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Cylinder Head Temp Question on 2013 BOSS

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I was playing with the Gauge modes yesterday while driving around and noticed there was a lot of fluctuation in the Cylinder Head Temp display, it was first 204degrees, then it jumped to 214 degrees, then back to 208. Is that normal? And which cylinder heads is that sensor reading? All of them or in the firing order?
 
fduboss302 said:
Gary/anyone else know if limp mode gets triggered by 240 deg ECT or Cyl Head temps?
I "think" it's 255 ECT. I've hit 251 several times and pegged the dummy temp gauge and lit the red thermostat light on the dash. I think I've been as high as 254 and still not triggered limp mode. I'm not sure on CHT.
 
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I got my head temp to 264 this past weekend and my car didnt go into limp mode. I had a check engine liht come on after a while so I took it to teh dealer and the coolant reservior cap needed to be replaced.
 
byronj said:
I got my head temp to 264 this past weekend and my car didnt go into limp mode. I had a check engine liht come on after a while so I took it to teh dealer and the coolant reservior cap needed to be replaced.
That means you overheated the coolant then. I'm surprised it didn't go into limp mode. Any idea what your ECT was hitting? The rad caps are one-time use so if you pop it you need a new one. I always carry a couple spares at the track. They're about $8.
 
2,198
1,065
Bay Area
cloud9 said:
byronj said:
I got my head temp to 264 this past weekend and my car didnt go into limp mode. I had a check engine liht come on after a while so I took it to teh dealer and the coolant reservior cap needed to be replaced.
That means you overheated the coolant then. I'm surprised it didn't go into limp mode. Any idea what your ECT was hitting? The rad caps are one-time use so if you pop it you need a new one. I always carry a couple spares at the track. They're about $8.

No I dont know what my ECT was hitting. I thought it would have gone into limp mode also but it didnt. I just let the car cool down and took it easy on the way home and the head temp was in my average range of 205-215. But I did take it into the dealership and have them check it out to to be safe and replace the cap. I never thought about carrying a couple extra caps. Thanks for the advice.
 

PeteInCT

#LS-378 - So many Porsche's, so little time....
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rpm3dinc said:
I was playing with the Gauge modes yesterday while driving around and noticed there was a lot of fluctuation in the Cylinder Head Temp display, it was first 204degrees, then it jumped to 214 degrees, then back to 208. Is that normal? And which cylinder heads is that sensor reading? All of them or in the firing order?

The numbers jumoping around seems odd. On my '12 LS, using the Aeroforce gauge, my head temps usually track my coolent temps and run +9 to +12 degrees above coolant. I've never seen the coolant or head temps 'jump around' per se, they just follow with how hard i'm pushing the car at the track.
 

steveespo

Lord knows I'm a Voodoo Child
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Cookeville TN
I am just speculating but maybe cht is used to adjust fuel and spark timing as the localized temperature around the combustion chamber most affects potential detonation issues. ECT is the general parameter in which the whole engine can run up to. This maybe the threshold for limp mode as exceeding the high limit here will cause cylinder bore warping, head and deck surface warping and head gasket failure etc etc. just my .02.
Steve
 
PeteInCT said:
rpm3dinc said:
I was playing with the Gauge modes yesterday while driving around and noticed there was a lot of fluctuation in the Cylinder Head Temp display, it was first 204degrees, then it jumped to 214 degrees, then back to 208. Is that normal? And which cylinder heads is that sensor reading? All of them or in the firing order?

The numbers jumoping around seems odd. On my '12 LS, using the Aeroforce gauge, my head temps usually track my coolent temps and run +9 to +12 degrees above coolant. I've never seen the coolant or head temps 'jump around' per se, they just follow with how hard i'm pushing the car at the track.
Pete I haven't been tracking head temp on my Aeroforce but maybe I should. Which head temp is valid again? Is it CHT2? I'm pretty sure Steve is right about the CHT threshold causing limp mode. The ECT if too high though will pop the rad cap.
 

PeteInCT

#LS-378 - So many Porsche's, so little time....
Moderator
2,848
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Connecticut
CHT2 is correct, you'll see values anywhere from 9 to 15 degrees above coolant temps. CHT1 is only reading battery voltage.
 

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