steve911
Enthusiast
For those who have changed out the stock T'stat on a gen 3, what degree did you replace it with?
This would be on a N/A car with a PCM mod.
This would be on a N/A car with a PCM mod.
What degree thermostat are you using?
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Mamba52
Enthusiast
love to know myself.
Leave the Gen-3 & 4 T-stats alone. They are low enough.
JoelW
Enthusiast
Folks at Woodhouse said leave it alone and the ought to know. New cars are made to run hotter and with aluminum heads you don't want to go foolin' around. If you are trackin' and want most horsepower and are really stressing engine it might make sense but not for street use. If you are worried about cabin heat, change exhaust, thermostat won't do it. Otherwise leave it alone.
Hmm, never heard running hotter is better, but ya learn something everyday. But here's what I thought I knew, on the Shelby GT500, which is aluminum heads & block (like my 2011), we do heat exchanger upgrades/fans, tstat and computer tune, all to reduce temps, for street performance, not just racing, heat causes IATs to retard timing advance like mad and yank HP, as much as 50hp can be lost from heat, so hotter is definitely not better there. With the above I hit 525rwhp and cool eng temps.
On the viper, DC Perf requires a tstat lowering change (* All calibrations require use of a 170-degree thermostat) - from their web site, I did the SCT tune & 170 like 2-3 yrs ago from them & my car picked up 4mph in the 1/4, to 126mph and runs under 200 on the guage regardless of the ambient temp.
Maybe there's a change in this philosophy where people now say hotter is better, maybe check with Dan at DC, they still req the tstat change to 170 on thier website, and they're very respected in their knowledge fo viper & perf cars. It would take serious convincing to make me think dropping 10-15 degrees and picking up timing advance isn't a good thing, but you never know. Wouldn't be the 1st time I was wrong, or heard the wrong thing.
On the viper, DC Perf requires a tstat lowering change (* All calibrations require use of a 170-degree thermostat) - from their web site, I did the SCT tune & 170 like 2-3 yrs ago from them & my car picked up 4mph in the 1/4, to 126mph and runs under 200 on the guage regardless of the ambient temp.
Maybe there's a change in this philosophy where people now say hotter is better, maybe check with Dan at DC, they still req the tstat change to 170 on thier website, and they're very respected in their knowledge fo viper & perf cars. It would take serious convincing to make me think dropping 10-15 degrees and picking up timing advance isn't a good thing, but you never know. Wouldn't be the 1st time I was wrong, or heard the wrong thing.
Toma
Viper Owner
The viper hates heat. Hennessey, DC, Roe etc all reccomend lower.
I've used both 170 and 160 depending what was available.
Heat leads to detonation, or more accurately pre-ignition. In some of the faster "door car" classes now, we are seeing competitors pump ice water through their blocks so when they come upto the line with the engine are below ambient to help the chamber shed more heat....these are aluminum engines....
Anyway, stock Viper also does not turn the fans on till 200f, and the motors run at 210-220.
BUT.... the stock tune is pulling 1.5 to 2.5 degrees timing by this point.
The only thing a hot engine is good for is slightly better mileage and emissions, not performance.
Now, making sure oil temperature is upto ***** before you jump on it... THAT is important.
I've used both 170 and 160 depending what was available.
Heat leads to detonation, or more accurately pre-ignition. In some of the faster "door car" classes now, we are seeing competitors pump ice water through their blocks so when they come upto the line with the engine are below ambient to help the chamber shed more heat....these are aluminum engines....
Anyway, stock Viper also does not turn the fans on till 200f, and the motors run at 210-220.
BUT.... the stock tune is pulling 1.5 to 2.5 degrees timing by this point.
The only thing a hot engine is good for is slightly better mileage and emissions, not performance.
Now, making sure oil temperature is upto ***** before you jump on it... THAT is important.
Check out my links in this post:
http://forums.viperclub.org/2930936-post41.html
http://forums.viperclub.org/2930936-post41.html
Yea, a point of clarification ... in both my examples I also list a computer mod, IMO doing just a tstat swap isn't worth it without a computer mod or unless you're doing other mods that can lean things up. I don't believe you get a bang for the buck on cooler temps unless a retune is taking advantage with running fans accordingly and reworking the timing.
