Wastegate/Actuator Discussion
- on April 06, 2020
- Categories: Tech Articles
What is a wastegate/actuator, what does it do, and when do I need one?
In short, the wastegate is a “gate” (or door), on the turbo’s exhaust housing, that opens up to redirect flow AROUND the turbine.
The actuator is a mechanism that “actuates” (or moves) this gate/door open or closed, based on the pressure sent to the actuator.
I’m sure most of you understand the basics of how a turbocharger works, and how we use them to make power. But just in case, here is a quick rundown: All turbocharges consist of two wheels; a turbine wheel and a compressor wheel. The turbine wheel is placed strategically in the exhaust path, so that the exhaust flow spins the wheel (like a windmill). The shaft connecting both wheels causes the compressor wheel to also spin at the same rate. The higher the exhaust flow, the faster the turbine wheel will spin, transferring that energy to the compressor side, generating positive pressure (or boost) under certain conditions.
Now that we understand the way a turbocharger works, how can we control the boost that it generates accurately? A very successful method is to divert some of the exhaust energy away from the turbine wheel, resulting in less energy transferred to the compressor wheel. Think about it, if the turbine wheel was always in direct path of exhaust flow, then when would the turbo stop building boost? Exhaust flow increases rapidly as your rpm’s increase to redline (airflow typically follows RPM). If this flow is increasing to redline, how does my boost stabilize and stay flat on my way to redline? Very simple! We place a door (wastegtate) between the exhaust flow source, and the turbine wheel. When that door opens, the exhaust flow will take the easiest path out the door, bypassing the turbine wheel. This in-turn decreases the energy transferred to the turbine/compressor wheels, and stabilizes boost pressure (if tuned correctly). So to recap, hold the door closed and build boost quickly, and open the door and boost will either stabilize or even decrease in some cases. How much the door opens, and at what rate, is going to vary by application.
The actuator is comprised of a sealed can (that connects to a boost source), and a threaded adjustable rod. The actuator is mounted to the turbocharger, and the rod is secured to the wastegate door. As the boost pressure in the vacuum line increases, the actuator/can reacts by extending the rod. The higher the boost pressure, the further the rod is extended (to a limit). Most actuators have a spring pressure rating around 5-7 psi (on Ford’s) and 12-15 psi (on Mazda’s). Typically at this (crack) pressure, is when the actuator will begin reacting. I have discovered that the OEM actuator is very responsive to small pressure changes (fully open at 8 psi), whereas the aftermarket actuators respond on a much broader pressure spectrum (fully open at 15 psi), and move much more smoothly. We will discuss this some more below.
So now that we understand how everything works, let’s take a look at the whole picture and get an idea on how it used in every day driving. As long as you are below the actuator spring pressure (95% of driving; idling, cruising, decel, free rev, etc.) the wastegate door will be closed, allowing you to quickly build boost as needed. Now when you do start building boost, once you reach the spring pressure of the actuator, the actuator pushes the door open. And the energy starts being diverted around the turbo, and boost stabilizes. Viola!
What about pre-load? What is that?
When the actuator is installed on the turbo, the threaded rod is secured to the wastegate door in a manner that is actually applying pressure on the door, holding it closed. In other words, think of a threaded rod controlling the operation of a door. Counter-clockwise rotations of the rod open the door, and clockwise rotations close the door. Now if you used that clockwise rotation of the rod to close the door, and then put 3 MORE FULL ROTATIONS on that rod, it would actually have force applied on the door holding it shut. THIS is preload. We want preload on the actuator so that we can build boost quickly and efficiently. If the actuator/door had some play, then boost would leak past the door when we did not want it to, resulting in poor boost performance.
When should I replace my actuator? (this applies to Ford vehicles only)
The Ford ECU uses very advanced calculations to determine desired boost pressure, and based off those calculations, it uses the wastegate to control boost. Ford engineers have spent countless hours building and developing these tables for consistency and accuracy. In my opinion, NOTHING is ever as good as OEM (as long as the system works correctly, lol). So for this reason, I like to stick to OEM logic as much as possible, and have used the same guidelines on all my Flash Tunes.
