Ecodiesel power derating as temps rise?

[CrazyCooter]

That's been the same conclusion of every article I've read on it, ever one.
Electric is more efficie

Funny thing - I found a couple of other similar tests, too. One with a sports car..........same effect.
If you look as the shape and placement of the shields and baffles in there, makes some sense.
But I'm not a member of SAE.

Glad to have you here in my discussion thread Mr. Bill!

It makes total sense to me........The area under the hood is probably a low pressure area at speed helping draw more in air through the grill. Air dams increase the pressure in front of the grill while inner fenders with rubber flaps seal the engine compartment so the low pressure under the vehicle contiues into the engine compartment.

This is a big reason why I have resisted changing inner fenders or any other change until I know no other problems exist. I've been doing this long enough to know every change can have an unintended consequence........one we may or may not be able to live with depending on our use.

90s ground effects? Hot pink wiper blades too?

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[ShadowsPapa]

Glad to have you here in my discussion thread Mr. Bill!

It makes total sense to me........The area under the hood is probably a low pressure area at speed helping draw more in air through the grill. Air dams increase the pressure in front of the grill while inner fenders with rubber flaps seal the engine compartment so the low pressure under the vehicle contiues into the engine compartment.

This is a big reason why I have resisted changing inner fenders or any other change until I know no other problems exist. I've been doing this long enough to know every change can have an unintended consequence........one we may or may not be able to live with depending on our use.

90s ground effects? Hot pink wiper blades too?

I haven't looked - I hate to admit - to see how well sealed the area around the radiator is on the JT.....
For example, on my cars there's shields that prevent air from going over the radiator between it and the hood, and between the bottom of the radiator and the lower radiator support. One of my cars had a stainless steel "spoiler" that forced air up behind the bumper into the radiator area. It looked like a chin spoiler but was actually intended to direct air behind the bumper and up right to the radiator.

 

[CrazyCooter]

I haven't looked - I hate to admit - to see how well sealed the area around the radiator is on the JT.....
For example, on my cars there's shields that prevent air from going over the radiator between it and the hood, and between the bottom of the radiator and the lower radiator support. One of my cars had a stainless steel "spoiler" that forced air up behind the bumper into the radiator area. It looked like a chin spoiler but was actually intended to direct air behind the bumper and up right to the radiator.

I could do the same thing by removing the skid plate and building a scoop, but it would just be a guess without a wind tunnel. Then I go back to......If it was that easy, the designers would have installed a plastic one!

 

[CLM]

I admit, I did not read the whole thread. But that seems to seal the coffin on my Diesel JT Rubicon dreams. Thanks again for the honest feedback and data.

-TJ

I could do the same thing by removing the skid plate, but it would just be a guess without a wind tunnel. Then I go back to......If it was that easy, the designers would have installed a plastic one!

The issue is called "heat soak". This happens when the powertrain is asked to perform excess work over a specified time that the engineered cooling system is incapable of discharging into the ambient environment. This problem is worsened at high altitudes, steep grades, overgearing, heavy vehicles, insufficient cargo weight capacity, turbo engines, absence of intercooolers, absence of oil to air coolers, poor aerodynamics, high cylinder temperatures, high ambient temperatures, and other factors. The JT Rubicon Diesel does many things well but it's a poor choice for towing. It's a rock crawler, not a load hauler.

 

[CrazyCooter]

I swapped the 37's off for the OEM tires, re-calibrated the tire size, and removed the Mopar winch bar before performing the same test as yesterday. This time the vehicle combo was lighter due to smaller tires/wheels, I remover the motorcycle tires from the bed, and we were 4 gals lighter on fuel......Well below the rated max GCVWR for this trip.

Ambient temp in the valley was 104° and 94° at the top of the grade.....couple of degrees cooler than yesterday.

Overall the results were really close to the same..... The engine oil temp was above 260 and power derating well before the 9% grade. I was able to pull the 9% grade at 24mph with the flashers going and water temp climbed to 247, so it didn't go into limp mode, but I suspect another 1/4 mile and it would have........

