Go Back   iRV2 Forums > MOTORHOME FORUMS > Class A Motorhome Discussions
Click Here to Login
Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on iRV2
 
Thread Tools Search this Thread Display Modes
 
Old 05-03-2013, 08:43 AM   #15
Senior Member
 
SteveSkinner's Avatar
 
Monaco Owners Club
Join Date: Jun 2011
Location: Montana
Posts: 807
Re the Jake Brake.

Just did the drive thru highway 12 and 24 Bryce to Moab.
These roads are twists turns up and down with 8% grades. I hardly touched the brake pedal.
The jake will hold an 8% grade in 4th gear without touching the service brakes.
From memory a PAC brake would require you to be in 3rd gear and assistance from the service brakes every few seconds to hold the coach back.
Remember its only the big engines that have a jake brake. That's because there driving coaches near and more than 40000 lbs.
__________________

__________________
2005 Monaco Signature Castle 1V
2013 Subaru Outback Toad
SteveSkinner is offline   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 05-03-2013, 09:20 PM   #16
Senior Member
 
Rich-n-Linda's Avatar
 
Join Date: Nov 2011
Posts: 884
I don't know where so many of you got the idea that TORQUE is what gets you up a hill. Folks, that's just plain wrong...for ANY engine.

It is HORSEPOWER that determines how fast you go up a hill. Horsepower is a measure of how FAST a given amount of work can be done. Torque is just part of what determines horsepower. RPM is the other part of the equation. For those of you that get into the math, the formula is Torque x RPM divided by 5252.

Here's an admittedly absurd example:
Torque rating = 5,000 foot pounds
Maximum RPM = 500
HORSEPOWER OF THIS ENGINE IS 476 HP.


And another example with the numbers swapped...
Torque rating = 500 foot pounds
Maximum RPM = 5,000
HORSEPOWER OF THIS ENGINE IS 476 HP

Which engine will get you up a hill faster? Take your choice...they're equal. You just have to run one at a faster RPM than the other to get that 476 HP.

It's HORSEPOWER folks, not torque, that gets you up the hills.
__________________

__________________
Rich-n-Linda is offline   Reply With Quote
Old 05-03-2013, 09:40 PM   #17
Senior Member
 
Skip426's Avatar


 
Join Date: Apr 2011
Location: Powell River, B.C.
Posts: 14,971
Quote:
Originally Posted by Rich-n-Linda View Post
I don't know where so many of you got the idea that TORQUE is what gets you up a hill. Folks, that's just plain wrong...for ANY engine.

It is HORSEPOWER that determines how fast you go up a hill. Horsepower

It's HORSEPOWER folks, not torque, that gets you up the hills.
Here we go again folks HP vs torque

JMHO . you can get 500 hp out of a 3.5l V-6 engine BUT it will not move a 40,000lb M/H up a hill . Sorry I'll add unless your diff gear is 11 to 1 and you can run the engine at 9000 rpm. in that case the engine would last a week. I'll take 350 HP with 1000 ftlb over 400 HP with 700 ftlbs any day.
And given the limited gear ratios available , both in trans and diffs in MH chassis your better off with more torque.
__________________
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.
Skip426 is offline   Reply With Quote
Old 05-03-2013, 09:50 PM   #18
Senior Member
 
Steve Ownby's Avatar
 
Join Date: Nov 2008
Location: Cosby, Tn
Posts: 6,397
Quote:
Originally Posted by Rich-n-Linda View Post
I don't know where so many of you got the idea that TORQUE is what gets you up a hill. Folks, that's just plain wrong...for ANY engine.

It is HORSEPOWER that determines how fast you go up a hill. Horsepower is a measure of how FAST a given amount of work can be done. Torque is just part of what determines horsepower. RPM is the other part of the equation. For those of you that get into the math, the formula is Torque x RPM divided by 5252.

