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NISSAN PATROL Y61 3.0 Di (ZD30) 09/2000
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Discussion Starter #21 (Edited)
With comments and notes :

EDIT : the pwm range is a bit different from the ZD30, but close. May be the actuator, or the solenoid, or ... ? are slightly different. I would need to check in the archive. That curve would not work on a zd30 as with the stock configuration, the lever hit the limiting screw (max vanes aperture) with less than 55.9% pwm. (with Solenoid to ground through Mosfet).
Nota : Digibooster does NOT do this at all, very far from, and is very very simplistic. pwm (VNT) tuning must be done by as little as 0.1% pwm variations ! You now understand better why I threw it to the bin.

517075
 

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Phdv61, a great discussion. I have a TD42T, but I still find the data and graphs interesting. On the turbo efficiency graphs, I thought the pressure ratio was the ratio between EMP (turbine back-pressure) and boost pressure, not ambient pressure vs boost.
 

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On the turbo efficiency graphs, I thought the pressure ratio was the ratio between EMP (turbine back-pressure) and boost pressure, not ambient pressure vs boost.
The vertical axis represents the pressure ratio of the compressor. It is calculated by taking the absolute outlet pressure and dividing by the absolute inlet pressure. Pressure ratio is used instead of boost because atmospheric pressure changes with altitude / weather conditions and inlet conditions can be variable with filter and pipework restrictions.

This map and all generic comp maps you see from manufacturers are only focusing on the compressor and doesn't care about what the turbine is doing other than its associated shaft speeds. EMP:IMP is something tuners use and graph themselves on individual vehicle setups.
 

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NISSAN PATROL Y61 3.0 Di (ZD30) 09/2000
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Discussion Starter #24
Phdv61, a great discussion. I have a TD42T, but I still find the data and graphs interesting. On the turbo efficiency graphs, I thought the pressure ratio was the ratio between EMP (turbine back-pressure) and boost pressure, not ambient pressure vs boost.
@AusRoamer ,
I fact, although this is for a 3.0CRD, I also provided lots of my "findings" for my own ZD30.
All these principles are applicable to any VNT. But you need to have access to a minimum number of sensors to be able to 'tune' your air, the same way remappers tune diesel.

On older cars, very often you don't have RPM, MAF, and MAP data through an interface you can acquire data from.
So you need to develop your own to some extent. Graphs talk better than gauges and list of hundreds of data.
Then, it is 'just' a matter of time and effort, and many trials.

At the same time, controlling an electronic IP diredtly on an older car may not be very complex, as sometimes they just have a 'diesel volume' solenoid which is simply controlled by a pwm signal, the same way the vacuum solenoid is.
Here too, it would be a matter of recording TPS, MAP, MAF and pwm orders to the pump solenoid, to understand how it is managed and then modify the pwm control to increase fueling when it is 'required'. It is the case of the 6 CYL TD 2,8 T -

I have been exchanging with one of you who owns a DT2.8T, and has a plan to do so He started to develop a simple acquisition system based on an Arduino. If I had one, I would too replace the wastegate turbo by a VNT turbo, and do this. May be your DT 4.2T is similar ? I don't know.
 

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NISSAN PATROL Y61 3.0 Di (ZD30) 09/2000
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Discussion Starter #25 (Edited)
To mimic what the ECU is doing on a CRD, this is the arrangement I would suggest :

One needle, quite closed, between boost hose from the IC and actuator hose. Quite closed to provide 'gentle' boost flow inside the vacuum hose of the actuator, and therefore slow opening of the vanes down low.

IN PARALLEL, A dawes or Tillix, + Needle behind it (on the actuator hose side), with Dawes/Tillix set to open at 450 mbar, with the needle behind controlling the quantity of positive flow pouring into the actuator hose.

The opening of the dawes will provide a quick raise - EDIT : DECREASE ! - of vacuum needed to open the vanes rather quickly so as to reach the mid-aperture of the vanes. The accurate setting of the Needle will define the maximum boost which can be reached at higher Revs.

This arrangement will be quite close to what is needed. And close to what I I believe is needed on a ZD30 too, as explained elsewhere.

The same can apply to any VNT, providing it has a vacuum actuator, and vacuum/boost references available 'on board'.
 

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Thanks for the clarification guys. I’d like to instrument my setup and contribute, but time is my enemy at the moment..
 

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To mimic what the ECU is doing on a CRD, this is the arrangement I would suggest :

One needle, quite closed, between boost hose from the IC and actuator hose. Quite closed to provide 'gentle' boost flow inside the vacuum hose of the actuator, and therefore slow opening of the vanes down low.

IN PARALLEL, A dawes or Tillix, + Needle behind it (on the actuator hose side), with Dawes/Tillix set to open at 450 mbar, with the needle behind controlling the quantity of positive flow pouring into the actuator hose.

The opening of the dawes will provide a quick raise - EDIT : DECREASE ! - of vacuum needed to open the vanes rather quickly so as to reach the mid-aperture of the vanes. The accurate setting of the Needle will define the maximum boost which can be reached at higher Revs.

This arrangement will be quite close to what is needed. And close to what I I believe is needed on a ZD30 too, as explained elsewhere.

The same can apply to any VNT, providing it has a vacuum actuator, and vacuum/boost references available 'on board'.
It's interesting that you an I have come to a similar set-up regards the dual needle and Dawes controller ( I know you have moved on to an electronic controller now). I initially started trialling a restriction in the boost side using a MIG welding tip with different apertures 1.2 through to 0.6mm to test the effect of reducing boost volume entering the valve and the vacuum side in an attempt to stop boost bounce as the valve opens changing pressure and vacuum far too aggressively. The restrictions did work, but I felt that it needed to be even more restriction than the smaller size MIG tip I had available and ideally adjustable. I also tried to increase volume on the vacuum side using a small fuel filter just after the Dawes also in order to lessen the sudden change as boost pressure enters into the vacuum side. So that is when I went to another needle valve.

