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12-10-2004, 01:09 PM

#21

Sharif@Forged

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Dave, can you elaborate on the crank angle resolution issue? How does the AEM Standalone know the exact crank angle position if the resolution is only 12 teeth??

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12-11-2004, 09:35 AM

#22

dynamic6er

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Quote:

Originally posted by gq_626
Dave, can you elaborate on the crank angle resolution issue? How does the AEM Standalone know the exact crank angle position if the resolution is only 12 teeth??

Sure. Maybe I should clarify a little bit. The AEM can "see" or log the input of additonal teeth, but does not factor them into the ignition or injection cycle. The position of the crank is interpolated between teeth.

The screen capture below is from a table created by SA an engineer at AEM for a Bosch 60-2 (58 tooth) wheel. Based on the other information in the calibration file I believe it is for an VW/Audi 1.8T.

AEM CRANK TOOTH TABLE

(the picture may be down because our server is being upgraded)

This is from the A_Tooth Table help file in the AEM Pro software. The numbers on the Y axis of the graph are the instuctions for the AEM to follow each time it detects a tooth. The X axis is the imaginary number each tooth has been assigned.

Tooth Control table – In order to improve timing pattern flexibility, the crank signal is processed by the Tooth Control table, accessed with the value of A_Tooth, the actions to be taken are encoded in 3 bits:

Number Function
0 Do nothing.
1 Process significant edge.
2 Process alternative edge, used for crank firing.
3 Force reset of A_Tooth, if loss of sync.
4 Test for synchronisation
5 Process significant edge and Test for synchronisation.
6 Process alternative edge and Test for synchronisation
7 Reserved

As you can see the EMS is directed to detect 12 teeth and ignore the other teeth. The teeth that are processed are at 5. The unprocessed teeth are at 0. The teeth at 4 are a place holder for the 2 missing teeth on the BOSCH trigger (60 minus 2 or 58) they are technically processed, but unused for calibration.

Take a look at the Subaru calibraitions. In the AEM PRO software go to SETUP/SENSORS/CAM/CRANK SENSORS/<<ADVANCED CAM/CRANK PICKUPS>>/ADVANCED PICKUPS. It will be a similiar situation to the 60-2 shown here.

This all makes sense, because the EMS system was originally designed for the Toyota Supra TT. The 2JZ uses a 12 tooth crank trigger.