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Old 10-14-2002, 01:47 PM
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JimF JimF is offline
'94 S500: only 793 sold!
Join Date: Mar 2001
Location: San Diego, CA
Posts: 1,925
Well the misconceptions in operating engine

temperature is almost as bad as 'what af should I use' or 'what engine oil is best'?.

As JimSmith put it "80 to 87C is best". For my car, the CD-ROM says that all emissions, specs, etc. are met at an engine operating temperature of 80C or above.

Now using that as the demarcation line, how much above 80C is tolerable or wanted? We all know that at higher engine temps the timing is retarded so the higher it goes, the less efficient the car becomes!

Last month, my car needed a CA smog test. At the test, had the VFC mod running, my Cool Harness installed and 80C tstat. The engine temp (let it idle at the CA smog station w/ A/C on) was 88C. (A/C was shut off at test time).

RPM --- HC(ppm) ---- CO(%) ---- CO2(%) ---- O2(%)
650 ------ 2 --------- 0.00 --------- 5 -------- 1.9
2450 ----- 3 --------- 0.00 --------- 8 -------- 1.8

So the closer that you can hold the engine's operating temperature to "around" 80C, the better the car will run. Take that to the bank!
Regards . . . . JimF
'94 S500 Cpe

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Last edited by JimF; 10-15-2002 at 12:34 AM.
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