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Old 08-01-2011, 05:53 AM   #7577
The Jerk
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Joined: Mar 2006
Location: Brooklyn, NY
Oddometer: 2,658
Originally Posted by Lion BR View Post

A stepper motor, AFAIK, in response to ECU commands, would optimize engine performance by advancing/retarding timing on Variable Valve Timing engines according to changes in ambient and engine temperature, for example. My bike, when it stalls, the timing seems to be a bit advanced (specially on warm conditions), as engine at times will not stall but you hear a knock in the situation it would stall (blipping the throttle) and it catches up. And when it stalls, it is sudden, with no sputtering like it could do as a result of a fueling issue.
Ok you've got some bad info in here so I just want to clarify a couple things so the issue does not become even more confused.

A stepper motor is simply an electric motor that is configured to make very fine movements.

You are confusing ignition timing and valve timing which are two wholly different concepts. No motors or moving parts are used to adjust ignition timing (these days). The ignition timing is part of the ECU tune and is adjusted electronically via the ECU according to the map.

Valve timing is static and is set by the engine designers when the camshafts are designed and manufactured. Triumphs do not have variable valve timing.

The stepper motor in Triumph's case is a small electric motor (or motors - I can't recall if there's just one or if there's one for each throttle body) whose job it is to make fine adjustments to throttle angle to maintain a stable idle at the target idle speed as programmed within the ECU map. The ECU map provides for a target idle speed which is based upon coolant temperature.

Here's a screen shot of the idle speed mapping as shown in TuneECU. You can see that the ECU has a few reference points for what the target idle speed should be for various coolant temperatures and it extrapolates the points in between the defined target points.

You can thank Microsoft for the shitty quality of this jpeg.

I'll be interested to see how this angle plays out.
2000 Kawasaki W650

The Jerk screwed with this post 08-01-2011 at 02:17 PM
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