DIS for GMECM

Thu Dec 7 01:58:07 GMT 2000

By the way, the Opti spark system was mostly a Mitsubishi design and was a
poor one.  If any of you are using one I recommend dropping the stock plug
gap to .035.  The secondary insulation (read: cap and rotor) can't take the
high ignition demand and will burn thru quickly.  No big deal if you like
yanking the water pump every time you wait too long to change the plugs.

Darryl
----- Original Message -----
From: Len Sabatine <sabatine at epix.net>
To: <gmecm at diy-efi.org>
Sent: Wednesday, December 06, 2000 8:39 AM
Subject: Re: DIS for GMECM

>    Hey John , have heard of DIS on LT Marine  Apps , have not seen though,
> got any Pics ? . You mention OptiSpark 92-4 Spline drive , Ha , New LT1s
had
>    a sloppy  chain , kinda defeated the 1d res of the dist. Gm offered an
O
> size crank gear as a slop fix. At any rate, the Nstar style Pkg would
> indeed eliminate
>    the monkey motion for sure. While still lots of Plug wire , multiplying
> spark and dividing the load X 8 ,  Can't be wrong by any stretch. Yes,
> crank reluctor with
>    Lo-Hi Res sensor positions and "usual" module sense scenario does lend
> itself to wider usage on other controllers that process like signals.
> Marine Apps ,
>    not needing to do FTP certifications, can be  OEMs  spring board
> development arena for Wana Be Vehicle programs to come.
>     Len
>
> >Exactly!!  Makes me think back to the LT1 Optispark distributor.  All the
> >hoopla about 1 degree resolution with the 360 deg optical sensor, and
then
> >go and hook it all together with a timing chain and a little splined
drive
> >off the front of the camshaft!  Many folks are unaware of the fact that
> >when the LT1's were used in the Mastercraft ski boats, they used the
> >Northstar DIS, NOT the Optispark. The Nstar reluctor wheel mounts on the
> >back of the harmonic balancer, and a new timing chain cover is used with
> >the 2 crank sensor mounting saddles cast right into the cover. It's a
neat
> >little package! The 2 crank sensors feed directly into the full-function
> >DIS module, it decodes and processes the signals, and then you have the
> >usual connection to the ECM (REF HI, REF LO, BYPASS, and EST. In the
> >marine application they used the MEFI-2 controller, but hey, it COULD
have
> >been a 730/727 controller.
> >
> >         John
> >
> >
> > >Date: Tue, 05 Dec 2000 18:46:42 -0500
> > >From: Len Sabatine <sabatine at epix.net>
> > >Subject: Re: DIS for GMECM
> > >
> > >
> > >Think , elimination of distrib gear , rotor ,cap , carbon brush , air
> > gaps,  slop in the timing sys , ionization ,torsional vibes traveling
thru cam,
> > > oil pump disturbances , coil and plug wires and their routing. All
> > the >monkey motion and associated spark delivery problems , GONE,
> > especially with
> > > CNP ignition sys. Spark scatter and inductive X fire tendencies ,
> > GONE.  " Nearly" perfect spark delivery and repeatability is now
possible .
> > > Add to  that , Coil drivers are on each coil , not on PCM Motherboard.
> > A very high degree of "recovered loss" in Ignition efficiency has come
to
> > pass. The
> > > ms latency ,spark propagation time has also been reduced
substantially.
> > > Hope I've gotten the idea across.
> > >     Len
> > >
> > >
> > >>So the benefit to going w/o distributor is to prevent missed/deformed
> > >>sparks?  I always figured it was to get better timing accuracy.  I
sorta
> > >>figured you'd get more energy jumping the spark gap with coil-per-plug
(is
> > >>there a industry buzzword for this?) than with systems that use
> > >>conventional ignition wires.  Is this not the real reason?
> > >>
> > >>  On Tue, 5 Dec 2000, Bruce Plecan wrote:
> > >>
> > >> >
> > >> >
> > >> > Allz said and done, DIS will get you about a 2% less misfire rate.
> > >> > Meaning thou the AF mixture was lit, the flame front for what ever
> > reasons
> > >> > was unusual, and genereated less energey for that event.   Not to
be
> > >> > confused with a *miss*.
> > >> > Coil per Plug can get you an addition 1% improvement, and get right
near
> > >> > 100%.
> > >> > Bruce
> > >> >
> > >> >
> > >> > > As best I understand it DIS allows a longer dwell (charge time)
for a
> > >> > given
> > >> > > coil at higher RPM's, resulting in a hotter spark.   You also
> > eliminate
> > >> > the
> > >> > > wear of air gaps at the distributor caps.   Less moving parts,
less
> > >> > failure
> > >> > > points is good from the OEM point of view.
> > >> > > Also, advance is "unlimited" since you don't run into rotor
phasing
> > >> > issues.
> > >> > >   This still confuses me, since it's my understanding that
there's
> > almost
> > >> > > no app that you would want more than 45 or so degrees of advance
> > anyway,
> > >> > > from the tone of a lot of messages recently.
> > >> > > -> Bob Valentine
> > >> > > -> bob at tecmark.com
> > >> >
> > >> > > At 06:51 AM 12/5/2000 -0800, you wrote:
> > >> > > >DIS=Distributorless Ignition System?
> > >> > > >So what's the point of trying to get a "DIS" working on an
AUJP/730
> > >> if my
> > >> > > definition of DIS is
> > >> > > >wrong?  Explain to me why there is this holy-grail of getting
DIS
> > >> running
> > >> > > on a V8/730.
> > >> > > >Squash
> > >> > > >--- Chipsbyal at aol.com wrote:
> > >> > > >> This is not a DIS system as it is a distributor less system.
> > This is a
> > >> > CNP
> > >> > > >> coil near plug system. Each cylinder has its own ignition
> > module, coil
> > >> > and
> > >> > > >> plug wire. The interface that was at the show only drives the
> > separate
> > >> > > >> modules. Speed Pro also had an interface to use this CNP
> > ignition for
> > >> > > their
> > >> > > >> systems.
> > >> > > >> AL
> > >> >
> > >> >
> > >>
>
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> >
>
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