[Gmecm] TBI Swap - Iron Duke Tech IV

[Steve Ravet]

> -----Original Message-----
> From: gmecm-bounces at diy-efi.org 
> [mailto:gmecm-bounces at diy-efi.org] On Behalf Of Dave Williams
> Sent: Monday, February 27, 2006 11:50 PM
> To: gmecm at diy-efi.org
> Subject: Re: [Gmecm] TBI Swap - Iron Duke Tech IV
> 
> Tomas J. Sokorai Sch. wrote:
> 
> >>   I was thinking of cutting some notches in the crank 
> pulley when I 
> >> noticed that the wire names and color codes between the 
> DIS coil pack 
> >> and the distributor and coil were the same, so I wired up the 
> >> distributor in place of the coil pack.  It started and 
> ran, first try.
> 
> > And runs OK at high RPM too? ... for what I read, the 
> problem of the 
> > DIS v/s dist code is the dwell calculation.
> 
>   All I've done is drive it around the back yard since I'm 
> still sorting out parts of the engine swap, so I don't know 
> that there's anything different about the high RPM operation.
> 
>   I thought dwell was a built-in function of the module in 
> the distributor?

Did you folks read the dist/DIS article I posted a few days back from
Shannen?  One piece of the problem is changing the reference angle in
the code to match the system (-60 for DIS, 0 for dist).  The other part
is modifying the "sanity checks" the code does after calculating
advance.  The code has upper and lower limits for the advance value.  If
the calculated value exceeds these limits then it's clamped to the
appropriate limit.  Calculated values for dist and DIS will be different
by 60 degrees, which is enough to always violate one of the limits,
meaning the computer will have the timing fixed at the limit at all
times.  No amount of MAP or rpm will be able to move it.  If the limits
are set to values that match the system (dist/DIS) then the calculation
happens, the value is accepted, and timing is correct.

--steve


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