This summer we were towing a 16,000 lb trailer and a 2,000 lb boat on the back of a F350 powerstroke dualie. We were going down a hill at 75ish ~ 3000 rpms. When we started going up with hill, slowly the rpms started dropping and so were the mph. I know this is due to the load on the motor but this is my question... I know when i see dyno graphs a car makes a certain amount of hp and tq at a certain rpm... so at 3000 rpms for the truck it is making around its most hp... so when the rpms fall does the truck do anything to try to make more horsepower at those lower rpms such as inject more fuel? just wondering....

-Dakota

 

If you're using the cruise control, then yes. When the truck slows down, the cruise will add some throttle (and therefore some fuel), which generates more power, in order to maintain your speed.

If you're not using the cruise, and you don't do anything with the accelerator, then no, the truck doesn't do anything differently.

 

Not really, or to answer your question, no.

I know for a fact with my Ranger, if my foot is not on the pedal and I'm basically coasting, the injectors shut off. Most vehicles these days are probably like that.

The engine will only make the hp's it's designed to when it's designed to. Injecting more fuel without modding the engine to do anything with extra fuel will not help any.

Oh well, I did my 12 hours at the plant, but maybe I answered your "?" a little bit...

 

so when you put a heavy load on the motor, what exactly is happening to the engine, tranny?

 

That's a really hard question to answer, as phrased. What do you really want to know?

 

so when you are going up a hill with 18,000 lb load on your truck, what is happening to your motor as the truck is going up the hill?

 

Well obviously your motor is working alot harder under a load, but trucks are built for towing so unless you exceed the towing capacity you shouldn't have anything to worry about.

 

i know it is obviously "working harder" but what does "working harder" entail

 

Using more fuel, and applying more stress to pretty much everything.

 

More fuel/air, thats why Bigger engine's like V8's are prefered for towing.

I've pulled some decient loads, I normally use momentum to keep it going after coasting down and hill and start up on the gas before I loose too much speed like the truckers do