Open Source Electric Supercharger

[jamesm]

Originally Posted by solma

Funny, would said thing for 2 option. A PIC uc program in Assembler, way more efficient and simple, but that because I am use to program in assembler, I think best is to go with what you know best.

agreed. i think we'll find a common ground that will allow as many people as possible to contribute. yet another reason to use something popular like arduino .

if you don't intend to have others contribute, i would use whatever your most comfortable with.

[solma]

Originally Posted by jamesm

i agree with most of that. my main point of contention would be throttling down when the system detects it has reached target. it would be best to just return early and let it loop over, no need for unnecessary motor control (one of the most computationally expensive operations in the system), and it will result in oscillation in all cases.

of course when the system is armed a simple scaling of throttle percentage to motor speed is less than ideal as well, as we're not concerned with motor speed, we're concerned with boost. it should read map, then compare to a boost target referenced from rpm and throttle position. this is a far more flexible design, imho.

I agree with James, you will not be able to control in closed loopback the motor speed vs pressure sensor. Like James said, your are better looking at motore speed vs fix map(open loopback).

That why they use blow off valve in turbo application, the actuator can not react fast enougth+compressor wheel can not change speed to fast(due to is weight).

[SloS14]

Arduino clones could be had for <$10, even in small quantities. Just sayin'. The ability for and end-user to reflash easily would be a plus...Not saying that's not possible with other solutions.

[jamesm]

Originally Posted by SloS14

Arduino clones could be had for <$10, even in small quantities. Just sayin'. The ability for and end-user to reflash easily would be a plus...Not saying that's not possible with other solutions.

absolutely. i think both should be supported: arduino with a custom circuit, or an integrated board that runs the same atmega. this would allow people with an arduino to 'DIY' and others who want simplicity could buy an inexpensive integrated board. they're not mutually exclusive, it's more of a packaging concern than one of development.

[solma]

An other thing you will have to design/buy is for the charging of the Capacitor, you will have regulate the charging current if you do not want to surcharge the alternator/electrical system of the car when they are empty/low voltage. The system you are designing is similar to what Im use to design, where you need a constant current input in the cap and a large discharge current in short burst at your load.

When you will designing your power stage(depending on what type of motor you choose), always think that wire in the motor are like long water pipe, you can stop feeding them abrutly, or you will endup with high voltage spike destroying the FET

[neutron256]

Originally Posted by jamesm

i agree with most of that. my main point of contention would be throttling down when the system detects it has reached target. it would be best to just return early and let it loop over, no need for unnecessary motor control (one of the most computationally expensive operations in the system), and it will result in oscillation in all cases.

of course when the system is armed a simple scaling of throttle percentage to motor speed is less than ideal as well, as we're not concerned with motor speed, we're concerned with boost. it should read map, then compare to a boost target referenced from rpm and throttle position. this is a far more flexible design, imho.

Your assuming that a static situation when you are in standby and just trying to maintain a minimum pressure. As the engine revs up and down the speed of the motor will need to rise and fall.

Maps are great idea but right now I'm just looking at a prototype. It's hard to make a map when you don't even know things like what sort of max boost you can get.

Also keep in mind that this system is limited, and you most likely will be maxing out the motor very quickly as you move up through gears/revs. At that point your boost pressure will just start to fall no matter what your map says

[jamesm]

Originally Posted by neutron256

As the engine revs up and down the speed of the motor will need to rise and fall.

presuming you're talking about when in 'standby mode', i think we need to validate this assumption. you may find that in trying to match compressor rpm to the intake requirements of the engine, you create more restriction than you eliminate. i'm not sure, just saying that this will require experimentation to validate that it's even a problem.

i'm led to believe this by knowing that if you cut the belt on a centrifugal supercharger and it's just sitting there dead in the intake tract, the car will run and drive like a stock, non-supercharged vehicle. it doesn't seem to create significant intake restriction. don't ask how i know

[mid_life_crisis]

Originally Posted by neutron256

Your assuming that a static situation when you are in standby and just trying to maintain a minimum pressure. As the engine revs up and down the speed of the motor will need to rise and fall.

Maps are great idea but right now I'm just looking at a prototype. It's hard to make a map when you don't even know things like what sort of max boost you can get.

Also keep in mind that this system is limited, and you most likely will be maxing out the motor very quickly as you move up through gears/revs. At that point your boost pressure will just start to fall no matter what your map says

No, the map in reality is a max acceptable boost level. Ideally the values would also be realistic targets you could anticipate reaching, but the reality of it is that in many cases (especially high engine rpm) it will never be reached.

[jamesm]

Originally Posted by mid_life_crisis

No, the map in reality is a max acceptable boost level. Ideally the values would also be realistic targets you could anticipate reaching, but the reality of it is that in many cases (especially high engine rpm) it will never be reached.

Ill just note as well that having a target higher than what the hardware can reach is not an issue, presuming the hardware can handle being run full throttle for extended periods of time (exactly as the kit in the other thread does now). It can try all it wants, it'll just constantly be trying to increase 'throttle' only to find out that it has reached a hard limit for the value. This will repeat again and again until at some point the map becomes >= the target, when it'll begin to throttle down and eventually settle very near the target. Of course this all takes place at the highest frequency possible.

We are effectively building an EBC that changes motor rpm instead of the position of a bleed valve.

[mid_life_crisis]

Toma pointed something out in the other thread that we need to keep in mind over here.
In the immortal words of Montgomery Scott: "The more they over think the plumbing, the easier it is to stop up the drain."
I'm mostly concerned with adding bypasses and things like that.

[mid_life_crisis]

Originally Posted by jamesm

We are effectively building an EBC that changes motor rpm instead of the position of a bleed valve.

Exactly. No effectively about it. This is exactly what we are doing.

[solma]

I am starting to be mixup on what you want to built, is it a short burst WOT system or to you want to emulate a belt driven supercharger that can constantly pressurized the intake?

[SloS14]

Originally Posted by solma

I am starting to be mixup on what you want to built, is it a short burst WOT system or to you want to emulate a belt driven supercharger that can constantly pressurized the intake?

If you're asking me the answer would be somewhere in between but leaning towards the short burst.

I'd like to be in 6th on the interstate, give it some throttle and get *some* boost (1-2psi would be great) without having to go WOT and getting full boost, then level off to cruising speed and recharging.

[neutron256]

Originally Posted by solma

I am starting to be mixup on what you want to built, is it a short burst WOT system or to you want to emulate a belt driven supercharger that can constantly pressurized the intake?

That's what I'm looking for, the only difference being that I want it to activate a little before WOT (say 80%) and then to start low and quickly ramp up to full boost by the time it's at 100% throttle. As you let off the throttle the same processs would happen in reverse. The only objective of this is to give a smoother transition into boost.

I think the mapping ideas are great but I think it's over engineering for what I want. From my prospective I only want this boost during hard acceleration, and I want as much as it will give me so what is the point of a map?

The other side is when the system is in standby to keep it running at a minimum speed to prevent the compressor from causing restriction in intake. I think this is something that will require some testing to determine how best to go about this, and if it really is a benefit at all.