boost pin adjust screw - page 1 - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.

• boost pin adjust screw by boxer246 on 11 Mar, 2008 20:35
• I guess this is more commonly referred to as the "smoke screw" right?  
  I know this has been covered before, but my searches have turned up not much, so here goes.
  
  Basically, if you turn the screw in, you are sort of adjusting the "starting point" or baseline of the boost pin?  So, by doing so, you are allowing additional fueling to be delivered earlier in the RPM range?  
  
  Ok, so if you adjust the starwheel so that the spring seat is lower, then there is less preload on the spring, therfore it takes less boost to move the boost pin, therefore making fuel come on quicker with less boost?  So, if you adjust the smoke screw in, or downward, and move the spring seat lower, then in effect you will get more fuel starting sooner, and it will continue to build with less boost pressure than before?  
  
  Now, someone had a good write-up about the relationship between the max fuel screw and the boost pin movement, but I could not find it.  If anyone comes across it please post it again.  Otherwise, I'm not too sure how these two adjustments will affect one another, except to mess with them using trial and error.  
  
  Now that I have the motor running decent (1.6TD) it has somewhat underwhelming midrange performance.  I realize some of this is characteristic of the 1.6TD what with the big T3 turbo....slow spool etc.  But honestly I expected it to be significantly better than my NA in the midrange, but its not too much, if at all.  To get things going, I have to really tromp the throttle and when the turbo spools, it makes power, but its on the high end....with my foot almost to the floor.  
  
  I cant be too hard on the motor just yet anyway because its fresh, and being broken in, and I have no EGT or boost pressure gauge yet.  
  
  The motor itself is stock, with the IP governor and advance mod done, head port castings cleaned up, intake manifold castings cleaned up, gasket matched, rebuilt turbo, stock injectors.  Exhaust is 2.5 inch turbo back with  hi-flow muffler.
  
  Maybe a set of better injector nozzles, such as GTD's would provide for larger power potential in the midrange.  I've never heard much about them.  
  
  An intercooler is next on my list of things to do.
• #1 by jimfoo on 11 Mar, 2008 20:45
• Don't forget you can remove the cover and rotate the boost pin to change the steepness of the cut, allowing more or less fuel in relation to boost. The smoke screw and starwheel just change how fast the fueling changes, but rotating the pin changes how much.
• #2 by boxer246 on 13 Mar, 2008 10:16
• Jim thanks for the input.  I am going to mess with the pin...rotate it to maybe the opposite side of the eccentric, and see how that affects things.  
  
  Nobody with a 1.6TD has any comments on this?  It would be helpful.  
  
  Jim hows your project coming?  Did you get your IP figured out and engine running?
• #3 by burnt_servo on 13 Mar, 2008 10:49
• i ground the hell out of my pin , the steepest setting didn't have enough fuel for my liking . even now i'm thinking i'll grind it a bit more .
  
  i also bottomed out my starwheel , and turned the smoke screw up wards so the pin that rides on the ground fuel pin at the bottom of the fuel pin .
  
  i also ground about 1/8 of a inch off the bottom of the fuel pin , to allow it to drop farther .  i also shaved the white plastic washer on the fuel pin in 1/2 to allow it to drop down farther .
  
  the whole idea was to increase max power , BUT also increase millage when just crusing.
  
  i also blocked off my blow off valve on the intake , and turn up the waste gate for higher boost presure , which will force the fuel cone down father at max presure .
• #4 by KTZed on 13 Mar, 2008 10:58
• Im pretty much in the same boat as you...1.6TD, T3 turbo etc. and am also quite underwhelmed by the slow spool/low-mid range power.
  I have yet to make any mods to the pump (it decided to start leaking so that has to be fixed first  :roll: ) so I can't really give you any 1st hand experience, but I am also looking for the right combination of pin/screw/wheel settings to make it spool faster. Let us know what you find!
• #5 by boxer246 on 13 Mar, 2008 11:18
• Burnt....I'm not sure I understand why you moved the smoke screw upwards, yet all the other mods you did were to make sure the pin was able to move downwards farther.  When you say you still want more fueling, after all that, what makes you want more...in other words, do you think it isn't putting out enough at full boost? or medium boost?  I guess you have little to no smoke?  
  
