I am preparing to retest Charlene, who posted high HC marks on the last go-around. (see website for test results.) I've contacted the owners of the shop who put my exhaust system together, and they assured me again that their high-flow cats were the best made, and should easily scrub HC's as well as OEM's.
They ran down other possible causes, and one clearly stuck out: a low-temp thermostat. (He indicated that worn O2 sensors may have contributed, but probably weren't the culprit unless the MIL was lit.) I told the tech that the engine had a 180 installed, and he indicated that this may be the problem, even if the engine is running in closed-loop mode and no MIL is set. I've always heard that engines do indeed run slightly richer when cooler, making a bit more power.
Cosmic truth or bullshit?
I installed this little gem early on to prolong the life of underhood parts. Is it possible that I've shot myself in the foot with this homebrew el-cheapo mod? Would switching from the OEM 205 to a 180 degree thermostat indeed raise tailpipe HC content enough to test high, without setting the MIL?
If this is indeed the case, I will cease suggesting that others install 180's, power-increase or not. (For the record, I did NOT notice any power increase after installing the 180, but left it installed figuring it wouldn't affect anything but underhood temps.)
Any educated comment appreciated. Please, no flamebait. I'm sure Ford spec'd a 205-degree thermostat for a reason. Could it be to lower tailpipe emissions? Improve driveability? Faster warm-ups which lower overall tailpipe emissions? To warm my Birkenstocks' faster on frosty mornings?
-JD
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