I did these tests over the last two days. (06 JGC SRT8, 4500 miles) The stock 203* thermostat; starts opening at 205* and fully open at 211*, my new NAPA 381-190 thermostat; starts opening at 193* and fully opened at 197*. My HW cooling temps runs at 197*, plenty of heat to warm your toes. W/O a cooling fan switch the thermostat change alone will not give the full advantage because of Heat Soak Problem, after a hard run, my temps peaks at 215*. The LX Cars has a much better system, my opinion. Why? Dual cooling fans, better routing of the top radiator hose. Could this be installed on the JGC, Maybe? (The Intake System piping is in the way) The JGC relays would work on the dual fan set-up just fine. Would I do it? Maybe? Any dual fan does cool better and it worked just fine on my Buick GN! (single to dual fan conversion) The PCM does look at Coolant Temps and pulls out timing to help cool the engine! (I've been told as much as 4* of timing or less) HTH Gene

Thanks for the info, Gene.

How did you run? Was the cold Wisconsin air conducive towards lower ET's?

I did these tests over the last two days. (06 JGC SRT8, 4500 miles) The stock 203* thermostat; starts opening at 205* and fully open at 211*, my new NAPA 381-190 thermostat; starts opening at 193* and fully opened at 197*. My HW cooling temps runs at 197*, plenty of heat to warm your toes. W/O a cooling fan switch the thermostat change alone will not give the full advantage because of Heat Soak Problem, after a hard run, my temps peaks at 215*. The LX Cars has a much better system, my opinion. Why? Dual cooling fans, better routing of the top radiator hose. Could this be installed on the JGC, Maybe? (The Intake System piping is in the way) The JGC relays would work on the dual fan set-up just fine. Would I do it? Maybe? Any dual fan does cool better and it worked just fine on my Buick GN! (single to dual fan conversion) The PCM does look at Coolant Temps and pulls out timing to help cool the engine! (I've been told as much as 4* of timing or less) HTH Gene


During the SRT Q&A session, the engineers said that it was normal for the JGC and the LX to run about 215. I would assume that all their calibrations are set up and optimized at those temperatures. Why would you change the system if they said it was normal?

During the SRT Q&A session, the engineers said that it was normal for the JGC and the LX to run about 215. I would assume that all their calibrations are set up and optimized at those temperatures. Why would you change the system if they said it was normal?

Hey Gene,
Imagine the nerve of this guy quoting what the Engineers said to YOU.:)

This probably is true but cooler temps makes HP! The local 300C runs 12.97 ET at 109 mph mostly stock but runs a 180* thermostat, and fan switch. I drove this car, an animal, it flies! His coolant temps run at 174*, with fans running. ( saw the temps drop steadly from 197* down to 174*) The PCM still pulls out timing! Why? Wheel Spin. The anti-locks sends a signal to the PCM (detecting wheel spin), applies braking to the spinning axel, and pulls out timing, a fact. (he back pedals some to get max performance) So does the JGC. I'll be tuning mine more now, and using some of my Buick GN Tune Tricks? If they work I'll post them and the Results. I'm on a miser budget so expensive mods aren't for now, yet? MHO Gene

Hey Gene,
Imagine the nerve of this guy quoting what the Engineers said to YOU.:) Not me but remember they are thinking Emissions and saving the drive train. Remember mine now runs only 4* cooler than the stock thermostat. Conservative reduction in MO. I'm not sure any performance gains through this change alone but the cooling fan switch would help heat soak idling not HW speeds. More for us Drag Racers not HW Cruisers. The 215* temps are after the thermostat is completely opened, what they said! Gene