Greetings,

Are there any boost controllers that drive the wastegate directly with a motor of some kind, rather than with the normal actuator?

It would be for an 89-91 turbo, though not exactly on a 2nd gen RX-7.

Thanks,
Rusty

 

ummmm?????

 

the 89-91 have a stock eletronic boost controller. by the oil filler neck.

if you are talking about moving the WG open and closed?? rather then contolling vacum to the the actuator. then no

 

I haven't seen anyone who sells an off-the-shelf boost controller using direct waste-gate actuation. Everyone has been standing behind the tried-and-true pneumatic actuators. I talked to some 'pros' about the idea, and they all gave me strange looks when I described the concept.

I'd like to experiment with it, but I haven't done the work. There're really two aspects: the actuator itself (and all the mechanical bits and pieces), and the controller.

If you went with a solenoid mechanically controlling things, you could pretty much repurpose anything off the shelf (e.g. PRofec), as long as you were careful about the current requirements of your new solenoid.

To me, stepper motors are a more interesting route, because you can carefully control the flow rate of exhaust gasses through the wastegate. I don't know if it'll end up being that useful, but it'd be fun to experiment with.

To go with a stepper motor, you're obviously going to need to develop a controller board to manage driving the stepper motor (not to mention actually hooking the stepper motor up to the flapper). If you've got any EE friends, and know some CS folks, you could cook up a controller board using off the shelf ICs, and basic prototyping techniques in a couple weeks of part-time hacking. Or if you know the software, but are scared of the hardware, you could repurpose a MegaSquirt or AVRMegasquirt to do such a task, using their idle stepper motor controller to control the waste gate instead.

After everything is said and done, you'll get a desk that looks like this .

 

Yep, that's what I was talking about. Stock actuators are all sprung at too high pressure for what I need, though I could attempt to modify one. If I could find an aftermarket unit that used some sort of servo motor to actuate the wastegate, that would eliminate one problem. The next problem is having it reference pressure to absolute, so altitude doesn't change the MAP.

Thanks for the useful reply.

 

Good answer

I've wondered about the concept with the RX-7, but never had a good reason to do anything about it, since the normal boost control methods work pretty well. However, the airplane is another matter

What I actually need to do, is have a controller that references absolute manifold pressure, and sets the boost based on that. In other words, 33 in MAP (3 psi) at sea level would still be 33 in MAP at 14000 ft. I can easily imagine some sort of servo motor that is controlled by a custom made circuit, while referencing MAP. There are at least a couple EE's on the rotary aircraft list, and I'm I can enlist their help. I'm an electronics tech, so this should be doable.

Thanks for the comments. I don't mean to drag the 2nd gen forum into aircraft turbo theory, but since I'm using a 2nd gen turbo, I figured it was as good a place as any to ask.

Thanks,

 

Yah, it sounds like it'd be an exciting project.


Let me introduce you to Motorola's fine line of resonably priced pressure sensors. What you're going to want is probably something like the MPX4250D. We've (my company) been using the MPX4250A for some of our boost control work, and I've been pretty happy with the results.
Send me an email if you want to talk more about this privately. It seems like an electronic boost controller for airplanes would be pretty useful for some people.