Bluedemon_II
New member
I'm starting this tread to compile information to generate knowledge and understanding of the requirements to implement a VGT turbo setup on an sti or a EJ25 equiped subaru for that matter. Ill start with a brief explanation.
Brief Explanation:
A variable geometry or variable nozzle turbo is equipped with a special exhaust housing that allows change in the volumetric size of the turbine area threw an actuating mechanism that is proprietary to each turbo manufacturer. The system works by moving a set of vanes that will enlarge or contract, open or close, to allow a change in the exhaust gas flow thus affecting turbine impeller velocity. This is the main way to control boost and turbo spool times in this turbo chargers.
Availability:
As some of you might have noticed, vgt is only used on the most rare of oem setups. Take for example the very exotic Porsche vgt turbo using materials that are state of the art. You will mostly find Vgt setups on Diesel operated engines. This turbos offer the capability to become an effective engine brake when couple with other parts in the exhaust system. For reference on engine brakes please fallow this link :> http://auto.howstuffworks.com/auto-parts/brakes/brake-types/engine-brakes.htm
Design issues:
If you have connections and deep pockets you might be able to find a Porsche vgt turbo to work with your setup. Sadly the rest of us wont. This will leave you with 2 options: Use a garret vnt turbo or use a diesel engine vgt turbo. As any one that works with a diesel engine will tell you, Egt vary from one fuel source to an other. Diesels for the most time burn at colder egt than a gas operated engine. This means that the structural and operating components in the turbo will be subject to grater thermal stress. To put it simple, something can or will melt if Egt get out of control on a normal diesel designed turbo. On the garret side of things, their vane control is flawed. Their exists to much slack in the vanes to allow them to move when the materials undergo thermal expansion, this in turns allows build up of carbon deposits on an area that cannot be self cleaned. What happens is that the vanes slowly begin to get stuck, regular inspection of the vanes is required. The system uses a mechanical actuator that leaves some users wanting more control.
Introducing the Holset Vgt:
The holset turbocharger model HE351 uses a different Technic to control and actuate the vanes. The holset only uses about 3 points of movement to control the vane actuation. This system is more robust than any other in the market at the current time. From here on after this thread will concentrate on this turbocharger. If any other comes to my knowledge I will make changes accordingly, if it can be implemented.
Here is a cut out of the turbo "notice that this turbo presents a pneumatic actuator for the vgt vanes, the HE351 uses an electronic actuator":
The HE351 was designed above and beyond the capabilities of a normal ranges of operation for a diesel engine turbo. It's complete construction relays on the fact that its going to see high load scenarios for sustained periods of time. Holset claims that on the HE line of turbos, they used cast aluminum compressor wheels and a inconel alloy for the turbine. I my self will confirm this on a future time when I'm able to use a metal analyzer to see what alloy comes up in the scanner. As of now materials remain unconfirmed by the end user.
The turbo impeller shaft takes a different approach to the conventional design. The shaft is larger towards the exhaust side, this design offers a more robust design on critical control points. No other turbo has this type of design, it has proven it self on the holset HX and HE family of turbochargers.
This turbo is water and oil cooled, and the 2 can be used on an STI. I plan on implementing them to control turbine temperatures. If temperatures become a persistent problem, a small cooling unit can be attached at the inlet line. I don't think that this will be a problem but I'm prepared to make the adjustments.
The turbo vgt vanes are actuated by an electronic microprocessor that controls a brush less bipolar motor that is equipped with hall effect sensors to measure the motors shaft current position and thus relaying information of the vanes position to the processor. The turbo also has a bigger Speed sensor "also hall effect" that measures shaft speed. This is used by the ecu to control turbo speed by opening or closing of the vanes. The controller itself has enough electronics inside of it to act independently of any vehicle ecu, it just needs the inputs of some reference sensors to work.
The problem is that the controller uses Holset by Cummings proprietary commands that some have tried to crack and or talk to the unit with out success.
