Open Source Electric Supercharger

[Calum]

Originally Posted by mid_life_crisis

There was a good reason for wanting to know the motor speed but I can't remember it right now. Sucks getting old. It'll come back to me eventually though.

Motor overspeed maybe? Or perhaps compressor surge?

[jamesm]

Originally Posted by Calum

Tuning gain is great, but a system like this would require the ability to correct offset as well. Otherwise the system could settle out at the wrong boost pressure and as long as the error signal (feedback compared to setpoint) is steady then the system wouldn't correct for it.

I've calibrated and rebuilt more then my fair share of pneumatic controllers that can do this, but I have no idea how to do it in the digital world. Basically for this to work well a controller that can do both proportional and integral adjustment is what to look for. A full PID wouldn't be required though, I don't think.

Or am I an idiot and that's already in the code above?

Also, I really think we need to get past the idea of boosting to the back of a partially closed throttle. That's inefficient and with a setup like this shouldn't be required. If BRZ edit could be used to remap the throttle plate vs. pedal maps, then you could just set WOT to something lower in the pedals travel range then 100% and then use the rest of the pedal's travel to increase boost pressure to a max.

The code above, as over-simplified as it is, will not settle outside of the target unless the target is unreachable due to a hardware limitation. It's pretty simple, basically says "keep increasing motor speed by x until map == target boost, them quit, if map >= target boost, reduce motor speed by x". Rinse and repeat. Again very simplified and not representative of a full implementation, but that's the idea, and it works well enough to control head speed to within 1 or 2 rpm @ 3k rpm.

Certainly there are improvements to be made, just advocating the general idea of using a boost target and a feedback loop.

[neutron256]

Ahhaha programming drives me nuts. I've never had a knack for it. I'll stick with the hardware/electronics side of things.

[mid_life_crisis]

Originally Posted by Calum

Also, I really think we need to get past the idea of boosting to the back of a partially closed throttle. That's inefficient and with a setup like this shouldn't be required. If BRZ edit could be used to remap the throttle plate vs. pedal maps, then you could just set WOT to something lower in the pedals travel range then 100% and then use the rest of the pedal's travel to increase boost pressure to a max.

I'm still of the notion that I don't want to have to reprogram the car's ecu. With a 3-d table we can set the boost at low rpms and partial throttle positions to levels that won't trip a code.

[jamesm]

Originally Posted by neutron256

Ahhaha programming drives me nuts. I've never had a knack for it. I'll stick with the hardware/electronics side of things.

Please do, we need that even more

[jamesm]

Originally Posted by mid_life_crisis

I'm still of the notion that I don't want to have to reprogram the car's ecu. With a 3-d table we can set the boost at low rpms and partial throttle positions to levels that won't trip a code.

Yep. You could have any boost at any combination of rpm and throttle position, within the limits of the system. You could set it up any way you like, and alter it as needed when you upgrade in the future. It's a pretty exciting idea really.

[DAEMANO]

Originally Posted by mid_life_crisis

I'm still of the notion that I don't want to have to reprogram the car's ecu. With a 3-d table we can set the boost at low rpms and partial throttle positions to levels that won't trip a code.

Unichip?

[mid_life_crisis]

Originally Posted by DAEMANO

Unichip?

The idea here is to have a kit that requires no additional purchases that we can just hook up and have it work. You buy a list of parts and put it together. We would make available the code with instructions on how to load it. I bet there would be members who would build them for a small price for those who either can't or don't want to.

[DAEMANO]

Originally Posted by mid_life_crisis

The idea here is to have a kit that requires no additional purchases that we can just hook up and have it work.

[neutron256]

Originally Posted by jamesm

Please do, we need that even more

That's easy. I expect I'll have the hardware prototype ready to test in a couple weeks depending on my free time and motivation.

Originally Posted by DAEMANO

Unichip?

I'm currently running Unichip and I think this is a great idea. It supports this type of mapping, it's already getting the most of the data needed, and could probably directly output a control signal to the motor controller.

If I recall correctly its $200 for the tunner software/hardware. Not bad if I knew for sure I could get it to work.

[mid_life_crisis]

So now I have to look up Unichip and learn about those so I can participate in those discussions. sigh...

[jamesm]

Originally Posted by neutron256

That's easy. I expect I'll have the hardware prototype ready to test in a couple weeks depending on my free time and motivation.



I'm currently running Unichip and I think this is a great idea. It supports this type of mapping, it's already getting the most of the data needed, and could probably directly output a control signal to the motor controller.

If I recall correctly its $200 for the tunner software/hardware. Not bad if I knew for sure I could get it to work.

the problem is that it is proprietary. it would be great if it could be controlled by as many engine management systems as possible, but you wouldn't want to require it.

[Toma]

Originally Posted by jamesm

the problem is that it is proprietary. it would be great if it could be controlled by as many engine management systems as possible, but you wouldn't want to require it.

Why not a Microsquirt. Literally 200 $ and you could output one of the ignition channels or whatever and have lots of additional output or inputs for other toys.

[ft_sjo]

Is this more of a programming exercise than an automotive engineering one?