V8tdi "stage 2"

altz1

Veteran Member
Joined
Jan 15, 2015
Location
Estonia
TDI
A8 4H 4.2TDI, Cayenne 4.2TDI, 6.0TDI
Hello all,

About a year and half ago i started 4.2tdi swap into 2007 Porsche Cayenne Turbo S. The original 4.5T engine had failed cylinder liners and at the time it seemed like a good idea to swap in 4.2TDI from Q7. To keep things more complicated i used various parts from various model years building the driveline and also engine. For turbos, i used GTB2260vk units from v12tdi. I have driven with this setup now few months with engine producing close to 600hp (currently limited by CP3L110 capacity, as it can not keep the desired rail pressure with modified Metering unit, presupply pump and even with 3bar feed pressure).

Anyway, i decided to take the thing appart again, and enter into "stage 2". I yesterday bought 8-speed Aisin AL-1000 transmission + differentials, so driveline will get upgraded and also the pump will be upgraded to unit from MAN truck.

While the engine comes out, i would like to change the turbo department also, as there are few bottlenecks in my piping and for some reason, spool-up is not perfect. I get full boost only around 3000rpm. I think the problem might be in the minimum flow setting, but im not sure about this, as both turbos have the original adjustment/location electronic actuator.

So the plan now is to go quad turbo, and this is where i would like to hear your toughts and ideas. Lets watch this project as 2x 2.1L R4 tdi, as Bank 1 would be just mirror from Bank 2. Should i build compound setup or sequential like VAG 2.0 and 3.0 bitdi engines?

HP turbos will be GTB1749VK, stock units, i will only change the compressor wheel to billet (stock size, but extended tip) controlled by VNT. But what should i use as LP turbos?

Option 1 would be to convert the GTB2260VK into GTB2565VK (with 51/49mm turbine wheel) and use them with fixed vane geometry, that could be manually adjusted in place (lets say PR 2.5 at full load to feed the HP-stage), and not touched anymore the VNT adjustment. Has anyone tried it with VNT turbos? This way i do not need any WG on LP turbo.

Option 2 would be to buy 2x GT30 turbos from 3.0Bitdi and use these instead. I think these have built in WG but then again, this would need some controlling.

With GT30 as LP, sequential setup would be possible, as i can map the gtb17 to open fully its vanes, lets say after 3000rpm, and use poppet valve on intake side to bypass the gtb17. Between GTB17 and the larger turbo, i would use Wastegate, controlled by intake pressure (or exhaust pressure?).

Theoretically i could probably use the intake swirl flap motor outputs (they are currently free as i eliminated swirlflaps) to build some sort of Map controlled bybass valve between turbos, but this adds complexity and not so easy to get working perfectly (im doing my own tuning) so wastegate would probably be easeir solution.

Ultimate goal for this project would be to get it the powerband as wide as possible with enough air for 700hp with clean lambda on a 8 cylinder engine.

I will add pictures of my current setup as soon as i find place where to upload pics. Please share your toughts about the new turbo setup layout.
 

TDIMeister

Phd of TDIClub Enthusiast, Moderator at Large
Joined
May 1, 1999
Location
Canada
TDI
TDI
There's no reason why you can't get 900 HP by doubling everything here:

The how-to were described in minute detail, what turbos to use, how to control them etc.

In a nutshell: I recommend using VNTs for both HP and LP, but using the same N75 PWM signal for both turbos simultaneously, then design compressor and turbine bypasses using a RaspberryPi controller (I personally think Arduino will be too underpowered and slow but other might have tried it with success). tdisyncro would be an invaluable help to you, but a lot of the knowledge is already in the thread.
 

adamss24

Veteran Member
Joined
Nov 2, 2005
Location
Great Britain
TDI
audi a4 2.5 tdi 98 quatrro 6speed
Most us mere mortals are happy with 200-300 Bhp…I wonder what speed freak are you that your appetite doesn’t get satiated with 600 Bhp ! Well, I would spend my money on a fast bike if I was you…good luck with your project, it’s insane !
 

altz1

Veteran Member
Joined
Jan 15, 2015
Location
Estonia
TDI
A8 4H 4.2TDI, Cayenne 4.2TDI, 6.0TDI
This car is heavy, 2540kg empty. It needs a lot of torque and power to get moving :) To be honest, im mostly doing it for the build process. As soon as things are ready, i get bored quickly or like in current case, start to look things i dont like about the end result.

Keeping both setups VNT sounds interesting, but would it give me any benefit? How about backpressure if both are in closed position during spool?
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
COLORADO (SE of Denver)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
This is crazy. Sub... please make some videos or at least tons of pictures. please
 

TDIMeister

Phd of TDIClub Enthusiast, Moderator at Large
Joined
May 1, 1999
Location
Canada
TDI
TDI
I'd suggest you leave the twin GTB2260VKs you have now and just add to them. You can use a pair of LPs attached directly at the turbine outlets of the HP or put a gigantic single above the bellhousing, whichever packages better for you.

With a custom controller you can modify the common N75 signal with a limiter (so that when the ECU commands the vanes to close completely, one of the stage's vanes will still remain open a certain amount to prevent excessive EMPs. Or you can have programmable variable PID gains or add a hysteresis so that each stage will get different vane opening strategies from a single common N75 signal. Lots of degrees of freedom to play with.

 
Last edited:

altz1

Veteran Member
Joined
Jan 15, 2015
Location
Estonia
TDI
A8 4H 4.2TDI, Cayenne 4.2TDI, 6.0TDI
Thanks for feedback. I would like to get the boost down to lower rpm/lower gears. Something similar to oem response with 1,2 and 3 gear. Perfect would be 2bar at 2000rpm climbing to 2.8-3 bar all the way to 4500rpm.

Original actuators are controlled by CAN so in case of LP being a VNT i would need to use just standalone controller for this stage. Do you or someone has developed something that could be bought?
 

altz1

Veteran Member
Joined
Jan 15, 2015
Location
Estonia
TDI
A8 4H 4.2TDI, Cayenne 4.2TDI, 6.0TDI
Soon will make new pictures, as the engine is coming out and turbos + transmission will get an update.
 
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