Need help with N75 and boost issues

by **zluevano** » Sat May 07, 2022 3:15 pm

Greetings, I'm in need with my 2003 ALH TDI fully stock, minus a EGR/Cooler delete and a muffler chopped off.

So I'm not sure if I'm not understanding this right but I've been using Vagsuite for my tuning on the EDC 15. So the problem I've been having is I seem to loose a majority of my boost from 20PSI to around 10PSI once it hits 3000 RPM give or take, with the exhaust making a change in tone at that point. My first thought was my N75 map, then I thought, oh maybe it's limited my fueling since I'm at 4500ft and I've lowered the torque limiter for higher altitudes, but air density is higher than sea level right now so that's not it.

Maybe the cat? Or the VNT actuator?

With the N75 I can squeeze 5 PSI or so more to 15 at 3000-4000 RPM, but I'm worried to mess with this more as I have to set it at 60% all the way up to 4k RPM. and this doesn't make sense to me, I thought at higher RPM the fuel is getting burned faster and thus it would spin up the turbo faster and thus you'd need to increase the N75 %-wise but it seems to severally limit it past 65% or so.

I should note I did mess with my SOI, I applied max duration at 4000RPM for the voltage, and then got a factor and lowered it down to around 3k RPM, The SOI was retarded to around 17 degrees at max, climbing up from 3000 RPM which is also the same factor as what I did to the duration to keep things mostly linear, I'm wondering if I retarded it too much and the fuel isn't getting the turbo to spin fast enough at that RPM which could also explain the sound change.

What's odd is that I can get more boost if I go WOT at >3000 RPM when I'm already up there where it seems to hold better, sticking veins?

Also... I've been hearing that the ALH map is reversed for the N75? I had no idea and this would explain a the effect, but I hear that 100% is acutally closed all the way so it's making the most pressure for low RPM, and 0% being fully open, and thus max flow. Please correct me if I'm wrong.

Lastly… I still have my OEM ECU file for testing purposes.

Seriously any help would be great, I'm not looking to grenade my turbo too fast

by **selveti7** » Sat May 07, 2022 3:38 pm

i think should clean and rework the vanes if they are blocked perhaps not all of them but 1 vane if its not moving free it will cause problem in boost regulation....

by **Alonedar** » Sun May 08, 2022 8:54 pm

can be cause because the original electonic is bad ??? :lol: :lol: :lol: :lol: :lol: :lol: :lol:

by **zluevano** » Sun May 08, 2022 9:13 pm

Alonedar wrote:can be cause because the original electonic is bad ??? :lol: :lol: :lol: :lol: :lol: :lol: :lol:

I wouldn’t be posting if I knew the answer. Are these symptoms related to a failing n75?

by **Mk4pd130** » Sun May 08, 2022 11:35 pm

zluevano wrote:
Alonedar wrote:can be cause because the original electonic is bad ??? :lol: :lol: :lol: :lol: :lol: :lol: :lol:

I wouldn’t be posting if I knew the answer. Are these symptoms related to a failing n75?

Whats the stock alh n75 map at low rpms, 20/30% or 70/80.

If 20 30 percent then n75 is not flipped. If 70 80 then it is flipped as compared to asz maps, mail me ur map il have a look