To clean, or not to clean, that is the question...

[2manytoys]

Get your hands on Vagcom and log timing and correction during a 2nd or 3rd gear run. If your intake temps are low 20C's your timing should be ~30 Degrees (with maybe only a few degrees of correction at the very high rpms).

Get a 90 Degree Bore scope and have a look at the top of the valves, or if you pull just the flexible intake hose/throttle body you can get a bore scope into two of the valves/intake runners. See here: http://www.youtube.com/watch?v=wAiViR8x0Qo

Other than that I'd put the car on the Dyno and check the shape of the power and torque curve.

I'd do all of these things before I removed the manifold. Most Audi dealers will remove/pull the bumper and it's a real pain to get it to line up again. I wouldn't risk that unless you are sure you have a problem.

[ArthurPE]

yours was the worse I've seen...having said that I'm guessing something else was at play
despite this, relative performance, before and after, seemed ~ the same

chassis dynos imho are not useful, except for back to back comparisons, and ebven then accuracy and repeatability are variable....

to the gent re: borescope, I imagine you can see it snaked in thru the throttle body
but if your car is running well, don't sweat it

In true engineering form Arthur you have some very interesting and creative methods to do this which I’d like to see the results of but, and it’s a big but, having seen the extent of the build-up on my motor I couldn’t see any alternative to taking the engine out and having the heads off.

Mine dyno’d at 355bhp 2 years ago pre-clean. I had her dyno’d a couple of weeks ago post-clean (and an extra 20k miles) at 405bhp although on the road it would appear to be the same performance as P_G’s car. Make your own mind up!

On a slightly different subject I’d be very interested to know if any of you manage to get any of this work done under warranty……..I didn’t! Audi claim it’s a cleaning issue and they don’t pay for cleaning, end of.

Good luck with your decision Arthur, keep us informed on what you decide.

[pad125]

You may well be right Arthur, there may have been something else contributing to the problem that exasperated the condition. I’d love to know what it was, I’d even give up a few weeks of sex to find out……..ok so maybe I wouldn’t go that far but your synopsis remains valid.

I spent a lot time considering dyno output in my youth, 2-stoke racing is a very fickle animal and you tend to rely on all the help you can get. 4-stroke engineering is a lot more stable and the results should be more consistent but again, the set-up of said measuring equipment can vary from house to house.

I’m not convinced that 30 or even 50bhp is noticeable on the public roads using the ‘arse’ dyno and for that reason my opinion remains open. My humble opinion would be that if you’re concerned about the output of your motor then carry out the following

3rd gear 3k~8k time (as per your findings)
Dyno test your car and try and compare it against other RS4’s that have been on the same dyno
Get an independent emissions test done that shows the results in figures not just ‘pass’ or fail’

If all this points towards a negative result then have a physical check done on the manifold/valves. This should leave you with enough information to determine if corrective surgery is necessary. This is all a result of my own personal experiences, hope it helps others

[PetrolDave]

I’m not convinced that 30 or even 50bhp is noticeable on the public roads using the ‘arse’ dyno

How much do you think the power output is reduced by running on 95 instead of 98 octane? 30-50bhp? Less? More?

I think anyone on here who has had to run 95 octane (due to non-availability of 98 octane) will tell you that the reduced power output is immediately obvious with the 'arse dyno'.

[pad125]

I’m not convinced that 30 or even 50bhp is noticeable on the public roads using the ‘arse’ dyno

How much do you think the power output is reduced by running on 95 instead of 98 octane? 30-50bhp? Less? More?

I think anyone on here who has had to run 95 octane (due to non-availability of 98 octane) will tell you that the reduced power output is immediately obvious with the 'arse dyno'.

I’ve been in that situation but I can’t say I’ve noticed that much of a difference but then I’ve never been that sensitive to power changes, when I raced bikes I just rode them harder if they under performed……..could never understand why I crashed a lot

[PetrolDave]

I’ve been in that situation but I can’t say I’ve noticed that much of a difference

There's a motorway exit near me where accelerating from rest doing a left turn at the top of the slip road with 95 octane you can full throttle accelerate and get round the corner easy enough, but with 98 octane you just have to back off the throttle. That's an obvious power difference IMHO.

[pad125]

I’ve been in that situation but I can’t say I’ve noticed that much of a difference

There's a motorway exit near me where accelerating from rest doing a left turn at the top of the slip road with 95 octane you can full throttle accelerate and get round the corner easy enough, but with 98 octane you just have to back off the throttle. That's an obvious power difference IMHO.

How long did you have to run the 95 before you had that kind of power difference Dave? I’m guessing the electronics adjust the timing etc for the fuel but is it instantaneous?

[PetrolDave]

How long did you have to run the 95 before you had that kind of power difference Dave? I’m guessing the electronics adjust the timing etc for the fuel but is it instantaneous?

It adjusts the timing as soon as the lower octane fuel gets through to the injectors - as that's when the knock sensors will sense the difference.

I guess how long it takes depends on how much 98 you had left in the tank? If you had only a few litres left and added 60+ litres of 95 then I reckon it could be pretty much instantaneous?

[sonny]

Total agree, I was forced to run on 97 Esso, and noticed the difference against V-power. I am remapped on V-power, minor difference. On the track it was frustrating, wish I had push further afield to get V-Power.

[pad125]

Total agree, I was forced to run on 97 Esso, and noticed the difference against V-power. I am remapped on V-power, minor difference. On the track it was frustrating, wish I had push further afield to get V-Power.

Maybe mine didn't respond to the 'good stuff' when it was coked up (quite bad if you remember the pictures). I was without the car for so long (3 months) it was like getting a new car all over again. I've never driven it on anything else but V-Power since I've had her back which it 9k miles now so I don't really have anything else to compare it with. Interesting point though guys

[Stoffle32]

Would there be any risks using the steam method to clean the engine?
What is the full process?
Engine at full temp etc...

Would been keen to try it and see if there are any differences, maybe before and after dyno?