icsamerica

<center><img src="http://www.icsamerica.com/s8/MVC-013F.JPG"></center><p>What is this large thing in the S8 air box? The bottom of the air filter comes very close to this thing so I suspect it's an air restriction? Any opinions?

Andy P.

I'm assuming it's not the mass air flowmeter, as that would normally be further down stream. I'm not familiar with the engine layout (still trying to find an S8!), but does it look like a motor and air pump? If so, it will be the electric air pump which forms part of the secondary air injection system (SAI). This pumps air into the exhaust system upon cold start-up for the first minute or so. This causes a reaction in the catalyst brick to reduce catalyst warm-up time (known as light-off) and therefore reduce cold-start emissions. This is due to a catalyst not functioning effectively until it reaches about 600degC.

Hope this helps.

Andy P.

M5 ETR

Looks like the mass air sensor to me... This is about where it was on my Q45 (not further "downstream".....)

happycow

On A8 the mass air sensor is in the top of the air box and it looks like this, but not sure on the S8. Don't have that parts CD-ROM.

UberVier

exhaust gas recirc system, in order to reduce emissions during startup. Just a guess...