[Diy_efi] quick query re max ign advance ?

[Mike]

This is great - thanks John,

my existing factory ECU doesnt retard timing at all when boost
rises (as far as I can tell), its possible I could do it with
a diaphgram (no jokes;) and suitable linkage, my first step is
to get the ign display properly functioning, thanks for the
fedback, So if I set the abitrary ref to 60deg before real
TDC then I have plenty of room to count backwards (as it were)
to arrange start of ignition or as timined injector start...

rgds

mike


At 10:06 AM 18/11/2002 -0500, you wrote:
>I am not familiar with your application, but can provide this
>information. 
>
>On an Audi 2.2L turbo at 7000 rpm advance varies between 39.8 deg BTDC
>and 18.1 deg BTDC. The lower figure being at 0% load, and the upper at
>100% (which also corresponds to about 2.5 bar absolute boost). Low
>advance is necessary at high boost to prevent detonation.
>
>Hope this helps.
>-John
>
>
>
>-----Original Message-----
From: diy_efi-admin at diy-efi.org [mailto:diy_efi-admin at diy-efi.org] On
>Behalf Of Mike
>Sent: Monday, November 18, 2002 1:58 AM
>To: diy_efi at diy-efi.org
>Subject: [Diy_efi] quick query re max ign advance ?
>
>Hi chaps,
>
>I'm putting together a low end micro based distributor timing
>verification unit to suit by GMH VL T3 turbo straight 6cyl 3L.
>The initial purpose is to indicate what the CAS and ECU are
>actually doing and view this in degree increments whilst driving
>and in due course to prepare a feasability for simple unit to
>work with the existing ECU and replace the mechanical spark
>distributor with a 3 coil waste spark driver - or if the coils
>are cheap enough a 'coil pack' equivalent driver...
>
>The distributor (classic 6 cyl rotor spark unit) includes
>a crank angle sensor (CAS) that gives out 2 logic signals:-
>
>a.	Degree pulse - 360 rising edges per CAS rotation and
>	as the CAS rotates once for each two crank revolutions
>	I can use the falling edges as well for 720 occurences
>	hence get 1 deg resolution on actual crank rotation.
>	(no I'm not interested in any interpolation yet)
>
>b	Main index, high going pulse thats coincident with 9 CAS
>	pulses at TDC otherwise coincident with 3 CAS pulses for
>	the other 5 index pulses. ie There are 6 of these main
>	index pulses in total per CAS rotation, standard stuff.
>
>For a calibration on the car, the CAS is rotated to give 15 deg
>ignition advance at idle (750rpm), so I infer the effective TDC
>signal is somewhat ahead of the real TDC of cyl 1 such that ECU
>algorithms are simplified. There is no fixed TDC reference for
>any cylinder and the mounting allows for approx 45 deg variation
>in CAS rotation during timing cal.
>
>My question is what is the anticipated maximum advance that one
>would expect on a 4 stroke engine - would it be as much as 60
>degrees advance for say 8000 rpm  - for the crank/CAS difference.
>
>ie. The actual difference from indicated TDC by the CAS to real
>TDC of cyl 1 ?
>
>
>
>
>
>
>Regards
>
>Mike Massen
>Hm 08 9444 8961,  Mb 0438 048961
>
>Some power stuff here: http://www.iinet.net.au/~erazmus
>
>Ancient Sufi saying:
>        "Should your God save you from adversity, choose another God"
>
>
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