Hi all,

With reference to the following image:



Why is it if I temporarily pull off the hose going to the wastegate (top left) the idle increases by about 800 rpm (as expected), but when I temporarily open hose "W" (that goes to the EGR solenoid) the idle isn't affected at all?

Note that I am on speed density so the unmetered air is not an issue. Also my EGR valve is deleted too, so normally my hose "W" off the TB is capped off.

I am just trying to understand the air routing. As far as I can tell both the above hoses are post-butterfly, so why would one raise the idle, but the other not? Unless hose "W" is blocked off at idle for some reason? The "W" pipe is much smaller than the wastegate pipe, but I would still expect SOME change, however slight.

Thanks!

S.

 

When you pull off the "wastegate" hose (which is actually your Dump Vale or Blow-Off Valve), did you plug the air leak with your finger? Or did you let the air leak into your intake manifold plenum? If you plugged the nipple, idle shouldn't have increased.

 

Sorry I meant vacuum line to the BOV, not waste gate.

And yes, I let air in via that line which raises idle as expected (if I block the line with my finger idle returns to normal, again as expected). My question is why doesn't idle increase when air is let in via the post-butterfly nipple on the TB?

Thanks!

S.
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Theoretically, it should also raise idle unless it is clogged on inside.