It doesn't matter how obscure MS is, you didn't even say that and I didn't imply you did what you did say was the control method of configure able pwm tables is obscure, infact it is standard and expected on all standalones these days.
Yes you can easily buy servos that powerful that are also super fast.
They are, of course, relatively slow. Not sure if "slow" in the world of robotics is the same as "slow" in the world of engine management. I've never actually logged the operation of an EBC to see how rapidly it makes large changes in commanded position.
I'm the servo torque matter, I'd been considering the waste gate valve being under pressure, but in reality it's just under whatever pressure the exhaust exerts, correct? If so it should be real low force. I'd probably try one of the servos without gear reduction and see if it has the guts. Return spring plays into that force of course.
And be sure to keep them way away from the turbo, those plastic cases will turn to soup if you don't.
Unless you can link to the waste gate with a rigid linkage you'll need a return spring of some kind to close the waste gate. Whether it's built in or not in not sure (i know motion control stuff, not turbos). I've always assumed you'd end up needing a cable to move the actuator away from the turbo.
Servo at 0% duty cycle holds the wastegate shut. Servo at 100% duty cycle holds the wastegate open.
it's simple, but not that way
every 20 ms you can send a pulse from 1 to 2 ms
1 ms = 0°
1.5 ms = 90° etc
the servo can rotate from 0 to 180°, but near the limit is a little flappering, even for the expensive units
I don't know how to write ms codes, but I think it can be done.
I've got some 16 kg (35 lbs) servo with metal gears, they are very powerful: if I hold a position I can't move it with my hands!
sadly I have a rev ms2 unit: I don't want to add the hardware for the servo...
you need a 5v power supply for the servo up to 1.5 A (an indipendent one is better) and the logic level pulse for the servo signal (before the mosfet or whatever you are using to drive the ebc solenoid)
please, someone make it!
the heat is not a problem for a pull or two, you are just testing. If it works: heatshield.
The late EA888 engines from VAG (audi,vw, etc) using IHI turbos with electric wastegate and electric dump valve. I'm using the middle size turbo from this series on my miata ( around 300hp at 1,5 bar). I had to remove the wastegate motor, because of the lack of specific controller in my aftermarket ECU. The electric BOV integrated into the cold side housing. My ecu can drive it, it's much better than the mechanical one. (only ON or OFF state, unlike the mechanical one)
Interestingly there are 2 different size/type from this wastegate servo motor. The smallest turbo, using smaller wastegate controller motor, the bigger ones using the same big robust one. On the small one, the return spring keeping the wastegate flap closes, on the big one it's the opposite. It's interesting they made such change... I disassembled the big one , attached several pictures.
It seems to using a simple driving mechanism with a return spring, and a magnet and magnetic field position sensor for feedback. The return spring keeping the wastegate flap open, without a control signal.The motor is quite strong. I planning to scope a the control signal in an OEM car in the future, to see how it's driven.
It was a 12V DC Servo with a potentiometer for feedback. The ecu I had at the time was able to control it via a 2D table (using MAP) or 3D one (MAP and RPM). I used a 2D table, basically opening the wastegate fully during low loads, then keeping the wastegate closed untill just below the target boost, and then tapering the valve open. This worked very well. Turbo spoolup was improved, Economy was a tiny bit improved, but my favorite part was that I was able to run any boost level I wanted quickly by adjusting a few parameters. I could turn the boost down all the way to zero, or run as much boost as I wanted to.
Eventually one of the butterfly valves I used failed, and the entire thing was binned. I think I'll build something similar again, but using a much more durable wastegate valve. The oem option above looks promising!
I'm not sure what motor it uses or what the feedback signal is, but if it's just a 12V motor with 0-5V feedback maybe this is a suitable and affordable controller:
Why not use an electronically controlled 4-port solenoid. I've read about this a lot on the Honda forums. I think connecting a servo to a glowing turbo would be a bad idea unless you could find some reliable way to stop it getting cooked.
Here is a diagram that Jaydee made for a twin supercharged K24.
He's using a MAC 4-port solenoid to control a 38mm Tial wastegate which looks to be very successful. He's running boost by gear and can dial in max boost via his steering wheel. I think you need to run a lighter spring in the wastegate so that you get a good range of adjustable PSI.
A setup like this is what I want to run when I upgrade to a Rotrex.
Before I go buy a 4 port MAC and a 2 port actuator, has anyone gotten anywhere on this?
I've got some of the 1/4 scale super cheap hobby servos and would be willing to give it a go. I'd probably just start with a separate uC with a pressure sensor to save the trouble of trying to get the MS to do it to prove if works well or not.
If I were to try it I would use some stupid long linkage. And then a uC. I wouldn't use a pressure sensor though. Just translate DC from the MS to output position. Then boost control should still work fine.