KA24E High Res Crank Cam Input

Testing and development of Megasquirt 3

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Stingy49
MS/Extra Newbie
Posts: 14
Joined: Thu Jun 22, 2017 11:15 am

KA24E High Res Crank Cam Input

Post by Stingy49 »

Hey All,

I Just got my MS3 working pretty well with my ka24e motor and now I want to try and get sequential fuel working on the stock optical cas. From what I've found online the optical disk/trigger wheel is slightly different to the one found in a sr20. The ka24e optical disk has 1 larger slot and 3 identical narrow slots. Here is a picture of the ka24e optical disk (first photo) versus a sr20 optical disk (second photo).

Image

Image

While my car was idling I captured some scope data of the low and high res channels https://drive.google.com/file/d/0B3z-Gm ... sp=sharing. From this data I was able to gather that the leading edges are evenly spaced between the four slots. The smaller slots have 3 high res slot falling edges occuring and the larger slot has 9 high res falling edges occuring. It should be noted that the first high res falling edge within each of the 4 main slots occurs very close to the rising edge of those 4 main slots. Maybe this would only be seen as 2 and 8 rising edges occurring inside the 4 main slots.

I still need to determine the offset of the large slot relative to TDC of cyl 1. It would make sense that it is 0* but I am not sure.

All of the following is assuming I can figure out how to create a new sparkmode setting. Looking at ms3_ign_wheel.c in the 1.4 source code, and assuming I would copy the sr20 code, it looks like I would need to change the "no_teeth" variable to be 2 (assuming 2 and 8 high res slots per main slot) and then set the "trigger_teeth" variable to values of 4,1,1,1. I think the "no_triggers" variable would change to be 4 also. Developers what is the "last_tooth" variable for? In xgate.s it looks like I would have to change the assembly compare lines from +-16 to +- the values im using (2 and 8 ). Developers is there anything major I am missing?

I'll post some matlab screenshots of the scope data once I have a chance to make the plots later this weekend.

-Derek
jsmcortina
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Re: KA24E High Res Crank Cam Input

Post by jsmcortina »

Do you have a composite log to post?

James
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Stingy49
MS/Extra Newbie
Posts: 14
Joined: Thu Jun 22, 2017 11:15 am

Re: KA24E High Res Crank Cam Input

Post by Stingy49 »

Here you are. I took one with the interrupt set to falling edge and rising edge.
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