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M3.3 waste spark

 
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Mykk



Joined: 05 Sep 2015
Posts: 96

PostPosted: Tue Dec 12, 2017 11:49 am    Post subject: M3.3 waste spark Reply with quote

Hey guys, can any confirm or deny if the Motronic M3.3 goes into waste spark when cam sensor is disconnected?

I've heard about the injectors going into batch fire and was wondering if ignition also went into waste spark. Thank you!
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olafu



Joined: 26 Jul 2016
Posts: 83
Location: Finland

PostPosted: Tue Dec 12, 2017 8:16 pm    Post subject: Reply with quote

Yes, coils will fire "wasted spark" and also, knock sensing will switch off, and ignition timing reduced for safety. (M3.3.1)
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Mykk



Joined: 05 Sep 2015
Posts: 96

PostPosted: Tue Dec 12, 2017 8:33 pm    Post subject: Reply with quote

Thank you. Any way to find that timing reduction table?
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olafu



Joined: 26 Jul 2016
Posts: 83
Location: Finland

PostPosted: Tue Dec 12, 2017 11:24 pm    Post subject: Reply with quote

I think it is that knock prevent table combo. I will check. Also, i think, raise knock control load threshold to 254 and timing reduction is gone.

olafu wrote:
I have intensively tried to find that correction what is changing "LOAD" by IAC-valve position in "Alpha-N" mode. But without success. But i found something else:
413/623 BIN:
0xE039 and 0xE050. We know, this "E039" is some kind knock prevention table what it is controlled by intake air temperature and coolant temperature. This E050 table expands this "knock prevention" to load and rpm dependent also. They are multiplied by each other, so, if you put value "0" to either table, whole correction is off. Seems like if you put 255 to one and something to other one, that other one follows x*0.75 correction to ignition angle. In case you put lower values than 255 to that other table, the effect will be reduced.

But both tables has effect to injection pulse width also. Bigger values in those tables will increase injection pulse width. (like that we know about that IAT vs. CLT table)

Also knock control "LOAD" threshold value is combined to those. In case of "forbidden 255" in that load table leads to case those E039 and E050 tables are always in use with maximum effect. If using value 254 in that knock control load table, those E039 and E050 will be still traced, but they have no effect to ignition angle or pulse width.

With zero values in E039 or E050 there is no matter if knock control load threshold is forbidden 255.. Ignition angle will follow main ignition tables.

This thing needs more research, too much "maybes" and darkness.
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Mykk



Joined: 05 Sep 2015
Posts: 96

PostPosted: Wed Dec 13, 2017 3:45 am    Post subject: Reply with quote

Thank you very much. I'm prepping my car for a race event in Tucson Az in a month, I'm mounting an MSD DIS-4 and two waste spark ign coils.

I've considered jumping the triggers of the ignition coil drivers internal in the DME to pair up the cylinders and only using cyl 1-4 ignition out for the MSD.
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olafu



Joined: 26 Jul 2016
Posts: 83
Location: Finland

PostPosted: Wed Dec 13, 2017 7:57 am    Post subject: Reply with quote

You propably must put some "dummy load" for every coil output. I think ECU cuts fuel from the cylinder which it detects the ignition primary failure.
About 1kohm resistor from "ign feed" to "coil output" is enough, so ecu detects there is 12 volts present between primary pulses.

In case ECU detects missing secondary current (no signal from secondary shunt resistor) it cuts fuel from that cylinder. But if all pulses missing from shunt resistor, it detects fault in secondary current monitoring, and doesn't cut fuel.

You cannot use that shunt resistor in wasted spark system, so leave it disconnected or ground it. In 6 cyl, i tried to cheat ecu, and hooked it to tacho output pin and didn't get fault codes Smile But i don't know how "safe" it is.
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Mykk



Joined: 05 Sep 2015
Posts: 96

PostPosted: Wed Dec 13, 2017 10:35 am    Post subject: Reply with quote

When I deleted the IAC my idle control tables were no longer being used by the DME. Instead I wired two LED's on the IAC wiring, shared +12v and the two controlled grounds from DME. It successfully tricked DME into thinking IAC was present and it started pulling data from idle tables again.

I'll experiment with a couple ideas; simulated load, deleted ground resistor...etc
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Hairyscreech



Joined: 20 Jun 2017
Posts: 146

PostPosted: Fri Dec 15, 2017 5:57 am    Post subject: Reply with quote

Why are you fitting the MSD box with the stock ECU?

Seems like a step backwards from the standard ECU and a big reliability decrease.

If you are running a NA engine then the stock ECU and coils is more than up to it, even boosted people have made 4-500hp on the stock M50 ECU, the ignition is not a weak point other than the age of the coils.

If you just want standard coil packs then mounting LSx style pack and using short HT leads is fine with the stock ECU.

You might be making life hard for yourself here.
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olafu



Joined: 26 Jul 2016
Posts: 83
Location: Finland

PostPosted: Fri Dec 15, 2017 10:04 am    Post subject: Reply with quote

Indeed. There is no reason for use compromissed ignition systems. Example with vw (tsi, fsi and others...) cop coils and some improvisation you get full features out of motronic.
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