First of all, what makes you think it's rich? Under what conditions?

If it's carbon on exhaust tips, so look at any EcoBoost vehicle. It's not a proper indicator of a rich operating condition. If you are checking plugs and can truly read them, then you may be onto something....but the richness isn't the plugs. Highly unlikely. Since all 07-14 GT500's operate in "closed loop" at idle and cruise, the short and long term fuel trims will correct fueling to achieve a commanded Lambda of 1.00 (1.00 x the stoich of the fuel used. So, if you're using E10 like most of the country your AFR will be 14.08:1. If you use pure gas it'll be 14.7:1. E85 is 9.80:1. Literally 1 x the stoich of each fuel. Lambda makes it simple) IF the car is truly "rich", it's far more likely that you are getting poor feedback from the O2s, which dictate the fuel trims. At half-throttle, you go into "open loop" or power enrichment and then it's a matter of what you are commanding in the fuel table vs what shows up on the wideband.

Either way, start by logging your fuel trims first and see what's getting in the way of proper feedback and correction.

Mmmm, no you probably don't. A thermostat's temperature to open has zero effect on peak operating temperature. None. Additionally, you compromise the engine's efficiency.

The engine is designed to operate at a 200-210 range. If your thermostat opens too early, you're potentially building up more moisture and byproducts in the oil....because the oil is not coming up to temp properly either. Earlier opening can also lead to excessive time to have O2s, cats, etc heat up properly, resulting in codes. The engine needs more fuel when it's in cold-start range (sub-160f). Most engine wear occurs when an engine is cold.

Years ago, Raische was the leading source of colder thermostats for S197 GT500s. The instructions said to trigger low fan at 182 and high fan at 188. With the broad use of variable speed fans, the ability to trigger these at set temperatures was lost. I spoke at length about this with them and they said the variable speeds simply didn't offer the control nor benefits. But again, on 90% of cars, there's a greater downside than upside to using a colder thermostat. I'm attaching a look at a stock variable fan table from a 2012 GT500. You can see that at 82f ambient, the system only commands 20% fan speed until coolant is at 212f. I start with a small amount at 192 and scale up until 205 and then I command 70%, and 80% onward. The system is designed to allow the engine to heat up properly and maintain an optimal temp for best operation; for both performance and emissions efficiencies. So, if we tell you that you need a heat exchanger upgrade, that does not and should not include a colder thermostat. There are a number of tech articles, videos and even AI that will tell you exactly the same thing.

OK.....here we go. THIS IS SPECIFICALLY REGARDING 2011-14 GT500s.

First, your heated OXYGEN sensors may not be delivering optimal feedback EVEN IF you're not using extensions. Why? Because there's a significant difference in the heat of a cast iron exhaust manifold (with the driver's side O2 right next to it and the passenger side O2 screwed into the cat housing). Thin wall stainless steel will not have the same thermal properties and it'll all heat up more slowly. Additionally, your front O2s are now FEET from the exhaust port instead of inches. O2s are heated by electricity as well as exhaust temps. You can't see the O2s cycling on a 2011+ "wideband car" as simply as watching the O2 voltage swing from .20 to .90 volts on an earlier car but the concept is the same. Now...."no cat codes". The ONLY way you're not seeing a P0420/P0430 with no cats is by running spacers or defoulers. We explain to every customer that we do not turn off any federally mandated emissions monitors or controls. Thus, you'll get a catalyst inefficiency code unless you Google your options. A simple "defouler" is not an option. Why? Remember, it's an OXYGEN sensor. It measures the content of the exhaust gasses. If it's moved out of the stream it won't read correctly. Let's say it's reading less oxygen content in the gasses. Soooo, it's rich, right? That's the feedback, so the trims reduce fuel to achieve commanded lambda. Correct often enough and STFT become LTFT and if it's outside the parameters, bam. CEL.

FACT: When the rear O2s are working correctly, on decel a signal is sent, commanding the FRONT sensors to recalibrate, thus keeping everything at optimal operation.

Are we saying "don't use headers?" NO. We're simply stating the differences between stock and modified so you can work toward the correct answer for you. Once more thing, if someone tells you they "turn them off" for you, run. They're a hack.

More in future posts. If you want more information on your car, call us at Venomous Tuning 352-800-4407