6.7L 200 degree thermostat - Experimental Idea

[Mopar1973Man]

Starting back in the beginning of 2023 winter I opted to play with 200 degree Cummins thermostat from a 6.7L Cummins. Now as winter got to the coldest of minus 7 degrees I was happy to keep a warm cab and engine. I watched over the winter time and as I was able to keep temps above 80 degrees in the intake manifold (IAT) I noticed an improvement in MPGs because cold air does rob the engine of ignition quality and more heat energy is not wasted to the coolant jacket. 

 

Now fast forward to now. I made a trip to Lewiston ID for monthly supplies and food. Still running a 200 degree thermostat in 90 degree weather. This is a Gates Thermostat and seems to hold steady between 200 and 210 degrees of coolant. Even climbing 7% grades everything still running normal specs and no issues. I'm happy to say MPG wise I didn't quite use a 1/4 tank more like 3/16 of a tank in a one way pass from home to Lewiston ID. Level ground EGT's are still cool. Engine oil temperature barely touched 178 degrees even climbing long 7% grades. Boost was between 10 and 13 PSI.

 

 

Flat ground cruise

Edited May 15 by Mopar1973Man

[01_Cummins_4x4]

Mike, do you have the part # for the t-stat, or which year of 6.7 Cummins to look for?

 

 

[Mopar1973Man]

Here it is...

[Mopar1973Man]

Update...

 

I produced a towing tune and took off for a 5 day camp trip down near Fiddle Creek which is just south of Lucile ID. I can say I hit proper timing in the first try and oil temperature where still 175 to 178°F and coolant ran like usual around 204 to 208°F no problem. I was seeing 12 to 14 MPG flat ground travel. No issues to report even towing. I'll post up my towing tune here shortly. I'm still running around haven't been home much more than few hours and left again. 

 

[Mopar1973Man]

 

Yeah Mark and I stayed here along the Salmon River for 5 days.

 

As for the Quadzilla tune, I will say my timing is the same but I zeroed out my cruise timing and disabled that knowing I rarely can reach the cruise state and I can't move the cruise state higher in engine load without possibly blowing the head gasket. Then for the retard settings you need to retard pretty much fully to get the spool you need for pulling grades and climbing with weight. I know I can hold WOT and have no issues with EGTs on level 3 as usual.

 

Engine oil temperature remain in the 170's and coolant was still normal. EGT's I have been under control.

 

As for me and my cancer, I spent those 5 days just relaxing, eating, and enjoying some quiet time without my cellphone and internet. I will do this as much as I can as I heal from my coming surgery and even before if I can squeeze one more trip in.

 

 

Now notice I'm running more retarded timing and my EGT's are still in check. I know you can't see boost here but I'm still below my 15 PSI break point for adding fuel. Even now I'm only using the 150 HP injectors but no added fuel by the Quadzilla. No smoke issues and temperatures across the board are still under control. Cooant, Engine Oil, EGT's, etc. All stable and not ramping up even scaled out at 17,500 pounds with the RV fully loaded with water, food and supplies for 5 days.

Edited May 28 by Mopar1973Man

[5akman]

Mike, glad to hear you're healing well and seem to have a positive mindset, (with or without bags!!  )

 

Will this new version of your tow tune be available to purchase (tweaked to an individual rig)? I have your tow tune that I bought a year or so ago but just purchased a larger trailer so I'm curious to how the prior tow tune will perform vs this new one you came up with. 

 

Thanks, 

Lance

[Mopar1973Man]

36 minutes ago, 5akman said:

Mike, glad to hear you're healing well and seem to have a positive mindset, (with or without bags!!  )

I'd be happier without the bags. Either way I get up every morning and do what I can do like yesterday got two other guys Einar and Mark to do the big work of getting my water fixed here for the yard. I did the pipe jointing. Today I'm going to be a bit lazy and rest and recharge it was a long day doing some basic work. 

 

38 minutes ago, 5akman said:

Will this new version of your tow tune be available to purchase (tweaked to an individual rig)? I have your tow tune that I bought a year or so ago but just purchased a larger trailer so I'm curious to how the prior tow tune will perform vs this new one you came up with. 

PM sent.

[Mopar1973Man]

Another update. Still very controlled temperatures on Beast. We are hitting 90°F here and even climbing 7% grade it's still very controlled floating 200 to 208°F coolant temperatures and 170 to 175°F engine oil temperature. 100 to 110°F IAT temperarure. No updates to the Quadzilla tune being it still very wicked pulling a 25 MPH corner at 40 to 45 MPH and feel the rear tires break loose and keep powering the corner. Very sweet power even on level 3.

 

 

[Doubletrouble]

 Coolant Temps aren't surprising. The cooling system on these trucks us very efficient when working properly. 

[Mopar1973Man]

Just made a run at 80 MPH in 90 degree weather on I84 to Boise for a doctor appt.

 

 

[Doubletrouble]

So at 80mph tour at 22.74 mpg? Wow

[Mopar1973Man]

Doing all I can with Beast with all my medical appointments and most of them being in Boise ID. With even today it was a bit more than a 1/4 tank to get home but I had to school a flatlander how to run the canyon. Sure couldn't keep up with Beast.