sawood12

Anyone know if servo controlled wastegates exist? This seems to me to be a far better way to control wastegates than relying on pressure signals that can be at risk from pressure leaks and blockages. I'm thinking an electronically controlled servo wastegate that is sprung open so in case of servo failure the wastegate fails in a safe position. There could be a piggy back system to control boost that reads the manifold pressure and opens the wastegate in a controlled way as per a user-defined boost profile. It could also be used to take the sting out when boost kicks in by slightly cracking open as the boost builds as a mode for use in wet or slippery conditions when the boost kick can catch you out. The control system could also be connected to the KLR computer so that when knock is detected it can open and provide protection.

Multiple boost profiles could be defined and made to be switchable from a switch in the cockpit. It would be a tasty piece of kit!

RKD in OKC

I think it would be expensive to get a solenoid that would last very long in the high temperature environment of a wastegate. Consider that both the stock boost control and electronic boost controllers are basically solenoids that send a pneumatic signal to operate the wastegate. In fact, you pretty much described the stock boost control.

ibkevin

"you pretty much described the stock boost control." yep, same idea behind Profecs settings.

Pauerman

I use a electronic solenoid to control my wastegate through my piggyback controller. I have the solenoid plumbed in a dual port configuration and my piggyback uses a 16x16 RPM vs Boost Pressure table to set the solenoid duty cycle. I've also wired a 3 Bar MAP sensor to my piggyback, so that's how I get my pressure reading. It's a really nice setup - very stable once you've plotted the boost curve.

The price of the piggyback I use is comparable to a good EBC and for all the added functions the piggyback offers (excellent datalogging, multiple PWM outputs, etc) it was a far better choice when I was looking into boost control options.

DanG

The original poster isn't talking about EBC, he's talking about a wastegate that is DIRECTLY acted on by an electronic solenoid or servo. There is no pneumatic wastegate can or actuator, the wastegate valve is moved by an electromechanical device only. Its easier to picture this on an internally gated turbo with a poppet valve arm + pneumatic actuator than the external wastegates found on our cars.

This is a cool idea, but the pneumatic actuator has been proven out to work so well that its really not worth the expense and hassle. You can accomplish almost the same level of control using a simple EBC/pneumatic actuator setup. Sure you could make an electronic servo do wild things that the EBC couldn't, but it wouldn't gain you any real advantages as far as control of a turbo goes.

gt37vgt

its not complicated pneumatics so its still pretty reliable anything you could do with the servo can be done without it with a couple of soliniods and a dual port gate

sawood12

I was thinking that you might be able to get more precise control with a servo. The downside I can see with the pnuematic system is that you cannot apply higher pressure than the intake manifold pressure to open the gate. If you had a motor driving a cam directly onto the valve you have total and direct control over the opening of the valve and should give you more fine tuning capabilibty. The EBC's don't actually directly control the wastegate pressure signals, if for some reason you have to open the wastegate but manifold pressure isn't enough to do that then you are screwed.

If i'm honest I still don't fully understand the cyling valve function in relation to boost control. I understand that the KLR can switch the cycling valve to expose the wastegate pressure input to the full manifold pressure to fully open it but what pressure signal is the wastegate pressure input exposed to under normal circumstances?

I accept that the environment is not condusive to electromechanical devices though.

NeoRules

I would think a spring loaded waste gate that failed to the open position would be the place to start.
Then use a solenoid to pull the waste gate shut when the ignition switch is activated...
There are many systems that could be used to employ this technique but the issue of weight and current draw become a problem.
As heat increases in the solenoid the resistance goes up. And as the resistance goes up so does the heat. In that environment it could be a serious problem. That is one reason electromechanical valves aren't used in combustion engines much. They would be hella fast and timing would be all electronic but they would weigh a lot and be prone to failure. The faster they activated the more heat they would generate blah blah... POOF...
But something small with little mass to move like an injector isn't so bad. Those have a spring to keep them closed and and have fuel pressure trying to open them.. A smaller solenoid could give the extra umph needed to open it without drawing much current as the fuel pressure is helping a lot.
And since they are supposed to fail to the closed position it is a nice arrangement.

It's not the amount of pressure you are fighting in the wastegate but the size of the valve and it's close proximity to the heat.

But on the other hand there are many valves that would work in place of the waste gate. I will get a couple of links once I figure out the temps we are working with. What is the spring pressure required to keep the valve closed?


Just my 2 cents... take my comments for what they are worth
JC

eniac

My guess would be at least what your back pressure is inside the crossover pipe. If you have 30psi of pressure then you need a spring that's at least that. At least that sounds reasonable to me.

smkn951

wouldn't the pressure constantly build on a servo actuated as opposed to a spring controlled wg?
i think the simplicity of the design is really good. spring rate adjust to the rapid change in exhaust pressure. just my .02.

Fishey

The easiest way to do it would be to write a program for it and use a map sensor. As the boost level reading is being is being changed by the map your computer could change the output to the servo controller, controlling boost.