I think I need to have more testing of the adjustment as you suggest, try a much lower Dawes valve opening pressure. I have mine set at approximately 15 psi gauge pressure where you are suggesting as low as 6 psi and to use the needle restriction to allow boost to still rise above that set point. I set the valve using a regulator and gauge on the bench, but that does not take into account the vacuum effect on the other side of the valve pulling it open, so actual opening boost I know will be less than my set pressure. I might try adjustment with also including the vacuum connected at idle speed and slightly higher revs.

Anyway, here is the interesting part, I have also been monitoring temperature with a surface contact probe at the turbo outlet, on the first metal pipe to avoid measuring heat soak of the turbo compressor body itself. In addition, I monitor temperature after the intercooler to see how effective it is.

I have the second needle valve for vacuum bleed mounted in cabin which allows me to adjust boost both rate of increase and maximum from in cab under different driving conditions towing, or cruising etc. Temperature of the turbo outlet is very responsive to high boost 15 psi or higher and particularly at high sustained boost levels at cruising freeway or highway 100 to 110 km/h. At 100 km/h if I adjust sustained cruising boost above 12 to 15 psi then the outlet temperature quickly rises above 100C. Maximum I have seen so far was 145C when passing a truck on the highway holding over 18 psi probably up to 25 psi for a short burst under load for a good 45 seconds or more reaching around 130 km/h in passing.

I believe as you are suggesting above the turbo is reaching the maximum range of its efficiency and producing more heat than volume at higher boost levels. Boost, I measure after the intercooler in the inlet manifold plenum to take account of the cooling effect or pressure drop. Post cooler temperature I measure at the piping between the intercooler outlet to the intake manifold, this climbs quickly to around 50 to 55C under hard load conditions but recovers to 40C or below fairly quickly afterwards (this was with around 30C ambient temperature).

Cruising at 100 km/h turbo outlet temperature will only remain under 100C if I open the needle valve to reduce sustained boost to below 12 psi. Longer periods held at 100 to 110 km/h become progressively harder to keep turbo outlet below 100C. Possibly heat soak is an issue despite my insulation and other temperature control efforts.
 

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NISSAN PATROL Y61 3.0 Di (ZD30) 09/2000
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Discussion Starter #28
All what you say is coherent with all my findings, and the "books".

If you use your turbo as a compressor, with 'less hot air volume' going into the cylinders, your turbo has clearly a reduced efficiency and provides 'heat', like any air compressor.

As I have said (written in fact) here all the time, despite what some apparently still (wrongly) believe, the one dawes or one tillix and one needle arrangement is NOT ideal, very far from. It forces you to reduce spool-up, and keep the vanes closed all the time, converting your fantastic VNT into a sort of two stages wastegate turbo. A nonsense.

Some still seem to be happy seing high boost. on their gauge, whilst others have already changed their arrangement.
Airflow is what matters !

Thank you for sharing your valuable information.
 

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NISSAN PATROL Y61 3.0 Di (ZD30) 09/2000
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Discussion Starter #29 (Edited)
I have used some of my time staying at home to investigate a bit more what my ECU was doing, or trying to do before I embarked on doing my mods. Unlike the CRD, on which the vanes management seem to have been improved, even if some artefacts can be seen on the PID used for boost regulation on the data provided ( but it works ok if you don't apply mods... of course), the ZD30 vanes mangement is a bit more "rudimentary".

Here is an old record where I had recorded most parameters provided by ECUtalk, on a long slope going from 0 to 80km/h, from gear 1 to 5. I have extracted gear 2 to 3, to 4 to have a look at what the ECU was doing with the vanes.

I will not comment anymore. This is only for your perusal. That did provide me with further ideas to improve my own electronic vanes mangement a bit more. In particular, look at the flat portion at 33% pwm when accelerating continuously from 2500 RPM on ( and whilst the boost/airflow is building up).

The little bumps in airflow, when accelerating after a change of gear, are similar to the ones seen on the CRD, and correspond quite certainly to little bumps in boost, like on the CRD. It is an effect of the vanes management strategy used by Nissan/Bosch engineers.

517315


I like that one ( self explanatory)
VNT Turbo SV1 provides the PWM value sent by the ECU to the Solenoid. It gives you the level of vanes opening (vs RPM on this graph)
55.9% fully closed 20% fully open.

517320
 

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That second graph layout is sweet, can't get enough of this stuff! Can really see what's going on with the vanes while following along the plotted line
 

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NISSAN PATROL Y61 3.0 Di (ZD30) 09/2000
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Discussion Starter #31 (Edited)
You start in 2nd, end of acceleration starting at 2700RPM. Vanes position is 33%pwm ( 2/3 open roughly).
you continue to accelerate, up to 3100. pedal up. RPM continue to go up a bit whilst the ECU opens widely the vanes ( pwm 20%). then, follow the green line, and the comments.

Edit : ooups. Sorry, I misread "can't" instead of 'can'. Hence my reply. Apologies.
 

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Discussion Starter #32 (Edited)
I wanted to re-check that the ECU was opening the vanes for 250-300ms when changing gear. It does on my ZD30. That supresses any weird noise when you have an agressive spool-up. You can't do that with valves ( unless you add an electric valve and some electronics to create that 'pedal-up' effect). @OldMav explained this. closing the vanes too quickly when all exhaust gaz are not yet gone creates 'stress' on the turbo.
With one dawes and one Needle only, unless you reduce spool-up by opening the needle, you may welll hear that noise...
Add a second needle as advised, and reduce opening pressure of your dawes/Tillix to fix and increase airflow !
 
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