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Old 27th March 2017, 14:26   #1
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Default Motorbikes: How Electronic or Fly-by-Wire Throttle works

This is an attempt to simplify the new tech that was earlier seen only in bigger and more expensive bikes and with the launch of the new KTM 390, we would seeing this electronic throttle mechanism too.

We were discussing the change from cable driven throttle to the newer optical sensor /fly by wire systems which were noticed en masse on the Triumph Tiger and now we find that the KTM 390 too will have it. A completely new segment of riders will be shortly introduced to this technology, probably just one of many new things to come to India soon.

Indian riders born and brought up with the constant fear of substandard cables and the like, always had questions and even figured out which Yamaha or Pulsar cables for their Harleys. Now with the advent of the Optical Sensor (or throttle position sensor) driven throttles, the fear of dust, rain and physical damage continue in the mind of the riders.

I have tried to explain how the new system is built with a certain 'vision' and thought and how this works.

The signal from the throttle control actuates a transponder which generates electrical impulses. This is almost similar to the volume button on an older amplifier that can be found in almost any house. Depending on the twist, the the signal that goes to Electronic Control Unit (ECU) of your bike is varied. The ECU calculates th demand and the urgency (rate of change as seen by the OS/TPS and therefore commands the throttle butterflies to open at a given computed rate. This involvement of the ECU then permits a few things to be managed very well- cruise control, variable power requirements like rain, of road, track etc. Any yank on the throttle when in off road-situation would instantly result in a more relaxed command to the throttle body than what its cable driven counter part would- possibly resulting in an unwanted jerk, which could result in wheel spin and therefore a crash too.

This is the good of the 'fly by wire' till such time that the desi mentality of 'what if..' creeps in? What if dust enters the optical sensor or the resistor (depending on the bike) which is generating the throttle position reading, and the unthinkable happens. 500Km from home and possibly 700 from the nearest service center! Let me try and explain how the system is integrated in the Triumph Tiger and how redundancy is built in.

The optical sensor (OS) that works with the throttle, has a secondary sensor with it. In the failure of the first sensor and when the ECU detects the lack of a signal from OS1, the OS2 takes over and the motorcycle can carry on till its destination and then service center for repairs.

The cynical rider came up almost immediately with plausible events on Indian roads- fall- unintentional in a parking lot, crash, or an errant stone from under the tire of another vehicle- ten different scenarios. We agree to one scenario- and proceed. So the motorcycle has a fall or is physically damaged and in the unlikely event of both OS'es getting damaged, then what?

Should the ECU detect failure of both the OS it sends an emergency override signal to the engine, and will lock the throttle at 3000 RPM constant. This enables the bike to get itself home in a 'limp home' mode and the 3000 RPM is enough for the bike to maintain a steady and relatively safe 60kmph in 6th gear- enabling it to ride on almost any highway in the world.

IF one puts logic to it, then it suddenly seems very simple. It would be interesting to learn from others on topics that are new to our sub-continent- also where my knowledge or writing may be incomplete, please do feel free to pen in your comments.

Last edited by GTO : 28th March 2017 at 11:26. Reason: Paragraph spacing - thanks for sharing!
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Old 28th March 2017, 12:20   #2
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Default Re: Motorbikes: How Electronic or Fly-by-Wire Throttle works

Quote:
Should the ECU detect failure of both the OS it sends an emergency override signal to the engine, and will lock the throttle at 3000 RPM constant. This enables the bike to get itself home in a 'limp home' mode and the 3000 RPM is enough for the bike to maintain a steady and relatively safe 60kmph in 6th gear- enabling it to ride on almost any highway in the world.
This is so cool, definitely a life saver. Any idea if a similar feature is available on the new Duke 390?
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Old 28th March 2017, 20:22   #3
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Default Re: Motorbikes: How Electronic or Fly-by-Wire Throttle works

Difference between car and bike throttle by wire systems?

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Old 29th March 2017, 11:19   #4
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Default Re: Motorbikes: How Electronic or Fly-by-Wire Throttle works

Duke 390-
am not aware of the systems in most other bikes, and therefore no comment on the 390. Maybe they have a robust sealing system or whatever works for KTM globally.

Likewise for the Car FBW systems- I would not know about redundancy cascade there.

The only update I got was that the limp home is more like 3500rpm and possibly equating to 75kmph in 6th.

The focus of my article was to increase the awareness in how it works, and the fear of what if it breaks- using one specific example, that of the Triumph Tiger.

Once someone figures out the 390 and car systems- Please update us.
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Old 9th August 2017, 03:09   #5
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Hi
The fly by wire actually originated from aircrafts. I have few friends flying airlines who do not like this new technology and reasons are that the onboard computer controls the power which finally needs to be delivered. Its them who should judge this and not a computer. They also have overrides but it's in case of emergency only. Not sure about cars but yes as it's been mentioned in the above posts their are two sensors independent of one another and an emergency power lock in case both fail.
Well the what if does create many questions in hypothetical scenarios but it doesn't stop the development. Maybe drive by wire initially will face lot of issues as motorcycle manufacturers would like to have this technology but not increase the costs because of competition so might end up getting low quality sensors but it is the future and we better start getting use to it.
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