A thermostat has next to nothing to do with how HOT a car runs. it has to do with how COOL the car CAN run.
The stock Viper thermostat is 185. Meaning, if you are running warmer than that, a thermostat is not going to do a thing for you.
The further you get from 212, the harder it is to boil out moisture from the oil.
The further you get from 185, the more likely it is that you will register a code for "engine not warmed", or freeze your adaptive fuel updates, which can lead to codes, fuel consumption issues, detonation issues, etc.
The Gen-3 & 4 Viper engine was designed around a nominal temperature range of 185-200. These are not Gen-2 cars with 195 T-stats and a fan temp in the 215-225 range, and the inability to recover in warmer climates.
Leave them alone. I have never installed a lower thermostat in a Gen-3/4, and I wasn't ever planning on starting. Gen-1/2 is a whole different ballgame, and they should be changed to run comparably to the Gen-3/4 cars.
Everyone has a different opinion of this, and that's fine. That's mine.
The stock Viper thermostat is 185. Meaning, if you are running warmer than that, a thermostat is not going to do a thing for you.
The further you get from 212, the harder it is to boil out moisture from the oil.
The further you get from 185, the more likely it is that you will register a code for "engine not warmed", or freeze your adaptive fuel updates, which can lead to codes, fuel consumption issues, detonation issues, etc.
The Gen-3 & 4 Viper engine was designed around a nominal temperature range of 185-200. These are not Gen-2 cars with 195 T-stats and a fan temp in the 215-225 range, and the inability to recover in warmer climates.
Leave them alone. I have never installed a lower thermostat in a Gen-3/4, and I wasn't ever planning on starting. Gen-1/2 is a whole different ballgame, and they should be changed to run comparably to the Gen-3/4 cars.
Everyone has a different opinion of this, and that's fine. That's mine.
Toma
Viper Owner
True
It will begin to circulate water sooner, thus preventing hot spots and steam pockets
I suppose. But a dish of water on the counter top evaporates in a day or two, I imagine if a minute amount condensed into the crankcase, all the violence and sloshing and 170 degree oil temps would take care of it.
Maybe. We can debate the necessity or even desirability of adaptive fuel trims another time in regards to anything past simple part throttle closed loop short and long term trims. Not unusual in performance modfied cars today to shut off adaptive control and long term trims. Or at the very least disable the adaptive learning having control anywhere else but within a very narrow range.
But they never run at 185-200. At least I have never seen one that can do that.... and ALMOST all modern cars are delivered from the factory, and not unusual to log 210-230 ECT's. But then again, that parameter was in mind with the stock, unmodified vehicle. Not something being asked to make 10 or 20% more power. But why is that relevant? They have a different mission. Emissions, fuel economy, etc.
Just because the stock Viper AF ratio goes to 10.8 or richer at the top of the rpm scale, are you suggesting we leave that cause that is how the "factory designed it"?
I am not THAT against the idea as long as the fans are reprogrammed to target 185, sure, you may sacrifice a hair of power, and reliability, but it's not bad, I would be more conservative on the timing. Also thermostats have a percentage error, so your particular stat may open at 190 or 180. The hotter the engine, the more heat soak into the intake, and that is another problem.
Personally, I prefer a 160 or 170 stat, fans programmed to maintain around 180.
Incorrect. The thermostat only has to do with coolant circulation out of the closed loop engine circulation system. Hot spots and steam pockets will not occur in a properly working Gen-3 or Gen-4 cooling system. Water does not boil until 212, without coolant additives, and not under pressure. 185 is nowhere near the point at which they would form in any properly working cooling system, let alone in a system as efficient as the Gen-3/4, under pressure, and with a coolant mixture.
Incorrect. Water cannot evaporate when encapsulated by oil. It would require temperatures over the boiling point to release the liquid water and turn it into steam bubbles which will break and be carried out through the PCV.
The only instance in which this is true is on a large cam car with an overlap sufficient to corrupt the AFR reading that a narrow or wideband would see. In ALL other cases, no, its not desirable or correct to have a system operating in open loop, especially a car that has catalytic converters. Any REAL engine management will operate with a feedback device. If you exceed the capability of a narrow-band based system, the correct solution is a wideband based system with closed loop functionality.
