VWDiesel.net The IDI, TDI, and mTDI source.
Engine Specific Info and Questions => IDI Engine => Topic started by: 72malibu on August 06, 2020, 04:26:46 pm
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Will be doing the gov mod, hopefully this weekend. I know there is another mod that can be done, I believe its a timing advance modification? If I remember correctly, best to replace the internal spring with a 'green' one, which I do not have, but, there are spacers that can be removed to inmprove the timing advance?
Now, if I am not just totally lost about the timing advance mod, can they BOTH be done? Or is it an either/or, and, if so, which is the better?
Thank you for your time.
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Found my copy I had printed off. It is a timing advance modification.
Again, thank you.
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The real timing "mod" is to check the internal fuel pressure and get it up to spec. Most people find the spring needs MORE shims after getting the internal pressure right, because the advance spring is actually worn out.
https://web.archive.org/web/20160420200053/http://www.vwdieselparts.com/forum/viewtopic.php?f=8&t=5936&sid=586e5a76498c92e807bae59d3c04498d
Easiest test is the fuel output, measure the amount of diesel coming out of the pump at idle. To adjust the pressure you have to make a gauge and tap the pressure regulator pin in a tiny amount.
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Thank you very much. I will look into this.
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a spare "out" bolt or fuel-stop solenoid can be sacrificed for tapping a standard oil pressure gauge into.
to adjust the fuel pressure regulator pin, soaking it with penetrant helps. If you go too far in you have to take it out and tap the pin back (not fun)
If you get the internal pressure right, with the big advance spring being typically really old, the dynamic advance will be effectively modded. My static timing had to be adjusted back to .90 after I did it.
The governor mod isn't needed if the throttle and fuel-screw are adjusted for good power. You just give it more throttle if you need it, it's all the same to the injectors.
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Just tapped on the pressure regulator yesterday. Now I need to check flow per min and timing. I think it may have changed. Needed a bit more pressure to bring the dynamic advance in earlier on the turbo enhanced 1.6L
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Another timing advance mod is to shorten the timing piston so it can move 2mm farther.
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Don't you need to be careful on that one to make sure you only take off material on one side and not the other? Then you must put the piston in the right way so that the greater travel distance is on the side that allows the advance mechanism to move that direction? Best to mark it as it comes out of the hole which requires you to tear down the pump. Not such an easy thing for some to grasp.
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Another timing advance mod is to shorten the timing piston so it can move 2mm farther.
(https://i.imgur.com/HdqdpaOl.jpg)
(https://i.imgur.com/X10HHqCm.jpg)
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There isn't very much that the piston can be shortened before the pin hits the case. The TDI pin is also machined to an hourglass shape to allow even more advance. The TDI dynamic advance cap also has a cutout for the piston so it can travel further as well. All of that said, the right amount of advance for a given rpm is a much better thing than too much advance. Use super-powers for good and not for evil.
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Instead of taking off part of the piston has anyone taken off part of the spring? I know there are four colors for various compression ratios and green is the weak one thus more desirable. But if you shorten up the spring does that make any difference?
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probably be too much advance at idle (clack)
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I had a Gold Rabbit TD that sounded nice at idle
but got all clackity at higher RPMs.
I played with adding more shims and it ran much quieter at 2500 RPM.
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Indeed. That's exactly what I meant by the right amount of advance being better than too much advance.
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https://vwdiesel.cokenet.org/viewforum.php?f=23
some deep-digging thoughts left behind in that old forum