Re: Ignition timing question

["nacelp" <nacelp@bright.net>]

Crankshaft degrees = 1/2 camshaft (ie distributor)
But yes, with the modern marvel of electronics, advance can be run much
closer to what the engine wants/needs.
  JGTSY (Just goes to show ya) what 30+ years does.
Grumpy


> I was going through some of my *old* engine stuff & came on some
> distributor curves once set on a '65 SBC.
>
> The timing was around 15° static, centrifugal max about 25°, starting @
> 1000 (engine) RPM, maxed @ 3000 RPM (total = 40°).  Vacuum advance would
> add another 12° or so at low engine loads.
>
> Studied some timing specs for various Syclone (7749 ECU) chips just now -
> *radical* differences!  Overall timing looks to be about *half* what the
> old dizzy specs were.
>
> Assume the normally aspirated section of the Advance vs. MAP & RPM table,
> i.e., ignore values above 1 bar.  Timing maxed at 3200 RPMs at about
> 16-17°; around 20° max added for light load conditions.  Naturally, retard
> needed under boost, but the NA part of the table is real different from
> what I'd expect.
>
> Seems to me *lots* of timing could be added at cruise & light load (light
> for a turbo) conditions - am I missing something here?  Are these big
> differences for emissions reasons?
>
> Thanks for any clarification -
>
> Puzzled - Barry - Sy#26
>
> Timing looks to be about half what the old distributor curves were
> --------------------------------------------------------------------------
--
> To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes)
> in the body of a message (not the subject) to majordomo@lists.diy-efi.org
>

----------------------------------------------------------------------------
To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes)
in the body of a message (not the subject) to majordomo@lists.diy-efi.org