Some of you may have heard of something called CCF (or Cobb Custom Features). I am linking the document, if any of you would like to take a look at it. Cobb has found a way inside the ECU, where not only can we edit the OEM table data, but we can actually disable the OEM logic, and use custom tables that Cobb created and implemented into the original ECU! This is pretty amazing! It gives us features like map switching, LC, FFS enable, timing advance adders and subtractors, OAR starting points, and new wastegate control! For as long as the Ecoboost ECU’s have been tunable, tuners have constantly struggled with reliable and consistent boost control, due to the overly complex boost strategy. Cobb’s custom tables completely override the complex OEM strategy and allow you to enter data directly into an RPM/Pressure based table. I have avoided these custom tables at all costs, because like I previously mentioned, NOTHING is ever as good as OEM. Both my V1 and V2 Fiesta Flash Tune utilize the OEM logic.
Now, to go back to the actuator response I was mentioning before; I had said that the OEM actuator is very quick to respond to pressure changes, and the aftermarket actuators tend to move much slower and smoother to larger pressure changes. This response has a direct effect on boost control. The quicker responding OEM actuator tends to work well with the OEM logic, but not so much with the Cobb custom tables. The quick response can actually cause some boost oscillations. The aftermarket, slower responding, actuators tend to work well with the Cobb custom tables, and I do use these tables on all big turbo cars that I tune, as there is no other option at this time.
Why am I mentioning this? It has recently come to my attention that other tuners (and I will not mention any names) have actually refused to tune Ecoboost vehicles, unless they replace the actuator with an aftermarket unit, like Turbosmart. What does this tell me? This tells me that they are refusing to use the OEM logic tables, and would rather take a shortcut by using an aftermarket actuator, along with the Cobb custom tables. Rest assured that your Dizzy Tuning Flash Tune or custom tune has taken ZERO shortcuts.
I plan to do extensive testing on actuators over the next few weeks, and as always, will post up my findings. But of the dozen or so cars that I have tuned with aftermarket actuators, have made NO performance gains while running higher boost! So why risk the longevity of your engine and turbo, for no gains? Stay tuned for more info!
https://cobbtuning.atlassian.net/wiki/spaces/PRS/pages/86081651/COBB+Custom+ECU+Features
In short, the wastegate is a “gate” (or door), on the turbo’s exhaust housing, that opens up to redirect flow AROUND the turbine.
The actuator is a mechanism that “actuates” (or moves) this gate/door open or closed, based on the pressure sent to the actuator.
I’m sure most of you understand the basics of how a turbocharger works, and how we use them to make power. But just in case, here is a quick rundown: All turbocharges consist of two wheels; a turbine wheel and a compressor wheel. The turbine wheel is placed strategically in the exhaust path, so that the exhaust flow spins the wheel (like a windmill). The shaft connecting both wheels causes the compressor wheel to also spin at the same rate. The higher the exhaust flow, the faster the turbine wheel will spin, transferring that energy to the compressor side, generating positive pressure (or boost) under certain conditions.
Now that we understand the way a turbocharger works, how can we control the boost that it generates accurately? A very successful method is to divert some of the exhaust energy away from the turbine wheel, resulting in less energy transferred to the compressor wheel. Think about it, if the turbine wheel was always in direct path of exhaust flow, then when would the turbo stop building boost? Exhaust flow increases rapidly as your rpm’s increase to redline (airflow typically follows RPM). If this flow is increasing to redline, how does my boost stabilize and stay flat on my way to redline? Very simple! We place a door (wastegtate) between the exhaust flow source, and the turbine wheel. When that door opens, the exhaust flow will take the easiest path out the door, bypassing the turbine wheel. This in-turn decreases the energy transferred to the turbine/compressor wheels, and stabilizes boost pressure (if tuned correctly). So to recap, hold the door closed and build boost quickly, and open the door and boost will either stabilize or even decrease in some cases. How much the door opens, and at what rate, is going to vary by application.
