Interest in adjustable IP sprockets? - page 1 - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.

• Interest in adjustable IP sprockets? by 935racer on 19 Sep, 2006 23:09
• On the newer tdi's and late model 1.9 IDI's they are gifted with an adjustable 2 piece injection pump sprocket. What this means if the crank timing and cam timign are all lined up you can adjust the injection pump timing without loosening the injection pump. Its really nice, on a mech tdi I recently built I was trying all sorts of weird timings and it was so quick, just simply rotate the engine to TDC (just look at the mark through the tranny) and when its at TDC you loosen 3 bolts than you can turn the injection pumps input shaft and adjust the timing, than tighten up the three bolts and away you go. You can actually adjust your timing in less than 5 minutes. For a serious tuner I say this is a must.
  
  I will have to get some hubs custom made to fit our idi 17mm injection pump shafts, but if the interest is there I will do it. Here are some pics from another thread.
  
  
  Here is a picture of a stock tdi sprocket beside a lightened version (I did a real quick lighten on the lathe with this, I will do a finish pass and balance all the ones I would sell, still need to remove a little more material, maybe 40grams more) and a 1.9 IDI sprocket under neath.
  Topside
  
  Bottom side:
  
  Topside:
  
  Bottom side:
  
  Topside:
  
  Bottom side:
  
  
  Weights are as follows:
  stock 1.9tdi: 1552grams
  lightened tdi: 705grams
  1.9 idi: 660grams
  
  The finished lightened tdi should be around 680grams, I can also make some holes similar to the 1.9idi sprocket to drop the weight even further, I am doing that on my personal tdi.
  
  Lets here what you think.
• #1 by burn_your_money on 19 Sep, 2006 23:31
• How do you know how far you've advanced/retarded your timing? or am I missing something...
• #2 by 935racer on 19 Sep, 2006 23:36
• You can still use a dial indicator. Or if you have the "feel" just give it a little bit  Even with using the dial indicator you can still make an adjustment in under 5 minutes, I do it all the time, its sweet.
• #3 by Kudagra on 19 Sep, 2006 23:49
• Holy crap...did they have a glut of steel in Germany when they made those??
  
  How about lightened balancers for 1.6s?  
   
  Im interested in an I/p pulley for a 1.6.
  
  Still trying to get more of my money huh?
  
  
  
  
  
  
  
  
  Resurected in the correct forum.
• #4 by 935racer on 20 Sep, 2006 00:07
• Yeah I am working on the possibility of a lightweight aluminum harmonic balancer, anyone else interested in one of those?
• #5 by scopefrfd on 20 Sep, 2006 00:50
• I'm interested in the custom hubs...I'd rather keep the heavy pulley though to help smooth out the pump action especially on the bigger pump heads.
• #6 by Kudagra on 20 Sep, 2006 07:54
• Gaaaaah.
  
  I was just figuring out what I had to take to my machinest  for balancing and now you come up with this.
  
  Let me know Ill get one.
  
  
  
  Is there really any benefit of the 210mm flywheel over the 200mm? Its only 10mm.
• #7 by 935racer on 20 Sep, 2006 11:01
• No I don't find the switch to a 210mm flywheel to be worthwhile.
• #8 by QuickTD on 20 Sep, 2006 11:16
• If you're running a large pump head I think it would be beneficial to keep the mass of the TDI pulley. The extra inertia would take some of the shock load off of the timing belt. I think the higher pressure TDI pumps really need the mass, it's kind of scary to watch a TDI timing belt flap at idle, the torque fluctuations at the pump are huge.
  
  The adjustabilty of the 2 piece pulley is a great feature though, worth doing.
• #9 by 935racer on 20 Sep, 2006 11:24
• You find the tdi belts flap? Even with all the extra rollers??? I have zero flapping issues with the tdi's. Its the IDI's that have flapping belts, I have added rollers to those. I was under the impression that one of the reasons IP's with larger head assmblys was due to extra reciprocating mass... Shed some light Bruce
  
  Anyways I have been using these for a while and I have been using hte stock IDI pulleys on 12 mm head pumps with no issues...
• #10 by QuickTD on 20 Sep, 2006 17:51
• Quote from: "935racer"

  You find the tdi belts flap? Even with all the extra rollers??? I have zero flapping issues with the tdi's. Its the IDI's that have flapping belts, I have added rollers to those. I was under the impression that one of the reasons IP's with larger head assmblys was due to extra reciprocating mass... Shed some light Bruce
  
  Anyways I have been using these for a while and I have been using hte stock IDI pulleys on 12 mm head pumps with no issues...

  
  
  I've only seen a few TDI's run without the covers on at GTG's and all made me a bit nervous, looking down in at the longer runs of belt and watching the tensioner "dance"... The run of belt between the pump and cam is smoother on the TDI due to the extra roller, but I think my IDI and others I've worked on seem smoother in the pump drive as a whole.
  
   I was always under the impression that the heavy TDI pulley was designed to take the shock load off the belt by providing a bit of flywheel to the pump drive shaft, I don't think they were just trying to dispose of extra iron   . The pump only draws torque in very short spikes coinciding with each injection event, a little inertia helps the pump get over the hump and lessens the sudden torque rise on the belt. Automatic TDI's use smaller nozzles and a larger plunger. This results in higher injection pressures, higher peak torque required to drive the pump and thus more stress on the belt, making shorter change intervals necessary. I don't think the tiny change in reciprocating mass of the plunger is of much consequence. The IDI's don't need much pulley inertia as the torque spikes at the pump shaft are just a tiny fraction of those in the TDI due to the much lower IDI injection pressure. I would have no qualms at all with using a lightened pulley on a stock IDI.
  
   It's likely impossible to predict what, if any, negative effects would come from using the lightened pulley on a TDI. Like anything else, I expect experience to tell the whole story.
• #11 by 935racer on 20 Sep, 2006 19:10
• Thanks for the insight  I have been running one for about 10,000kms with no negative effects. I understand the extra inertia would help smooth things out but perhaps it is compensated by running a lot more fuel :twisted:  a la 14mm head. I think the heavy ip sprocket is just a luxury like the excessively heavy flywheels. I know I sure like running a 6lb flywheel compared to the stock unit.
• #12 by zagarus on 20 Sep, 2006 19:13
• whats stock 1.6l flywheel weight?  wanna make me a 6 pounder?  
• #13 by 935racer on 20 Sep, 2006 19:50
• Yes I am planning on selling 6lb flywheels again and maybe offer them as a special with the performance clutch kit, this would make doing the performance clutch upgrade really quick because you wouldn't have to take your flywheel out to a shop to get resurfaced, because I will ship them out lightened, balanced and surfaced. So install and send your core back. Would you guys like that?
• #14 by burn_your_money on 20 Sep, 2006 20:22
• I'd like a preformance clutch setup once I get to that stage