Multi-Spark Ignition
03-14-2021, 11:01 PM
#1
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Multi-Spark Ignition
This came up in a spark plug thread (https://mbworld.org/forums/e-class-w...60k-miles.html ), and Mercedes Multi-Spark Ignition was new to me.
Here’s what the “Introduction into Service” manual for the M278 says,
Here’s an example of what’s reported online, https://www.roadandtrack.com/new-car...ech-explained/
I assume that the multiple sparks per cycle is only for lean conditions, and that during higher loads with richer conditions the system only fires the plug once per cycle.
Anybody have any definitive, additional information on this?
Here’s what the “Introduction into Service” manual for the M278 says,
“Multi-spark ignition - In contrast to the single-spark mode, several sparks are used in multi-spark operation. Rather than producing a succession of sparks by the single-spark method, the coil is recharged in the mean-time in order to provide sufficient energy for more sparks. A multi-spark ignition cycle begins in the same way as a single-spark cycle. The coil is initially charged to a desired target primary current. At the firing point the charging current is shut off, producing an ignition spark. However, in multi-spark mode the coil is not discharged completely. The secondary current, which is directly dependent on the charge level of the coil, is measured in the coil. If it drops below the secondary current threshold, the coil's electronic control reopens the power amplifier allowing the charging current to flow again. The level of the primary current is also monitored. When the primary current threshold is reached, the power amplifier closes the primary circuit and high voltage is generated once more. This causes another spark to be produced. Subsequent sparks are generated in the same way. In multi-spark ignition mode it is possible to drive with a much leaner mixture with stratified combustion. The advantage of this is lower fuel consumption.”
I assume that the multiple sparks per cycle is only for lean conditions, and that during higher loads with richer conditions the system only fires the plug once per cycle.
Anybody have any definitive, additional information on this?
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pierrejoliat (03-15-2021)
03-15-2021, 01:07 AM
#2
MBWorld Fanatic!
you'd probably need to hook a recording scope up to one of the coil trigger wires, and drive around monitoring what it does under various load conditions to know for sure. I got the impression from some reading that it uses fewer sparks at higher RPMs but still is multispark, ditto at higher throttle settings. our US 276/278 engines are *NOT* stratified charge in the same way the .EU engines are, because they had issues passing US NoX limits, and the true SC motors required a 2nd cat, which ours don't. The .EU motors are also like 13:1 compression (at least for the normally aspirated V6 that I have) while our US motors are 12:1... either of these is far higher than the more typical 9:1 or 10:1 of a gasoline engine that met US EPA specs 10 or 20 years ago.
gasoline direct injection is a whole new ball game in a lot of ways, its using a bunch of technologies originally developed for diesel engines, like my 2002 Ford 7.3 diesel uses split-shot direct injection.
gasoline direct injection is a whole new ball game in a lot of ways, its using a bunch of technologies originally developed for diesel engines, like my 2002 Ford 7.3 diesel uses split-shot direct injection.
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pierrejoliat (03-15-2021)
03-15-2021, 09:02 PM
#3
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Thread Starter
You're right, there's a lot of tech on these that I don't know about (and, heck, mine is 10 years old now!)
I spend enough time data logging my "fun" car, and I don't have any tools for the MB.
What we need is to have an MB engineer on this site to give us "the story"
What we need is to have an MB engineer on this site to give us "the story"
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Left Coast Geek (03-16-2021)
