 | Home > Puma (Tdci) > Temperature difference |
 
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| redline Member Since: 28 Jun 2015 Location: Mountains and Lakes Posts: 221  
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Yup, I have the same range of discrepancies, which is likely within the overall sensor and calibration "tolerances".
I would be more curious to know what CHT you are seeing in operation? I am regularly seeing 118-119degC which I thought is odd as my understanding is that the engine will go into limp mode if CHT>116degC. Water cooling temp recorded at same time is normally 92degC. |
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25th Aug 2018 11:00am |
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| Harald Member Since: 30 May 2012 Location: Flanders Fields Posts: 81  
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Hello Redline, Thnx for response. I also see the extreme high CHT and would really like to know what is normal!
Limp mode is triggered by the calculated Engine Coolant Temperature. When that temperature reaches 112 degrees the engine goes in Limp Mode. Something I had this summer when the ambient temperatures over here were 30+. I also see that the CHT will rise very fast as I accelerate, drive up a mountain etc. Do you also have that? I could sent (PM) you 2 graphic logs if you are interested, than we could compare. Live values are great, but if you don;t know what is normal or not.......  .
 Click image to enlarge |
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25th Aug 2018 11:55am |
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| redline Member Since: 28 Jun 2015 Location: Mountains and Lakes Posts: 221
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Hi Harald,
Yep, PM me the logs - will be interesting to compare. The CWT in your last image *looks* high to me. Mine usually runs at 91-94degC, recorded through OBD2 and on Madman which has an independent sensor. CHT rises very quickly with engine load, so accelerating hard or driving up a hill will cause it to shoot up. More important than how quickly it changes is the value that it reaches though. CWT is normally quite stable and independent of short duration loads, because the cooling system has thermal "inertia" and is designed (thermostat etc..) to keep temp within an optimal operating range. Good to know that limp mode is triggered by CWT > 112degC rather than CHT! Thanks for that info... |
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25th Aug 2018 12:53pm |
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| Bergos Member Since: 08 Aug 2015 Location: Somewhere in Portugal Posts: 95  
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I can be wrong but I think that the limp mode is triggered by CHT>115°C Bergos
LR Defender 110 HT 2007 (2.4 Puma) https://www.facebook.com/LR.Wanderlust/ |
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25th Aug 2018 5:13pm |
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| Harald Member Since: 30 May 2012 Location: Flanders Fields Posts: 81
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Hello Bergos,
I have seen CHT temperatuur up to 118 degrees, without the ECU going into limp mode. But as soon as the (calculated) engine temperature goes higher than 111 degrees limp mode is activated. From that point fuel rail pressure drops stepwise, and manifold air pressure goes down. Have a look at the live values below. Click image to enlarge Probably the sort of device you use te measure this will also have something to do with the differences in temperature we are talking about. Another thing I noticed is that when you read about all the Defender Puma overheating problems in most cases the Y-shaped thermostat is only tested on 'opening'. But even more important is the simultanious 'close down' of the vertical upper thermostat passage. That triggers the coolant to travel through the radiator (long (hot) circuit. I tested this on 3 thermostates, and there was a lot of difference between them. But even the 'best' thermostat had (when warm) still 'issues' with this. The 2 or 4 holes (depending on what thermostat) don't have that much resistance. I would have expected the short (cold) circuit would be more 'closed' when hot. Not completely, just 'more'. |
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28th Aug 2018 8:19am |
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