Well, I've been getting a lil bored with the same ol stuff on this forum so I figured I'd add a possible interest area:
I've started work a system that has an actual active feedback loop which I surprisingly haven't seen in a system yet! I'm using an industrial stainless pressure transducer that is mounted on the alky pressure line to tell the controller exactly what the alky pressure is. I'm also going to have a lil digital readout for the alky line pressure and flow rate (calculated internally based on total nozzle sizes and pressures) since I could never find a cheap alky compatible pressure gauge! A system like this is analogous to closed loop fueling with an O2 sensor in a standard ECM.
I've always intended my current kit to have this but could never find a reasonable price on a compatible transducer. Well, I've found one, and it's not cheap but it's at least cheap enough for me to start fooling with for one or 2 setups.
The benefits of providing line pressure feedback:
1. Nozzles used are fixed flow (well based on differential pressure which is known) so you can have an actual flow rate that is entering the engine. This means people could now calculate accurate fueling.
2. Final flow rate is NOT solely dependent on the pump motor's speed. Normally progressive controllers (including mine!) modulate motor speed to get some flow rate. While this is effective to some degree, the controller really doesn't know if there is a fault in the pressure line. I use what I call 'binary feedback' in my current controller which is nothing more than a pressure switch. This only tells two states to the controller: yep, there's line pressure, or no, theres not. Also, the pumps wear out over time... both on the pump end and the motor end. This means that over time, shooting the same duty cycle to the motor will result in changed line pressure and correspondingly, flow rate. With feedback telling the controller what the pressure is at any moment in time, it can now detect line faults, clogs, broken lines, bad check valves, and most importantly flow can be maintained over time. Since the pump duty cycle (meh... speed) is BASED of off the desired line pressure, the controller can now automatically adjust the motor speed to obtain the same flow rates needed.
3. Like stated above, now that there's already a pressure reading sent into one of the ADC inputs, we can use it for an accurate electronic alky pressure gauge. Since we already have a MAP input and can easily enter a nozzle size, we can now find an actual alky flow rate, which too, can easily be calculated by the microcontroller! I usually use a mechanical style pressure gauge, but you really don't want one of these on the system at all times and especially you don't want one in the interior compartment. Gauge failures with flammable liquids = fire. The transducer is extremely strong and the wetted components are stainless. There are also burst proof units avail, which come with certs, but these are extremely expensive. A final benefit to having some visible pressure reading is that you can hide the central controller completely... You can put the small readout pretty much anywhere and get the same info as you would from the front panel of a controller.
I don't know if I'm ever going to offer anything like this for sale due to price, but maybe it will open up some more elaborate DIY schemes than the simple ol pressure switch turns on pump deal! One final design I have yet to start is one in which a 'variable nozzle' is used. Now the pump can spin up to some monitored pressure and the orifice changes size from movement of a stepper motor. Steppers are extremely accurate and so long as a step isn't missed they can be repeatable in the < 0.001" range! This type of system will give the most accuracy, but probably approaching too much of the leveling proceeds portion of the accuracy to price plot! Maybe one day for kicks, idk.
I hope to post the progress of the active feedback system here, and/or on my personal website which still isn't up yet!
Phil
I've started work a system that has an actual active feedback loop which I surprisingly haven't seen in a system yet! I'm using an industrial stainless pressure transducer that is mounted on the alky pressure line to tell the controller exactly what the alky pressure is. I'm also going to have a lil digital readout for the alky line pressure and flow rate (calculated internally based on total nozzle sizes and pressures) since I could never find a cheap alky compatible pressure gauge! A system like this is analogous to closed loop fueling with an O2 sensor in a standard ECM.
I've always intended my current kit to have this but could never find a reasonable price on a compatible transducer. Well, I've found one, and it's not cheap but it's at least cheap enough for me to start fooling with for one or 2 setups.
The benefits of providing line pressure feedback:
1. Nozzles used are fixed flow (well based on differential pressure which is known) so you can have an actual flow rate that is entering the engine. This means people could now calculate accurate fueling.
2. Final flow rate is NOT solely dependent on the pump motor's speed. Normally progressive controllers (including mine!) modulate motor speed to get some flow rate. While this is effective to some degree, the controller really doesn't know if there is a fault in the pressure line. I use what I call 'binary feedback' in my current controller which is nothing more than a pressure switch. This only tells two states to the controller: yep, there's line pressure, or no, theres not. Also, the pumps wear out over time... both on the pump end and the motor end. This means that over time, shooting the same duty cycle to the motor will result in changed line pressure and correspondingly, flow rate. With feedback telling the controller what the pressure is at any moment in time, it can now detect line faults, clogs, broken lines, bad check valves, and most importantly flow can be maintained over time. Since the pump duty cycle (meh... speed) is BASED of off the desired line pressure, the controller can now automatically adjust the motor speed to obtain the same flow rates needed.
3. Like stated above, now that there's already a pressure reading sent into one of the ADC inputs, we can use it for an accurate electronic alky pressure gauge. Since we already have a MAP input and can easily enter a nozzle size, we can now find an actual alky flow rate, which too, can easily be calculated by the microcontroller! I usually use a mechanical style pressure gauge, but you really don't want one of these on the system at all times and especially you don't want one in the interior compartment. Gauge failures with flammable liquids = fire. The transducer is extremely strong and the wetted components are stainless. There are also burst proof units avail, which come with certs, but these are extremely expensive. A final benefit to having some visible pressure reading is that you can hide the central controller completely... You can put the small readout pretty much anywhere and get the same info as you would from the front panel of a controller.
I don't know if I'm ever going to offer anything like this for sale due to price, but maybe it will open up some more elaborate DIY schemes than the simple ol pressure switch turns on pump deal! One final design I have yet to start is one in which a 'variable nozzle' is used. Now the pump can spin up to some monitored pressure and the orifice changes size from movement of a stepper motor. Steppers are extremely accurate and so long as a step isn't missed they can be repeatable in the < 0.001" range! This type of system will give the most accuracy, but probably approaching too much of the leveling proceeds portion of the accuracy to price plot! Maybe one day for kicks, idk.
I hope to post the progress of the active feedback system here, and/or on my personal website which still isn't up yet!
Phil
). They said it'll be ready for me by the end of the month. As far as some readout, I was just going to do a 3 digit 7segment that did different blinking patterns for possible fault indications.
