Home-made Electronic Boost Controller
11-30-06, 02:54 PM
#26
Engine, Not Motor
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Originally Posted by nik
I think what we are getting to here is closed loop boost control. I run a profec B in my car and it is annoying to have to retune it based on the temp differences between night and day. For a while my HIGH setting was my day, and LOW was my night. I frankly expected a bit more for the hundreds of dollars that unit cost.
My arrangement with the MAP sensor and PWM circuit is probably the simplest form of closed loop you can do. As the voltage from the MAP sensor rises, the PWM duty cycle goes up and the wastegate opens more. As it falls, the opposite happens. A voltage divider made of a single resistor and pot between the two set the boost level....The more I talk about it now, the more I want to pull that stuff of the shelf and work on the design.
I could have a $75 closed-loop EBC. By switching out various resistors based on gear or TPS (use the spare output on the Microtech...) it could be duel, triple, quadruple, etc. stage. 
Haltech EBC is not closed loop in the e6x, but is in the higher models. Of course, this requires buying a haltech.
A well designed system will have the failure modes result in wastegate boost, not ovreboost(although the originally proposed system does not satisfy this). Also there is always overboost fuel cut for emergencies.
Actually this kind of circuit is very effective...
Is the megasquirt control closed loop? If it is that would be a great starting point.
11-30-06, 11:08 PM
#27
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some info on the MS boost control:
http://megasquirt.sourceforge.net/extra/boost.html
http://megasquirt.sourceforge.net/extra/boost.html
12-01-06, 09:34 AM
#28
My arrangement with the MAP sensor and PWM circuit is probably the simplest form of closed loop you can do. As the voltage from the MAP sensor rises, the PWM duty cycle goes up and the wastegate opens more. As it falls, the opposite happens. A voltage divider made of a single resistor and pot between the two set the boost level....The more I talk about it now, the more I want to pull that stuff of the shelf and work on the design. I could have a $75 closed-loop EBC. By switching out various resistors based on gear or TPS (use the spare output on the Microtech...) it could be duel, triple, quadruple, etc. stage.
12-01-06, 09:39 AM
#29
12-14-06, 08:49 PM
#30
Aaron,
I've been thinking about this... mainly because I don't want to study for my final tomorrow haha. Anyway, how do you plan to keep the thing from overshooting? It's the same basic problem in any closed loops system--keeping the error band and # of oscillations from the target point as small as possible.
The reason I say this is that lately I've been looking through the instructions for the AEM EMS. I'm going to be helping a friend of mine try to at least get his turbo Integra at least driveable on it. I flipped to the section about their onboard boost control system, and it is indeed a fully closed loop system:
http://forum.aempower.com/downloads/...ide%20V2.0.zip
Jump to page 121. Notice that it uses a P + I control system, like a closed loop O2 sensor (I guess it doesn't use a derivative... or it doesn't mention it at least). See http://en.wikipedia.org/wiki/PID_controller for reference on this.
Would your boost controller use integral control? If I understand this correctly, the AEM uses a standard tuning practice in industrial control mechanisms. It finds the error (deviation from set point), applies a basic multiplier to it (the proportional gain), then calculates an integral of the error over time as another correction factor to decrease the overall error band.
I'm not sure I understand where the self-correction will be in your system... you still have to correct the pulsewidth based on how close the boost gets to its targer.
I've been thinking about this... mainly because I don't want to study for my final tomorrow haha. Anyway, how do you plan to keep the thing from overshooting? It's the same basic problem in any closed loops system--keeping the error band and # of oscillations from the target point as small as possible.
The reason I say this is that lately I've been looking through the instructions for the AEM EMS. I'm going to be helping a friend of mine try to at least get his turbo Integra at least driveable on it. I flipped to the section about their onboard boost control system, and it is indeed a fully closed loop system:
http://forum.aempower.com/downloads/...ide%20V2.0.zip
Jump to page 121. Notice that it uses a P + I control system, like a closed loop O2 sensor (I guess it doesn't use a derivative... or it doesn't mention it at least). See http://en.wikipedia.org/wiki/PID_controller for reference on this.
