Originally Posted by
Bernett
Wow! Great explanations to my questions. Unfortunately I have some more. Does the solenoid’s action work like a valve? Meaning since it works only on and off to get less fuel you probably increase the on and off pulses. Would a valve that you could control also work? Has anyone looked for a small variable controllable valve? My other question is have you tried using rpm as the way to set the solenoid? If the solenoid reacts to air pressure and temperature then it should be able to react to rpm. You can get rpm from the ignition system and then program in a preferred idle rpm and many other points along the curve and would the solenoid be able to hold the rpm close to what the program called for? Sort of like a gyro holding the plane in the same altitude. The solenoid could hold the engine in the proper rpm setting as long as the throttle wasn’t changed. Thanks again for all the information. Your explanations are easy to understand.
Basically, the solenoid works near EXACTLY LIKE a controlled valve, with some special properties. Best visual is this one:
As can be seen here, flow control is very proportional, BUT with the complete absence of "hysteresis". A servo operated valve, due to friction and clearance, will not return into the exact same position if moved and returned. GFor example, valve command is 50% due to friction, actual position is 49%, if a short command 75% is given, then returned to 50%, the valve will be 51%. Numbers as example only)
The solenoid does not do that. If it is controlled to 50% duty cycle, it will ALWAYS be 50%, regardless of whatever immediately prior different command was given.
The other very beneficial property is in that a controlled valve gives a laminar flow, an oscillating valve gives a non-laminar flow. YOu can see this in the video, when the solenoid is at 100% dutycycle (stops rattling), the outflow immediately changes to a smooth flow, but during the controlled phase, outflow is non-laminar.Ïn the case of engines and carburettors, this GREATLY enhances fuel atomisation, leading to significantly leaner mixtures and a much cleaner burn.
As for including RPM in the valve control: Nope... The system still is by and large just an orifice passing fuel based on pressure differences, and the deeper carb vacuum and higher muffler pressure are the correcting factors here. The engine will find a stable operating point, the trick is to find the suitable dutycycle for each throttle position, for the engine to stabilize in an optimal operating point.
Originally Posted by
Bernett
Has anyone tried a peristaltic pump? It should work as pump for fuel pressure but it may be able to be used to replace the solenoid if you used a controller similar to the one for the solenoid. Has anyone measured the flow rate the solenoid puts out at different throttle settings? If you knew the flow rates then finding an alternative to the solenoid may be easier because you could set the controller to mimic the flow rates of the solenoid. It may help in finding base settings for something like a peristaltic pump. I know all of you have spent a ton of time working on your present solution so looking for alternatives may not interest you. All of the work you have done is inspiring and I like looking at different ways of doing things. Thanks
Yup... been there, done that. Does NOT work, because peristaltic pumps have a "fixed" flow (do not allow the engine to self-stabilize by means of deeper carb vacuum or higher muffler pressure. An engine can be run like that, but it is EXTREMELY difficult to get a stable operation, and setting curves is sheer horror. Mind you, I used glow at that time, because of the "self correcting effect" of glow ignition, and even then it was sheer horror to even get the engine started. That is why I never managed to make a vid of the starting. Took me ages to apply starter, get the correct fuel for ignition, then immediately after removing the starter, "catch" the now free accelerating engine with the right amount of fuel.