Good afternoon and happy Wednesday!
I own a few Alfa Romeo Spiders with a mechanical fuel injection system called a SPICA - see photo 1. A part on the system goes bad every couple years and the cost of replacement has risen to $500 for a rebuild. As an engineer, I've come up with a solution, but I'm not a production guy, so I have no idea how to build it for a reasonable amount of money and I don't know which off the shelf parts are the best to use.
Background info: The SPICA is a mechanical fuel injection system that was originally used in diesel engines in Italy. Alfa decided to start using them in their cars in the late 1960's - it's actually a pretty cool system - it's a belt driven pump (with four tiny cylinders) controlled by a mechanical "computer". Each cylinder pumps fuel into the intake via steel fuel lines. The "computer" receives inputs (barometric pressure, water temperature, throttle position) and adjusts the fuel output. The problem being these parts are now up to 40+ years old, so there's plenty of maintenance/wear issues and OEM parts are not available, so aftermarket and rebuilding is the only option. The part of the SPICA that gives us Alfa owners problems is a variable idle adjustment (helps idle when warming up) called a Thermostatic Actuator (TA). The TA takes the heat from the cooling system (coolant in the engine) and expands freon in a tube to move a lever in the SPICA system. It reminds me of an HVAC expansion valve, but instead of aerating the freon, it's purpose is to move the lever via freon expansion. They say it takes 9lbf to move the lever when the spring is installed.
Idea: My idea is to remove the spring in the SPICA pump (photo 2), use a lower power solenoid to move the lever and a temperature switch to control the solenoid. The original spec is for the lever to move incrementally as the water temperature rises, but most of us are only concerned with the lever being up when cold and down when hot (160 or 170 degrees). When cold, the TA is in it's normal state and the spring pushes the lever up. This tells the SPICA pump to send more fuel than needed (rich mixture) to speed up the warm up cycle, so the engine idles and it'll reduce emissions (get to operating temp quicker). When warm, the TA pushes down on the lever, counteracting the spring and the SPICA pump sends the normal amount of fuel.
One of us Alfa guys created a system that uses a manual switch inside the car to control the solenoid. The problem is two fold. First, the solenoid is so large that the other adjustments can't be done. Second is based on the old choke issue - people forget to turn it off. Running rich for too long isn't good for the plugs and the combustion chamber. See photo 3 below.
I'm thinking of using a thin and long solenoid, removing the spring in the SPICA lever so much less force is required, using a temperature switch to control the solenoid and getting 12V from a switched source with a fuse in line. I want the default to be a lean burn, but when the temp is below threshold (160 to 170), it throws the lever and it runs rich. The solenoid action should be 5-6 mm. The plunger is out when lean - preferably this way with no power, but it needs to be able to hold that position with normal vibration from the engine, so power may be required. When cold, the plunger will pull in and move the lever up to a rich position. Any of these criteria could be changed, except the 160-170 operating temp, 12V DC supply and the 5-6 mm throw. Oh yeah, what would be incredible is if an inexpensive solenoid exists that has a screw on the back where I can adjust the starting position of the throw.
Here are some pictures with important items marked and some notes of mine.
Thanks guys!
1. Here's a motor with the SPICA system and a few components marked:
2. Here's a close up of the SPICA fuel pump with the TA removed and the inspection cover off:
3. Here's the system someone has fabricated:
Electromechanical Device - I Need Help on This One!
Re: Electromechanical device - I need help on this one!
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