Maximum advance

[Shirley, Mark R]

Applications like this is where you start looking into revising
the cooling system to take more hotspots out of the combustion chambers.
Reverse cooling systems where the heads are cooled first, followed by the
cylinder liners are the best.

Mark

> -----Original Message-----
> From: Axel Rietschin [mailto:Axel_Rietschin at compuserve.com]
> Sent: Wednesday, July 25, 2001 6:47 AM
> To: diy_efi at diy-efi.org
> Subject: Re: Maximum advance
> 
> 
> > 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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