RI A6

It's pretty much 15 to 20 lb-ft of torque that is losst above 4500 rpm when that flap doesn't open. The entire torque curve from that point on is elevated when the flap is open, and depressed otherwise.

15 to 20 lb-ft = 22 to 30 HP @ 7800 rpm

daveak05

where are you getting that torque loss number? don't tell me from a couple dyno runs. how do you know that any torque losses above 4500 rpm are not caused by something else.

the flap is there for a reason, which was listed here awhile back(Audi literature). it also mentioned car speed, which thows a monkey wrench into any solely rpm theories. i would want it working properly, just like you. hell yes!

i don't however agree with how you are arriving at your torque loss cause and effect, or the number you have put out there(25 lb ft).

also, i'm wondering how it can reach its peak torque w/o flap opening, and then have losses from there "all the way up", as you say.

see, this is what happens here: you have these "diagnosis" by people here, not based on facts, and then others are scurrying around trying to figure out what to do with their flap and reported power loss. more unverifiable posts, and then "how do i remove it" becomes epidemic.

can you see the reasoning here?

daveak05

that would actually make some sense...for emissions.

the Audi literature, IIRC, mentioned a combination of RPM and car speed(??) actuating it.

i'm wondering how the speed factor figures in. are they making the assumption of dramatically more airflow available at speed, with the flap then able to open and provide the addtl air into intake?

daveak05

if opening it is noisy, and they keep it closed majority of time to reduce noise, then why have it there at all? if it wasn't there, it wouldn't need to be mitigated for noise purposes.

other mfgrs reduce intake noise thru resonator chambers in the air intake(usually offset). seems like an awful lot of trouble for Audi to go thru if only purpose is noise reduction.

RI A6

The engine does not reach it's torque peak without the flap opening. The engine starves without enough airflow. And yes, I did determine this through a few dyno runs on multiple days. Up until the intake manifold geometry is changed when the ram flap actuates, my dyno runs on multiple days look correct and makes sense, even in the before and after Milltek exhaust runs. But above 4500 rpm, there is clearly power starvation going on. The only explanation for this is that the intake airbox valve is not opening. There is just nothing else that can make this drastic a change in torque.

Now, if you can come up with another explanation of my dyno runs, and why about 75% of all RS4 dyno runs show a suppression of torque above 4500 rpm, I'm all ears and would like to hear it. Please feel free to refer to any Bentley documents that you can find. Several of us have scoured all we can find. The point is, the factory torque curve shows maximum torque at 5500 rpm. Several independent dyno runs show a torque peak at around 5500 rpm. Most dyno runs do not show a torque peak at 5500 rpm, and do not show the torque boost. Please Dave, tell us why this is. I've hypothesized that it is a failure of the N335 Intake Air Switch-over valve to open. What's your theory?

I would like to know the reasoning behind the ECU programming. The reason I've not pulled the flap myself is that I'd like to install a switch to bypass the ECU and control the flap myself. Then I can make accurate measurement of MAF and dyno the chassis to show the open and closed flap effect. Why the flap is not opened by the ECU sometimes is up for debate. The official literature is not totally correct. I've still got people at Audi US trying to find the answer. So far, no one knows. Probably the only people who know are the designers, and so far I've found no one that has access to them.

Instead of being the spoiler, Dave, why not provide some helpful information? So far, all the information that I have I've reported. If you disagree, please feel free to provide some alternative interpretations. We can walk through the one by one.

daveak05

Scott, resist the temptation to lecture me about engines, please.

my response was based on your comments, where you said that peak torque is reached, and then losses occur, which i have to assume you meaning based on the flap not doing it's job(opening) when it should, as that is what you have been talking about.

i am not confused by this idea, but only by your conclusions.

you have to know that there is almost universally a torque and HP drop off after max. that's the nature of engines running out of rpm or starved of air...or fuel, or both.

if you are basing the flap not opening having adverse effects on power, as you have done here countless times, AND attempting to prove the direct correlation thru dyno results, well, where ya going with that?

by the looks of this thread, many aren't even clear on its actual purpose. is it performance(at top end)? is it emissions? is it noise reduction?

since this seems to be your baby more or less, then lets try not to form any premature conclusions on its exact purpose and where it's going wrong...if at all.

you want some useful information? okay, forget the purely rpm and vacuum action on the flap, and look at the electrical also present. that's where the ECU may be controlling or overridng the normal flap operation, whatever that is. then, you might want to determine what paramaters the ECU has designed into it in order to exert that influence over the flap activity, aside from high rpm and resultant high vacuum.

seems to me that it is meant to be actuated by vacuum, but can be overidden by the ECU via an electrical switch.

finally, since you are unable to determine what is causing it not to open, then why are you trying to qualify torque losses down to a specific value, based on road tests and independant dyno info. in other words, looking at those, w/o the torques losses you seem to be experiencing, how can you just automatically make the leap that the flap is responsible. again, based on info that you have cherry picked and are wrongly using as your basis for evaluation?

in the meantime, people are yanking their flaps for any number of reasons, which YOU have put forth here...power, Euro sound regulations, etc.

RI A6

here's everything we know about the "power flap"

To ensure a sufficient supply of air to the engine at high RPM, the power flap in the air filter is opened at engine speeds higher than 5000 RPM and at road speeds higherthan 200 kph.

The power flap is opened and closed by a vacuum actuator which is map-controlled by the ECM via the
Intake Air Switch-Over Valve N335.


Here's the vag measure group:

097,0,Intake Air Change-Over
097,1,Engine Speed,(G28)
097,2,Engine Load
097,3,Coolant,Temperature (G69),Range: -40.5...+135.0 °C\nSpecification (Warm): 80.0...115.0 °C
097,4,Status,Intake Air Flap,Display Range: ON/OFF


We also know that it does not always open at 5000 rpm. We don't know why.

RI A6

When they want to lean the mixture, the ECU controls the fuel injection pressure and injection time.

daveak05

which is essential to the air/fuel mix for any engine to run properly. doesn't matter how much the injectors are squirting at any given time. without the right airflow, big problem.

let me give you an example: some of the newer PZEV cars use air injection to lean out mixture at cold startup and initial operation in order to reduce emissions.

the fuel mix is leaned out dramatically, but compensated for by a more complete burning(atomization) of the fuel. these cars all have typical MAF's and injectors. the difference being more air introduced by an auxiliary source.

daveak05

and have you figured the car's speed being a part of when the flap opens yet? i have an idea, if you haven't already thought of it.