I'm making 12 electronic boost controllers for a project in my Robot Sensors and Actuators Class. They use the signal from an existing 2 or 3 bar MAP sensor to control an air solenoid valve. They're adjustable by a **** from where ever you mount the circuit board. Parts cost is just over $100 if you want to assemble it yourself (requires soldering), or i'll build it for you for $140.

 

Any chance you can tie another 2 inputs (VSS & Tach) to the microcontroller? I'd like it to control boost based on which gear you're in. What are the size of the air ports? This would have to control 2 wastegates in my case. What is the impedence of the MAP input? I just want to make sure it doesn't mess w/ the map signal going to the ECM. While I'm dreaming, if the microchip is flashable, can outputs be left enabled to work as a shift light as well, if you've got an RPM input? Good luck w/ the project!

Thanks!

 

The chip used is a simple voltage comparator, so the current draw from the MAP signal is on the order of nano-amps (negligable). It compares the signal from the MAP sensor to the voltage on a potentiometer (****). When the MAP voltage reaches a set point the air solenoid is opened allowing wastegate diaphrams to be subjected to boost pressure. I designed the circuit for use with a 1/4" pipe threaded valve that could be T'd for mulitiple wastegastes (I run two also). That valve is almost $60, so a smaller 1/8" valve could be used for around $40.

As for RPM and VSS inputs... I don't know anything about the tach and VSS protocol (aka what the signal looks like)

I could add any analog signal inputs very easily.

 

what solenoid are you using?

BTW, how do you like JHU? What campus are your classes out of (they do engineering classes out of a few different campuses under different programs, like I know that they do some out of the APL RE Gibson library (my wife works there))

 

The solenoid is just one I found on McMaster.com I could get the part number if interested.

I go to the Homewood Campus at the end of 33rd and N.Charles street in Baltimore. Its called the Whiting School of Engineering. I love the school and I love to learn, but I HATE the workload. I put about 60hrs a week into school work during the semester. The social life is non-existant as you can imagine.

 

Yea, I'm intrested in the PN...

Social life... you mean school isn't fun enough for you?

 

the McMaster part number is: 6124K277 (which is the 12VDC version of 6124K513). Its on page 919 of the online catalog if you want to check it out.

 

whats the boost setting range on these?

 

You can pretty must design the adjustablity range with a single resistor change. The design uses a simple two or three resistor voltage divider. You'd need a GM MAP sensor to work with them.

If you have a 2 bar sensor: It could easily adjust from 0-14.7psi or 7-14.7psi etc
If you have a 3 bar sensor: It could easily adjust from 0-30psi or 14.7-29.4 psi etc
The 7-14.7psi and the 15-30 psi would obviously have better resolution and accuracy. It could be designed to adjust from almost any range within the capabilities of the MAP sensor with the addition of more resistors or another potentiometer. now I'm geting more ideas...

Also, the professor ended up not having the boards made for the class, so the only prototype was on a breadboard, and it was never used in a car. If I could sell like 4 or 5 of them it would be worth ordering the boards myself, but I don't want to do that without testing on a car.

Testing would be difficult for me because my internal wastegates are way too small for my motor. The wastegates are set for 7 psi, and they actually produced 8psi on my old turbos because the internal flapper valves were smallish. With the new turbos (smallER flapper valves), boost constantly creaps, then peaks at 190kPa at 5700rpm which is probably past the safe maximum for my motor. In other words, my wastegates are so unpredictable, testing would be inconclusive on my car.

Edit: It would be pretty sweet if there was a tach input that could up the boost with rpm. If someone wants to help me on that one... What does the signal from the tach wire behind the distrubuter look like? pulse? how does the guage cluster tach work? the signals gets converted to analog somewhere along the way, but where and how? Is it like a frequency to analog convertor of somekind? I have no idea. never really researched ot too hard though.