[Diy_efi] Timing Advance Curve?

[Geddes, Brian J]

I was already thinking that what you describe below was true - good to =
get confirmation.  I'm running a '90's designed 6-cylinder turbocharged =
engine (6G72, Mitsubishi 3000GT VR-4) with over 1 bar of boost, so I'm =
guessing that I'll reach the ping limit at boost well before the torque =
limit. =20

- Brian


Further a few words to timing advance. Engines of newer conception (4V, =
=3D
central spark plug, CR~11) will have at loads lower than 50-70% their =
=3D
best advance before "pinging". At full load, knock limit is always the =
=3D
best.

		--- so long ---, klaus.


There also remains a problem with late model 4valve engines in that some =
of
them hardly detonate at all! I have seen Mazda MX5 (Miata) engines on =
the
dyno which don't ping, or at least give no indication of pre ignition
audibly with well over 40 deg advance, WOT and max. torque. The only
indication was a drastic reduction in power.

I have also seen one F3 engine builder destroy dozens of Mitsubishi =
engines
(4G63 I think) before they got the timing right. Part of the reason was =
that
the dyno guys had trouble figuring out where the ping limit was. Then =
when
they installed the engine and it was subjected to ram effect through the =
air
box, Kabang! Admittedly, these engines run air restrictors and CR's in =
the
region of 13:1, so getting the ignition map right is an art form in =
itself.

The really clever engine builders (Neil Brown, Speiss Tuning) use the =
method
prescribed by Klaus. But the cost of the test equipment is horrific.

Just a word of caution for anyone trying this theory with modern 4valve =
N/A
engines, that's all.


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