RE: RPM limits of GM computer/ignition module?

[rahmrh@cableone.net]

If you are talking about the SDI unit, they don't make
it anymore, and it has serious reliablity issues, and I
don't know what its rpm limits are.

Mine had an issue and at least one other had exactly the 
same issue (all conditions matched), and at least 1 other
had related issues that caused all 3 do uninstall the SDI
and go back to the optispark.

I have heard people claim that it is the coil itself
that cannot spark that fast, so replacing the coil
with one of the aftermarket ones may do it.   I believe
TPIS claims this, and probably others.

I believe mine has a hypertech coil and mine appears to 
run smoothly until I hit the rev limiter (6700).

			Roger

 



-----Original Message-----
From:	"owner-gmecm@diy-efi.org" <owner-gmecm@diy-efi.org> on behalf of	"Bruce Plecan" <nacelp@bright.net>
Sent:	Thu, 22 Feb 2001 11:54:42 -0500
To:	"gmecm@diy-efi.org" <gmecm@diy-efi.org>
Subject:	Re: RPM limits of GM computer/ignition module?


I've forgotten the supplier, but there is a Optispark to Coil Near Plug
Conversion.
If none of the LT1 guys remember, holler at me and I'll track it down.
Bruce



>
>     Have a friend with a solid roller 400 LT1, and regardless of computer
programming
> can't seem to rev over 7000-7100 rpm - it basically feels like a rev
limiter is hitting
> in that range.   He is using an '8051 95LT1 pcm - tried rev limiter values
from 7500
> to 9000 with no difference, so we are thinking it's hardware related.
(Car has a
> msd digital 6, rev limiter there set at 7500).
>
>      Some people have indicated that it may be a problem with the stock
computer -
>  though Ed Wright says that they have had cars that would turn that high
on the
> dyno with the stock computer, and he thinks it's opti-spark related.
>
>     The best hypothesis I have heard is from an individual who believes
it's
> ignition module related - and that starting at 6800-7000 you get horrible
> spark flutter and the unit just isn't reliable anymore.    IF this sounds
correct what
> kind of aftermarket units would interface with the opti-spark?
>
>     Thanks again for your help,
>     Chris Bennight
>
> --------------------------------------------------------------------------
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