I have yet to see a Viper SRT-10 around here that does not run within 200 +/- 10. And regardless, the thermostat has ZERO to do with its operating maximum. The FAN and COOLING SYSTEM have to do with that aspect. The thermostat is open after 185. It cant get... MORE OPEN.
Absolutely not, and that is a completely different topic altogether. The Viper is tuned like that for an extreme safety margin, and a one-size-fits-all approach on a system that in effect has zero feedback device capable of reading at that level. They need to do it because of variations among cars. Cooling systems have fans and feedback devices working all the time. Apples and oranges.
You would NEVER want a cooling fan to target the same temperature as the thermostat. The thermostat is not an on/off switch. It has a window of operation of a number of degrees. All you would end up with is a fan trying to cool an engine through a partially closed thermostat, resulting in your fan running at higher speed than needed all of the time, with zero extra affect. the radiator would be ice cold, the fan maxed, the PS pump/motors stressed, and make a whole bunch of noise. The factory target is 200.
That's your prerogative, of course... but its not mine, and people should be aware that there are two sides to everything, and make their own decisions.
JoelW
Enthusiast
Never said hotter is better. When I was drag racing, heat was an enemy. That said, I didn't try to drive a race engine on the street. You think every tuner is smarter than the factory about drivability? Yes, you can get a bit more horsepower for a while with a cool engine but driving it on the street is different. Losing 50 horsepower on a dyno run in a 30 second test is not like driving it on the street for hours at a time. I have seen terrible drivability problems when I had a shop with failed thermostats when an engine is running too cold. If colder is better, why don't these engines make more horsepower and run great? As some have said, a 160 thermostat will not make your engine run 160 all the time.
But, as everyone pointed out, you are entitled to your opinion.Toma
Viper Owner
We can obviously do this all day, so I wont. My last post on this.
You are making the giant assumption that just because the engine is 200 at the thermostat housing, that all areas of the water jacket are the same temperature. This is clearly not the case. This is simply an "average", and does not account for pockets that WILL inevitably be hotter or potentially cooler....
Plain not true, but I wont argue further as I consider running at 212+ to "boil off water" bottom of the list of reasons to torment an engine to that sort of temperature. Cars would not come equipped with oil coolers if that was the case....
Who said anything about running in open loop? We got onto this topic cause you claimed that running too cold would freeze the adaptive fuel tables.... you did not claim (nor is it accurate) that it would kick the car into open loop..... or did you? A well tuned car has no need for adaptive learning, nor do I want a vehicle that has learned a correction at part throttle potentially due to a miss (bad plug or wire), a slight decrease in compression due to age etc applying it to my perfectly tuned WOT..... the Viper is a special case, I realize, but clarify your point, and discern between adaptive, and closed loop pleas.
What can I say, every single one I have seen is stuck at 210 or a bit more, specially after a couple blasts.... Who said it gets more open? I am confused by what point you are trying to make.
Well I disagree, your argument was "that's how Chrysler designed it, leave it alone".... seemed a silly to say.
You do realize cars ran just fine before EFI and widebands? How did they handle "variations" then? These variations are not THAT variable, ESPECIALLY today.
See, we agree, a colder thermostat with lower fan on temps, and its a matched system.
Bottom line is, you can make more power, push timing further, and lean a motor out more if the motor is cooler....within reason of course. Its a sliding scale. A turbocharged smallblock making 3000hp, the motor cant really be too cold. We ice the block, we dry ice the fuel.... a low performance engine if too cold simply wont burn the fuel as it wont have the cylinder pressure, compression, swirl and "violence" to atomize the fuel....
Viper's simply lose a ton of power when too hot. I've idled them for 15 minutes with the hood closed, stock stat, stock fans, then made a a couple dyno pulls. Then tossed in a colder stat, targetd 180, repeated the test the same way, and with no tune changes, the car picks up 20+.... AF may be a little fatter (not enough for the power loss).... anyway.
