[Diy_efi] quick query re max ign advance ?

[John Petersen]

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"


_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://www.diy-efi.org/mailman/listinfo/diy_efi


_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://www.diy-efi.org/mailman/listinfo/diy_efi