Towing at highway speeds

[mescobar350]

I recently bought a 2 horse trailer for our 21 Expedition. It gets up to speed with absolutely no problem weighing in around 5-6k. But at highway speeds of 65-70 it seems to run hot and a ton of boost to maintain. I put my scanner on and at 70 I am running 215 degrees (engine temp), trans 205 but maintaining about 5-8psi of boost. Is this normal?
I feel like my trailer is dragging me the way the doors are (the rear doors do not sit flush and look like they would cause major drag). But this is the first time I have towed in 25 years without a dually. Are these temps and boost numbers appropriate? I will mention that within about 5 minutes of towing in stop and go temps fell to 185 almost immediately.
First time poster. Be kind

 

[JasonH]

Try locking out the top two gears. In the taller overdrive gears you're going to run more boost while towing at those speeds. More boost and lower RPMs means more heat.

 

[mescobar350]

So a bit of an update. Locking out 9th and 10th has helped. But it seems to still run hotter than normal at 65-70 (trans gets up to 210 and engine 220). Question is, how hot it too hot. Are these temps ok?

 

[JasonH]

Cooler is obviously better, but those temps are beneath the danger zone. What RPM are you running? If you drop down another gear or reduce speed and the temps decrease, then it's obviously the higher boost causing all the heat. But how much boost you're running is also highly dependent on the trailer profile, speed, and wind direction. Sometimes you might need to drive a bit slower to reduce the work the engine is doing. Make sure you're running premium fuel and check your IAT temperature. If the intercooler is heat soaked the engine will pull timing and that will result in more boost to maintain speed. I haven't towed in awhile, but my recollection is that I was around 4 - 7 psi while towing my camper at ~65 mph.