Solenoid Actuators
Turbo Mini Forums

Has anybody ever seen an electric solenoid used as an actuator? I was just thinking about boost control in different gears and at different RPM and what a pain it is to plumb into a pneumatic actuator.

For example if you have a 10psi actuator you can never run less than 10psi and the spring might not be strong enough to hold onto 25psi. However if you have a solenoid acting directly on the wastegate then you can just switch it on and off whenever you want from 0psi to infinity. This will obviously rely on having a separate electronic box of tricks, but this is no big issue these days.

Has anyone tried this? Am I overlooking an obvious reason why this is not done. Please don't say because if it fails you will overboost, because this is the same as a pipe disconnecting, which is all to common. Solenoids are simple electro mechanical devices, and in my eyes perfectly suited to the job.


Ben

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

I have beeen thinking about this as it looks particuarly applicable to VNT's,

The only problem with the solenoid is that it is effectly an on-off switch, although you can get some to oscilate at high frequency and achive some form of control by varying the frequency.

How about using a stepper motor. The stepper motor that I use for idle control off a peugeot can be bought for a few quid yet has a lot of potential. It winds in and out under control from the ECU.

The control would be a bit more complex but I would have thought it could be configured for a simple control circuit without a logic controller.

Just an idea.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I was also thinking about that Paul,

I have a cheap stepper RC motor on the way to me that I was going to have a play with,

I'll stick some of my thoghts down when I get home and get a beer in my mitts.

Taking both Joe and Paul's points, so far as I'm aware the modern turbo diesels with VNT use a stepper motor to move the guide vanes (the guide vanes being the VN* bit of the turbo).

My Mondeo TDCi piece of cr*p has a conventional actuator on the guide vanes but the year after mine used a stepper motor.

Not sure if a wastegate could be driven fast enough by a stepper motor though, or if a stepper motor could cope with the mechanical loads ???

Schrödinger's cat - so which one am I ???

I know what you are saying paul, but a normal actuator with either an electronic boost controler or a MBC is effectively a switch too. Think about 10psi actuator only seeing 15psi as the MBC opens, I bet it opens very quickly. So from a control point of view I can't see a problem. It will osscelate a little as normal actuators do.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Ok,

I came across this a while ago....

http://www.msextra.com/forums/viewtopic.php?f=67&t=18971

It enables a 4 wire stepper (such as the pugeot, ford or fiat idle stepper) to be driven from a PWM MS idle signal.

I was thinking at the time that it may enable me to control the VNT using an idle stepper from the megasquirt boost control map.

for conventinal wastegates I think the simple solenoid may work quite well working against a sprung wastegate, after all you can get fairly strong solenoids cheaply, i'd imagine an equivalent stepper would be pricey.

i think something like this could drive a solenoid, and in turn could have a pressure sensor pluged into the input rather than the pot. you may find that it oscilates though.

http://www.discovercircuits.com/PDF-FILES/SIMPLEPWM2.pdf

Edited by Joe C on 18th Feb, 2010.

But isn't wastegate control somewhat modular in so much that the actuator sets the wastegate position so that it achieves the set boost? It is not a simple open or closed situation, or is it?

I always thought that the wastegate actuator only opened the wastegate as far as it needed and then effectively modulated to control the boost.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

yep, hence the 555 doing a voltage to PWM conversion above,

I'm thinking as boost rises a pressure sensor tells the 555 to increase the PWM signal, which in turn moves the solenoid,

In pracice it may well not wok like that though.

Would heat be an issue? I'm not sure how long a linear actuator would last if you stuck it next to a turbo.

I've considered this in the past, you could have a long actuating arm to position the solenoid away from heat. Would be great to have so much control over boost.

Not to repeat myself, but just consider the MBC control, surely an open and shut case.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

not quite Ben,

I belive the MBC itself is open or shut, but when it is open the actuator then works in a linear fashion from that point on.

That's what I thought. The MBC just fools the actuator which carries on doing a simple control loop but at a different boost level.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

my concern here would be exhaust gasses pushig the gate open, affecting asolenoid, a servo would be un affected. its quite a substancial force, especially if a small turbo is used!!

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

whats a wastgate hole diameter? about 3/4"?

that equates to 1.75 sq inches,

if we assume TIP= 2x boost, and boost = 20psi that means 70 lbs pushing against the solenoid/ servo

Edited by Joe C on 18th Feb, 2010.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

My understanding is this:

A 10 psi actuator will, if set with the correct preload, control the boost at 10 psi. As boost rises to 10psi, it will start to open. As the wastegate opens exhaust gas will be bled off. The wastegate opening will reach a point of equilibrium where the amount of opening sustains the boost at 10 psi. As revs rise, it will open further to bleed of more gas but it may never fully open.

The MBC does modulate by only letting the actuator see enough pressure to hold the boost higher, but the wastegate will not open as far.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Is see what you are saying. If the 10psi is reached and the boost then increases the actuator opens further this reducing boost. However, if it open further then the boost will drop and the actuator will try to close again back down to its 10psi position. So it must also be to do with the pressure of the exhaust gas on the wastegate as well. Which makes it a much more complex system and difficult to replicate.

So if you wanted to use a solenoid you would need a multiposition one which is a stepper motor, which is not worth the effort.

A worthwhile discussion I think. I still need to improve the boost control on the TT though.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

I'm a newbie to electronics, but I would have thought that there were ICs out there that would do the job.

Just thinking out loud, but you would need a MAP sensor, a reference voltage that you could control from a potentiometer, then an IC that would give an output to a stepper IC.

The MS drivesthe stepper with one of these:

http://www.allegromicro.com/en/Products/Pa.../2916/index.asp

There must be a way.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

On 18th Feb, 2010 mini13 said:
whats a wastgate hole diameter? about 3/4"?

that equates to 1.75 sq inches,

if we assume TIP= 2x boost, and boost = 20psi that means 70 lbs pushing against the solenoid/ servo

Edited by Paul S on 18th Feb, 2010.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

huh?

where does the /4 come from?

It's radius squared not diameter.

Jean

http://www.jbperf.com/

DOH!!

what a berk...