  How did these adjustments increase both economy and power....as you say?  Maybe the increased fueling in the midrange area will allow boost to build better (or quicker), thereby allowing for a more complete combustion and better economy?
• #6 by burnt_servo on 13 Mar, 2008 11:43
• Quote from: "boxer246"

  Burnt....I'm not sure I understand why you moved the smoke screw upwards, yet all the other mods you did were to make sure the pin was able to move downwards farther.  When you say you still want more fueling, after all that, what makes you want more...in other words, do you think it isn't putting out enough at full boost? or medium boost?  I guess you have little to no smoke?  
  
  How did these adjustments increase both economy and power....as you say?  Maybe the increased fueling in the midrange area will allow boost to build better (or quicker), thereby allowing for a more complete combustion and better economy?

  
  
  what i did was increase the range that the fuel pin could move upwards , and downwards , meaning that at low boost it restricts the fuel more than stock , and at high boost dumps way more fuel than stock .....
  
  maybe i should go take some pics , it might help ... brb
• #7 by burnt_servo on 13 Mar, 2008 12:22
• 
  
  
  
  
  
  
  
  
• #8 by burnt_servo on 13 Mar, 2008 12:22
• first pic shows the washer i cut in half
  
  2nd pic , side veiw of my ground boost pin
  
  3rd pic shows the range of movement all the way down to the tip of the pin
  
  4th pic , shows the range of movment that i had before the mods , the wear mark is  about in the middle of the cone .
  
  the 5th pic compares a stock pin to mine , and shows how much i ground off of the foot .   maybe more like 3/32 of a inch  rather than 1/8 .
  
  
  
  also be aware  i'm also running 18 pounds of boost and a 2.5 inch exhaust  , doing this to a stock engine might cause your egt temps to skyrocket ....  watch how much black smoke your making , and adjust acordingly , or better yet get a egt gauge .
  
  
  *edit * ... also see this thread too ,   http://vwdiesel.net/phpBB/viewtopic.php?t=645
• #9 by boxer246 on 13 Mar, 2008 13:55
• Burnt....thanks a bunch.  I understand what you did.  I'm just gonna play with  it trial and error and see what happens.
  
  I have no EGT gauge at the moment, but thats the next thing on my list.  I have 2.5 exhaust and I also disabled the blowoff valve.  I assume my turbo is only putting out 11 psi or so (or whatever they are wastegated to stock) because as of now I do not have a boost controller.  I will probably install one after I put in a EGT gauge, boost gauge and intercooler.
  
  I think my next step is to turn the star wheel down some then turn my smoke screw upwards a bit.
• #10 by boxer246 on 13 Mar, 2008 13:57
• What are thoughts on GTD nozzles?  Anyone use them?
  
  Would I only expect to see gains in higher end horsepower with those?
• #11 by MontanaGTD on 13 Mar, 2008 15:57
• What would happen if you removed the plastic washer??
  
  My GTd spools up pretty quick and all i have played with is the fueling! Still need the boost turned up, just not sure how to do it at the moment!
• #12 by hillfolk'r on 13 Mar, 2008 18:58
• get rid of the plastic washer......
  ive found that having the smoke screw in too far really killed my mileage
  yea turn it in some(i think mines in like 1.5turns),but more to be had by completely bottoming the starwheel,and adjusting the pin(or cutting like you)
  
  get an extra starwheel spring and do the lowrider trick: heat it cherry red man....has a similar effect as the smoke screw if you think about it,and since its weaker,itll go full fuel with minimal boost anyways
• #13 by hillfolk'r on 13 Mar, 2008 20:41
• yep
  i used sandpaper wheel on my dremel,then a felt polisher wheel with some toothpaste(crest is great polish) :wink:
• #14 by burnt_servo on 13 Mar, 2008 22:18
• the plastic washer acts like a cushion when the pin is driven downwards , i wouldn't recomend removing it .
  
  as you can see my pin isn't being pushed all the way down any way by boost presure , so the next best thing is to grind deeper into the pin where the small pin rides on the fuel pin , allowing more fuel in the range that the small  pin rides on the fuel pin .
  
  
   and yes  after your done grinding , it has to be polished smooth .