Re: Cam tuning

[Scott Knight <scott@scottknight.com>]

Shannen Durphey wrote:
> 
> Well, today I was replacing one of those same optisparks, and I

Heh.  All too common...

> realized that the optispark is still a distributor, it just happens to
> have an optical sensor installed.  If we can make the coil spark, then
> we can run the engine, since the rotor and cap work the same way a
> rotor and cap always have.  I want to check on this tomorrow, but I
> think the opti disk could be replaced with one which had 8 "pie" cuts
> to generate a signal for an older ecm.  Another thought is to use the
> crank sensor and wheel from a Vortec smallblock.  The vortec sensor is
> in the timing cover, and the "wheel" is sandwiched between the
> balancer and the timing gear.

Actually, it is easier than this.  The Opti low-res portion has the
required 8 evenly spaced slots and should be suitable for triggering any
ECM/PCM with the leading edges.  It is just that the LTx PCM uses the
different length slots to signal what cylinder it is working on with the
trailing edges.  The sensor voltage goes from 0 to 5v when a leading
edge comes up.  Does an ECM care when the voltage goes low again?

There is one more fun fact.  The OBD-II LTx engines have a CPS
(crankshaft position sensor) integrated right into the front cover as
well...might even be the same pickup and reluctor wheel as the Vortec. 
Would be interesting to find out, since I have the new LTx pieces here
in my office.  This is what I am going to use to trigger the Speed Pro
controller on my LT1.  I could have just used the low-res side of the
Opti, but I rather prefer a real crank sensor than one that is subject
to timing chain quirks.  Especially since the newer LTx engines have
such a nice one already available.

You bring up a good point though.  The Vortec pieces would be great to
use on a traditional SBC instead of a distributor or external trigger. 
Anywhere I can see pictures?
-- 
Scott Knight  mailto:scott@scottknight.com
http://www.scottknight.com/ IRC:SS396man
'95 Black Impala SS
'94 Ducati 900SS CR
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