The Ultimate Enthusiasts Guide to Fully become One with the TDI, as told by Burpod....

[roder]

For a vnt15, during the test, you should see a decent deviation in boost shown in VCDS, something like 100mbar, i forget exactly. The larger the turbo, the smaller the deviation as 900rpm and ~4mg of fuel simply cannot spin the large compressor enough to create boost - one might even see boost values less than current barometric.

I am seeing actuals at 190F, ~900rpms of ~860mbar when requested is 999mbar. Is that the expected deviation you were referencing?

I just completed cleaning the exhaust side of the OE VNT15 turbo vanes, upgraded to a VNT17 cold side compressor (from xmanturbos). I upgrades to a Darkside FMIC, and a Profidiesel 2.5 de-catted turbo-back exhaust. I thoroughly cleaned the EGR and intake manifold. I deleted the EGR, but left tghe ASV operational. I also added a 3mbar MAF sensor, for future tuning.

I tested the N75 output and was getting about 17hg at 24.5% charge pressure. When I did the charge pressure control test, it was as expected for an ALH - 24hg @ 0% and 0hg at 100%. When I tested vac supply by the pump, it fluttered rapidly between 18hg-21hg. I added a video.

I haven't road tested yet, and haven't gotten any under boost codes or limp mode, and I haven't heard any sucking or leaking sounds. I used hairspray and clamped hard on the IC plumbing.

Should I be concerned about the difference in requested mbar vs actuals?

 

[boertje]

Fluttering vacuum usually means the vacuum pump nipple is loose and leaking. Should be at least 24” Hg and steady.

 

[roder]

Fluttering vacuum usually means the vacuum pump nipple is loose and leaking. Should be at least 24” Hg and steady.

Thanks for the pointer! Is the vacuum pump nipple a component of the vacuum pump? Any diagrams that I can identify that part?

 

[boertje]

Yeah its a known issue and there are recent threads on how to seal the nipple back up.

 

[IndigoBlueWagon]

The nipple on the pump (the hose to the brake booster attaches to it) is tack welded to the pump housing and can come loose with time.

 

[P2B]

Thanks for the pointer! Is the vacuum pump nipple a component of the vacuum pump? Any diagrams that I can identify that part?

How I deal with loose nipples...vacuum pump repair

Here is how I deal with the ALH's loose vacuum pump nipple problem. I have tried the peen-over method and it works for a while but if it failed the first time then it probably will again. This will eliminate the o-ring's function that seals the joint. It seems like a weird failure prone, short...

forums.tdiclub.com

 

[roder]

Thanks @P2B @IndigoBlueWagon @boertje !

Y'all know of a way I can diagnostically prove this is my case? If it were a positive pressure leak, I'd use soapy water, but I don't think that will work in this case.

 

[P2B]

Thanks @P2B @IndigoBlueWagon @boertje !

Y'all know of a way I can diagnostically prove this is my case? If it were a positive pressure leak, I'd use soapy water, but I don't think that will work in this case.

Grab the hose and push it and the nipple towards the pump. Vacuum should stabilize or at least the fluttering should be greatly reduced.

 

[J_dude]

Thanks @P2B @IndigoBlueWagon @boertje !

Y'all know of a way I can diagnostically prove this is my case? If it were a positive pressure leak, I'd use soapy water, but I don't think that will work in this case.

If it's loose, it's leaking.

 

[burpod]

finally filled in one other little section, on modifications. all my own opinions of course