How do you tune an ECU without knock control

[Bernd Felsche]

Hugh Keir tapped away at the keyboard with:

> A series of articles by Autospeed  http://www.autospeed.com/ based
> on Tim White's Bachelor of Engineering thesis entitled 'The Effect
> of Spark-Knock on the Performance of a Modern Spark-Ignition
> Engine' suggested to me that maximum power is achieved around the
> onset of spark-knock.

For practical purposes, the limit is when there is just enough
boundary layer left to protect the surface of the piston, cylinder
and head.

> I have also read other articles that suggest power is still
> increasing at the onset of spark knock, never mind that your
> engine may be detonating through carbon buildup / other
> overheating malodies.

It really depends on the geometry of the engine. If the integral of
the instantaneous torque is still increasing, then more power will
be available by advancing further. It's conceivable that for some
geometries, that the mechanical advantage of the conrod and crank
will mean a reduction in overall torque despite the higher pressures
early in the stroke.

> Motec and Autronic are generaly classed as highly competent
> systems by most commentators, yet they have no integrated means of
> displaying / reading knock.

Users of those systems can usually afford pumping extra fuel into
the cylinders to reduce the ONR (Octane number requirement) and to
run with less-agressive advance due to rich mixture and often no
need to comply with emission regulations.

> This begs the question for a DIY-er with no access to an engine
> dyno, how do you tune the ignition advance without risking blowing
> up your engine.

You always risk blowing up your engine. :-(

Acoustic method is better than none.

-- 
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