[Diy_efi] 2.0 diss module with the 1227749

[Shannen Durphey]

Djfreggens at aol.com wrote:
> 
> yeah i have found the stuff on the diy-efi website. most of it it actually
> useless garble. 
Funny, I posted some of that info because I felt it was helpful.  At least
it was to me.  The spark timing vs crank position diagrams were a great
find.

> i geuss i going to have to find a cavalier and get a couple
> of probes out and use the osciliscope. 
One issue with using a running car is that engine rpm actually varies
enough to make it difficult to determine offset with a scope.  You need to
know the engine rpm (fairly exactly, too) at the time you are taking your
measurements in order to calculate the number of degrees of timing offset
based on the time difference between similar points on the REF and EST
signals.  


> im sorry others have let you down. has
> anyone ever checked the output of the ecm to the module ??? i keep hearing
> that the duty cycle is 50% or so. also that is uses a high low refrence.
> formt eh schematic i looked at it was pretty simple. 
The only thing the schematic doesn't say is that the crank sensor pulses
can't be too many degrees away from the actual EST pulses.

> the module handle all
> the tpu need for the coil firing and the ecm simply provid a command siganl.
There are calculations for dwell included in the dizzy spark timing code
which are not needed in the DIS timing signal.

> just like a normal module on  hei would. 
A normal HEI module is only a trigger.  The ecm calculates both dwell and
timing for the distributor based modules.  The ecm also calculates maximum
timing advance/12.5 ms period to prevent insufficient burn time at the
plugs.  This is common to both spark systems.

>i think yr battle is in the ref
> angle and the output signal. 
I have already posted the physical reference angle.

> ill be a nice guy and get a couple of shots of
> the actuall dis module runnig on a car and comapare it to a normal hei shots.
> the answer has got to be pretty simple.
> ill get back to you in a few days. my
> question was basically has anyone done it and did it work. i got
> 
>  no and no .
That's not quite true.  The short answer is yes and 1 kinda, 1 maybe, one
not too bad, and one nowhere near good enough to call "good." You really
should search the gmecm archives and read some of the posts there.

> 
>   thats ok. ill get it working or at least figure out why it doesnt work. but
> if i can provide you with why the pid loop doenst work can you help me recode
> the 749 to operate properly. ???im pretty sure the answer is under our noses
> staring us in the face as always.

The more I see that you're not a "couch potato hobbyist" the more I'm
likely to find that I can share.
Just tired of folks underestimating the value of someone else's work.
Shannen

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