MembersPage/OveJohansen (2006-06-29 17:25:48)

Currently planning a Audi AAF/7A 20v VEMS Install in a 83'Audi 80GTE quattro (4000q for you yanks :-)

AAF 2,5l 5cylnder engine

7A 20v head and intake

89' 20v tubular exhaust manifoild

S4 camshaft pulley and tensioner

VEMS gen3.3 with fully sequentional injection and COP

I am not shure if I will go with the auditrigger setup, since it seems to have some issues.

I would rather not use the distributor for timing, but it may have to do for now. I allso have another approach to the audi 3-trigger system i would like to test, as soon as I have the engine running.

Consept: The audi 20v engines have 3 sensors:

A even 135 tooth starter gear vith VR sensor.

A single tooth Crank gear with VR? sensor.

And a single window Hall sensor in the Dizzy.

The original CPU uses ONLY the single tooth crank-signal wich comes at the same times as the hall signal from the dizzy.

This, I believe is done with a gate circuit, because these signals MUST come at the same time, wich can be a pain in the ass!

This should be just as easy to do with a divider chip, set to divide by 2. Use the cam signal to reset the chip, wich then will count to 2; only the Crank-signal on the second revolution after reset gets to the CPU.

Here, the Crank sync and Cam sync must NOT overlap, as the overlapped crank-signal would be skipped.

Why would this be better than the v3.x trigger setup ? The LM1815 detects the crankhome-VR, and the LM1815's output is masked (pulled down) with the cam-HALL.

The divider is not done in HW, because the divider in firmware doesn't take much time anyway (much less than the missing tooth detection): the CPU-load of dividing the 135 tooth in interrupt is no problem at all.

Any ideas are welcome!