a/qjt7O#0

Anyways, I’ve been chasing down a P0308, misfire cyl 8, at WOT for months now. I found myself a local audi mechanic who had experience with v10s (strangely, there are a ton of v10 S8s in Sofia, more than S6s) who was willing to work with me on it. We’ve done the following:

  • reseal the upper valve cover gaskets to keep oil from leaking into plugs (cleared a rough idle on cold start)
  • swapped coil packs and plugs from cyl 7/8
  • ran through 200ml of G17 fuel additive, plus another 1000 miles

Despite the claims to the contrary in many of the forums, I think the additive did help. But it took about 1000miles for it to do the trick. Now I get a few intermittent P0300 codes at WOT, but never a CEL. My mechanic suggested I run another 200ml of G17 plus 1000 miles, and then we’ll inspect the intake manifold for carbon deposits. But at the moment, the engine is running well.

The other bugs to the system are:

  • front passenger door lock mechanism will only unlock/open from the inside. once unlocked, the door opens fine
  • the car was momentarily disabled (wouldn’t start). coincidentally, this happened exactly when the passenger door opened just fine. I got out, locked and unlocked the door, and then was able to start the car just fine. My theory is that the car was immobilized - maybe because the passenger door was not properly closed before opening. HOWEVER, my mechanic said that this might be a sign that the fuel pump is on it’s last legs. Apparently, the fuel pump primes for a few seconds when the doors are unlocked. Has anyone every heard of this before? Regardless, this issue hasn’t happened again.
  • my mechanic suggested that if the misfires come back, he could do intake manifold ‘tumble flap’ removal mod. I’ve read about this in sigs, but can’t find any details. any thoughts?

I’m still reading through the info dump, so I’ll pipe in again after I have finished. But just wanted to say hello.

#2

Welcome to the forum! A bunch of great info in here!

#3

Your in the right place for good information. If the misfire was just about the peak tq range that would make sense and could be related to an injector with either a carbon issue or just a failing injector.

Did you do a carbon clean

#4

Welcome!

Always great to have another S6 join the forum. You are definitely in the right place.

As you probably have figured out, misfires on the v10 are a common issue with many different potential root causes. I continue to try and gather data on every case I find, so that we can better understand the causes. Some guys like Justin will jump in to help you troubleshoot the situation.

There are a great bunch of Technical guys here willing to help. And even more important, there is some level of filtering in place, so you can be confident that any technical advice you get here is solid.

When you have a chance, please post a quick intro with your pics in the C6 members thread.
http://audirevolution.net/forum/index.php?topic=3097.0

Regarding the tumble flaps, is that common practice to remove them on the S8? From Audi’s documentation,

Intake Manifold Flaps
The intake manifold flaps are controlled according to a
characteristic map in the Engine Control Module. They
are activated in lower engine load and RPM ranges.
The flaps are brought into contact with the port baffles
in the cylinder head and seal the lower part of the
intake port. The intake air mass now flows through the
upper section of the intake port and induces a tumbling
charging motion inside the cylinder.
When not activated, the intake manifold flaps are open
and the cross-sectional area of the port is maximized.

These are the flaps just above the cylinder intake ports, not to be confused with the ones in the middle of the dual path intake manifold.

I am not sure why you would want to remove them to deal with a random misfire on one particular cylinder. If anything, have the entire intake manifold cleaned of carbon, along with the cylinders, as Justin suggested (if that has not already been done recently). When you have the manifold off, check for proper opperation. There is info in the Info Dump regarding intake manifold issues (recent update).

The tumble flaps are on some other Audi’s, so I am interested to hear what other guys on hear have to say about their removal.

Keep us posted

#5

I haven’t done a carbon clean yet, but after reading through the info dump, I also remembered that we:

  • replaced the vent hose because the old one was was torn/taped near the oil separator.

We’re going to take off the IM after one more round of G17 and check for carbon.

#6

Carbon clean should be at the top of the list. If you had a leak on a vent hose there might be more damage further down. Usually there’s lots of little things that you find when you do carbon cleans.

#7

What’s the word on Octane with the V10s. I always got 93 in the US with my 2.7T, but that was because the ecu would dial it down at full boost when there was knocking. Do you get any benefit with a naturally aspirated V10? I am not getting any detonation under normal driving. The fuel door says 95RON and that’s what I’ve been putting in.

#8

On the NA Audi engines, I dont think youll get much b e n ef it going higher than 91. If you have a tune installed, then you can take advantage of the higher octane.

#9

Yeah what’s inside the fuel door is accurate for octane, however, look closely and it’ll probably be a range, not a single value. I think 91 to 95. I’d suggest using the best octane that you can get in your region, since the cost difference is negligible in my opinion. This is not a performance suggestion as much as it is a maintenance suggestion.

Good point by v8a6 - using any higher than 91 octane probably won’t result in any more power on factory settings. I live in Alberta, Canada, and I run 94 octane in both my Audis, but I do it more from a maintenance perspective.

Legit octane booster, vs crap octane booster, is a speech all on it’s own, but that aside, I’ve experimented with legit octane booster. I’ve ran on 98+ octane on a 1.8T, and on a GIAC tune (just “chipped”). My results using the butt dyno: there may be a power gain between 91 octane and 98+, or maybe it’s just a placebo, but it is not that significant.

I’m not 100% sure, but even between premium grade gasolines (91 vs 94 or 95), I imagine that using the lower octane could result in a fuel burn that is not as clean as would be the higher octanes, since the higher the octane rating, the more stable the fuel is for detonating exactly where you want it to (with regards to timing / piston travel).

Maybe someone with more technical info can chime in on this, but I believe that the higher your octane, the less carbon build up you’d see in the long run, since I think that there would be a better chance of more complete/cleaner burn using relatively higher octane. This is why I choose the highest octane I can find, for maintenance reasons. That being said, if the range inside the fuel door is in fact 91 to 95, then anything above 91 may not matter for complete/clean combustion, but I run 94 anyways.

#10

Also it bears mentioning, regarding the above, that the tune on my car is only for 91 or 93 (can’t remember at the moment), so the higher octanes don’t do anything for it, as far as performance.

On a side note, I’ve been told to be wary of buying premium gas in remote areas. Premium can sit for a lonnng time in these areas, unpurchased, and I’ve heard that as it sits for an extended period, it loses potency/octane rating.

#11

I’m talking Shell 95RON Nitro+, which is the mid-tier here, vs 100RON Nitro+ at the very top. I think the 95RON would be equivalent to 91 Premium RMS(?) in the US. In DC I could always find 93, but not in CA. I imagine Nitro+ is the same as V-power.

#12

These are premium fuel only cars. The compression ratio and hp levels require the best octane you can get at the pump. And that’s for even a 100% stock car.