The actuator is comprised of a sealed can (that connects to a boost source), and a threaded adjustable rod. The actuator is mounted to the turbocharger, and the rod is secured to the wastegate door. As the boost pressure in the vacuum line increases, the actuator/can reacts by extending the rod. The higher the boost pressure, the further the rod is extended (to a limit). Most actuators have a spring pressure rating around 5-7 psi (on Ford’s) and 12-15 psi (on Mazda’s). Typically at this (crack) pressure, is when the actuator will begin reacting. I have discovered that the OEM actuator is very responsive to small pressure changes (fully open at 8 psi), whereas the aftermarket actuators respond on a much broader pressure spectrum (fully open at 15 psi), and move much more smoothly. We will discuss this some more below.
So now that we understand how everything works, let’s take a look at the whole picture and get an idea on how it used in every day driving. As long as you are below the actuator spring pressure (95% of driving; idling, cruising, decel, free rev, etc.) the wastegate door will be closed, allowing you to quickly build boost as needed. Now when you do start building boost, once you reach the spring pressure of the actuator, the actuator pushes the door open. And the energy starts being diverted around the turbo, and boost stabilizes. Viola!
What about pre-load? What is that?
When the actuator is installed on the turbo, the threaded rod is secured to the wastegate door in a manner that is actually applying pressure on the door, holding it closed. In other words, think of a threaded rod controlling the operation of a door. Counter-clockwise rotations of the rod open the door, and clockwise rotations close the door. Now if you used that clockwise rotation of the rod to close the door, and then put 3 MORE FULL ROTATIONS on that rod, it would actually have force applied on the door holding it shut. THIS is preload. We want preload on the actuator so that we can build boost quickly and efficiently. If the actuator/door had some play, then boost would leak past the door when we did not want it to, resulting in poor boost performance.
When should I replace my actuator? (this applies to Ford vehicles only)
The Ford ECU uses very advanced calculations to determine desired boost pressure, and based off those calculations, it uses the wastegate to control boost. Ford engineers have spent countless hours building and developing these tables for consistency and accuracy. In my opinion, NOTHING is ever as good as OEM (as long as the system works correctly, lol). So for this reason, I like to stick to OEM logic as much as possible, and have used the same guidelines on all my Flash Tunes.
Some of you may have heard of something called CCF (or Cobb Custom Features). I am linking the document, if any of you would like to take a look at it. Cobb has found a way inside the ECU, where not only can we edit the OEM table data, but we can actually disable the OEM logic, and use custom tables that Cobb created and implemented into the original ECU! This is pretty amazing! It gives us features like map switching, LC, FFS enable, timing advance adders and subtractors, OAR starting points, and new wastegate control! For as long as the Ecoboost ECU’s have been tunable, tuners have constantly struggled with reliable and consistent boost control, due to the overly complex boost strategy. Cobb’s custom tables completely override the complex OEM strategy and allow you to enter data directly into an RPM/Pressure based table. I have avoided these custom tables at all costs, because like I previously mentioned, NOTHING is ever as good as OEM. Both my V1 and V2 Fiesta Flash Tune utilize the OEM logic.
Now, to go back to the actuator response I was mentioning before; I had said that the OEM actuator is very quick to respond to pressure changes, and the aftermarket actuators tend to move much slower and smoother to larger pressure changes. This response has a direct effect on boost control. The quicker responding OEM actuator tends to work well with the OEM logic, but not so much with the Cobb custom tables. The quick response can actually cause some boost oscillations. The aftermarket, slower responding, actuators tend to work well with the Cobb custom tables, and I do use these tables on all big turbo cars that I tune, as there is no other option at this time.
Why am I mentioning this? It has recently come to my attention that other tuners (and I will not mention any names) have actually refused to tune Ecoboost vehicles, unless they replace the actuator with an aftermarket unit, like Turbosmart. What does this tell me? This tells me that they are refusing to use the OEM logic tables, and would rather take a shortcut by using an aftermarket actuator, along with the Cobb custom tables. Rest assured that your Dizzy Tuning Flash Tune or custom tune has taken ZERO shortcuts.
I plan to do extensive testing on actuators over the next few weeks, and as always, will post up my findings. But of the dozen or so cars that I have tuned with aftermarket actuators, have made NO performance gains while running higher boost! So why risk the longevity of your engine and turbo, for no gains? Stay tuned for more info!
https://cobbtuning.atlassian.net/wiki/spaces/PRS/pages/86081651/COBB+Custom+ECU+Features
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