I didn't notice any power or shifting differences between the 2 different tire sizes other than it took less throttle to get rolling and she shifted into 2nd almost immediately.8th gear was not obtained in either test. I did notice that I liked the gear spacing better with the 37's installed........when climbing the grade this time, I was turning almost 4000rpm where with the 37's it was around 3600. Also noted when descending and downshifting to control speed, I was unable to keep the RPMs in the sweet spot to maintain 55 mph because the truck was in between gears due to gear spacing once again.

I conclusion, I can't honestly say the 37's or the winch bar made any difference other than maybe braking which I thought was pretty good considering both vehicles are right at max capacity.........1 degree cooler water temp would most likely have been from the 3° cooler ambient temp. Also the 37's seemed to put the engine into it's happy RPM range both climbing and descending rather than the assumed disadvantage.

 

[tjZ06]

I swapped the 37's off for the OEM tires, re-calibrated the tire size, and removed the Mopar winch bar before performing the same test as yesterday. This time the vehicle combo was lighter due to smaller tires/wheels, I remover the motorcycle tires from the bed, and we were 4 gals lighter on fuel......Well below the rated max GCVWR for this trip.

Ambient temp in the valley was 104° and 94° at the top of the grade.....couple of degrees cooler than yesterday.

Overall the results were really close to the same..... The engine oil temp was above 260 and power derating well before the 9% grade. I was able to pull the 9% grade at 24mph with the flashers going and water temp climbed to 247, so it didn't go into limp mode, but I suspect another 1/4 mile and it would have........

I didn't notice any power or shifting differences between the 2 different tire sizes other than it took less throttle to get rolling and she shifted into 2nd almost immediately.8th gear was not obtained in either test. I did notice that I liked the gear spacing better with the 37's installed........when climbing the grade this time, I was turning almost 4000rpm where with the 37's it was around 3600. Also noted when descending and downshifting to control speed, I was unable to keep the RPMs in the sweet spot to maintain 55 mph because the truck was in between gears due to gear spacing once again.

I conclusion, I can't honestly say the 37's or the winch bar made any difference other than maybe braking which I thought was pretty good considering both vehicles are right at max capacity.........1 degree cooler water temp would most likely have been from the 3° cooler ambient temp. Also the 37's seemed to put the engine into it's happy RPM range both climbing and descending rather than the assumed disadvantage.

Thanks again for collecting that data. It's definitely good to know, and reaffirms what I would have expected... but will silence the "take the 37s off that's your problem" crowd. If anything, only 1 degree higher ECT for 3 degree less ambient would be data supporting the 37"s might help, if anything - perhaps because it puts the engine into more ideal RPM ranges for any given speed, as you noted.

-TJ

 

[CrazyCooter]

Thanks again for collecting that data. It's definitely good to know, and reaffirms what I would have expected... but will silence the "take the 37s off that's your problem" crowd. If anything, only 1 degree higher ECT for 3 degree less ambient would be data supporting the 37"s might help, if anything - perhaps because it puts the engine into more ideal RPM ranges for any given speed, as you noted.

-TJ

Yes, if anything....Being 150-200lb lighter and the cooler ambient temp is where the 1° cooler ect came from. The winch guard bar could have helped too?

 

[briandmiles]

So I just experienced something like this. I was driving home to Salt Lake City from Boise. Temps were about 103 and I had been going for about an hour on the freeway at 80mph. All of the temps read as within a normal range. The truck starts to slow down for no apparent reason and eventually I'm at 40mph. I pull off to the side of the road, check the temps, check the DEF (I had filled it a few weeks prior so was pretty sure that wasn't the problem). I went to get back on the road and the motor would go up to 3000 rpm and then it wouldn't shift. I could let off the gas a bit and it would shift and then get stuck at 3000 rpm again. At that point, the check engine light came on and a message came up that there was an exhaust issue and that I needed to take it to the dealer.
Limped home for the next 3.5 hours going between 40 and 75 mph. When the dealer looked at it they said it was a regen code even though the particulate filter was only 29% full. They forced a regen and couldn't get the code to come up again so they said it was good as they could do. They did try to blame it on the Tazer Mini that had been dealer installed since I picked it up in November 2020.
No problems since getting it back but I'll be towing a SxS next week up to Island Park, ID and we'll see how it goes.