We are enthusiasts, we change our oil in case it overflows with water
, we race our cars, torture them in 90 degree ambient heats. We generally are not modifying them with headers, catless exhaust, cams etc for the sake of better emissions.Anyway, like I said, last post, this horse is dead lol
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351carlo
Enthusiast
I'd like to test this theory. I find it fascinating that an engine temperature of +- 20 degrees can have that drastic a power difference. Air intake temperatures would have to change by almost more than 20 degrees to have that substantial a power swing in an N/A Viper motor.
In the end the air charge temp is not changing by 20 degrees, maybe a few at most. The air is rushing through the intake and into the cylinders very quickly, conduction through the cylinder walls and intake doesn't work that quickly. The only benefit I can see by having a cooler engine would be detonation control and I can't see detonation being an issue at 200 degrees on a stock motor.
Wow. These tstats is complicated.
To the original question, on a N/A car with a PCM mod, if your PCM mod requires or recommends a particular tstat ... I say go with that tstat (call me crazy), as the PCM will control variables like fans, timing etc based on the that tstat. That's what I did & picked up 4mph in the 1/4. And driveability is far improved in every aspect over the factory EPA oriented stock tune. So I'd refer to your PCM mod vendor.
To the original question, on a N/A car with a PCM mod, if your PCM mod requires or recommends a particular tstat ... I say go with that tstat (call me crazy), as the PCM will control variables like fans, timing etc based on the that tstat. That's what I did & picked up 4mph in the 1/4. And driveability is far improved in every aspect over the factory EPA oriented stock tune. So I'd refer to your PCM mod vendor.
Yea, that's surprising. I could see it with a PCM tune for sure, if not more, but with just a tstat alone I wouldn't expect any significant difference. Interesting.
Anyone who knows me... knows that I am incapable of backing down from an argument. Sorry
And they're off!
And You, are making a giant assumption that I don't design, build, tune, and service these cars for a living.
Of course, I never said that there won't be some temperature variations, that goes without saying [Perhaps I should have stated that anything that will MATTER will not occur] However, if you think that the variations are so extreme that ~20 degrees for a matter of seconds it would take the coolant to reach the warmer temperature range [by comparison] is going to make a difference, you are splitting irrelevant hairs at best. The efficiency of a radiator is a function of temperature differentials between the coolant temperature and the ambient airflow temperature- So, if you think that Vipers have a cooling problem to begin with, how do you think they are going to hold up under load at a lower temperature where the difference in coolant to ambient is considerably lower? By your own description, the system would be increasingly unable to even accomplish this feat... ultimately putting it right back where it was with the higher thermostat under load in the first place
Obviously the above point was a run-around which I did on purpose, and is rather irrelevant overall
I would like to see how you evaporate water out of oil without exposing it to the atmosphere by boiling it out. While you are at it, make the soda in a 2-liter evaporate with the top screwed on
And sorry, cars come equipped with oil coolers to keep the oil from running TOO hot. There is a difference. Nominal oil temps are in the 210-230 degree range. 300, is too hot. Hence cooler.
You are correct- it was a side point based on the assumption that YOU were talking about Open Loop and turning off LTFT's and STFT's, even though this was not based on the original topic. Now that I went back and re-read it, I can see you were only talking about a partial shut-off of LTFT's only, not complete. However, to the original question, yes, the LTFT's will remain locked below ~180. STFT's will still function unless turned off. Technically still closed loop.
I dont know what to tell you. The Gen-3 SRT Fan Target is 200. It is a hydraulic fan with a duty based controller target. By the time you hit 210, the fan is cranking full force and will be one step from sucking your jeans through the front fascia. Its one thing if you have the A/C cranking as well [see temperature differentials again
] as the air entering the radiator is pre-heated. No amount of fan or thermostat will make a difference at that point if sitting still.My point was that you will exceed 160 so quickly under load due to temperature differentials that it makes NO difference after a minute or so which thermostat you are running, as you have exceeded the both the 160, and the 185, and will likely hover in the 185-195 operating temp range regardless, with the hydraulic fan cranking and trying to keep up. Of course, yes, this is a bit lower due to the fan routine being changed, but you are also effectively running a less efficient cooling system, and using additional PS pump power to run the fan at full tilt. At 190+ operating temp, it makes NO difference if you have a 160 or a 185 installed. Basically, the final point is that a 160 will only make a difference in a situation where you are cruising at speed, and at low enough load to keep the fan from running at full tilt. In essence, its the same situation where even a stock thermostat will be running VERY cool. It makes next to no difference overall after 30 seconds in how the car runs, other than the potential for the 160 to accumulate moisture, and freeze the adaptive update when cruising and allowing the system to get TOO cold.
