Power flap test - next step advice

[mark758]

Hi could somebody advise me if I can fix this myself or whether it has to go back to the dealer please?
Not experiencing a real kick at 5500 I have removed the inlet snorkel and lubricated the pivot points inside the airbox and also the visible hinge outside the airbox as per folks kind posts here.

After driving the car up to temperature then going to 6000 rpm stationary I cannot see the flap move at all. I can push the flap open reasonably easily with what just feels like resistance against a spring?

Two questions really,
1. Have I tested functionality properly such that the flap would have moved if all was well?
2. Does smooth movement of the flap mean I have a vacuum issue - I cannot see any lose pipes coming off the metal vacuum unit - I am not sure what I should do next to resolve the issue.

Any advice appreciated, thanks.

[Gumball0r]

Have you read the sticky?
http://rs246.com/index.php?name=PNphpBB ... ic&t=77235

[mark758]

Thanks, yes I did but I don't have access to Vagcom.

[PetrolDave]

Thanks, yes I did but I don't have access to VAGCOM.

Then you need to get access to VAG-COM - almost all diagnostics on modern cars need a PC based tool.

I bought VAG-COM about 6 years ago and in saved garage bills it has paid for itself many times over on just my car, add to that the savings on my wife's car (also a VAG car) and the savings I've helped other people make (all I ask is some beer for my time) and IMHO owning VAG-COM is a no-brainer.

[mark758]

Dave, is this something that should be covered under warranty if I take it in to the audi centre prior to getting VAGCOM?
Just seemed we are all self fixing the issue - and wondered if thats because we get no joy at dealers?

[sonny]

Thanks, yes I did but I don't have access to VAGCOM.

Then you need to get access to VAG-COM - almost all diagnostics on modern cars need a PC based tool.

I bought VAG-COM about 6 years ago and in saved garage bills it has paid for itself many times over on just my car, add to that the savings on my wife's car (also a VAG car) and the savings I've helped other people make (all I ask is some beer for my time) and IMHO owning VAG-COM is a no-brainer.

Whats the cost of VAG-COM, can it be downloaded to any laptop?

[Dom81]

Best place is Ross-Tech

They write the software and can send you a genuine lead. They're US based but mine arrived in a couple of days. Last time I looked it was about $350, which even with postage was cheaper than anywhere in the UK

[silverRS4]

OP,
Its possible the air box flap logic is not active when the car is not in gear. The ECM's are certainly aware that, despite the high RPMs, the engine is not under a load and there is no reason to open the flap. I've never accelerated (and held) the engine at 5000+ rpm with the car at a standstill to find out. I'm not going to just for your sake either! Another way to check the integrity of the vacuum system without Vagcom (and the car at idle) is to simply push the "S" button on and off SEVERAL TIMES while someone is verifying that the muffler flaps open and close on command EVERY TIME. This can only be done , of course, if you have a stock exhaust or one that utilizes vacuum-operated valves. If the exhaust flaps open on command, there should be sufficient vacuum to open a free-moving air box flap. The function test with Vagcom is far more definitive, however.

[ArthurPE]

I think the car has to be at a given road and engine speed...the tech manual is not clear on this

[mark758]

Many thanks folks for your replies.

The car driven and properly warmed up before I did this and revs not held longer than necessary but I shan't be repeating it!

I do have a stock exhaust and can confirm the exhaust valves open and close on command every time on depressing the Sport button.

After lubricating the flap's physical components the resistance to open doesn't seem very great and does seem smooth so I think that side is possibly okay.

I'm assuming the 'kick' at 5500 really is a kick - I can certainly feel an increase in acceleration past that but its very smooth as opposed to a jolt which is perhaps what other owners are experiencing?

[silverRS4]

Good to hear. Functioning exhaust valves are definitely a good sign. The torque increase (the "kick") in a healthy RS4 is an approximately 40-45 Nm increase in torque between 5000-5800 rpm in 3rd gear. In 4th gear, the increase is less, about a 25 Nm increase over the same engine speed. This, in addition to the reduced gearing multiplication, the 4th gear "kick" is much less noticeable. It is a noticeable and addictive increase nonetheless. The air box power flap is not responsible for the "kick", it is simply opening at 5000 rpm to ensure enough air flow for the complex event that's actually creating the torque increase.

In the event a vacuum problem keeps the air box flap from opening (not a linkage or binding problem), the same vacuum problem is probably leaving the tumble flaps in their "closed" position. This will indeed cause a power loss above 3500 rpm and a lack of a "kick" since the flaps are severely restricting flow into the cylinders. A CEL and EPC should light up in this case since the tumble flap position is monitored by the ECM's. The air-box flap position had no sensor.

[mark758]

Right- thanks Silver, I think perhaps some 3rd gear investigation is required....I have been trying it in 5th
Certainly no warning lights present and dyno power plots have been consistently climbing to the redline which hopefully is a positive also.

The car has to go back to the dealer next week anyway for some trim work....is the function of both types of flap something they could simply check via VAGCOM?

[silverRS4]

An Audi tool or Vagcom tool test of the flaps would involve a function test of the:

Intake Air Switch Over valve (N335) - air box flap
Intake manifold runner control valve (N316) - tumble flaps in the intake manifold

Probably (and sadly) not normal procedure for RS4 diagnostics, but any good Audi dealership should be able to do the test and watch with their eyeballs that the flaps actually move. In other words, the test just actuates the vacuum solenoids responsible for the movement. It doesn't indicate pass/fail of the flaps - they have to be observed during the test to ensure that a) the signal from the ECM's is reaching the solenoid and b) the flap mechanisms are also operating to their full range of motion as designed.

good luck

[tartan_rob]

Take the valves out.

[caldy]

Take the valves out.

Which ones?