[Diy_efi] Timing Advance Curve?

[Adam Wade]

--- "Geddes, Brian J" <brian.j.geddes at intel.com>
wrote:

> So there are basically two timing limints we're
> talking about.  First is the point where torque
> stops rising or rises very slowly - like a point of
> diminishing returns for timing.  The second limit is
> the point where the engine starts to knock on the
> fuel/IAT/etc combination that you're running.  

> The problem is that these two limits - knock and
> torque - do not necessarily come in the same order
> on all engines.  On some NA engines, the knock limit
> may be well beyond the torque limit.  On
> turbocharged engines, where the A/F mixture is
> pressuirized, hotter, and more knock-prone, the
> knock limit is most likely lower than the torque
> limit.  At least that's what I think I
> heard...anybody else care to confirm?

Well, if you are talking in that sense, simply up the
octane to cover the extra compression.  However, you
can run into a point of diminishing returns as far as
power output at higher rpms with the slower burn...

As far as what I *think* was initially being said,
that there is a power curve that is static and based
on timing advance, and some engines will ping before
they "get there", that's not so, as such.  What gives
you the ability to advance timing and get a "response
curve" to changing ignition timing at a set engine
load and speed is generally the shape of the
combustion chamber, and different shapes will give
different "response curves".  Some will be very brupt
in "going to ping".  Thus has been my experience.

=====
| Adam Wade                       1990 Kwak Zephyr 550 (Daphne) |
|   http://y42.photos.yahoo.com/bc/espresso_doppio/lst?.dir=/   |
| "It was like an emergency ward after a great catastrophe; it  |
|   didn't matter what race or class the victims belonged to.   |
|  They were all given the same miracle drug, which was coffee. |
|   The catastrophe in this case, of course, was that the sun   |
|     had come up again."                    -Kurt Vonnegut     |

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