You can disagree all you would like. It doesn't change the fact that it was done for a reason... on both counts. The Older Viper's are a different story. They HAD cooling problems, BIG ones by comparison.
Sure they did. They also fouled plugs, didn't want to start, didn't last as long, ran like crap, and had horrible emission issues in many cases. Different world, different technologies, different problems and solutions. Are you trying to tell me that there weren't carb'd cars that ran a 10.8:1 out of the factory just the same? Of course there were.
These variations can be quite large in some instances. As a tuner that you claim to be- are you telling me that you have never seen a factory fuel calibration that so heavily relied on the adaptives that it made you wonder if they tuned it at the factory or just used a dart-board? I have, plenty of them.
Well, of course it is. I never said it wasn't. I just happen to think its an answer for a question that no one ever should have asked.
Bottom line, you are making assumptions for other people based on the set of conditions used for a drag engine. What works well in racing, is not necessarily the best idea on the street. I can show you hot valvetrains that will work GREAT on the strip. Do you want to try and drive 50,000 miles on one? Are you sure? Really sure?
Extreme example, but the same point. If you are dragging your car, hell, the cooler the better! Everything else becomes irrelevant. However, for a street driven car where longevity and drivability are key, you should take everything into account.
............ that has more to do with the Vipers factory calibration and how it reacts to temp changes than it does your running temp itself. Would you like me to show you exactly where those items are in the Viper calibrations? So you can see near the same changes without the thermostat?
Regardless, the Dyno is NOT the street. Real world changes things. The car rolling down the street takes the fan out of the equation. The load and ambient temperature is going to dictate how hot the car runs, and the thermostat sets the lower limit. Either way, even cooler ambient at high loads, the car will heat soak beyond 160. The hair is being split here.
We are enthusiasts, we change our oil in case it overflows with water
I think I surpassed enthusiast about a decade ago. I should probably be committed, it would be a better fit given the current state of affairs. However, I still did not say any of my arguments were based on emissions [other that the open loop misinterpretation]. However, you cannot argue the fact that generally, a cleaner burning engine does... RUN CLEANER, and last longer, with less issues.
In MY opinion, the downsides are not worth the upsides. You are free to feel differently, of course, as this is all a matter of opinion. I choose nominal temperature ranges, cleaner burning, and fan motor life over a couple horsepower. You can do the opposite if you choose.
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Ive got over 50 dyno runs on my 03. Probally close to 75 pulls.
One thing I always noticed was this.....
A hot engine driven off the street and dynoed would put down 20-30 rwhp less than a engine that was allowed to kool down on the dyno with fans for 45 minutes.
Saw this first hand many many times were the car would go from 450 rwhp to 475 rwhp with nothing more than a kool down.
That all changed when I ordered a roe racing tune and lower temp thermostat
Now the differance between a hot driven off the street dyno pull and Letting the car sit on the dyno for an hour with an iced intake...
Is only 4 rwhp...
Thats right folks. Went from 482 to 486 rwhp.
I'm a belieaver with the lower temp thermostat as your car is ALWAYS in its maximum power range.
Stock thermostat and yea you can hit 450 rwhp on the dyno with a kool down on a stock gen3. But expect to be around 430 rwhp after a few spirited pulls or 1/4 mile passes..
I say its a worth while modification
BTW, to add even more fuel to this debate I added a lower thermostat to my corvette as the only modification and the car CONSISTENTLY ran a tenth and mph faster. And I lived at the drag strip 2-3 days a week all year long in Hawaii. KOOLER ENGINE EQUALS MORE CONSISTENT POWER
One thing I always noticed was this.....
A hot engine driven off the street and dynoed would put down 20-30 rwhp less than a engine that was allowed to kool down on the dyno with fans for 45 minutes.
