Exhaust valve mod with reflash
10-08-2008, 04:35 AM
#11
Was just trying to answer his question. Here is the dyno and the link to the OP
<center><img src="http://farm3.static.flickr.com/2188/1819418740_f98dcee128.jpg?v=0"></center><p><ul><li><a href="https://forums.audiworld.com/rs4b7/msgs/69141.phtml">https://forums.audiworld.com/rs4b7/msgs/69141.phtml</a</li></ul>
10-08-2008, 07:16 AM
#15
Minimal gains, but yes. Bob W. showed more airflow with MAF sensor logging and the dyno above showed
an increase as well. But I doubt you would feel much in your seat. It's too minimal.
The biggest reason to remove the air intake flap is to prevent it from sticking shut or not opening in the first place and causing a lost of power above 5500 rpm.
Another reason is that part of the reason Audi put it there was to reduce noise emissions so if you have the stock exhaust you will notice a louder growl from the engine. This combined with removing the vacuum lines to the exhaust flaps has been enough of a sound increase for some members to no longer want an aftermarket exhaust.
The biggest reason to remove the air intake flap is to prevent it from sticking shut or not opening in the first place and causing a lost of power above 5500 rpm.
Another reason is that part of the reason Audi put it there was to reduce noise emissions so if you have the stock exhaust you will notice a louder growl from the engine. This combined with removing the vacuum lines to the exhaust flaps has been enough of a sound increase for some members to no longer want an aftermarket exhaust.
10-08-2008, 07:23 AM
#16
It may be. Here is a nice diagram that will let you see where it is in front of the air filter.
No worries about sand or dirt bypassing the air filter:
<IMG SRC="http://www.jlosee.com/images/rs4/pdf/RS4_42FSI_intake_diagram.jpg">
With the flap removed, not only is the 3.5" hole always open, but the cross section of the flap itself is removed. We know this part of the intake is supposed to be opened at 5500rpm+ so removing the flap means the engine is performing as normal from 5500-8300rpm. You aren't gaining anything except the cross section of the flap(minimal) and the knowledge that it is always open when it is supposed to be.
At rpms below 5500 you may be getting some additional airflow with the flap removed, but you are also getting hot air from the air dam below the passenger side heat light that is drawn across one the additional coolant radiator. What this means for normal street driving is unknown. It could be slight faster(more air), the same(more air, but it's hotter so it balances out), or slower(hot air).
Hope this helps.
<IMG SRC="http://www.jlosee.com/images/rs4/pdf/RS4_42FSI_intake_diagram.jpg">
With the flap removed, not only is the 3.5" hole always open, but the cross section of the flap itself is removed. We know this part of the intake is supposed to be opened at 5500rpm+ so removing the flap means the engine is performing as normal from 5500-8300rpm. You aren't gaining anything except the cross section of the flap(minimal) and the knowledge that it is always open when it is supposed to be.
At rpms below 5500 you may be getting some additional airflow with the flap removed, but you are also getting hot air from the air dam below the passenger side heat light that is drawn across one the additional coolant radiator. What this means for normal street driving is unknown. It could be slight faster(more air), the same(more air, but it's hotter so it balances out), or slower(hot air).
Hope this helps.
10-08-2008, 07:56 AM
#18
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Not necessarily
the biggest concern would be allowing hot air(from heat sources nearby) into intake at idle and less than cruising speeds. The flap's design prevents this by only opening at 5000 rpm and a certain road speed.
Also, I think the idea that the flap malfunctions and doesn't open is very questionable. It's vacuum operated, so not much to go wrong there. When vacum builds to a ceratin point the flap opens.
There may be an overriding function of the ECU in determining actuation of the flap in addition to vacuum. That needs to be expored further. So far, no one has a definitive answer and no proof that airbox flaps are malfunctioning in their intended purpose.
Finally, I think there may well be some adverse results from deflapping that people may not be aware of...with hot air flowing into intake being one of them.
Also, I think the idea that the flap malfunctions and doesn't open is very questionable. It's vacuum operated, so not much to go wrong there. When vacum builds to a ceratin point the flap opens.
There may be an overriding function of the ECU in determining actuation of the flap in addition to vacuum. That needs to be expored further. So far, no one has a definitive answer and no proof that airbox flaps are malfunctioning in their intended purpose.
Finally, I think there may well be some adverse results from deflapping that people may not be aware of...with hot air flowing into intake being one of them.
10-08-2008, 08:04 AM
#20
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Sure there's more airflow, but story doesn't end there
is it cool air? Not likely based on where it's located.
I find it amusing that because RI RS4 mentioned a perceived flap opening issue several months ago, that a whole bunch of RS4 owners jumped on the deflap bandwagon, anxious to dig in and rip out the evil flap.
Know what you're doing. It's there for a purpose. Buried at the bottom of the engine bay right next to exhaust manifold and behind radiator and oil coolers, I wouldn't want it left open, period. The right air is coming from outside the engine compartment. The wrong air is coming in through a permanently open or removed flap in the airbox.
I find it amusing that because RI RS4 mentioned a perceived flap opening issue several months ago, that a whole bunch of RS4 owners jumped on the deflap bandwagon, anxious to dig in and rip out the evil flap.
Know what you're doing. It's there for a purpose. Buried at the bottom of the engine bay right next to exhaust manifold and behind radiator and oil coolers, I wouldn't want it left open, period. The right air is coming from outside the engine compartment. The wrong air is coming in through a permanently open or removed flap in the airbox.