Some S4 throttle body adjustment questions
#1
Rotary Freak
Thread Starter
Some S4 throttle body adjustment questions
As I'm sitting here dismantling the spare upper intake manifold & throttle body, I came up with a few observations & questions. I have no reason to believe this throttle body has ever been tweaked or adjusted, so I suspect my observations will hold true to most S4 throttle bodies.
First, the vacuum actuator for the double throttle system seems to be leaking. I checked this because a friend of mine mentioned that he tested his & it was leaking. This represents a vacuum leak. It's small, and goes through a bunch of things to get to the engine, so it probably won't be terribly noticeable - but it's still worth checking, and could still cause some idle fluctuations.
Next, the secondary throttle plates don't appear to open fully. They get to 90% or so, but with the primary plate wide open, they are not fully open. I suspect this does represent a power loss at high throttle settings.
On to my questions.
At highway speeds (75-80mph) the secondary plates are slightly open. Would adjusting the linkages so they remain closed at this speed improve fuel economy at all by allowing a higher primary port velocity?
Alternately, how does one adjust the throttle body so the secondary plates open fully? It appears that they can be adjusted to open with the primary plates, but then one would lose some of the low throttle smoothness that the sequential opening provides.
Or is it just not worth worrying about?
-=Russ=-
First, the vacuum actuator for the double throttle system seems to be leaking. I checked this because a friend of mine mentioned that he tested his & it was leaking. This represents a vacuum leak. It's small, and goes through a bunch of things to get to the engine, so it probably won't be terribly noticeable - but it's still worth checking, and could still cause some idle fluctuations.
Next, the secondary throttle plates don't appear to open fully. They get to 90% or so, but with the primary plate wide open, they are not fully open. I suspect this does represent a power loss at high throttle settings.
On to my questions.
At highway speeds (75-80mph) the secondary plates are slightly open. Would adjusting the linkages so they remain closed at this speed improve fuel economy at all by allowing a higher primary port velocity?
Alternately, how does one adjust the throttle body so the secondary plates open fully? It appears that they can be adjusted to open with the primary plates, but then one would lose some of the low throttle smoothness that the sequential opening provides.
Or is it just not worth worrying about?
-=Russ=-
#2
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Originally Posted by Syonyk
First, the vacuum actuator for the double throttle system seems to be leaking. I checked this because a friend of mine mentioned that he tested his & it was leaking. This represents a vacuum leak.
Next, the secondary throttle plates don't appear to open fully. They get to 90% or so, but with the primary plate wide open, they are not fully open. I suspect this does represent a power loss at high throttle settings.
At highway speeds (75-80mph) the secondary plates are slightly open. Would adjusting the linkages so they remain closed at this speed improve fuel economy at all by allowing a higher primary port velocity?
Alternately, how does one adjust the throttle body so the secondary plates open fully? It appears that they can be adjusted to open with the primary plates, but then one would lose some of the low throttle smoothness that the sequential opening provides.
Or is it just not worth worrying about?
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