Community Forums

troyrice76 · 05-19-2013, 04:51 PM

When driving up a long grade I am not to concerned about speed but don't want to run to hot. Should I try to keep the coach at a certain RPM to keep the engine spinning and cooling better.

Thanks,

TR

DSL417 · 05-19-2013, 04:55 PM

Spartan says use that diesel engine by shifting yourself. Don't worry about revving at 2100 RPM. Don't let it lug down. That's from the Chassis owner's Class week before last.

Steve Ownby · 05-19-2013, 05:07 PM

Quote:

Originally Posted by troyrice76

When driving up a long grade I am not to concerned about speed but don't want to run to hot. Should I try to keep the coach at a certain RPM to keep the engine spinning and cooling better.

Thanks,

TR

No long grades the accepted drill is to need the rpm p close to the hp peak which is generally at the governed rpm. If your engine heat keeps climbing then down shift another gear and back off the throttle some.

MSHappyCampers · 05-19-2013, 05:42 PM

I try to keep the engine RPM's above 2000. Don't know if that's right or wrong, but someone told me that back when we bought the MH!

rvjimmy · 05-19-2013, 07:14 PM

You only are going up the hill as fast as you have power. Find the speed that all runs good and don't bury your foot to the floor.Just back out of it a little and let it go up the hill as you keep your RPM at 2000 to 2100. Works for me and will use less fuel that keeping your foot in it.

Jim PS as I have a DP that's how I do It.

2 Stroker · 05-19-2013, 07:34 PM

I just had the SilverLeaf VMS 330 installed, it gives all the reading in real numbers and was told when going up a grade to keep the torque at the peak just before it drops off to get the best mpg plus it reads coolant temp, mpg, trans temp and the gear you are in and a lot more. Money well spent.
2 stroker

Dutch Star Don · 05-19-2013, 10:01 PM

Diesels are not like gassers and don't climb well by wringing their necks, like gassers do. That actually becomes counter productive. You should really find out what the max torque and horsepower rpm are for your engine. This will help you drive more in your power range and get better mileage. Mine climbs well at about 1700 rpm. If I try to rev past that, power just drops off. "2 Stroker" has it right, run the engine around the max torque rating. If it starts to get hot, either take your foot out of it, or drop a gear and bring the rpm's up to spin the fan faster, while slowing down at the same time.

After a few hill climbs, you should get to know your engine and it's capabilities/limitations. Pouring on the throttle when you don't have the power will just waste fuel and overheat the engine.

dons2346 · 05-19-2013, 10:23 PM

Quote:

Originally Posted by 2 Stroker

I just had the SilverLeaf VMS 330 installed, it gives all the reading in real numbers and was told when going up a grade to keep the torque at the peak just before it drops off to get the best mpg plus it reads coolant temp, mpg, trans temp and the gear you are in and a lot more. Money well spent.
2 stroker

That's right Floyd. With the RPM right at max torque, the motor will run most efficiently and won't overheat. You won't burn past anyone up the hill but then again, they aren't buying your fuel.

With our variable speed fans, we can run the RPM up and try and go up the hill faster at a lower torque figure. Those with rear radiators have to use higher RPM's to rely on the water pump to pass a large amount of water to cool the beast

Mr_D · 05-19-2013, 10:29 PM

Quote:

Originally Posted by 2 Stroker

I just had the SilverLeaf VMS 330 installed, it gives all the reading in real numbers and was told when going up a grade to keep the torque at the peak just before it drops off to get the best mpg plus it reads coolant temp, mpg, trans temp and the gear you are in and a lot more. Money well spent.
2 stroker

The "problem" with the torque and HP on any of the Silverleaf displays is that it's just programming in the unit. It doesn't actually measure anything. They just program in the power curve of the engine using factory info.
Got this info by asking on their forum sometime ago.

Ramzfan · 05-19-2013, 10:32 PM

I have been told by both Cummins & Cat Mechanics that if you want your engine to stay cool when climbing hills, keep the RPM's at 2,000 or more.

k9crazy5 · 05-19-2013, 11:46 PM

Freightliner RV chasis manual says climb at 2000. What goes up must come down. What is the proper downhill rpm? Does using an engine brake change the desired rpm range?

2 Stroker · 05-20-2013, 12:09 AM

Quote:

Originally Posted by Mr_D

The "problem" with the torque and HP on any of the Silverleaf displays is that it's just programming in the unit. It doesn't actually measure anything. They just program in the power curve of the engine using factory info.
Got this info by asking on their forum sometime ago.

All I can go by is what I was told by the person that installed it and he is the one that designed it, Dale Kemper--Service Director.
2 stroker

SteveSkinner · 05-20-2013, 03:09 AM

Quote:

Originally Posted by Steve Ownby

On long grades the accepted drill is to need the rpm close to the hp peak which is generally at the governed rpm. If your engine heat keeps climbing then down shift another gear and back off the throttle some.

This is the correct advice.
Torque maybe 1400 rpm and max Hp maybe 2000 rpm
Do not try and run at max torque but run at max hp.
Hopefully this means you have like 3/4 throttle 2000 rpm. Forget about everything else.
If its seriously steep you could be 2 nd gear at 25 mph or 4 th at 38 mph.
Nobody cares whether you are doing 25 or 38 mph but you need to care about keeping temps in the green and the above is the way to do it.

wb7auk · 05-20-2013, 04:08 AM

TR,
You are dealing with two different issues here.
Best fuel mileage or best engine cooling.
Cat and Cummins agree the best fuel mileage is at max torque or a little above.
Max cooling is some where above that RPM at the cost of extra fuel.
Depending on the cooling system of your vehicle you will find a RPM and gear that
will keep your engine temp in the safe zone.