Using solenoid as boost controller?

[altered7151]

All the electronic boost controllers I've seen use an electrically operated solenoid for the air control, but they use PWM to control it. What would be the downside to using the solenoid with a simple on/off switch to operate as a boost controller? In theory I thought it would operate much like a g-valve as it wouldn't allow the wastegate to see boost until it was opened.

[Wink]

nothing. I was planning on using a similar setup for a project car. All you need is a pressure switch and a 3 port solenoid. Depending on the switch, your setup could be adjustable too.

I was planning on going with a 3 stage setup like this, so I can maximize traction.

[altered7151]

nothing. I was planning on using a similar setup for a project car. All you need is a pressure switch and a 3 port solenoid. Depending on the switch, your setup could be adjustable too.

I was planning on going with a 3 stage setup like this, so I can maximize traction.

Okay, good to know. And it wouldn't be adjustable, its going to be programable:thumb:

[The S is Silent]

PWM? I have a roomate that is a wiz with electronics...mayhaps he can make something for me.

[altered7151]

Pulse width modulation. Basically the solenoid flutters open and closed real quick at different rates to allow the wastegate to open or close.

[89acclaim]

If I remember right the VGT turbo on the powerstroke uses PWM. Makes me think..... :D

Daniel Merrill

[SwiftTech]

ummm, doesn't the stock electronics use a PWM solenoid to control boost?

[The S is Silent]

next question...how do you modulate pulse width???

[altered7151]

ummm, doesn't the stock electronics use a PWM solenoid to control boost?

Yep, but my question is what are the downfall(s) of not using PWM to control the boost. So say you have the solenoid closed until it recieves the electrical signal, then its open allowing the wastegate to see pressure. Basically it would become an electrically operated g-valve.

[89acclaim]

Like this? http://www.turbododge.com/forums/showthread.php?t=71284

Daniel Merrill

[altered7151]

Yeah thats pretty similar. Okay here's my idea, when I was a freshman in college we had an introductory level engineering class. It focused around robolab robotics, we had different challenges and competitions each week. It was supposed to be one of those classes that taught you how to work as a team, think outside the box, blah blah blah. But the point being, we got to use the new(at the time) lego robolab kits (http://www.ni.com/company/robolab_how.htm) which contained a programmable "brain". Since my employer at the time paid for all my school expenses I bought my own kit, which I still have. The brain has 3 input and 3 outputs, and there are some guys out there that are super into these kits, and have designed their own sensors and output devices. Most interesting to us being the pressure sensor (3-bar, which is pretty convienient), voltage sensor, and an output to operate a relay or solenoid (see where I'm going with this?). The brain basically work on the labview lab software if anyone is familar with it. If you're not, it basically boils down to the fact that the brain can take in info from 3 devices (and there are ways to increase the amounts of inputs) and use the info to control 3 outputs. I think it would be a perfect platform to build a "smart boost controller". Parameters such as intake pressure, rpm (once converted to voltage from frequency), and possibly the TPS or O2 sensor could be monitored, then used to activate a solenoid to control boost, turn on water/alchol injection or intercooler sprayers, activate nitrous set-ups, or pretty much anything that can be operated by an electronic switch. Not only can the brain control all these functions, but it has awesome datalogging capabilities. So basically you could create a boost controller that would set your boost as a function of rpm and throttle position or speed (if it can monitor the speed-distance sensor), so you could ramp your boost up off the line to control wheel spin, cut it back if the rpms spike, and have a log of everything that happened in the run. Now granted the lego kits are like $250, but you can pick up the brains on ebay for about $40 or so, and can build the voltage and pressure sensors for about another $40, so for under $100 you could a pretty stout platform with almost unlimited capabilities.

[The S is Silent]

Instead of controlling off of speed or throttle position, why not control off of engine load? Injector pulse width would be perfect.

The brain sounds awesome. Does it have inputs for MAP tables? Could you create a table of engine load (pulse width) vs Boost?

[altered7151]

See this is where I fall short, the electrical stuff. I'm not exactly sure how to get the brain to read the pulse width. The way the sensors work as of now, is basically the brain sees them as a light sensor, so you get a reading from 0-100. The map sensor works by mapping the voltage out over that range, so 30psi is 100 and 0 is, well 0. If the load on the injectors could be feed into the brain as a voltage, they yeah there is abosolutely no reason it couldn't work. All the logic on the program has to be created from scratch, although there are quite a few templates out there, basically the language is C++ but uses icons for the operations. Personally the logic of controlling off of injector pulse width doesn't sound quite right to me though. The pulse width is a function of the map reading among other things, not the opposite. So your pulse width increases as your manifold pressure increase to compensate for the extra air. So if you were basing your boost control off of the pulse width it would never change. For example, if your program logic said dont raise boost over 20psi unless pulse width is less then say, 65% you would never raise boost since theoretically the pulsewidth wouldn't really change unless you changed rpm or boost levels.

[The S is Silent]

I think both controlling off of injector cycle and controlling off of RPM's are the way to go. Both are feed forward control strategies, as opposed to controlling boost pressure by measuring manifold pressure, and changing the wastegate position until the pressure is where you want it, which is feedback control.

The way I understand it is this: pulse width is a function of temperature, pressure, and engine speed. Temperature is set at whatever your intercooler and ambient temperature will let you achieve. Engine speed is chosen by you. Manifold pressure is whatever your control device tells it to be based on a set of process variables, whether its a MBC, EBC, or stock engine control. I'm thinking pulse width will be a better determination of what engine load is, as opposed to RPM, because 3000 rpm is different in 1st gear is different from 2nd or 3rd.

