DIY Carbon Cleaning, now we've started!!!

[madgreek]

Nice writeup. Your buildup was similar to mine at 39k. To slow down the buildup I'm spraying 3m cleaner directly into the intake every 3k miles, then changing the oil. Going forward I'm having the engine manually cleaned every 20k miles. Pics of my carbon mess can be found below:

http://www.allthingsaudi.com/All_Things ... ld_Up.html

[adsgreen]

I was thinking... The rs4 uses internal exhaust gas recirculation where the exhaust valve is held open during the intake stroke so some exhaust gas can be recaptured by the falling piston. Now in theory there should be more vacuum caused by the piston than in the intake manifold so no exhaust gases should escape but then what happens if the throttle butterfly goes from open to closes whilst this is happening?

I wonder if the increase in manifold vacuum will pull the exhaust gas through the intake valves and voila - unavoidable carbon build up.
Explains why a catch can would never work and even supercharged cars don't operate with a pressurised manifold all the time.

Would be interesting to put a glazed viewing panel in an intake manifold or video camera and add some smoked marker and see what happens on a dyno.

If this were the case the only thing that'd fix it would be to perhaps reduce the maximum level of vacuum the manifold reaches or even swap out the exhaust cams for ones that don't have any internal EGR featured.

[DazN]

Going on the dyno this Friday so let's see what happens!!!

[edge]

Going on the dyno this Friday so let's see what happens!!!

Best of luck

[Shoppinit]

I was thinking... The rs4 uses internal exhaust gas recirculation

AFAIK the RS4 doesn't use EGR. Did you mean PCV?

Something has been bugging me for a while about the carbon buildup issue... why can't the PCV be deleted so that only air is getting into the manifold? Or am I being a dumbass?

[adsgreen]

All cars have some form of EGR or they wouldn't pass emissions test for NOx.
The RS4 uses valve overlap to suck back in some exhaust gas from the previous combustion stroke to provide the required EGR (hence the "internal egr" designation). Other systems are generally a pipe from the exhaust manifold through to a electronically controlled valve and then another pipe to the intake manifold which is "external egr".

Not a dumbass question - I believe one of the first attempts to beat the carbon was to install a catch can to catch any oil missed by the PCV. I've read a case where somebody used some thin gauze (actually I think it was wife's stockings) to see what was being missed and the answer was "not much". Even the catch cans generally didn't catch too much - certainly not enough to cause the build up we see. Hell, some people have even tried venting the crankcase to the atmosphere (illegal in some countries) and this made no difference either.

[Shoppinit]

Gotcha Difficult to imagine the exhaust gas being able to get up so far back up into the inlet manifold, though. I think I would be tempted to try venting the crankcase to atmosphere after cleaning the manifold to see how accurate the reports that this makes no difference are. Let's be honest, if you've bought an RS4 then you're no friend of the environment

My musings lead me to wonder what would happen if you installed a supplementary injector in the inlet manifold that would inject very small amounts of petrol - turning the engine into something between an FSI and a single point injection. If the amount is small enough then the O2 sensors, in closed loop mode, should be able to compensate for the richer mixture within allowable limits and the petrol vapour would "wash" the carbon away before it builds up. In open loop mode, dunno... turn off the supplementary injector.

[DazN]

Well I had my dyno run today at Awesome GTi in Irlam and I can't quite believe the results.

Previous reading was 347bhp, after carbon cleaning the car I knew it felt better and expected around 380...

Result - 407.2 (max clutch power)

I do think the Dyno Demon test wasn't quite what it should have been, it was a very short run and I just wasn't convinced.

But the results are there and 407.2 is fine with me!!

[PJC]

Can't complain at that, well worth the effort.

[Steve_C]

Good result. When you got the 347bhp reading did you have any other problems, e.g. vacuum leak?

[edge]

thats super numbers mate, fair play!

[DazN]

Original was 328, then vacuum leek sorted, full service inc plugs and it only just hit 348.

So to get 60 from cleaning the carbon is well worth it!!

Notice the power blip - 678.13 - that must be the highest reading of any B7 RS4!!

[Steve_C]

Were both dyno runs on the same rolling road?

[S4Player]

Daz do you know what drivetrain setup your dyno tester used Ie centre diff then into shoot 44? I can't get my car to make over 450bhp on DD rollers but I make 565@Mrc I've tried 8 runs and can't get it right Ps superb results

[DazN]

Were both dyno runs on the same rolling road?

No, which is why I think dyno demons wasn't quite right in the first place.

Happy with result tho.

Met Andy Shaw too, nice motor and I need a milltek !!!!