Re: 7747 spark control questions.

["Programmer" <nwester@eidnet.org>]

>>Does the bias not reflect what the distributor initial timing should be
set
>at?<<
>
>All the timing decals I've seen are "0" EST bypassed.
>
>>Why would you have a value like this unless it was just for something like
>ALDL output?<<
>
>I don't recall even seeing a spark value on a scan tool for a 7747 truck
>app. Tech 1 maybe ?
>
>>> You could just add 10 degrees to the timing tables and set the
>distributor at 0.  No need for subtraction in the timing table<<
>
>Well---that's how I thought it was.
>
>What is the raw value for the 50kpa@600rpm?

Oops...hit the enter key <g>.

Just checked a 1989 SWB Chevy with a 5.7L auto 7747 equipped.
Base timing is "0" BTC with the EST disconnected.
30 kpa @ 1000 rpm (cold) measured timing is 43 BTDC.
34 kpa @ 800 rpm (cool) measured timing is 38 BTDC.
--Got interrupted when some freight showed up--
32 kpa @600 rpm (70C temp) measured timing is 22 BTDC.

And no--I did not use the diagnostic mode on the scanner which bumps up
the timing. TC's tables appear to be bang on...Winbin's you need to subtract
the bias value.

Lyndon.

>>--- Programmer <nwester@eidnet.org> wrote:
>>> Ok, EST bypassed is non computer dizzy timing. You should then be at TDC
>or
>>> 0 degrees as per the timing decal. If Bias warm is 10 deg. Bias
>>> cold is 20 deg (I think). Winbin table for 50 Kpa @ 600 rpm is 29.88 deg
>>> whereas
>>> Tunercat is 20.1 degrees BTDC. (Using an ARJT as an example).
>>> Winbin adds 10 deg or includes the bias--TC doesn't add it-- so what's
>the
>>> actual "engine" measured timing value at 50Kpa and 600 RPM ? I'm
assuming
>if
>>> the WOT table has a negative, it's adding 10 bias. So lets' say we have
a
>>> negative 3 at 100Kpa and 1000 rpm--we've got an actual 7 BTDC at that
>point
>>> provided we set the ignition timing as specified. If we add 9 degrees to
>our
>>> base timing, we've then got a physically measured16 BTC at 100Kpa and
>1000
>>> rpm. Is this not correct ??
>>>
>>> Lyndon.
>>>
>>> -----Original Message-----
>>> From: Shannen Durphey <shannen@grolen.com>
>>> To: gmecm@diy-efi.org <gmecm@diy-efi.org>
>>> Date: October 17, 2000 10:41 AM
>>> Subject: Re: 7747 spark control questions.
>>>
>>>
>>> >Depends on reference or initial timing value at 0x009.  If bias is at
>>> >10 Dizz base at 9, and static angle is 9, spark table is only 10 deg
>>> >biased.
>>> >Shannen
>>> >
>>> >Programmer wrote:
>>> >>
>>> >> You're at 9 BTC with the EST disconnected ? That adds another 10 with
>>> >> EST connected. You're going to be close to 35-40 BTC hot idle.
>>> >> Lyndon.
>>> >> -----Original Message-----
>>> >> From: Reid Bishop <rbish@ibm.net>
>>> >> To: gmecm@diy-efi.org <gmecm@diy-efi.org>
>>> >> Date: October 17, 2000 12:52 AM
>>> >> Subject: RE: 7747 spark control questions.
>>> >>
>>> >> >>>Dissies are set "0" with the EST disconnected. The bins should
show
>>> main
>>> >> >>>spark bias at 10 degrees.
>>> >> >
>>> >> >Really?  Hmmmm... my 4.3 dist is set to 9 BTC, and I my spark bias
is
>>> set
>>> >> to
>>> >> >10.  I could still use more advance throughout the curve, but not
>>> working
>>> >> >that yet.
>>> >> >
>>> >> >Are 4.3's the exception to this rule?
>>> >> >
>>> >>
>>>
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