J&S ecu for 5kT

[Orin Eman]

> 
> I was contemplating using a J&S system on my 5kT. If I do the 1.8 bar 
> upgrade, this might be useful. The J&S is pretty versatile and can be used 
> on the 5-cylinder engines. It does individual knock retarding up to 20 
> degrees. It's got a rev limit and can put out 7A to the ignition coil 
> [which actually doesn't seem important, b/c I think the ignition coil is 
> triggered by a low current signal from the hall sender on 5kT's].

The coil/booster is triggered by a relatively low level signal from
the ECU.  The hall sender only serves to indicate cylinder 1 to the ECU.
Timing is actually derived from two variable reluctance sensors, one
pointing at the flywheel teeth and the other at a pin on the
side of the flywheel (at about 62 deg BTDC, cyl 1).  Timing resolution
is about 1/2 a flywheel tooth or 1.33 degrees - it uses both
edges of the teeth.

> The only thing I don't understand is how the J&S makes a timing map. Can 
> you program a map that is adjusted by the knock signal? What does this map 
> look like? The thing that bothers me about the ecu, is it does not use any 
> sensors but knock sensor to figure out advance. The oe Hitachi ecu uses 

It doesn't need to figure advance, just retard.  It sits between the
OEM ECU and the coil/booster.  If it hears knock, it retards the
cylinder next time around.  Which incidently, is how the 3B ECU
works - a second CPU takes the ignition signal and delays it if
knock has been detected.

It should work fine with the MAC11, though you would need to
disable the OEM knock sensor...  Not as simple as just disconnecting it...
that would throw error codes AND give you an across the board retard!

Orin.