This rises the issue of finding a method to control the vgt vanes.
Vane control:
The biggest issue with using this turbo is to find a way to control the vgt system successfully. This will be a problem depending on the level of control that you require/want. My research has lead me to varius methods of control that have the up's and downs.
Current ideas and methods of control:
Turbo Size:
The HE351 is not for the faint of heart. This turbine is capable of supporting 600+whp on a subaru with out braking a sweet. It has a 63lb/min compressor capability. The exhaust side sports an ar of .35 fully closed to about 2.01 fully open. This is about 4cm^2 to about 25cm^2.
A turbo of this size would be spooling at about 5000 rpm on a normal setup. On an inline 2.0 engine this turbo is capable of making 15 psi at about 3,000rpm and full boost at about 4,000rpm. It spools considerably fast thanks to the vgt. This means that you could have that fast spooling, top end monster that most dream off. This is what I'm aiming for.
Here is a the only compressor map that I have found available on the web:
I'm going to try the next big thing, contacting Holset to see if they are willing to publish or confirm this is the real compressor map.
Keeping up with updates.
Brief Explanation:
A variable geometry or variable nozzle turbo is equipped with a special exhaust housing that allows change in the volumetric size of the turbine area threw an actuating mechanism that is proprietary to each turbo manufacturer. The system works by moving a set of vanes that will enlarge or contract, open or close, to allow a change in the exhaust gas flow thus affecting turbine impeller velocity. This is the main way to control boost and turbo spool times in this turbo chargers.
Availability:
As some of you might have noticed, vgt is only used on the most rare of oem setups. Take for example the very exotic Porsche vgt turbo using materials that are state of the art. You will mostly find Vgt setups on Diesel operated engines. This turbos offer the capability to become an effective engine brake when couple with other parts in the exhaust system. For reference on engine brakes please fallow this link :> http://auto.howstuffworks.com/auto-parts/brakes/brake-types/engine-brakes.htm
Design issues:
If you have connections and deep pockets you might be able to find a Porsche vgt turbo to work with your setup. Sadly the rest of us wont. This will leave you with 2 options: Use a garret vnt turbo or use a diesel engine vgt turbo. As any one that works with a diesel engine will tell you, Egt vary from one fuel source to an other. Diesels for the most time burn at colder egt than a gas operated engine. This means that the structural and operating components in the turbo will be subject to grater thermal stress. To put it simple, something can or will melt if Egt get out of control on a normal diesel designed turbo. On the garret side of things, their vane control is flawed. Their exists to much slack in the vanes to allow them to move when the materials undergo thermal expansion, this in turns allows build up of carbon deposits on an area that cannot be self cleaned. What happens is that the vanes slowly begin to get stuck, regular inspection of the vanes is required. The system uses a mechanical actuator that leaves some users wanting more control.
Introducing the Holset Vgt:
The holset turbocharger model HE351 uses a different Technic to control and actuate the vanes. The holset only uses about 3 points of movement to control the vane actuation. This system is more robust than any other in the market at the current time. From here on after this thread will concentrate on this turbocharger. If any other comes to my knowledge I will make changes accordingly, if it can be implemented.
Here is a cut out of the turbo "notice that this turbo presents a pneumatic actuator for the vgt vanes, the HE351 uses an electronic actuator":
The HE351 was designed above and beyond the capabilities of a normal ranges of operation for a diesel engine turbo. It's complete construction relays on the fact that its going to see high load scenarios for sustained periods of time. Holset claims that on the HE line of turbos, they used cast aluminum compressor wheels and a inconel alloy for the turbine. I my self will confirm this on a future time when I'm able to use a metal analyzer to see what alloy comes up in the scanner. As of now materials remain unconfirmed by the end user.
The turbo impeller shaft takes a different approach to the conventional design. The shaft is larger towards the exhaust side, this design offers a more robust design on critical control points. No other turbo has this type of design, it has proven it self on the holset HX and HE family of turbochargers.
