Engine Temperature Question - LotusTalk

EliseKid · 07-15-2006, 11:03 PM

Hey,
Today we took the Elise up to the mountains in about 98 degree weather. Because of the extreme heat I made sure to keep an eye on the temperature gauge. While on the freeway, with A/C full blast, the temperature was a steady 193 degrees F. (Keep in mind this is at 80mph.) When we reached the slower mountain twisties however, the temperature gauge shot straight up to a high point of 225 degrees F.(the average speed here was around 40-50mph) Becoming worried, I didn't know what to do and then realized that the A/C was still blasting. I turned it off quickly and the gauge immediently dropped to 198 degrees F in about 2 minutes.

So here's my question:
Was the engine really that hot? How could it possibly have lost heat that fast with just the push of a button?

charliex · 07-15-2006, 11:19 PM

it does go up and down pretty quickly, 225F is getting up there thats for sure.

kaz · 07-15-2006, 11:19 PM

It's normal don't worry...eventually your radiator fans will kick on too.

nvrblu · 07-15-2006, 11:22 PM

According to the service notes, the fans switch on at 98C at 1/2 speed on temperature rise, full speed at 103C. They'll switch back to 1/2 when the temperature falls to 98C and off at 94C. Above 85 mph, the fans switch off because inducted air flow speed exceeds the fan stall speed. The fans run at full speed whenever the A/C is on.

I've never seen temps above 200F while moving. 225 seems high but is still below the boiling point of proper coolant mixture and system pressure. So the engine probably wasn't too hot... but getting close to the limit.

The A/C condensor is between the fans and the radiator. When the A/C is running, you're pumping heat out of the incoming (warm) fresh air and into the condensor so the ari flowing over the radiator is much hotter than the 98 degree ambient air. When you shut off the A/C, the condensor cools and the air flowing over the radiator is subsequently cooler. You probably could have switched the A/C to recirculate cabin air and lowered the temperature by not pumping so much heat into the condensor.

07-15-2006, 11:03 PM	#1 (permalink)
EliseKid The Elisetalk Adolescent Join Date: Jul 2005 Location: Wyoming Posts: 118	Engine Temperature Question Hey, Today we took the Elise up to the mountains in about 98 degree weather. Because of the extreme heat I made sure to keep an eye on the temperature gauge. While on the freeway, with A/C full blast, the temperature was a steady 193 degrees F. (Keep in mind this is at 80mph.) When we reached the slower mountain twisties however, the temperature gauge shot straight up to a high point of 225 degrees F.(the average speed here was around 40-50mph) Becoming worried, I didn't know what to do and then realized that the A/C was still blasting. I turned it off quickly and the gauge immediently dropped to 198 degrees F in about 2 minutes. So here's my question: Was the engine really that hot? How could it possibly have lost heat that fast with just the push of a button? __________________ '05 Graphite Grey Elise w/ dark blue interior, starshield, touring.

07-15-2006, 11:19 PM	#2 (permalink)
charliex OSX Black hat Join Date: Feb 2005 Location: Las Vegas , NV Posts: 9,935	it does go up and down pretty quickly, 225F is getting up there thats for sure. __________________ Black Exige S - http://goth.am 265 Mule / Elan M100.ECU Tuning, http://www.elisetalk.com/forums/showthread.php?t=39660 West Coast Lotus Meet - Las Vegas - November 6-9 2009 http://www.westcoastlotus.com/

07-15-2006, 11:19 PM	#3 (permalink)
kaz JabStrongFierce Join Date: Oct 2005 Location: Downtown LA + SF Posts: 2,420	It's normal don't worry...eventually your radiator fans will kick on too. __________________ 2006 Elise : JFG \| Nitrons \| 2bular 8" Single \| Reverie diffuser and misc. carbon bits \| Tripoint Engineering W/A Intercooler \| Ronin supercharger \| DRS EFI and tuning

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07-15-2006, 11:22 PM	#4 (permalink)
nvrblu ... _ . ..._ . Join Date: Jan 2006 Location: Mesa, AZ Posts: 3,386	According to the service notes, the fans switch on at 98C at 1/2 speed on temperature rise, full speed at 103C. They'll switch back to 1/2 when the temperature falls to 98C and off at 94C. Above 85 mph, the fans switch off because inducted air flow speed exceeds the fan stall speed. The fans run at full speed whenever the A/C is on. I've never seen temps above 200F while moving. 225 seems high but is still below the boiling point of proper coolant mixture and system pressure. So the engine probably wasn't too hot... but getting close to the limit. The A/C condensor is between the fans and the radiator. When the A/C is running, you're pumping heat out of the incoming (warm) fresh air and into the condensor so the ari flowing over the radiator is much hotter than the 98 degree ambient air. When you shut off the A/C, the condensor cools and the air flowing over the radiator is subsequently cooler. You probably could have switched the A/C to recirculate cabin air and lowered the temperature by not pumping so much heat into the condensor.

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