Old Fashioned Tuning - Re: [Gmecm] EGT tuning (was BIG CAM TUNING)

[bcroe at juno.com]

19 Jun 2005  DV Fagan <dvfagan at yahoo.com> writes:
> Why not go to a drag strip, put a time only slip on it
> and make repeated runs advancing the distributor 2
> degrees per run until the et's fail to decrease.  

That assumes your advance already has the ideal curve.  
You might improve acceleration in one area while making 
it worse in another with a net  zero change that way.  

Instead I'd log period between sparks, which is 
the reverse of sparks per sec.  This will of course 
decrease as you accelerate.  Subtract the latest 
period from the previous one at each rpm to get the 
the first derivitive, Acceleration.  Plot A vs rev/sec.  
NOW move your whole curve forward and back a couple 
degrees, and plot those on the same graph.  You 
may see that a couple degrees more advance is 
better at some rev/sec, a couple degrees retard is 
better at other rev/sec, no change other places.  
Now reshape your advance curve for the best of 
each to be optimum everywhere.  

Likely taking the periods something like 20 sparks 
at a time will be more practical.  

The same problem comes with just varying fuel 
pressure.  Bruce Roe

Then
> at least  you will know what max ignition advance
> should be. It will be a fun evening and it shouldn't
> cost a lot.  On another evening you could increase
> fuel pressure with a  dozen quarters placed in the
> regulator one at a time in a like manner.  No
> programming and little cost (a gasket set for $6).  Or
> you  could reprogram the ecm 90+ times as some on this
> list claim they have done and spend years and
> kilobucks on chip programmers, erasers, ALDL
> interfaces, software, a laptop and PROM emulators. 
> It's your choice.
> Dennis 
> 
> --- Jay Vessels <jay at vessels-clan.com> wrote:
> 
> > Hi there!
> > 
> > A gas analyzer would be the best bet but it's not as
> > fast as a WB so 
> > you're probably going to only use it for a dyno with
> > a brake.