Would your boost controller use integral control? If I understand this correctly, the AEM uses a standard tuning practice in industrial control mechanisms. It finds the error (deviation from set point), applies a basic multiplier to it (the proportional gain), then calculates an integral of the error over time as another correction factor to decrease the overall error band.
I'm not sure I understand where the self-correction will be in your system... you still have to correct the pulsewidth based on how close the boost gets to its targer.
12-14-06, 09:35 PM
#31
Has anyone looked at the Independent Electronic Boost Controller that AutoSpeed created? http://autospeed.drive.com.au/cms/A_2541/article.html
It can map boost according to injector duty cycle.
It can be built for under $30.
I am going to build one this spring when i buy a TII.
It can map boost according to injector duty cycle.
It can be built for under $30.
I am going to build one this spring when i buy a TII.
12-15-06, 08:53 AM
#32
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Back when I had my Turbo DSM a lot of guys used a fish tank valve as a poor man's boost controller. IIRC, the valve was placed in line with the boost solenoid that would detect an excess of boost and open the WG.
There were a couple of designs that used the same principle but brought the control inside the car. One guy made one that had 3 modes, 2 that you could preset the boost, and the third was stock setting for just regular driving. Do a search in the DSM forums and you can probably find them. I don't know how similar the turbo system on the RX is compared to a DSM, but I would imagine the same principles would apply.
There were a couple of designs that used the same principle but brought the control inside the car. One guy made one that had 3 modes, 2 that you could preset the boost, and the third was stock setting for just regular driving. Do a search in the DSM forums and you can probably find them. I don't know how similar the turbo system on the RX is compared to a DSM, but I would imagine the same principles would apply.
12-15-06, 11:59 AM
#34
ohh you mean make something like this??
i needed a project for one of my microcontrollor classes! so i made a simple design as well. with lcd and key pad entry of boost limit, worked in the lab. been to lazy to test it yet though...
used an hc11 microcontrollor ( was hella over kill), a turbo II boost sensor, and a solinoide off the solinoid rack. then it was like 500 lines of assembly code bleh..... , tested it in lab with a hand pump haha
but hey i got a good grade and it was fun! ill test it one of these days
i needed a project for one of my microcontrollor classes! so i made a simple design as well. with lcd and key pad entry of boost limit, worked in the lab. been to lazy to test it yet though...
used an hc11 microcontrollor ( was hella over kill), a turbo II boost sensor, and a solinoide off the solinoid rack. then it was like 500 lines of assembly code bleh..... , tested it in lab with a hand pump haha
but hey i got a good grade and it was fun! ill test it one of these days
12-17-06, 10:22 AM
#35
Engine, Not Motor
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Nice design! A lot more involved then mine. Have you considered releasing it as an open-source project? A lot of people here (including myself) would be all over it...
12-17-06, 01:49 PM
#37
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very nice!
i like the use of the hc11
i got really annoyed and frustrated in my microcontroller class (that was using the hc12). but looks like it can have some fun real world applications
i like the use of the hc11
i got really annoyed and frustrated in my microcontroller class (that was using the hc12). but looks like it can have some fun real world applications
12-17-06, 01:56 PM
#38
haha first i learned using the intel v25 board, which was quite confusing indeed,
then the second time around we learned on a hc11 board and that was alot easier
i feel the hc11 is probably over kill for this kind of application, i was considering useing a PIC chip to run things ( they are ussually real cheap and compact)
then the second time around we learned on a hc11 board and that was alot easier
i feel the hc11 is probably over kill for this kind of application, i was considering useing a PIC chip to run things ( they are ussually real cheap and compact)
12-17-06, 02:04 PM
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yup, i guess you could say overkill, but hey if it's what you know how to do then it works
honestly i have learned more stuff on FPGAs than microcontrollers, so i would probably find it easier using those. imagine using an FPGA for this. i haven't touched assembly coding since that microcontroller class, but HDL code on FPGA i have done a lot of. but THAT would be overkill! haha.
honestly i have learned more stuff on FPGAs than microcontrollers, so i would probably find it easier using those. imagine using an FPGA for this. i haven't touched assembly coding since that microcontroller class, but HDL code on FPGA i have done a lot of. but THAT would be overkill! haha.