Saw this first hand many many times were the car would go from 450 rwhp to 475 rwhp with nothing more than a kool down.
That all changed when I ordered a roe racing tune and lower temp thermostat
Now the differance between a hot driven off the street dyno pull and Letting the car sit on the dyno for an hour with an iced intake...
Is only 4 rwhp...
Thats right folks. Went from 482 to 486 rwhp.
I'm a belieaver with the lower temp thermostat as your car is ALWAYS in its maximum power range.
Stock thermostat and yea you can hit 450 rwhp on the dyno with a kool down on a stock gen3. But expect to be around 430 rwhp after a few spirited pulls or 1/4 mile passes..
I say its a worth while modification
BTW, to add even more fuel to this debate I added a lower thermostat to my corvette as the only modification and the car CONSISTENTLY ran a tenth and mph faster. And I lived at the drag strip 2-3 days a week all year long in Hawaii. KOOLER ENGINE EQUALS MORE CONSISTENT POWER
Ive got over 50 dyno runs on my 03. Probally close to 75 pulls.
One thing I always noticed was this.....
A hot engine driven off the street and dynoed would put down 20-30 rwhp less than a engine that was allowed to kool down on the dyno with fans for 45 minutes.
Saw this first hand many many times were the car would go from 450 rwhp to 475 rwhp with nothing more than a kool down.
That all changed when I ordered a roe racing tune and lower temp thermostat
Now the differance between a hot driven off the street dyno pull and Letting the car sit on the dyno for an hour with an iced intake...
Is only 4 rwhp...
Thats right folks. Went from 482 to 486 rwhp.
I'm a belieaver with the lower temp thermostat as your car is ALWAYS in its maximum power range.
Stock thermostat and yea you can hit 450 rwhp on the dyno with a kool down on a stock gen3. But expect to be around 430 rwhp after a few spirited pulls or 1/4 mile passes..
I say its a worth while modification
BTW, to add even more fuel to this debate I added a lower thermostat to my corvette as the only modification and the car CONSISTENTLY ran a tenth and mph faster. And I lived at the drag strip 2-3 days a week all year long in Hawaii. KOOLER ENGINE EQUALS MORE CONSISTENT POWER
Uh... Twister... your car isnt exactly the model for a direct comparison. You had multiple tunes from multiple vendors and multiple findings depending on conditions. Did you do a back to back dyno pull with ONLY the thermostat being changed, and ZERO other changes, on the same tune both times? If you installed a tune at the same time as a thermostat, how exactly do you know which part of the equation caused more of the gains?
No one seems to be factoring in temperature based corrections here either, and the fact that they can be edited, without the actual temperature change when tuning.
The car was ALWAYS less on the first hot pull. Depending on how hot the day was and how hard I had driven the car would be anywhere from 10-30 rwhp differance from the hot pull to a kooled engine.
With a stock intake with KN filters and a few bolt ons and the origional Roe raceing SCT tune from Sean the car hit 443 rwhp. Then after a 30 minute kool down the power went to 454.
Still on the same origional SCT tune from Sean,we installed the KN air inatke and thermostat and the power went to 460 rwhp. We did a few more back to back pulls as we were baffled why my car was dynoing so low and collected AFR data and the car stayed right at the 460 rwhp range.
pior to the thermostat the car would lose power on each back to back pull
Back in early 2010 I went on a hot dyno and put down 445 rwhp. After a kool down she put down 475 rwhp.
You of course know these cars inside and out. Just telling you my observations with my car
With a stock intake with KN filters and a few bolt ons and the origional Roe raceing SCT tune from Sean the car hit 443 rwhp. Then after a 30 minute kool down the power went to 454.
Still on the same origional SCT tune from Sean,we installed the KN air inatke and thermostat and the power went to 460 rwhp. We did a few more back to back pulls as we were baffled why my car was dynoing so low and collected AFR data and the car stayed right at the 460 rwhp range.
pior to the thermostat the car would lose power on each back to back pull
Back in early 2010 I went on a hot dyno and put down 445 rwhp. After a kool down she put down 475 rwhp.
You of course know these cars inside and out. Just telling you my observations with my car
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