12 valve Hot thermostat?

[rebar]

What I'm gathering, is that mpg will improve running a 12 valve hotter than the one and only 180 degree cummins Tstat allows it to. Running hotter will also keep the engine at a more consistent temperature reducing heat cycles.

MPG is very important to me because I plan to "full time" RV with this truck in the future, so a 1 mpg increase means substantial savings when traveling as much as I plan to.

Iv read some people are running a 195F NAPA #532090 for a 440 Mopar. And another person a Murray 15479.

Is anyone here running a "hot" thermostat? And can you post what T-stat and model # and if you gained mpg? Is anyone running the cummins 24v 190 degree stat in a 12 valve?

Thanks!

 

[GAmes]

No way is a little hotter thermostat going to give you an additional mile per gallon. Yes, it will make the engine a bit more efficient, but it is doubtful you will be able to measure a short term increase. Perhaps over the course of 10,000 miles if all miles are pulling the trailer. But that means 10,000 miles of pulling the trailer with a 180 t-stat to establish a base line.

 

[mothertrucker]

I am more concerned with cooling than trying make the truck run hotter here in the desert of S/E Arizona but, the fact that you mentioned aftermarket T-stats prompted me to post my experience with them.

I experimented with several different aftermarket T-stats on my '97 3500 & all produced wild fluctuations on the temp gauge.

Finally installed a genuine Cummins T-stat { Cummins part # 3928499 }.
This is the T-stat that Cummins recommended based on the engine serial number.

The Cummins T-stat looks nothing like any aftermarket one I had ever put in the truck.

I have not had any cooling problems or crazy gauge readings since.

If I were you I would contact a Cummins dealer & start off with the correct T-stat that is recommended for your engine.

You can always use a winter time radiator cover if you want it to run hotter than the Cummins engineers designed.

 

[rebar]

Yeah I may end up replacing the napa THM 291 stat I just bought, but it was cheap enough to give it a go.

Games it's been proven the mpg drops off if the stat sticks open and runs cold. Unless you have data to prove your point its just a opinion I will disagree with

Its this video that makes me want those temps because mine runs like the stat wont fully close.But I cant find anything about Murray even though Ive heard their tstat mentioned in a few different forums.
Another tidbit I found.. "The solution has been reported by Gerry Willomtzer <dax@yukon.net>: 195 degree t-stat Dodge PN 3418459 intended for a 70's gas engine"

 

[NIsaacs]

Games it's been proven the mpg drops off if the stat sticks open and runs cold.

Isn't that another subject v/s a 180 or 190 thermostat?

The THM291 will not work, note the difference in the two pictures. Note the disk on the bottom of the "real" one, it opens and closes the bypass port. These trucks can run hot towing in hot climates, I would stay with the oem stat. Keep in mind your oem fan clutch might not cycle right with a 190.

 

[GAmes]

I agree that you could get a bit better mileage, it has been proven countless times. It is the 1 mpg improvement that I doubt. Plus, without a baseline, how will you know?

 

[Ozymandias]

If it would have been that easy to gain 1MpG (10%) fuel savings then Cummins would have done it from factory.

 

[rebar]

OK fine. If nothing else, I feel all warm and fuzzy now.

But I'm real happy with my $7.84 napa THM 291.. No rubber collar to get swallowed up either. Warmed up to operating temp in less than 2 miles, then held pretty consistently except for the second stop where looks like it dropped to 175 which is warmer than my factory stat ran at.

 

[rebar]

The THM291 will not work, note the difference in the two pictures. Note the disk on the bottom of the "real" one, it opens and closes the bypass port. These trucks can run hot towing in hot climates, I would stay with the oem stat. Keep in mind your oem fan clutch might not cycle right with a 190.

View attachment 109288 View attachment 109289

I get it now NIsaacs.. Without the disk, the bypass is always open and reduces the effectiveness or capacity of the cooling system. But it may also smooth out the bouncing when unloaded. I wont know if there is a problem until I'm towing in hot weather, which would be a bad time to swap in the cummins stat..

 

[NIsaacs]

Yes, I think so, it is there for a reason. I just assumed that it would help the temp swings but I have not used one without so I really can't compare. Keep us posted this summer on how it does. My '01 has a complete new cooling system and it will still run hot, towing on a hot day. However, I don't think Dodge built it for an Edge Juice

 

[fest3er]

The other, cheaper, way to make the engine run hotter is to block (cover) part of the radiator. It's worked nicely for me for many years when it's cold out.

 

[rebar]

The other, cheaper, way to make the engine run hotter is to block (cover) part of the radiator. It's worked nicely for me for many years when it's cold out.

Thought about that.. Card board cuts off air flow to the intercooler and will raise egt's and lower mpg.

Yes, I think so, it is there for a reason. I just assumed that it would help the temp swings but I have not use one without so I really can't compare. Keep us posted this summer on how it does. My '01 has a complete new cooling system and it still will run hot, towing on a hot day. However, I don't think Dodge built it for an Edge Juice

The cummins bypass opening and closing will make it swing worse, but more capacity. The reason my napa stat doesn't swing as much, is that the system is already closer to full capacity (btu's removed) since a open bypass reduces ability to remove btu's. Should be interesting this summer..

 

[Stox5225]

Thought about that.. Card board cuts off air flow to the intercooler and will raise egt's and lower mpg.

In the winter, I put my cardboard between the rad. and intercooler. Keeps the intercooler getting that nice cold air [emoji106][emoji2532].

 

[fest3er]

I found a pice of thin 'foam' sheet with a pocket at one end. Slip a dowel (or PVC pipe) into the pocket, and hang it between the radiator and cooler. Works great and lasts a long time.

 

[NIsaacs]

Thought about that.. Card board cuts off air flow to the intercooler and will raise egt's and lower mpg.

The cummins bypass opening and closing will make it swing worse, but more capacity. The reason my napa stat doesn't swing as much, is that the system is already closer to full capacity (btu's removed) since a open bypass reduces ability to remove btu's. Should be interesting this summer..

I think the key here is what fest3er said, cover "part" of the radiator, not all. Unless you are towing heavy or have fueling mods, EGT's are not an issue.

This is old info so it may or may not apply. Years ago, Cummins resisted intercoolers and continued with water cooled aftercoolers even after most engines were using intercoolers. They said that intercoolers would actually cool to much, too fast. Especially on a down hill, right after a hard uphill pull. The thinking was, it was hard on valves and valve seats. I have always remembered this so I tend to get out of it, towards the top of a hill, if I know a down hill is next. I also use the exhaust brake as much as possible, keeps the heat in.

I think part of the reason for the t-stat bypass disk is to assist in heater core flow. With the bypass always open, the coolant might just take the easy road and not flow as much through the heater core, especially at low rpm or idle.

 

[ofelas]

Actually, when the thermostat is closed, the bypass port is open.

This is to ensure coolant circulation through the head & prevent hotspots.

Since the heater inlet is fed by the cylinder head outlet, this helps the heater core put out heat quicker.

When the stat is open, the bypass port is closed by the bypass disc/or a tapered seat depending on the generation of truck.

I've lasered the temps with & without a bypass style thermostat on identical back to back hot runs, and there is no difference that I found.

I think part of the reason for the t-stat bypass disk is to assist in heater core flow. With the bypass always open, the coolant might just take the easy road and not flow as much through the heater core, especially at low rpm or idle.

 

[NIsaacs]

So what the heck is it for then, Lol? If the stat works fine without it, why have it?

 

[ofelas]

LOL.

It likely helps some, in a severely loaded towing application in hot weather.