larger plunger/head assembly - page 2 - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.

• #15 by QuickTD on 29 Jul, 2005 18:14
• Half the battle (and the primary reason for the large plunger) is getting the fuel in soon enough to ensure a good mix and a clean burn. The maxed out 9mm setup will be pushing in a bunch of of fuel late in the cycle, where it tends to create smoke rather than power. A maxed out 9mm pump will smoke WAY more and produce less power than a 12mm pump delivering exactly the same quantity.
• #16 by fspGTD on 29 Jul, 2005 22:43
• VWMike: By "maxxed out governor", I am indeed assuming in all boost level scenarios that the LDA rotation and depth are maxxed out.
  
  Mark The Miser - although I don't think it's the pic you are referring to (I don't think I still have that one!), here is one of my more recent "smokey" favorites, :wink: from the 2003 SCCA Solo 2 Nationals:
  
  
  QuickTD: It seems like while more pump capacity indeed can shorten the injection window and thereby increase efficiency, going too far in unused displacement could also be a double-edged sword, where the power loss from the additional parasitic drag off the injection pump to drive the larger plunger could be greater than the power gained from the efficiency increase.
  
  I am curious what the optimal pump size would actually end up being, and would be interested in hearing about any experiments (TDI, IDI, or otherwise) done with plunger upgrades.  Shortening the injection window is indeed an important consideration of mine for upgrading the plunger in my GTD Autocrosser.
• #17 by RedRotors on 30 Jul, 2005 12:53
• Jake, im running a 12mm head/plunger in my TDI Golf, ok it's a TDI, but im also running big injectors with stock ECU program at 15psi. I have a little puff of smoke when starting at a stop, and little smoke between gear shift. At WOT, running at 110mph ,i have 15psi substained and i have an haze at the tail pipe. I went from a 10mm to an 11 and then a 12mm and let me tell you that the power is very linear and very strong until 4500rpm ( limitted by the ECU ). I don't have excessive smoke.
  
  I agree with Bruce that one of the main purpose to upgrade the pump is to get much more fuel in a shorter window. I have a friend here that run his 1.9TD with a 12mm pump @22psi, the smoke level is tolerable and his ride is real fast.
  
  So i don't think that a 12mm is too much for an 1.6 or1.9TD if the pump is correctly set.
  
  Marc/
• #18 by fspGTD on 30 Jul, 2005 14:58
• Thanks for the info, Marc.  My 1.6lTD Rabbit GTD Autocrosser is limited to stock turbo and stock boost pressure (9-10psi) under its class rules.  We are however free to do any fuel injection modifications at all.    What are your thoughts about using a 12mm plunger on this application... think it would be most optimal plunger size?
  
  PS - keep in mind your TDI at 1.9l displacement and 15 psi boost is ingesting significantly more air per stroke (I estimate about 42% more) than my 1.6l at 10psi.
• #19 by RedRotors on 30 Jul, 2005 15:12
• You might try the 10mm first, it might give you an idea, but beeing limitted at 9-10psi, i think that the 12mm will smoke. The 12mm will need the later camplate from the 1.9TD, because the plunger foot is a little bit bigger than the 1.6 and won't sit in the camplate as well as the 10,11mm TDI head/rotor.. I don't know about the other ones.. Some ajustments on the pump will be needed to tune the idle, but im sure you won't have any problem to do this..
  
  Marc/
• #20 by fspGTD on 30 Jul, 2005 15:21
• Thanks for the info!  I am looking forward to trying the 10mm.
  
  PS - are the 12mm plungers only compatible with pumps that have the larger input shafts, like the ones in the TDIs and later 1.9lTD pumps?
• #21 by QuickTD on 30 Jul, 2005 16:36
• Quote

  PS - are the 12mm plungers only compatible with pumps that have the larger input shafts, like the ones in the TDIs and later 1.9lTD pumps?

  
  
  It's not the input shaft that is the problem, it's the recess in the camplate that isn't large enough. If you put in a late model 1.9TD camplate you're all set.
  
   The late model 1.9TD pump does not have the large 20mm input shaft, but does have some similarities to the ALH TDI pump. The timing pulley attaches to the pump with a 3 bolt hub. The "nose" diameter is also larger and will not fit the early style pump bracket.
• #22 by fspGTD on 05 Dec, 2005 11:53
• FYI - I took apart the mitsubishi mid-80's pickup 10mm pump to do some learning about its internals and do some comparing with the 1.6lTD (from a 1984 Jetta) pump parts.
  
