PaulW

When Bob would rev his engine in neutral and then let it return to idle, it would make a noise like a relay chattering or a racheting device clicking a few times. This was listening to the front of the engine with the hood open.

I believe it's probably the variable length intake runner on the intake manifold changing position when the engine is reved, the after the throttle is lifted, it spring returns and bounces on its stop.

The vacuum thing on the right side of this picture actuates it....above some certain RPM it moves it, I'm sure it's spring loaded when it releases....

<img src="http://www.audipages.com/Tech_Articles/enginemechanical/tbp12.JPG">

Here's some pictures of the 32 valve intake manifold and variable length runners....it rotates at high RPM to make the runner short and straight and at low RPM's it's long to use a ram effect to increase power.

These are courtesy of Jeff B who is redoing his motor right now.

<img src="http://www.audipages.com/Tech_Articles/enginemechanical/manifold1.jpg">

<img src="http://www.audipages.com/Tech_Articles/enginemechanical/manifold2.jpg">

<img src="http://www.audipages.com/Tech_Articles/enginemechanical/manifold3.jpg">

<img src="http://www.audipages.com/Tech_Articles/enginemechanical/manifold4.jpg">

<img src="http://www.audipages.com/Tech_Articles/enginemechanical/manifold5.jpg">

<img src="http://www.audipages.com/Tech_Articles/enginemechanical/manifold6.jpg">

<img src="http://www.audipages.com/Tech_Articles/enginemechanical/manifold7.jpg">

<img src="http://www.audipages.com/Tech_Articles/enginemechanical/manifold8.jpg">

<img src="http://www.audipages.com/Tech_Articles/enginemechanical/manifold9.jpg">

A8CT

thanks,..I'll check this weekend. I think I'm the only A8 w/this problem.. anyone else ?

KaMaKaZieP -ALUMIN8-

on the throttle body.. would we benefit from any of this, i already see thet the primary and secondary are pretty much as big as can be, but i dont have a good shot of the insides..

borden

Paul, what happens if the vacuum actuator (vacuum thing) on the righ of the pic is liacking?

Any sideeffects in performance/damage to engine?

Mine might be leaking. and is 140$ at the dealer!

PS that part is also used by VW in Passats. (so the dealer told me)

Thanks

Dennis

PaulW

He ran his car on a dyno for other reasons, it ended up producing something like 280 or 270 HP....then he figured out (actually the tech did) that it wasn't working....fixed it and got his power back as I recall.

pw

borden

Thanks