I have to think about it more.

[Wink]

I feel that many of you are not understanding the operations of the stock boost control setup of the cars. The solenoid doesn't modulate open and closed by a "pulse width", it modulates as the PCM reads boost pressure from the MAP sensor. The stock setting, lets say for my old 89 TI, is 10 psi. When ever the MAP sensor's signal voltage equals 10 psi, the PCM tells the solenoid to close, and prevent venting boost into atmosphere. This is the cycle point. Anytime the boost goes below 10 psi, the valve opens. Then it will close again at 10 psi. In essence, it's pulsing when ever the boost pressure crosses over the threshold point.

[altered7151]

I feel that many of you are not understanding the operations of the stock boost control setup of the cars. The solenoid doesn't modulate open and closed by a "pulse width", it modulates as the PCM reads boost pressure from the MAP sensor. The stock setting, lets say for my old 89 TI, is 10 psi. When ever the MAP sensor's signal voltage equals 10 psi, the PCM tells the solenoid to close, and prevent venting boost into atmosphere. This is the cycle point. Anytime the boost goes below 10 psi, the valve opens. Then it will close again at 10 psi. In essence, it's pulsing when ever the boost pressure crosses over the threshold point.

Okay, that make a little more sense then, and shouldn't be hard to duplicate at all. Now does that apply to the aftermarket electronic boost controllers as well? Like I said I suck at electrical work, but I was always under the impression that they controlled boost by modulating the solenoids to control the air pressure to the wastegate.

[Wink]

Okay, that make a little more sense then, and shouldn't be hard to duplicate at all. Now does that apply to the aftermarket electronic boost controllers as well? Like I said I suck at electrical work, but I was always under the impression that they controlled boost by modulating the solenoids to control the air pressure to the wastegate.


Yes, this applies to electronic boost control devices as well. They take the boost signal and open and close a solenoid to control boost. The only difference is that these units can be programable to control boost levels at different rpm levels. They do this because on certain setups, you don't want full boost before the peak torque levels of the motor. This causes increased sensitivity to detonation. So, if you limit boost in the lower rpms, then you reduce the chance of detonation.

My setup will be more or less gear dependant.

[altered7151]

The setup I have in mind will be both rpm and gear dependant, so you would have a more aggressive boost curve in higher gears, and less aggressive in 1st. So Wink, since it seems you're up on the electrical aspect of stuff, do you know if the tach signal coming from the LM to the factory tach is coming in as a voltage signal or a frequency signal?

[ShelGame]

I feel that many of you are not understanding the operations of the stock boost control setup of the cars. The solenoid doesn't modulate open and closed by a "pulse width", it modulates as the PCM reads boost pressure from the MAP sensor. The stock setting, lets say for my old 89 TI, is 10 psi. When ever the MAP sensor's signal voltage equals 10 psi, the PCM tells the solenoid to close, and prevent venting boost into atmosphere. This is the cycle point. Anytime the boost goes below 10 psi, the valve opens. Then it will close again at 10 psi. In essence, it's pulsing when ever the boost pressure crosses over the threshold point.

Actually, the stock ECU (SMEC and SBEC anyway) does modulate the WG with a PW. The PW is calculated from RPM, Boost setpoint, and ignition retard mainly. There is also an adaptive function to improve the WG response (similar to the fuel PW adaptives).

I don't think a simple pressure switch and solenoid will provide very precise boost control. Air is compressible, and we typically have a pretty large volume of it in the complete intake tract, so there will always be a delay from when you activate the solenoid until the boost comes down.

Also, the stock ECU calculates boost from RPM, Coolant, Charge Temp, TPS Position, and Speed. Get D-Cal, and you can tune all of those yourself. As well as the WG PW.

[Phreakish]

http://www.seattlerobotics.org/encoder/200210/servoex/ServoExcerciser.htm

simple no? set it up right and have a dial - or use several switches for different PW. The frequency is fixed, so you can actually control the overall duty cycle.

I've found others before that are a bit simpler, but basically a 556 timer will allow you to fix the frequency and alter the PW.

[The S is Silent]

sweet. Thanks for that...really it's the last part we need to make a boost controller. Here's my idea:

Injector pulse width monitor to measure the load on the engine. The output to this device can be sent to the LED display...and to a memory bank that stores your manifold pressure vs. pulse width tables.
http://www.ggimages.com/rx7/pwm.html

I'm not exacly sure how you'd set up a table, I havn't figured that out yet. It's just a black box on my brainstorming schematic. The output to the black box would be the input to the dial for the PWM board, setting the pulse width of the solenoid to bleed the wastegate pressure signal.

The output from the injector duty cycle monitor would be referenced to the table, and the output of the table would set the frequency on the PWM board.

I think it would work...but I'm no electrical wiz. I'll have a working prototype as soon as my roomate stops doing school stuff.

I'd like to make something like this: http://autospeed.drive.com.au/cms/A_2541/article.html

[Russ Jerome]

http://hometown.aol.com/russjerome/images/3stagefar.jpg

One aluminum block for 2 G-valves and 1 manifold source out.
One toggle switch, ON/OFF/ON, one bleed and 2 solenoids.
3 stage boost control from one switch.

Extra stuff that may be visible are WOT switch to disable
high boost at anything other than WOT. Hobbs switchs for
5th and 6th injectors, flame thrower enable ect.