Brian

 

[Abnmarine]

I have 16,000 miles on my JTD. It has a 4” lift and 37’s with stock gears. I left Florida last Sunday and arrived in Moab today. I’m towing a 3,800 lb Rpod 189 and maintain 65 mph without using cruise or the AC. The temps were up to 95 degrees and so far I’ve climbed up to 7k feet. No derating issues but I do monitor the temps.

I typically see temps at:
225 coolant
235-240 oil
208-210 trans

this was the highest temps that I’ve seen and it was after a long grade. Nothing too bad yet, we will see what Colorado brings next week.

I did see decent mileage that I’m happy with.

 

[CrazyCooter]

I have 16,000 miles on my JTD. It has a 4” lift and 37’s with stock gears. I left Florida last Sunday and arrived in Moab today. I’m towing a 3,800 lb Rpod 189 and maintain 65 mph without using cruise or the AC. The temps were up to 95 degrees and so far I’ve climbed up to 7k feet. No derating issues but I do monitor the temps.

I typically see temps at:
225 coolant
235-240 oil
208-210 trans

this was the highest temps that I’ve seen and it was after a long grade. Nothing too bad yet, we will see what Colorado brings next week.

I did see decent mileage that I’m happy with.

You were right there........another couple of mins under the load, couple of degrees warmer, or ac on and you would have slowed way down when oil temp reached 260.

 

[Abnmarine]

You were right there........another couple of mins under the load, couple of degrees warmer, or ac on and you would have slowed way down when oil temp reached 260.

I agree 100% and actually expected this to happen. I did notice that the AC would increase the temps a bit and cruise tends to hunt 5-6 gears on a climb.

Trust me I wish it would stay cooler regardless and I’m interested in ways to achieve this. Just posting what I’ve experienced so far.

 

[CrazyCooter]

I'm actually a little concerned with the short life span of the plastic parts under the hood with all this heat. I bought the 125k warranty. Thinking this will just be a vehicle I get to enjoy till it turns into a liability and then toss it in the dumpster.

I'm still driving my 91 Why-J to work daily, but most of it is easily serviceable and much less plastic!

 

[CrazyCooter]

I have some more time before I tow a larger rv.......We ordered a new 16' GeoPro back in April and were expecting delivery any day now.......Dealer called last week and told us the manufacturer raised the price $4k, so the OTD price was going to be $32-33k....Hard pass! I'll wait a couple of years for the nonsense to correct.

I do feel kind of unequipped though.......I've had an rv since I was 19yo and now have a few tents?

 

[mayerrony]

I have some more time before I tow a larger rv.......We ordered a new 16' GeoPro back in April and were expecting delivery any day now.......Dealer called last week and told us the manufacturer raised the price $4k, so the OTD price was going to be $32-33k....Hard pass! I'll wait a couple of years for the nonsense to correct.

I do feel kind of unequipped though.......I've had an rv since I was 19yo and now have a few tents?

Highly unlikely this nonsense will correct. Coming from a south american country, we are used to inflation, and devaluation of national currency.

With previous bailouts from years back, and now covid, all this mass printing and handing out of money, without anything to back it up, has caused the dollar to go down for the rest of the world. Hence these "shortages" and pricing of foreign goods going up. If anything, it will get worse over time.

Unless large amounts of printed dollars get taken out circulation, it will not correct. If it were me, I would buy now.

 

[CrazyCooter]

Highly unlikely this nonsense will correct. Coming from a south american country, we are used to inflation, and devaluation of national currency.

With previous bailouts from years back, and now covid, all this mass printing and handing out of money, without anything to back it up, has caused the dollar to go down for the rest of the world. Hence these "shortages" and pricing of foreign goods going up. If anything, it will get worse over time.

Unless large amounts of printed dollars get taken out circulation, it will not correct. If it were me, I would buy now.

I really hope not, but Im afraid you are correct! I just figure eventually we would run out of free money and things would crash.......not that I want that to happen. Maybe I should raise my shop rate $50hr and just pay the $32k? Its been 1.5-2 years since I raised it........hmmmmm.

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