a8 4h 4.2 tdi turbo upgrade.

Ley

Member
Joined
Jun 12, 2018
Location
uk
TDI
3.0 4.2
Hi all. I`m thinking to upgrade my a8 d3 3.0 tdi to a 4.2 tdi from 2011. This one i left it stock because of gearbox limitations. I would like to know the limits of 4.2 tdi engine and especially gearbox torque limit, i`ve seen 1100 nm on these. Would like to get a bolt on turbo upgrade if possible, or maybe turbos from 2014 model, 380hp ones can be upgraded? Would like to get around 500hp, i`m open to any sugesstions or possibilities and informations that can help me in taking decisions. Thanks.
 

altz1

Veteran Member
Joined
Jan 15, 2015
Location
Estonia
TDI
A8 4H 4.2TDI, Cayenne 4.2TDI, 6.0TDI
Get your current turbos upgraded with bigger wheels, and you can get close to 500hp with Dpf out. Gearbox is plenty strong on 4h. Same with your current 3.0, 6hp19 box can take up to 800nm if in good condition.
 

TDIMeister

Phd of TDIClub Enthusiast, Moderator at Large
Joined
May 1, 1999
Location
Canada
TDI
TDI
Confused. Do you ultimately want to swap the whole engine or just the turbo? The V8 is biturbo and the V6's single turbo sits on a pedestal between the Vee.

If you want to swap engines, do that first and get that sorted out - it will be lot of work by itself - before venturing to modifications.
 

Ley

Member
Joined
Jun 12, 2018
Location
uk
TDI
3.0 4.2
@altz1 pm sent . thanks
@TDIMeister i will sell this car(3.0 tdi a8 d3) and get the newer model a8 d4 4.2 tdi and start working on that one. Sorry for the confusion. All info appreciated.
 

Ley

Member
Joined
Jun 12, 2018
Location
uk
TDI
3.0 4.2
Get your current turbos upgraded with bigger wheels, and you can get close to 500hp with Dpf out. Gearbox is plenty strong on 4h. Same with your current 3.0, 6hp19 box can take up to 800nm if in good condition.
Thanks for that. Do you know if those turbos from sq7 , GTD2056VZK , are bolt on on 4.2 tdi? cant really decide between upgrading to 2014 turbos and change everything inside them or get 2 GTD2056VZK ... advice needed.
 

altz1

Veteran Member
Joined
Jan 15, 2015
Location
Estonia
TDI
A8 4H 4.2TDI, Cayenne 4.2TDI, 6.0TDI
There is absolutly nothing similar with sq7 turbos and 4.2tdi turbos. Not easy to install there, but they sure would work good.
 

TDIMeister

Phd of TDIClub Enthusiast, Moderator at Large
Joined
May 1, 1999
Location
Canada
TDI
TDI
I think you will be constrained more by availability and cost more than any other factor. SQ7 turbo pairs don't come on sale on eBay every day, actually neither of these turbos do. Upgrading the compressor wheels only to the otherwise stock turbos is also an option but the turbine side will become restrictive; based on the wealth of experience with 4 cylinder TDIs, 250HP on a GT17 frame turbo is a stretch. All depends on what your HP target is and how deep your pockets are left after you've spent the money to trade up to a 4.2 V8...
 

altz1

Veteran Member
Joined
Jan 15, 2015
Location
Estonia
TDI
A8 4H 4.2TDI, Cayenne 4.2TDI, 6.0TDI
Probably using gtb2056vzk tw and cw both in original gtb17 housings would be the best bet. This is what i did with my old car with older type 17vk turbos.
 

[486]

Top Post Dawg
Joined
Mar 1, 2014
Location
MN
TDI
02 golf ALH
Could always just plumb up a big dumb VGT turbo from a semi-truck, every manufacturer runs them nowadays and they go real cheap used because people are scared off by vanes.
 

Ley

Member
Joined
Jun 12, 2018
Location
uk
TDI
3.0 4.2
So, after long research hours, i have more info and ofcourse, questions. My 4.2 tdi engine code will be CDSB that have 2xGTB1749VK. Can i fit the new turbos from 4.2tdi 2013+ CTEC engine that have 2x GTB1749VZ ? Are they plug and play? They will be hybridized anyway, just thinking about these VZ , i read alot of nice things about VZ ones. Which ones can take more when hybrid, VZ or VK ? Thanks.
 
Last edited:

hevimental

New member
Joined
Feb 11, 2021
Location
Poland
TDI
4.2 TDI
Hello, Im new here. Owning A8 D4 2010 4.2 TDI. I'll have to regenerate turbos pretty soon. Looking for some upgrades. Anyone can share some experience with bigger wheel etc turbos in 4.2 tdi?
 
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