5.0 and a lower thermostat

I'm confident one of you guy's out there will know the answer to this question.

When I had my 2009 Challenger SRT8, one of the most popular mods was to change the stock thermostat of I believe 208 degrees and put in a180 degree stat.

Just like on this forum, at the end of your post you list your car and all of its mod's

Why is it that I never see that with the 5.0 Mustang?

Is it not needed?

Did the chhallenger run hot or what is the reasoning behind it?

I get that a motor running cooler is probably better, so why not the Mustang?

Main reasoning IAT

Mustang uses MAF no need for thermostat mod.

Motors run more efficient at higher temperatures but make more power when cooler. That's why temps have gone up over the years.

Running a cooler thermostat, such as the 180, in a mustang would force the car to never get hot enough to get into proper operation of computer and would run way too rich and inefficient all the time. I do not know how dodge does their programming.

Just like any other performance part, before just doing things, you (for example, or me) need to know all the different things that will be affected.

Another consideration is, many times, too cool a thermostat won't allow the water to stay in radiator long enough, resulting on too hot of water returning to motor resulting in overheating.

Factory calibrations, whenever possible, shoot for stoichiometric (a clean burn). However, there is usually a little more power to be had gently tipped to the rich side of the scale, towards "bad emissions and melted cat" land..

Traditionally PCMs were forced into open loop under WOT, which the PCM then uses coolant temp as a fueling correction factor, colder coolant means more fuel at this point.

Older narrow band 02 sensors weren't accurate enough to control fueling under WOT, the new wideband 02 sensors used in the coyote are accurate enough to allow the PCM to stay in closed loop even under WOT, so a lower CHT or ECT won't make noticeable power at that point.

also, Brent makes mention of an IAT. If the challenger has no IAT at all that can be a factor as well, that would make the PCM rely more heavily on ECT/CHT as a modifier for initial fuel calculation.

If the Challenger has no MAF, then it's running Speed Density EFI, which then makes ECT a HUGE factor in calculating incoming air. The MAF directly measures incoming air mass allowing the PCM to use the target Air/Fuel ratio to simply calculate the fuel needed.
With Speed Density, now the PCM is using, engine speed, barometric pressure, throttle position, engine temp, etc.. to calculate an estimated airflow amount.

MAF measures, Speed Density guesses.. which one is easier to trick?

on a related note, for some reason Ford is going back to Speed Density on Ecoboost engines like the 3.5L TT. Probably due to the MAF latency, being at the air filter makes it a long haul going through the turbo, to the intercooler and then into the throttle.

B-Fox said:

Factory calibrations, whenever possible, shoot for stoichiometric (a clean burn). However, there is usually a little more power to be had gently tipped to the rich side of the scale, towards "bad emissions and melted cat" land.

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For N/A applications it's reverse. Compared to stock, leaning out the a/f mixture typically results in power gains, to an extant of course. FI cars typically gain with a richer mixture as going rich is 'safer' and allows more boost/timing to make power. Just generalizations of course.

B-Fox said:

If the Challenger has no MAF, then it's running Speed Density EFI, which then makes ECT a HUGE factor in calculating incoming air.

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Yup, IIRC, the Challengers use a Speed Density setup. That might be one reason they don't take as well to mods/tunes as Mustangs do.

scottpe said:

Yup, IIRC, the Challengers use a Speed Density setup. That might be one reason they don't take as well to mods/tunes as Mustangs do.

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speed density was what 1987-88 mustang 5.0s used lol...

5.0GT said:

speed density was what 1987-88 mustang 5.0s used lol...

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I know, crazy right?

5.0GT said:

speed density was what 1987-88 mustang 5.0s used lol...

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Garbage IAT...Damn trash can lid.

Grimace427 said:

For N/A applications it's reverse. Compared to stock, leaning out the a/f mixture typically results in power gains, to an extant of course. FI cars typically gain with a richer mixture as going rich is 'safer' and allows more boost/timing to make power. Just generalizations of course.

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Timing is the key, Rich is definitely safer for boosted applications, but I just cracked open Greg Banish's engine management book, and he is saying peak power is typically 12.6:1 but can change with different engines.

I remember my stock tune in my 5.4L 3V would actually shoot for .85 lambda under WOT, which is about 12.4:1, so leaning out the stock tune a little may have made more power, but either number is still considered rich. so.. we're both right? or maybe I left out the part about the PCM being able to target a specific A/F ratio that isn't stoichiometric under WOT, but shoot for it any other time.

5.0GT said:

speed density was what 1987-88 mustang 5.0s used lol...

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88 mustangs with CA emissions had MAF, 86 cars were speed density and the auto/CFI 85's as well...

scottpe said:

Yup, IIRC, the Challengers use a Speed Density setup. That might be one reason they don't take as well to mods/tunes as Mustangs do.

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ouch, yup. so a colder thermostat would "Band-Aid" tune for your CAI and exhaust.. kind of.

B-Fox said:

Timing is the key, Rich is definitely safer for boosted applications, but I just cracked open Greg Banish's engine management book, and he is saying peak power is typically 12.6:1 but can change with different engines.

I remember my stock tune in my 5.4L 3V would actually shoot for .85 lambda under WOT, which is about 12.4:1, so leaning out the stock tune a little may have made more power, but either number is still considered rich. so.. we're both right? or maybe I left out the part about the PCM being able to target a specific A/F ratio that isn't stoichiometric under WOT, but shoot for it any other time.

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Absolutely. There is that fine line and it requires a lot of testing to find the optimimum ratio for the given application. FYI Ford changed the stoich in 2011+ PCM's from 14.7:1 to 14.079:1 to account for ethanol content in the majority of fuels. 0.82-0.84 is the typical lambda I see in email tunes nowadays on mostly stock 5.0 Coyotes. For boosted engines I see about 0.78-0.80 but honestly I haven't looked at many datalogs of boosted cars.

Ahh ok, I was working on my '09 with SCT pro racer and had to adjust stochiometric for ethanol. didn't know they had actually changed it yet, good to know.

that is also why anytime I'm looking at fuel trims on older vehicles they are 6-10% positive due to ethanol.

Grimace427 said:

For N/A applications it's reverse. Compared to stock, leaning out the a/f mixture typically results in power gains, to an extant of course. FI cars typically gain with a richer mixture as going rich is 'safer' and allows more boost/timing to make power. Just generalizations of course.

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^^^^Yes. Thank you for clearing that up.