Will decreasing fueling also decrease boost ? - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.

• Will decreasing fueling also decrease boost ? by Baron VonZeppelin on 07 Jul, 2010 21:47
• My first TD.
  Like starting all over from scratch after years of NA.
  
  Got this Truck running pretty good now.
  Was a smoking slug when i got it, mostly due to slight improper coordinates on belt timing (he didn't leave cam sprocket loose) and guesswork injection pump timing from PO's attempt at new timing belt. But thats what caused him to sell, so it worked in my favor overall.
  
  Its an 82-83 CR code 1.6 - with all proper exterior TD garments complete from an 85 TD Jetta. Has 12mm head with 19mm crank bolt.
  The engine was done by the prior owner that he bought it from.
  
  I have it fueled just a little bit agressive right now. But not a big black trail. Still going to scale it back about an 1/8th a turn tomorrow.
  
  What its doing - it feels like at about 75-80% of full wind up power - it sort of stalls for the blink of an eye - then flattens out.
  Its still pulling and winding when this happens - and feels like it should/would go farther. But it goes kinda flat.
  
  I thought maybe it was bouncing off the Inj Pump governor, or starving for more fuel  ..... so i turned the fuel screw in a couple/few times on test drives. No help.
  
  Bought a 20 psi Boost gauge yesterday and put it in today. The boost climbs fast at WOT and gets to about 11-12 and then it drops - in perfect coordination with the stall / go flat symptom.
  
  #1 - So is that the Blow Off Valve doing that - i guess ?
  
  #2 - Will decreasing the fuel more and more, eventually make it stop doing that - make it stop getting that much boost ?
  
  #3 - If decreasing the fuel won't lower the boost - what will ?
  
  I don't need to kill this thing anytime soon and not after full maximum go-go right now either. Just want safe reliable power that doesn't stop at 3/4 of the wind up.
  
  Not that i wind them all the time or much at all really, but with a big load in the back -  might need to be able to stay on the pedal a little longer sometimes in certain situations. I can let out or shift by the boost gauge now that i know when its going to happen - but would rather not have to do it by that proceedure.
  
  Thanks guys.
  I'll have a lot of questions like this as TD time goes onward.
  I have 2 more to go through after this one.
  
  
  
  
  
  
• #1 by Baron VonZeppelin on 08 Jul, 2010 08:43
• Thank you Libby, very much.
  
  

  Quote from: libbybapa on 07 Jul, 2010 23:25

  If you are saying that once boost reaches 11-12 it then drops back to 5-6 psi and then builds again, then it sounds like the BOV (just to make sure we're on the same page, it's the black thing on the pulley side of the intake manifold).  The BOV is an abomination.  
  

  
  Yep, thats what its doing.
  
  I'll start with trying to crank that screw down tight.
  If its already tight to that point - i'll look into doing a spacer.
  
  Another question - what can i do to decrease the boost pressure to where it only goes up to about 10'ish total ?
  
  Other than letting the BOV do it.
  That is a freaky feeling when it does that. Worse than an old go-cart/mini-bike with a governor.
  
  No oil squirters on this block - even pulled oilpan to double check if they might have been added when it was reman'd. nada
  
  Boost is pretty tuff stuff. This is a boost/vacuum combo gauge.
  I can inhale about 15 on gauge, but can only exhale about 3.
  
  Pulled the driver side dash vent and removed diffuser, then put pipe wrap around gauge and squeezed it into the vent bezel.
  Sort of a tempo install for now.
  Used a beer can cooler/foamy to block off blower box opening. lol
  hillbilly magic i tell ya what.
  
  
  
  
  
  
  
• #2 by Baron VonZeppelin on 08 Jul, 2010 20:43
• I appreciate the info Libby.
  
  Screwed the wastegate adjustment all the way down.
  Turned fuel screw down/less a bit more too.
  
  Went for 75 mile roundtrip.
  BOV is out of the picture now, no more of that symptom.
  And like you mention - its regulating itself to around 11 psi now.
  Its a K24 kkk.
  
  All is well. 
• #3 by Baron VonZeppelin on 09 Jul, 2010 10:33
• Edit !
  
  I screwed the BOV adjustment all the way down - not the wastegate adjustment. Have not touched wastegate.
  
  Confused the pieces in my previous post.
  oops
• #4 by Rabbit on Roids on 09 Jul, 2010 13:32
• the boost dropping in the higher rpms is the governors fuel cut.. or do you have the gov mod done? thats all i could think of. the gov starts cutting fuel, then the turbo slows down.
• #5 by Baron VonZeppelin on 09 Jul, 2010 21:23
• It was the BOV farting itself open.
  It was making the boost drop like a rock in one quick shot.
  
  After running the BOV adj screw to the bottom/as far down as it would go - it stopped doing the boost drop deal.
  
  Now it boosts quick and steady to 11, and will hold at 11.
  No performance mods done to anything yet.
  Except for the BOV adjustment.
  
  I want to get some bigger/better pipes before doing anything else. Still has small stock NA size pipe. And need to change the mk2 downpipe for an mk1 Dpipe when that gets done.
  Maybe in 3-4 weeks i'll get to that.
  
  This engine isn't going to stay in it.
  But it needs to pull some road duty and earn some of its keep for a while. So just gonna stay conservative on the tune and drive it like an old lady would mostly. lol