Reische Performance 07-10 GT500 170deg Performance Thermostat

We've been working with Joel Miller from Reische Performance to bring a better thermostat solution to the GT500 market. Reason being is that the only options up until now have been the Napa 180 and the UPR 160. Although those units have worked up until now they are not the ideal thermostat for the GT500 as the GT500 uses a special thermostat similar to the one on the 4.6L SOHC which is different than the 4.6L DOHC one.

Here's what Joel found out.

"The GT500 uses a unique t-stat, the Motorcraft RT1185... it is similar to an SOHC t-stat but it reaches farther into a larger diameter bypass.

That NAPA thermostat is made for the cold-side 4.6L DOHC setup. Externally the two t-stats/bypasses are of similar dimensions but if you observe both t-stats opening you will see that the bypass plate does not move on a 4.6L DOHC stat. The bypass coolant flows up through the stem and is controlled by the pellet coming down and blocking the holes in the stem."

FORD 5.4L DOHC IDLE ECT DATA
Test vehicle: 2007 Shelby GT500 w/OEM radiator (03 DSG Snake)
Control conditions: 5 min hot idle with A/C on low, cooling fan on
Logging performed: August 31, 2009

*Stock OEM thermostat (Motorcraft RT1185): Sustained ECT of 196° @ IAT 98° - hood open
*170° Performance Thermostat (Ford 5.4L DOHC): Sustained ECT of 182° @ IAT 160° - hood closed!!

Cruise Data & Notes
SCT XCAL fan settings: High 188°/Low 182° (fan shuts off at 176°)
Ambient temp: 78°
A/C: Off

*Non-stop freeway cruise with 3-5sec WOT bursts: Nominal ECT range 174-178°
*Saw highest ECT of 180° after a few back to back WOT bursts, lowest ECT was 172°
*Fan did not run at all on the freeway

  Reische Performance's impressions/interpretation of the data:

In the 78° ambient temp it seems the ECT wants to settle around 174° as long as the car is moving at 50+ mph, which is a few degrees cooler than a 4.6L DOHC setup. Short WOT bursts resulted in no more than a 2° rise in ECT. Thermostat seems to flow to rad pretty well by 182° and the stock GT500 fan/radiator setup proved more than adequate, easily controlling temps with the low speed fan. I think this is testament that the GT500 cooling system is pretty well done. It's hot-side thermostat housing design is superior to the 4.6L DOHC and favors high flow to the radiator, maximizing the larger diaphragm t-stat, with the coolant forced to take a 180° turn around to go back into the bypass. I feel confident that the 182° low fan setting will keep ECT in a target range of 176-184° under most city driving conditions.