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.
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.
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. 
