Can 4-1 cam pickup be used for wasted spark?

[Fii]

I am using v3 main board with MSnS-E and I would like to run wasted spark ignition.
When I got the engine (Toyota 4A-GE blacktop), it came without the distributor, so I found a distributor in local junkyard which is from different engine, but physically fits.

I would like to use it for pickup in order to run wasted spark coils directly from MS.

The distributor has two wheels:
1) 4 tooth wheel with two VR sensors 90 degree apart, which seems to be connected in series to output one signal to ECU (red, white; bottom green wire connects both sensors).
2) 1 tooth wheel with VR sensor on top, which outputs second signal to ECU (green, white-black).

Can I use this setup with MS? How do I setup this in MegaTune?
Do I need to modify it somehow?

It seems that it gives enough information to ECU to run even COP, but does the software support this setup?

For details and pics of the mentioned distributor, please see this thread:
http://www.msefi.com/viewtopic.php?p=121504#121504

[mollama]

hi,
when the second sensor gives 1 signal per 720°crankshaft, and the first at least 4 in between you can use it for cops and with dual dizzy for wasted spark.

greetz Thomas

[Fii]

I already have wasted spark coils from my old 7M engine. I would like to use them if possible. Maybe it is possible to somehow configure, that every second spark event goes to the same coil output?

I think the pickup should be separate from spark triggering. Pickup should be used for figuring out the crank position, and then that information should be used to fire the coils at the right time. Am I missing something?

[jsmcortina]

I already have wasted spark coils from my old 7M engine. I would like to use them if possible. Maybe it is possible to somehow configure, that every second spark event goes to the same coil output?

The "dual dizzy" option will do this as mentioned above.

James

[Fii]

Thanks, I think i finally got it. However I have questions regarding the rest of the spark options. Below are my current draft settings. This is the first time I am doing something like this, could you point out, if I have made some wrong assumptions?

Wheel decoder base teeth: 4 (since there are 4 main teeth between 2nd trigger events)
2nd trigger enable: 2nd trigger (enable second wheel)
2nd trigger active edge: raising (not sure about this, which would be prefered in my case? What parameters impacts this decision?)
2nd trigger and missing teeth: no missing (I use 2nd trigger)
Trig pos A: 1 (1st teeth after 2nd trigger)
Trig return pos A: 0 (Since there are no tootth between two trigger teeth, it is not possible to use return pos)
Trig pos B: 2 (2nd teeth after 2nd trigger)
Trig return pos B: 0
Trig pos C: 3 (3rd teeth after 2nd trigger)
Trig return pos C: 0
Trig pos D: 4 (4th teeth after 2nd trigger)
Trig return pos D: 0
Trig pos E: 0
Trig return pos E: 0
Trig pos F: 0
Trig return pos F: 0
Dual dizzy mode: Dual dizzy (To run wasted spark with one 2nd trigger per 720deg on crank)
Wheel decoder routine: 024s9 style (I read that wheels with low number of teeth better works with this version)

Trigger angle: 60deg (Need more than maximum desired advance, just a guess)
Trigger angle addition: 0 (Don't know)
Cranking timing: Time Based (Since there are no trigger return pos)
Cranking advance angle: -10deg (Default value)
Hold ignition: 0 (Don't know)
Spark output inverted: Yes (I am using 2 x VB921 for wasted spark)
Experimental oddfire: No (Don't know)
Fixed angle: -10deg (To force reading from spark table)
Trim angle: 0deg (Don't know)

Do I get the following right?
1) When main wheel is triggered, the software assumes that the current crank position is 60deg BTDC for that cylinder and based on rpm calculates how long it should wait till actually outputing spark event to get it right according the table. Should this parameter be as close as possible to maximum advance + dwell time, or it does not matter so much?
2) 2nd trigger just resets the count, so when the main wheel is triggered after the reset it is assumed that the first cylinder should be fired.

There is a parameter "2nd trigger active edge". Why there is no corresponding parameter "main trigger active edge"? I understand that it is about when the trigger should happen - on the rising or falling edge of the signal. But what are the pros and cons of both of them? I noticed that teeth on my main wheel are not symmetrical - they are increasing gradually, and falling straight down - what is the reason for that?

[jsmcortina]

Main trigger active edge (at the CPU pin) is always falling. You can change the opto/VR wiring to give you rising or falling trigger.

The rest of you assumptions look on the right track. One slight clarification, the 2nd trigger resets the tooth count but it doesn't _have_ to be for cylinder one, that does make things simpler to understand though.

You may need to modify your distributor to phase the rotor arm correctly.

Also remember that triggering from the dizzy will still give you up to 5deg of timing slop. Crank triggering IS better.

James

[Fii]

Also remember that triggering from the dizzy will still give you up to 5deg of timing slop. Crank triggering IS better.

Is it because there are less teeth per revolution on cam, or it has something to do with how cam is driven from crank?

[shaodome]

5 degrees! whoa...i didn't think it was THAT much....

[jsmcortina]

Maybe I'm getting carried away quoting five degrees?

It is a mechanical issue due to chain or belt stetch and any play in the distributor drive gears.

James

[shaodome]

I figured you were meaning belt stretching, but on my engine when it was based off a dizzy tach input for spark timing, it only wandered 1-2 degrees at most. Seemed pretty consistent for Ryanpzz and I.