210°F is just where it is supposed to be, the stock thermostat begins to open at 199° and is fully open at 219°. So 210° indicates it is doing its job as intended. Installing UDPs will not change that as the pump will still flow plenty of coolant.
If it were not moving enough coolant installing a thermostat with a lower opening temperature (they are rated by there opening temperature) would not help because if there is not enough flow to keep the engine at 210° there certainly would not be enough to keep it at any lower temperature.
As to the thermostat itself 185° is as low as you can go without changing the tune, and even at that there are settings that really ought to be changed:
- Engine cooling fan low speed ON (stock = 214°);
- Engine cooling fan low speed OFF (stock = 208°);
- Engine cooling fan high speed ON (stock = 228°);
- Engine cooling fan high speed OFF (stock = 224°);
- ECT Stabilised Open Loop Fuel table switch (defines the ECT to switch to the SOL table default = 180);
- ECT Warm-up temp (the temp at which the PCM considers the engine warmed-up, default = 172°);
Those are the "biggies", they are a few others as well.
I run a 185° unit with these settings:
- Engine cooling fan low speed ON = 204°
- Engine cooling fan low speed OFF = 198°;
- Engine cooling fan high speed ON = 218°;
- Engine cooling fan high speed OFF = 214°;
note: these settings keep the fan from running "all the time"
- ECT Stabilised Open Loop Fuel table switch = 170°);
- ECT Warm-up temp = 168°;
A 175° thermostat would be far too low for out engines.
- 2003 GT, UPR X, FRPP 24lb/h, Magnaflow, PP 70mm TB & plenum, Delta Force tuned,
Steeda UDPs, Ralco flywheel, RAM HDX clutch, 3.73s, 262 rwHP/305 lb-ft.
New ride (7/1/2013) 1998 Mercedes SL500-5.0L 32V VVT 326/347 HP/tq