Timing Jump on 165/TPI System

[Mike Rolica]

Yes, noticed that with my 165 on the dyno.  In the code It calls for the
jump when in limp mode  (Which is where it goes when est connector is
bypassed.  The advance is to protect the engine from burning the exaust
valves out of it at higher rpm's  ran all my dyno test's like this cause I
knew the advance would be set at  2 points.  From numerous pulls  and
knowing what adv was at specific rpm, I found what timing it liked for max
power under wot thru the rpm range (Got a Wot adv curve. Of course ther was
allot of playing with fuel pressure ect  But now I have a better idea on how
to edit the spark tables..... I have a base curve for wot.  Using a 3d graph
in word I plotted it and and the aujp (730)  spark table.  Mine had an
overal higher trend.  I compared it to spark at wot on stock chip and
mached the trend contour over the whole table  (integrate  my test curve and
stock chip  find the difference.) Take the intergral of the the stock table
and add the  difference to it.   It made a huge improvement, but I have to
wait till the track opens to fine tune it
Mike Rolica
Meridian Magnesium Products
Strathroy, Ont 
Ext. 260


	-----Original Message-----
	From:	Craig Moates [SMTP:craig.moates at home.com]
	Sent:	Sunday, January 09, 2000 12:06 AM
	To:	gmecm at efi332.eng.ohio-state.edu
	Subject:	Timing Jump on 165/TPI System

	Folks,

	A question:

	With timing control connector disconnected (ie. setting timing on a
	165-based TPI motor), timing should sit still, which it does for me
at low
	RPM. However, when I idle it on up to say 2000 or 2500, it seems to
advance
	like 12 degrees or so, instantaneously, and hold up there until I
idle it
	back down. Then it jump-returns to the previous value. This is all
	timing-light based. Any thoughts on what is being seen? There's
about a 1-3
	degree drift on idle-up, probably from timing chain stretch, but
that's not
	huge.

	Anyways, fishing for thoughts. It's not problematic, just would like
to
	understand what's happening and why.

	Sincerely,
	Craig