FlaminRoo
Novice Class
Posts: 76
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posted March 11, 2016 03:30 AM
Limp Home Mode
What is affected when the 2002 ZX12 goes into Limp Home Mode, Timing and/or Fuel ??
  
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tuusinii
Pro
Posts: 1031
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posted March 11, 2016 03:39 AM
It depends what is broken. If TPS is broken then the ECU will use IAP and lock timing to fixed TPS position. If something else is broken it will normally lock that broken value to some fixed value. But yes, of course in the end all will affect timing and fuel 
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fish_antlers
Administrator
The Truth is Out There
Posts: 21894
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posted March 11, 2016 06:47 AM
Don't think I ever made it into limp home mode. Know freek basically live in it 
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What business is it of yours where I'm from, Friendo?
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FlaminRoo
Novice Class
Posts: 76
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posted March 12, 2016 02:11 AM
Thankyou Tuusinii,, Whats IAP ?
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tuusinii
Pro
Posts: 1031
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posted March 13, 2016 09:00 AM
IAP=Inlet Air Pressure. What ECU uses to calculate fuel at low TPS positions because it's more accurate than TPS at very low throttle openings. Me neither has ever went to limp home mode - only on purpose. So must have been lucky because allready over 160tkm (100k miles) on my two ZX12:s.
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FlaminRoo
Novice Class
Posts: 76
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posted March 13, 2016 01:02 PM
 Edited By: FlaminRoo on 13 Mar 2016 14:03
is there a "Fixed value" ??, if so, what is it, fuel and or timing ??
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tuusinii
Pro
Posts: 1031
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posted March 14, 2016 12:22 AM
What I mean by fixed value is following: The ECU calculates the requided fuel and timing advance from multiple sensors. If one sensor fails, for example Inlet Air Temperature, then ECU assumes that the temperature is fixed (like 23 degrees celsius or something else). Or if TPS fails then it calculates fuel by IAP and other still working sensors and fixes ignition to 0% TPS value. (ECU needs some information about the amount of air that goes in to the engine so it can switch from TPS to IAP control but if both fails it can't run anymore). But of course ECU can't make fueling fixed because engine needs different amout of fuel for different RPMs and throttle openings. So when sensor fails the ECU can't use that information anymore but uses a fixed value that is probably close enough for engine to run (limp home) but it will be off from optimum value. For example that temp sensor failure. If actual temp is higher than fixed value the fueling will be little rich or if the actual temp is lower then the fuelling will be little lean but the engine will still run somehow. Of course as ZX12 ECU is open loop the end result probably isin't optimum to start with and for the manufacturer the optimum isin't max power as they have to deal with emission limits and other factors too. But the prinsiple is that.
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FlaminRoo
Novice Class
Posts: 76
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posted March 14, 2016 01:35 AM
"Thankyou"
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