Towing and RPM

Freshaire

I'm looking for some guidance when it comes to towing and RPMs.  I just finished a trip of 3,200+ miles to Canada.  There were lots of ups and downs, some grades were 14%.  When traveling uphill, if I were to maintain the speed limit of 65 mph, my RPMs would go as high as 4,000.  I didn't like the sounds of the engine at those RPMs, so I backed down to around 50 mph, with the tach at 2,500.  Is that what I should be doing?  Do I use the RPMs to determine what speed I should be traveling when going uphill?

Conversely, going down hill, I know a lower gear is what you should use to help control your speed.  I wasn't sure if 1st or 2nd gear was appropriate.  Again, do you use RPMs to help you determine which gear is best?  My TV does not have a Tow/Haul setting.

I know I am going to get some great responses.  Thanks in advance!

rkj__

I’m ok with letting my truck run at 4K RPM. None of the hills I come across have it that high for more than a couple minutes. And most trips I take have no extended steep climbs that push it into that range. 

Doing downhill, I use RPM as a guide. I’d target 2k to 3.5k. 

pthomas745

Here are your engine specs:

http://www.hondanews.com/releases/2012-honda-ridgeline-specifications-and-features?query=

The Ridgeline apparently produces max torque of 247 ft/pds at 4300 RPM.  If  you are asking it to go up a 14 percent grade at 65 MPH, then it will be reaching 4000 RPM or more to get there.

This is from Wikipedia on "Power Band"

Specifically, power band is the range of RPM around peak power output. The power band of an internal combustion gasoline automobile engine typically starts at midrange engine speeds (around 4,000 RPM) where maximum torque is produced, and ends close to the redline after reaching maximum power between 5,000 and 6,500 RPM. Diesel engines in cars and small trucks may develop maximum torque below 2,000 RPM with the power peak below 5,000 RPM.

4ncar

Simply: use rpm not speed. Rpm also varies or 8 cyl, and whether gasoline or diesel. 

PS.  If it doesn’t sound good, then it probably isn’t.

Haloo

Hi @Freshaire, are you retired?  If yes, the speed limit is no longer something you need to exceed by 5mph or more.  It is now the upper speed limit of what you, should you so desire, attain with your camper under ideal conditions, i.e. flat or gentle terrain.  If you are not retired, well, you can practice as if you are!

The torque @pthomas745 mentions is the pulling power of your Ridgeline.  You have a moderate amount of pulling power.  A 14% grade is very steep.  You would be fine backing off the accelerator to keep your speed at or above 45mph on such a slope.  This will help keep the engine running temperature and transmission temperature in a safe range.  If cars stack up behind you, so be it.  Everyone expects campers to climb steep hills more slowly.  They’re just jealous you get to go camping anyway.

As long as you keep your engine below redline on your tachometer you will not damage it, even if the engine sounds angry at you.  It will work harder, and probably increase the running temperature a bit, but should be fine unless the hill is very long and the outside temps start to soar.  Just make sure to change your oil according to the more stringent guidelines for hard use.

I use lower gears going downhill to preserve my brakes.  I put my vehicle in the highest gear that helps me control the weight of camper, and allows me to only gently ease on the brakes periodically.  So, I may need to be only in 4th or 3rd gear to do this.  Sometimes I have dropped it into 2nd.  So far I haven’t needed to drop to 1st, but your truck may be geared differently than mine.  In any case, you still don’t want to run your engine above the redline on your tachometer.
 

Dalehelman

Look in your vehicles owners. Under specifications look for maximum torque RPM. Each engine size and make will be different. This applies to both gas and diesel. Use the highest gear which allows you to maintain that rpm. If you cannot maintain that rpm shift to the next lowest gear. It’s that simple.

Mouseketab

I watch my RPMs also, and try to stay in Overdrive. For small "rises" I don't try to maintain my speed just slow up a little to keep the RPMs steady. However, if need to get up a grade, I don't mind going up in RPMs somewhat. I do have a 4.6 V8 in my SportTrac with tow package (heavy transmission, and transmission cooler)

ScottG

It's worth noting that "lugging" your engine (running it at too low an RPM for the load placed on it) will damage it as much or not more than over-revving it.

According to a recent Car Talk column, both conditions generate excessive heat, and excessive heat accelerates engine wear.

Travelin3D

+1

ericnliz

X2

Marceline

Mouseketab said:

I watch my RPMs also, and try to stay in Overdrive. For small "rises" I don't try to maintain my speed just slow up a little to keep the RPMs steady. However, if need to get up a grade, I don't mind going up in RPMs somewhat. I do have a 4.6 V8 in my SportTrac with tow package (heavy transmission, and transmission cooler)

Towing in overdrive is probably fine for your vehicle but it can be a bad idea for others. Best to check the owners manual on this. 

Dalehelman

That is why it is important to know what your engines maximum torque RPM is. Your engine is running at it’s optimal speed in any gear. 

rkj__

Marceline said:

Mouseketab said:

I watch my RPMs also, and try to stay in Overdrive. For small "rises" I don't try to maintain my speed just slow up a little to keep the RPMs steady. However, if need to get up a grade, I don't mind going up in RPMs somewhat. I do have a 4.6 V8 in my SportTrac with tow package (heavy transmission, and transmission cooler)

Towing in overdrive is probably fine for your vehicle but it can be a bad idea for others. Best to check the owners manual on this. 

I never tow in overdrive.  In my vehicle, that leads to far too much shifting back and forth between gears. 

Verna

Per my Tacoma’s owner’s manual, towing should be done in the 4th gear, not in overdrive due to excessive gear shifting as @rkj__ pointed out.  

As @Marceline, pointed out, the owner’s manual is a great place to check for your individual tow vehicle. 

Ratkity

I am fortunate to have a "towing mode" and "Distance To Empty" (DTE) that calculates miles before my fuel is out in my truck.

DTE is a calculation can accommodate how many miles I have left before I run out of gas while in towing vs normal driving mode. DTE information is something I don't use, but it's above my gas gauge.

"Towing mode" allows the rpms of the truck to go higher on upgrades and downhill before it shifts into a higher gear. If the transmission temp gets to a certain number, I'll get a dashboard message to pull over and let the transmission cool. I also have an extended range gas tank. If I wait too long to fill, I get sticker shock at the cost to fill it! LOL It's 36 gal.

About max rpms, I was told by the family mechanic and even a truck driver friend who said that while you normally don't hear your engine rpms wind up that high (and it seems worrisome), as long as you aren't near the "red line" for rpms for your vehicle, engine braking going downhill is better on your brakes and prevents overheating of brakes. 

riooso

One thing to consider is that when you are doing 4K while towing a trailer the engine is under load so that all the forces inside are fairly constant. All is probably doing quite well but engine wear is up a tad.  I would just keep it down to 3.5K which is high enough in the power band to make it possible to easily increase speed if needed.