Author Topic: Quick tdi pump sprocket question could be useful for idi... (Read 3997 times)

shortysclimbin · « **on:** January 03, 2008, 07:39:24 am »

Does anyone know why the stock tdi pump gear is sooo heavy? Is it because of vibrations or flywheel effects? Has anyone lightened it and had ill effects? I can see it being an issue at start up to turn the pump initially but may help turn things over in the end. But the weight is there for some reason.... I am wondering if I could get away with removing the center mass a little to reduce rotational mass a bit more.... Any one try this yet?

Tintin · « **Reply #1 on:** January 03, 2008, 03:10:30 pm »

MK3 tdi (1Z/AHU) have a light pulley and do not have more or less power/torque, I think that the heavy pulley regularizes the rotation, less by-effect on the timing belt.

andy2 · « **Reply #2 on:** January 03, 2008, 05:26:26 pm »

The TDI inj pump builds higher inj pressures and has an agressive camplate when compared to the IDI pump and its lower pressure system.
The heavier Pully as Tintin mentioned is used to help dampen the shock to the timing belt and to smoothen out the pump as it goes up and over the camplates lobes,think of it as a flywheel on an engine.I use the ALH pump pully on my heavily modded 12mm IDI pump in an attempt help things out.I don't see any benifit to lightening this pully.

RabbitGTDguy · « **Reply #3 on:** January 03, 2008, 06:27:21 pm »

same response as the other guys here.

I actually used the ALH pump pulley on my mTDI. In order to get it to line up (without making a spacer) with the cam using it on the ALH pump hub and on my 4bt based mTDI pump, I had to "flip" the ALH sprocket on the hub...which allowed for PERFECT alignment. However when it was like this it hit the pump bracket itself. I then had the front "dome" of the ALH sprocket machine down just to remove the dome of the sprocket so it would clear. Worked perfectly... and thats the only reason I machined it.

There was a vendor I believe selling "lightened" injection pump sprockets but I doubt you'd see any "performance" benefits...
Oye...

Joe

Tintin · « **Reply #4 on:** January 03, 2008, 07:09:33 pm »

:lol:

andy2 · « **Reply #5 on:** January 05, 2008, 10:05:08 am »

:shock: Tintin whats that top pully form?

RabbitGTDguy · « **Reply #6 on:** January 05, 2008, 10:11:13 am »

Looks like maybe the cranksprocket off the PD

shortysclimbin · « **Reply #7 on:** January 05, 2008, 07:07:12 pm »

Ok good to hear guys. I was thinking there was some reason behind it and figured it was mass for the pump and most likely would not be something I should mess with without good info on why to do it.

jtanguay · « **Reply #8 on:** January 05, 2008, 07:16:48 pm »

actually that sprocket looks like its from the 5 cylinder engine. check out the AAT video in the TDI section or better yet check the video. looks like it helps reduce shock loads and vibrations on the pump...

http://www.youtube.com/watch?v=m6fYi13CBlU

RabbitGTDguy · « **Reply #9 on:** January 05, 2008, 08:44:35 pm »

damn!

Author Topic: Quick tdi pump sprocket question could be useful for idi... (Read 3997 times)

andy2

andy2