V8 DIS revisited

[Hector]

> If there's _any_ way for you to fix the width of your messages, that
would be
> very helpful.  They currently look like one giant sentence.  The
reply is hard
> to distinguish from the original post, as you'll see below.

Sorry about that. I changed to plain text and wrapped text at 70 char.
Hope that does it.

> ****
> It's a little more complicated than that.
> ****

>From looking back through the archives it seems you have been studying
this for a while.

> The problem with this approach may be that there's no way to start
the vehicle.
> The DIS module as used in the 2.8/3.1 V6 and the 2.0/2.2/2.3 4 cyls
fires at TDC
> when there is no voltage on the bypass line, then switches reference
pulse
> timing after 5V is applied by the ECM to provide a signal that's
advanced
> relative to piston TDC.  The signal is not 60 deg advanced for every
engine, nor
> is it 60 deg advanced for every type of DIS system.
> ***

So it won't work or it may not work. If maybe, I'll pursue it.

> You're speaking of two different issues.  The signal from the ecm to
the module
> is one area where a problem occurs.  This is the signal that some
people
> invert.  The signal from the crank sensor is an A/C signal, a
completely
> different beast.  Again, I'm speaking of the DIS system used on the
2.8/3.1 and
> others mentioned above.
> ****

Yes, that's the system I'm dealing with. I understand there are two
signals: one the module sees and one it sends to the ecm. My question
is whether the different reluctor design would delay the signal or
take the function of inverting it? Or, would it not matter and the
module revert to the same signal it sent out before? If someone has
inverted the signal, how? This seems the easiest and quickest way but
I wouldn't know how. Is it some type of gate or other Radio Shack
device?

> The difference in wave shapes can be attributed directly to dwell
control.
> Since this DIS system handles it's own dwell control, the ecm simply
cuts the
> time availabe between spark plug firings in half, and provides a
low/high
> signal.  Single coil distributor signals are calculated to rpovide
optimum dwell
> times, hence the varying width on/off portions of the signal.
> ****

OK, so by this statement you're saying it won't work. In order to run
DIS you have to run a DIS bin. Is this possible: run a 730 4 cyl DIS
bin with two coil packs. I understand you still end up dealing with
the two coil pack problems and of course the mask may not be available
for rookies like me.

> Timing and consistency are the most important parts of the DIS crank
sensor
> signal.  Any missed pulses from the crank sensor can result in the
module
> "resetting" #1 cylinder.

 Understood. If I pursue it, it'll have to be an exact thing.

> Better stop right there.  The reason that little's been mentioned
about the
> Caddy system is that no one's provided good information about the
system.  Do
> not
> assume that the 30 degree offset sensors proide the needed signals.
At least
> one individual who _should_ have Norstar DIS information has claimed
the sensors
> are part of a redundant system.
> ***

I should have taken a closer look when the engine was being swapped
out. Next time one comes in I'll inspect it a little more.

> ****
> You need to merge the output pulses from the modules, since each
would only
> provide 1/2 the needed pulses.  You'll need to separate the output
pulse from
> the ecm to be delivered to the correct module, since each handles
1/2 (and only
> 1/2) of the spark firing chores.

Wouldn't a constant single signal to the modules be OK? I mean, when
they are ready to fire, the signal would be for the right one, no?

> You'll want to synchronize the pulses from the
> ecm to the correct module to prevent firing the wrong plug.

I thought the ecm only handled timing duties, not cylinder selection.
A HEI bin doesn't know which cyl. is firing. Nor would a DIS bin
unless it had a cam sensor, or so I think.

>Remember that
> startup can cause either module to fire first.

Yes, it can but I don't see that as a problem as the spark will be
sent to the right plug regardless. The TDC mark will travel across the
crank sensor for one and 90* after, it will pass the other. The
correct module should fire the correct plug.

>Also, just for reference, the
> DIS systems that we're speaking of do not fire #1 cylinder first.
It makes
> little difference at this point, but it's somthing to keep in mind.
> ****

 That I didn't know but I guess it could be worked around. Which one
does it fire first?

> Welcome aboard.
> Shannen

Thanks and thanks for entertaining a redundant question. I guess I
have no clue as to what it's going to take to do this as it would've
been done already by someone with a bunch more experience than me. No
harm in trying though. I reckon the HEI will have to do for now. Who
knows, maybe something better is on the horizon!

Hector
http://soflaspeed.freeservers.com





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