How do you tune an ECU without knock control

[Bernd Felsche]

Bruce tapped away at the keyboard with:

> In the above statement you revert back to ignoring bearing damage.

Bearing damage will only result if the bearings aren't strong enough
to take the load under light knock.

> > The future may see
> > indirect pressure measurement being used in production cars; e.g.
> > piezo washers under head bolts. These allow the magnitude of
> > the pressures to be determined (ref SAE 1999-01-054).
> 
> Thought that was in use already.

e.g.??

> > Alternative technologies such as ion-current sensing are still being
> > refined (Bosch: SAE 1999-01-0204) to improve knock detection by that
> > method. Ion-current detection requires a "static" ignition system,
> > with a coil per spark plug and favours a non-central plug location.
> 
> If you limit yourself to Bosch's logic.

That's the typical implementation. Although an ionization current
only needs to be run for a short time after ignition, it's easy to
implement it with a coil per plug.

What are the other methods?

Or are you saying that the central plug location is preferred for
ion-current sensing?

> > The Bosch paper also describes some criteria for knock sensing and
> > nominal boundaries for pressure and knock-index.
> > It should be noted however that pressure is not in itself an
> > indicator of the likelihood of damage due to knock. It's the gas
> > velocity that does the damage; stripping the boundary layer and
> > exposing the surface of the metal to excessive temperatures.
> > The magnitude of the higher-mode oscillations in-cylinder is
> > therefore more significant than the primary mode due to knock.

> Guess you've never seen an engine *lift* a head.

No. Not due to knock. Strength of materials and rigidity issue.
I've "lifted" a head by over-revving.

> > The bounds have to be conservative, especially on German cars
> > because these can be used continuously at maximum power, possibly
> > for hours on end on public roads. It's expensive to replace engines
> > under warranty.

> Max power for hours on end?.   So in Germany the cars are sold
> without any speed limiters?.  Roads are that barren?.   That
> statement sure seems to follow form with some others you've made.

Yes. Maximum power, top speed for hours. Some roads are "that
barren" e.g. A31 North of Geeste and a number of others especially
early on summer Sunday mornings. On weekdays, traffic flows so
smoothly in most areas and lane discipline is so good, that you'll
be able to cruise at an indicated 180 (probably closer to 170 in
real terms) in a rental Polo (with "60bhp" engine) on a 3 or more
lane Autobahn until you're caught up by something much quicker, so
you have to get out of the fast lane.

Most German cars are sold without speed limiters. Volume production
models capable of over 252kmh have speed limiters that are easily
removed (it's usually just an ECU parameter) so many owners have the
limiter disabled at the first service.

-- 
Bernd Felsche - Innovative Reckoning, Perth, Western Australia
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