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Wasted Spark using 3 x VB921?


NZeder

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Anybody tried the WS setup using 3 x VB921 and MSNSe? On either a V2.2 or V3 board? I have been doing a bit of reading about this and my only real question is could I use the stock 280zxt dizzy as my CAS for this type of setup. Anybody know? Looking at the MSNS site under using Distributor Setup I see this pic so I guess it would be possible

vb921-driver-extras.gif

So I have not installed my MS yet - only just completed building it (I have been waiting for the time and more work to be done on the body work) I have a v2.2 board with the flyback daugther board so I am thinking of building another board to hold the 3 x VB921's and resistors etc. and for a WS setup from day zero.

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Ok I found the answer :)

 

replace the stock trigger disk with one from these guys :)

http://www.autronic.com/page_files/trigger_disks.htm

 

Given that I have read that a number of guys use the VG30 internals in the 280zxt dizzy then I will pick up one of these units (and maybe the CA18 for my other car + the RB30 unit so I do go down the install a RB CAS in the dizzy hole path then have this for Just in Case). I will then follow the 2nd trigger setup as stated here http://megasquirt.sourceforge.net/extra/wheel2.html

 

I have contacted the local dealer and I am now waiting to hear back re these disks

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To do true wasted spark, you will need three separate TTL outputs to drive the three VB921s. Yes, the MS can do this, but I'm not sure if the firmware supports it.

 

If you drive all three VB921s with the same ignition output signal, you will fire all six plugs simultaneously. Not sure how this would effect idle, performance, etc., but it should work.

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MSnSE 029q2 has support for 6 spark outputs - :) so you could do COP (coil on plug)

 

So what would be best a autronic trigger disk and the 2nd trigger circuit/setup or just go for a 36-1 or 60-2 wheel with a pick?

 

If I go with the missing tooth setup what is a good Hall sensor to use? Or will it have to be a VR type sensor? I am thinking I could custom make a disk for the 280zxt CAS dizzy that would be a missing tooth setup - would this work (in wasted spark setup I would not need the rotor or dizzy cap.

 

Cheers

Mike

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For actual COP you would need three magnets/teeth on the crank wheel and one magnet/tooth on the cam.

 

If you only want wasted spark, then you can just use a crank wheel.

 

I would recommend either 6-1 or 12-1. Ther is some indication that future code will be able to use the extra teeth for predicting rpm differences for more accurate timing.

 

The more teeth, the harder the processor has to work to sort things out, which is why I recommended the minimum or maximum.

 

You can use a hall sensor if you use magnets on/in the back of the dampner, if using teeth, you would need a VR sensor and the appropriate circuitry added (if using v2.2).

 

If you do a search on the MSEFI forums for hall and wasted spark, you should find a thread that has both a newer version of hall and the one SDS uses.

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  • 7 months later...

Well time to bring this back from the dead.

 

I am very interested in running a COP with my MS V3 using the stock 280ZXT distributor. We have a good bit of information going on this L28 post about using a 280ZXT dissy CAS to power a Wolf 3D EMS so why not use MS??

 

http://forums.hybridz.org/showthread.php?t=119783

 

So if we can use the stock dissy with modified CAS and say LS1/2 coils will we need to use VB921 for each of the coils??

 

If so what will be the output for each of the 6 coils, also what will the wiring diagram look like?

 

Hb280ZT

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The LS1 coils already have igniters built in (the VB921 is an igniter), so all the MS needs to provide is a +5V logic pulse, with it's width being the coil charge time (dwell). So you need to use three ignition outputs from the MS, each driving two LS1 coils. I plan on measuring the input current requirements for the LS1 coil input trigger. Once I know that, I can recommend a TTL (+5V logic) buffer to provide enough current to drive two LS1 coils in parallel. My next project will most likely use a 36-1 crank wheel, and LS1 coils with MS.

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