Q
 

Hi.
I have an idea and I am looking for some “technical help” with it. I am wondering if it is possible to make a FI system that give a constant PSI instead of one that rises and falls with RPM’s of the engine? Unlike a turbo or SC, I’m guessing this would have to be electrical in nature. Does any one know if this has been tried before or if the concept is some how incompatible with the workings of a combustion engine?
Grey

I would think that you want the amount of boost, or pressure, to vary with engine speed, otherwise you'd be forcing more air in at "idle" causing the engine to dump more fuel to keep the AFR correct, resulting in the engine making more power at idle than is needed. Maybe you meant at anything but idle, in which case I think you still want some variability in the boost, but not sure of why I think that.

A mechanical "salsbury drive" could keep the RPM of the FI system itself constant or variable enough to keep the boost constant. This works on the same principle as the "Continuously Variable Transmissions" found in some economy cars. Either way, it's complicated and not known for reliability.

A constant psi can be found throughout the rev range with a positive displacement SC - roots or twin screw. Such a unit will provide 8psi whether at 3k or 8k, the flow will be different but psi the same.

As for a unit being driven electrically, that would take a lot of voltage. Electric SC's have been marketed but none can give anything more than a 20-30 second burst of compressed air.

Thanks for the replies. Georgia8er made some good points for me to concider. I don't think i would be running presure while idling but i realy hadn't gotten that far ahead. It's just an idea and I still have to learn about all the contributing facters involved with engine management.
Red Devil's concern about enought power is also a priority concern of mine however I work in the electrical field and am looking into inverters for powereing the unit. Other wise I woould have to hook up a genny to the engine and if i do that I might as well just go with a SC. Still a lot of thinkingg to do before I can tell if this idea is feasable. feel free to send more thoughts on the matter guys and thanks again.
Grey.