hall sensor simple questions

[Toby Atwater]

As I understand it, a hall sensor can detect a metal mass approaching the
sensor i.e. a distributor cam rotating and a hall sensor sensing the lobes.

Crank shaft sensors can determine the position of the piston and therefore
give the ECU a timing reference inorder to inject fuel at the right time.
How many sensors do you need around the crank inorder to get a resolution
that is useful? Is this multiplied by each cylinder as well? or can the ECU
calculate where one piston is compared to another's location?

Crank shaft sensors seem hard to implement on an old engine with no stock
electronics what so ever. I was thinking about using the distributor's cam
with a hall sensor in order to get spark timing and as well as Fuel
Injection timing and thereby doing away with crank sensors completely. Is
this possible? are the hall sensors accurate enough to not only detect a
lobe peak but the lobe's approach and exit?

Please help out a novice here...
Thanks for your help

Toby Atwater
1969 Austin Healey Sprite
1971 Toyota Land Cruiser

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