What's the hottest you constantly tow at?

CorneliusRox

CorneliusRox

Seasoned Rookie
I was hauling ~14,000 lbs the other day and pretty much had to keep OD off if I wanted to stay under 1,000F unless I was doing 75mph or faster.

After looking up, it looks like Cummin's said the CR's can handle 1,350F constantly and be just fine, but that seems hot.

I've always tried to keep constant heat below 1,000F, but is that playing it way too safe?
 
my 7.3 w/ 16k behind it rarely sees 1500* at 70mph it hovers around 900. max temps to be concerned with obviously vary truck to truck/ build to build. id say a consistent 1400 would almost be concerning.
 
I do constant 1200 with my 333k mile 12v if the weather is cool enough that I can keep the coolant temps in-check. This usually only happens in winter/early spring. In the summer, I can only keep about 1100 constant cool enough engine temp wise.

Up here in the "mountains" EGT run rampant on the big grades and big head winds on the flats if you don't have a nice compound turbo system.
 
I don't back out of it till I am north of 1200* or the coolant temp is raising and not able to be kept in check.
 
I believe the 12v's were rated to handle consistent 1200* max and your CR spec also sounds right. 1200* is probably pretty safe (some safety margin?) but I agree, I don't like to see my pyro sitting that high when towing either.

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Man, you guys all make me feel way better about this. I was letting it sit way up in the RPMs to keep it cooler and felt bad for the engine.
It's been a while since I've hauled that much weight, but it just seemed excessive. I'm thinking I was just being paranoid.

Thanks again for the input guys!
 
I run about 1300-1400 constantly pulling my Jeep through the hills. Gearing up for some compounds though. Right now I have a single 66/73/14 and 37s with stock gears... not the greatest to tow with. This engine has about 200k miles on it so far.
 
I dont tow in OD... i run my truck at 2400rpm or so in 4th and i dont see much over 1000-1100 regardless of grade
 
I have been towing at 1000-1200 lately. And engine seems happy. Much past 1200 and I start backing out. I have not had a problem with coolant temp at all
 
this towing a stock trailer. its a wind brick. I will hit 1400 easy accelerating. once I get to spped is the pics I posted..this is common. the trlr I was pulling was only maybe 10 with the cows in it.
 

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Big Blue24 said:
I do constant 1200 with my 333k mile 12v if the weather is cool enough that I can keep the coolant temps in-check. This usually only happens in winter/early spring. In the summer, I can only keep about 1100 constant cool enough engine temp wise.

Up here in the "mountains" EGT run rampant on the big grades and big head winds on the flats if you don't have a nice compound turbo system.
Click to expand...

Will, what's your opinion on melting pistons at that temp. 1200F is safe because of oil squirters? or should I be worried about the fuel bowl lips since they're so far away for the oil?
 
CorneliusRox said:
Will, what's your opinion on melting pistons at that temp. 1200F is safe because of oil squirters? or should I be worried about the fuel bowl lips since they're so far away for the oil?
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Cummins rates them for 1225 or so continuous, I figure with the bigger injectors, timing, and other variables that are different from a stock truck, there's no need to push it past 1200F. If my coolant is running really close to overheat, I don't like to hold 1200 because in my mind, the oil temp is higher when the coolant is higher so there's less "safety" margin. Unfortunately, I've had the head off my daily driver a couple times and it still looks good inside, so I think my driving habits are conservative enough to not hurt the engine.
 
Where is cummins getting the number for the rating they use? Is it just the standard probe in the exhaust manifold?

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Spent 30 years driving semi's, the rule was not over 1200*, but that was post turbo.
Started reading on this and another forum when I did my 12v conversion and everyone was screaming 1200 max pre turbo. Had me wondering if these engine weren't as tough as I'd always heard they were.
That said in semi's we allowed 1200 on short pulls but normally stayed down below 950-1000 constant, I do try to stay below 1200 constant towing but allow 13-1400 on short pulls.
My pocket isn't deep enough to test the upper limits of egt's. Normally on long runs water temps become the limiting factor.
 
Most big trucks have steel pistons for the last 15 years or so...will handle lots of heat.

I have used 1300* pre turbo since I had a pyro with no problems, but don't pull 10 mile hills either. Longest pulls around here are 3 miles maybe. I also usually try to have enough power to not need all the fuel to get them that hot, too.

Chris
 
Big Blue24 said:
Cummins rates them for 1225 or so continuous, I figure with the bigger injectors, timing, and other variables that are different from a stock truck, there's no need to push it past 1200F. If my coolant is running really close to overheat, I don't like to hold 1200 because in my mind, the oil temp is higher when the coolant is higher so there's less "safety" margin. Unfortunately, I've had the head off my daily driver a couple times and it still looks good inside, so I think my driving habits are conservative enough to not hurt the engine.
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You are making me feel a lot better about my habits. I've messed so much with my fueling and gating trying to get a cool running truck while towing, but maybe I was shooting at the wrong mark. I've got a tow trip coming up, I think I'll let her sit closer to 1200F and see what happens.

chevota84 said:
Where is cummins getting the number for the rating they use? Is it just the standard probe in the exhaust manifold?
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That's a good point. I've still got a few friends at Cummins. I'll text them and see if they know.
 
Signature600 said:
Most big trucks have steel pistons for the last 15 years or so...will handle lots of heat.
Chris
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I retired from trucking 9 years ago and haven't been inside a engine less than 15 years old.
Engine's in the 80's and 90's had steel inserts in the ring area but I've never seen a STEEL piston.
The engines I was talking about operating at 1200* post turbo where those 70's-80's and 90's model engines I drove back then.
 
chevota84 said:
Where is cummins getting the number for the rating they use? Is it just the standard probe in the exhaust manifold?

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Click to expand...

Yes. The temps will run hotter close to the turbine inlet compared to sitting next to the exhaust port. Not by much though.
 
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