This turbo is water and oil cooled, and the 2 can be used on an STI. I plan on implementing them to control turbine temperatures. If temperatures become a persistent problem, a small cooling unit can be attached at the inlet line. I don't think that this will be a problem but I'm prepared to make the adjustments.
The turbo vgt vanes are actuated by an electronic microprocessor that controls a brush less bipolar motor that is equipped with hall effect sensors to measure the motors shaft current position and thus relaying information of the vanes position to the processor. The turbo also has a bigger Speed sensor "also hall effect" that measures shaft speed. This is used by the ecu to control turbo speed by opening or closing of the vanes. The controller itself has enough electronics inside of it to act independently of any vehicle ecu, it just needs the inputs of some reference sensors to work.
The problem is that the controller uses Holset by Cummings proprietary commands that some have tried to crack and or talk to the unit with out success.
This rises the issue of finding a method to control the vgt vanes.
Vane control:
The biggest issue with using this turbo is to find a way to control the vgt system successfully. This will be a problem depending on the level of control that you require/want. My research has lead me to varius methods of control that have the up's and downs.
Current ideas and methods of control:
- Wastegate actuator- There are setups out there that strip away the electronic controller to expose the vgt actuator shaft. Fabricating a bracket, you install a wastegate actuator with the psi that you want the vanes to react to. Mot people use an actuator that will start its movement at about 12 to 14 psi. This is to allow the turbo to enter a fast spooling stage and make the transition to a slower spool up top. The draw backs of using this method is that the system will be static, you will not be able to make any adjustments based on electronic inputs. The switch point will always be the same. It will be predictable but it lacks control options.
- Electronically controlled motor: By far this would be my preferred method of vane control. There are many setups that I can think off to control this, I am only limited by my ic programing knowledge "0" I can build a circuit using a schematic and have basic electronics knowledge. Still if you can source a pair of helping hands this can be an easier task.
The HE351 comes equipped with an array of hall effect sensors to monitor the brushless motor, this is the main way to reference the vanes position on the stock setup. You could use a variable potentiometer attached to the motor shaft and use that to reference the motor position if you are unable to tap and read the sensors. You can actuate the motor by using the input signal from a map sensor, tps, maf etc. You could program the vane position to open gradually in response to this signal. This simple setup would work by adjusting the motor constantly depending on the potentiometer or hall sensors. Problems whit this simple setup, if the vanes get pushed back by the back pressure in the exhaust system your motor adjustment will be wrong to begin with. The Ic will see the current vane position but if you don't implement a correction logic in the code, it simply wont work. This means that for an electronic controller to work you will need to implement a PID correction method to be able to keep the vanes in check.
This is easier said than done and requires extensive code programing and knowledge. If you have someone with the capability I have an even better sensor data reference input for vane control, the hall sensor monitoring the the turbine shaft speed. It is theorized that the most efficient impeller speed for the HE351 is about 111,400 rpm. If you can monitor the shaft speed with the hall effect sensor you can program your vane control method to keep the turbine speeds in this area, staying at the efficiency islands of the compressor map. The HE is capable of making 50psi of boost and still be in an efficient range of the compressor map.
Turbo Size:
The HE351 is not for the faint of heart. This turbine is capable of supporting 600+whp on a subaru with out braking a sweet. It has a 63lb/min compressor capability. The exhaust side sports an ar of .35 fully closed to about 2.01 fully open. This is about 4cm^2 to about 25cm^2.
A turbo of this size would be spooling at about 5000 rpm on a normal setup. On an inline 2.0 engine this turbo is capable of making 15 psi at about 3,000rpm and full boost at about 4,000rpm. It spools considerably fast thanks to the vgt. This means that you could have that fast spooling, top end monster that most dream off. This is what I'm aiming for.
Here is a the only compressor map that I have found available on the web:
I'm going to try the next big thing, contacting Holset to see if they are willing to publish or confirm this is the real compressor map.
Keeping up with updates.
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