  Although the camplates were constructed differently (the mitsubishi one seemed like a heavier piece), the displacement of the mitsubishi camplate is the same 2.2mm as I believe is on the 1.6 camplate.  From the picture it seems that the mitsubishi camplate has a slightly softer profile than the VW (IE: slower movement of the pump head), but it's hard to be certain just from looking, as they are pretty close (1.6 vw on left, mitsubishi on right):
  
  
  The two camplates also have as closely as I can tell, an identical recessed diameter for the "plunger foot".  (Tested by crudely measuring, as well as test fitting the same plunger into each and observing equal amounts of "play".)  The plunger drive pin in each is also a matching 3.5mm diameter.  (1.6 vw on left, mitsubishi on right):
  
  
  Takeaway: given the matching plunger foot diameter and similar camplate displacement, the 10mm mitsubishi plunger may be a suitable swap-in upgrade for a 1984 1.6TD VW pump (for either maintaining the original 1.6 VW camplate, or swapping the mitsubishi camplate along with the plunger.)
  
  ----------------------------
  
  Interestingly, the plunger return springs were not the same.  Although nearly identical in free length, the mitsubishi springs obviously had thicker gauge of wire, and also had one extra coil (1.6 vw on left, mitsubishi on right):
  
  
  Looking at both, I thought the VW one might be good for some more pre-loading and lift, if the wire material was strong enough.  Well, it turns out that the wire material was not strong enough to remain undeformed after being coilbound.  It actually deformed quite a bit. :shock:  (in pic below, two vw 1.6 plunger springs are shown, the one on left hasn't been coilbound and the one at the right has)
  
  Can the mitsubishi spring take being pre-loaded to coilbind?  I'm guessing it can get closer given it has less travel to go and also some thicker (& probably stronger) wire, but I don't wish to test it on my only pair of these springs.  I wouldn't mind testing and comparing the spring rate of these two different springs, if I can rig up such a test though.
  
  How much pre-load the plunger return springs should be set up with, and deep the plunger should be set up, I am not certain.  If anyone has any advice or VE technical service manual information covering this (any information on the topic - what methods are used to measure it and set it up, what the factory recommended settings are, etc), please let me know, as I would be very interested in it.  I have a feeling that it's pretty important and is something that the trained/certified VE pump rebuilders check and set.  I would really like to know what I'm doing and not blow up a pump if it could be avoided.  Thanks!
  
  It is likely that a plunger upgrade test of some sort will be in my future after I get my Rabbit autocrosser up and running and the fresh rings broken-in, and maybe the custom intake manifold fitted and tested.
• #23 by 935racer on 05 Dec, 2005 12:54
• Jake what do the plunger return springs look like when ther are installed in the mitsubishi pump? You can see them when the head assembly is installed with the top cover off. Its really important that when you swap head units that you keep the return springs that came with the head assembly, not the ones in the pump you are swapping them into.
• #24 by vwmike on 05 Dec, 2005 13:50
• the part numbers for many springs are the same across the board, from 8mm on up to 12mm.
• #25 by RedRotors on 05 Dec, 2005 15:36
• What's the bosch pump number Jake?
  
  Marc/
• #26 by Kudagra on 05 Dec, 2005 20:26
• Quote from: "fspGTD"

  Going from a 9mm to a 12mm plunger would make for an increase in pump displacement of 78%.
  
  [Edit:] and also, for changing from a 9mm plunger to...
  * 10mm: would give a 23% increase in pump displacement
  * 11mm: would give a 49% increase in pump displacement
  
  

  
  
  Can you post the formula you used to find this?
• #27 by QuickTD on 05 Dec, 2005 20:45
• Quote

  
  
  Can you post the formula you used to find this?

  
  
  
  πr²=area of plunger.
  
  Doubling the area for a given camplate lift will double the displacement.
• #28 by fspGTD on 06 Dec, 2005 09:57
• Marc - the mitsubishi pump is a Diesel-Kiki, NP-VE4/10F2100RNP167.  Pump no 104640-3080.
  
  The ID plate:
  
• #29 by RedRotors on 06 Dec, 2005 11:37
• Thanks Jake for the info, but unfortunatly, i don't have access to diesel kiki parts...   Even with the Bosch formula, i can't find nothing..
  
  Marc/