4 cylinder wasted spark with LS coils?

[jayhorsley80]

So I have 4 LS truck coils that I would like to run in wasted spark. Should I build circuit 5.3.1.3 in the msextra hardware manual pg 76? I will be running a 36-1 trigger wheel and no cam sensor. I am guessing that I should use the circuit and use the top R26 to feed Spark A and C, and use R29 to feed B and D?

[Matt Cramer]

What MS variant do you have?

[jayhorsley80]

It's an MS2 v3.0 after reading the manual that looks like what i have to do. it looks like I could just take the top of R26 and feed it into both inputs of one IC and that would give me the trigger for cylinders one and 3. Then the top of R29 would go into both inputs of the other IC and that would trigger cylinders 2 and 4. I have the ICs to build the circuit allready. I figure I can get an O-scope to check the signals to verify operation. I am attaching the screenshot of my ignition settings from tunerstudio.


[attachment=0]2016-06-20.png[/attachment}

[Matt Cramer]

That wouldn't work with a 1-3-4-2 firing order. Is this a flat four?

[jayhorsley80]

You are correct! Its an inline. How bout 1 and 4 then 2 and 3.

[prof315]

Your correct pairing would be 1&4 and 2&3 but if you are going to fire the that way you want wasted spark not wasted COP in your ignition options settings.

[jayhorsley80]

Thanks for the heads up on the spark setting. May I ask how wasted COP fires? Just for reference of course.

[prof315]

Thanks for the heads up on the spark setting. May I ask how wasted COP fires? Just for reference of course.

Wasted COP fires the coils in pairs as well but each coil has it's own driver so you would need 4 ignition drivers run from 4 channels.

[jayhorsley80]

Ah hah, thanks again guys for the info.

[jayhorsley80]

So if I am reading this properly. It will only take one TC4427 to drive my two spark channels to my 4 LS coils?

[herron_mac1]

So if I am reading this properly. It will only take one TC4427 to drive my two spark channels to my 4 LS coils?

I think you're half way there. I'm in the same boat as you except i am using Vw COP 20T Logic coils on my 16v. From what I read you need total of 2 TC4427s and said resistors. One TC4427 for each "pair" of coils. this is what creates the wasted spark, kind of like the injector banks. Any other input on this guys?

Also, just for my own clarity, when it says 15R 1/8, they are mentioning I need a 15k ohm? I can't pin in 15R in digi key...

[jsmcortina]

Just a note that LS coils aren't designed to run as wasted spark. They _can_ be used that way, but best to get a wasted-spark coilpack if that's what you want.

That resistor is 15 ohms (R is used to means ohms) they are not 15000 ohms.

James

[prof315]

So if I am reading this properly. It will only take one TC4427 to drive my two spark channels to my 4 LS coils?

I think you're half way there. I'm in the same boat as you except i am using Vw COP 20T Logic coils on my 16v. From what I read you need total of 2 TC4427s and said resistors. One TC4427 for each "pair" of coils. this is what creates the wasted spark, kind of like the injector banks. Any other input on this guys?

Also, just for my own clarity, when it says 15R 1/8, they are mentioning I need a 15k ohm? I can't pin in 15R in digi key...

Wasted spark needs 1 driver for every 2 cylinders. Each TC4427 has 2 drivers in it. So 1 TC4427 for a 4 cylinder engine running logic level wasted spark coils.

15 ohm 1/8th watt is the resistor value.

[jayhorsley80]

That is excellent news. I am running out of space on the proto area!
I was unsure on how much current draw two coils would have on the output of one channel. So that makes me happy. Thanks again everyone.

[dontz125]

Just a note that LS coils aren't designed to run as wasted spark. They _can_ be used that way, but best to get a wasted-spark coilpack if that's what you want.

There are very few logic COPs that run wasted spark. What's the issue? Operating frequency?

[jayhorsley80]

I can't see frequency being a problem here. A 4 cylinder running wasted spark should operate at the same frequency as a LS running sequential at a given RPM right? For the sake of learning could we be enlightened on the issue for LS coils running wasted spark?

[dontz125]

Not exactly. Whether 4 or 8-cyl, a wasted coil fires twice per cycle; a sequential coil only fires once. A COP fires just as often at 12000rpm as a wasted coil at 6000. If operating frequency is an issue, an LS coil firing wasted in my 250 would probably slag itself before it got down the block!

[herron_mac1]

So if I am reading this properly. It will only take one TC4427 to drive my two spark channels to my 4 LS coils?

I think you're half way there. I'm in the same boat as you except i am using Vw COP 20T Logic coils on my 16v. From what I read you need total of 2 TC4427s and said resistors. One TC4427 for each "pair" of coils. this is what creates the wasted spark, kind of like the injector banks. Any other input on this guys?

Also, just for my own clarity, when it says 15R 1/8, they are mentioning I need a 15k ohm? I can't pin in 15R in digi key...

Wasted spark needs 1 driver for every 2 cylinders. Each TC4427 has 2 drivers in it. So 1 TC4427 for a 4 cylinder engine running logic level wasted spark coils.

15 ohm 1/8th watt is the resistor value.

Thanks for the clarity. It looks as I split each of the legs from the TC4427 to 2 COPs. makes sense and is a whole lot easier. I have no plans to go full sync which would change everything anyway. Now have to remove my bips.

[billr]

Wait! "Get rid of the BIPs"? The TC4427 is not (much) of a coil driver at 1.5A, you will still need something like the BIP373 to actually power a coil.

[dontz125]

He's running VW logic coils.