Author Topic: Idle Fuel/Air Adjustment  (Read 1082 times)

Harry

  • Full Member
  • Gold
  • *****
  • USA, TN, Knoxville
  • Posts: 744
Idle Fuel/Air Adjustment
« on: December 15, 2023, 19:43:42 »
Hello everyone.  I had recently watched a video described on the Forum on how to do this (Problem Solver Garage), and he uses a process similar to what the Tech Manual describes except he uses a target idle RPM during his iterative process with the Idle Air Valve and the wheel at the rear of the FIP.  This is very similar to what our Tech Manual prescribes except our iterative process involves maximizing vacuum level and this same adjustment on the back of the FIP.
I would just like to understand the vacuum approach a little better.  I would expect that the IAV ranges from a full open position to a full closed position.  So I'm puzzled at how the max vacuum level can be attained at a point in the IAV adjustment between more open and less open?  Seems like vacuum would always increase as the IAV is closed.  That is, how can vacuum increase as we close the IAV, then begin to increase again as we continue to close the IAV?  Would the maximum vacuum level not be when the IAV is fully closed?
Thanks,
Harry
Harry Bailey
Knoxville, TN
1966 230SL
Automatic

rwmastel

  • Full Member
  • Platinum
  • ******
  • USA, OH, Canal Winchester
  • Posts: 4634
  • Pagoda SL Group: 20+ years and going strong!
Re: Idle Fuel/Air Adjustment
« Reply #1 on: December 15, 2023, 20:01:54 »
"So I'm puzzled at how the max vacuum level can be attained at a point in the IAV adjustment between more open and less open?"

Said another way, "somewhere in the midrange, between fully open and fully closed ".

Good question, Harry.  It helps us if we can understand the science behind why these tuning adjustments affect the engine the way they do.
Rodd

Did you search the forum before asking?
2017 C43 AMG
2006 Wrangler Rubicon
1966 230SL auto "Italian"

Harry

  • Full Member
  • Gold
  • *****
  • USA, TN, Knoxville
  • Posts: 744
Re: Idle Fuel/Air Adjustment
« Reply #2 on: December 17, 2023, 21:52:07 »
Just refreshing my request for some information on the Idle Fuel/Air adjustment procedure?
Harry Bailey
Knoxville, TN
1966 230SL
Automatic