Dear Ralph: I have a 2007 Ski-Doo MX Z 600 HO SDI. When I was adding oil the other day, I noticed a wire...

Dear Ralph:
I have a 2007 Ski-Doo MX Z 600 HO SDI. When I was adding oil the other day, I noticed a wire going into the muffler. What is this? I figured it might be a temp sensor, but that doesn’t make any sense, either.
via www.snowtechmagazine.com

Yes, the wire running down into the muffler is indeed a temperature sensor. This is one of the many inputs that is being analyzed by the on-board computer (ECU) as it keeps the engine running properly.
A muffler temperature sensor is different from an exhaust gas temperature of the tuned pipe. The sensor in the muffler of an SDI engine is a safety device to prevent the muffler from overheating. This is really only needed in lean-burn engines like the SDI. If the muffler gets too hot, the ECU will go through one stage of trying to cool itself down, before dropping to a limp home mode. During “normal operation” it does absolutely nothing.
Also of concern is unburned fuel entering a hot muffler, going “BANG” (the backfire when you turn the sled off). This is why, after a good hot run, you should always let your sled idle down for a few seconds before hitting the kill switch. If you come in hard and quickly turn the engine off, there will be more fuel coming through the exhaust and when it gets to a cherry-hot silencer, this is where the “BANG” can come from. This holds true for all two-strokes; you really should let them come down to idle before cutting the ignition.

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