Maximum advance

[Axel Rietschin]

> Axel Rietschin wrote:
>
> >
> > The true solution is to use an engine dyno. Chassis dyno is probably a
bit
> > better than open roads to make a ignition map, but it is still far too
noisy
> > to do a good job IMO. Also you may well melt a few engines before you
figure
> > out what is knock and what is not on the pressure diagrams, or while you
> > debug your filtering software.
> >
> > With a copper pipe bolted on the head and connected to a "stethoscope"
on
> > <snip>
> > the old way is still by far the best IMHO.
> >
> > --Axel
> >
>
> Just out of curiosity, was there a torque peak or other indication of
"good"
> timing at detonation - 2 deg. ???  Could torque have been higher at
detonation -
> 4 degrees ---- or 6 deg.???  Do you have any data logging that would
help???
> Just trying to skin the cat another way.  I realize that turbo motors have
> different characteristics (faster flame speed, etc.), ( and they are
easier to
> melt),  but we are looking for peak torque w/o detonation. Some engines
make
> more torque after detonation starts (diesels).   Tom S.

Tom,

Turbo engines are mostly constrained by the knock limit, i.e. they run with
less than optimal advance past a certain boost pressure. Actually, the
engine responded very well to increasing ignition advance but I had to stop
and back off when knock started, however, there was more in there :-) I
didn't want to _depend_ on water injection for engine survival and we
already had more than 530Nm so the compromize was to use water as an
additional safety only. The engine was mapped for 98RON fuel and I know that
using 102RON race fuel would allow for about 8-10% more power before the
knock limit is reached again. On most stock NA engines, given the proper
fuel, it should be possible to reach MTB without seeing knock but if, for
example, you increase the CR even a little, you may hit the knock limit just
as well.

--Axel


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