Here's an admittedly absurd example:
Torque rating = 5,000 foot pounds
Maximum RPM = 500
HORSEPOWER OF THIS ENGINE IS 476 HP.

And another example with the numbers swapped...
Torque rating = 500 foot pounds
Maximum RPM = 5,000
HORSEPOWER OF THIS ENGINE IS 476 HP

Which engine will get you up a hill faster? Take your choice...they're equal. You just have to run one at a faster RPM than the other to get that 476 HP.

It's HORSEPOWER folks, not torque, that gets you up the hills.
This post is 100% correct. The concept of horse power and torque and how they are related is difficult for us non engineers to understand. The torque you have available to you is multiplied by the transmission. The torque available to you in fifth gear is higher than the torque at any rpm in 6th gear. This is true in each successively lower gear.

The horse power your have available is a fixed maximum. It is not multiplied.

Your available torque in each gear gets you rolling and up to speed but when you are hammering up that 6-7% five mile grade, it's horse power that keeps your speed up.
__________________
Steve Ownby
Full time since 2007
2003 Monaco Signature
Steve Ownby is online now   Reply With Quote
Old 05-03-2013, 09:59 PM   #19
Senior Member
 
Rich-n-Linda's Avatar
 
Join Date: Nov 2011
Posts: 884
Quote:
Originally Posted by Skip426 View Post

...I'll take 350 HP with 1000 ftlb over 400 HP with 700 ftlbs any day.
OK, l'll take the 400 HP engine and be waiting for you at the top of the hill.
__________________
Rich-n-Linda is offline   Reply With Quote
Old 05-03-2013, 10:43 PM   #20
Senior Member
 
Craigls2's Avatar
 
Fleetwood Owners Club
Freightliner Owners Club
Join Date: Sep 2012
Location: WI
Posts: 271
This isn't a HP vs. Torque issue. They generally go together. Higher HP engines are mated to transmissions that can convert that HP into work by using different gears to create speed. However, HP vs. HP isn't always a 'fair' comparison and the Discovery cited earlier is a good example. The 2009 model year used a 350 HP ISB engine and a transmission with a max torque of 750 ft. lbs. The 2011 model year used a 350 HP ISC and a transmission with a max torque of 1050 ft.lbs. The coaches are nearly identical in weight so which one will perform better on a long, steep grade? Now fast forward to 2013 with a 380 HP ISC and the same 1050 ft.lb max torque transmission. Clearly if coach weight and the transmission are identical, then HP wins the day but when you add in transmissions that are geared differently and coaches with different weights, then HP isn't the only factor to account for in your comparison.
__________________
2013 Fleetwood Discovery 40G / 2012 GMC Acadia
Craigls2 is offline   Reply With Quote
Old 05-04-2013, 05:35 AM   #21
"Formerly Diplomat Don"
 
Dutch Star Don's Avatar
 
Newmar Owners Club
Join Date: Apr 2005
Location: Moorpark, Ca.
Posts: 9,306
Everybody likes what they have, but my opinion is that the Cummins 400 (ISL) is probably one of the best RV engines ever made. It's one of the most popular, it's a rocket in small to medium coaches. It's got the umph to move a large coach and when driven with a soft foot will get great mileage for an RV.

There was a small group of ISL's (about a 6 month build date) that had a wrist pin issue, but other than that, you rarely hear of any issues with them.

The 350 Cat would probably be my second choice for a very reliable engine.
__________________
Don & Mary
2014 Newmar Dutch Star - All Electric - 450 ISL
2016 GMC Canyon 4WD Crew Cab
Dutch Star Don is online now   Reply With Quote
Old 05-04-2013, 11:03 AM   #22
JCM
Senior Member
 
JCM's Avatar
 
Triple E Owners Club
Join Date: Nov 2004
Location: Williams Lake,BC Canada
Posts: 990
Best rule of thumb is 10 hp per foot (length of coach). A Jake brake is better than a exhaust brake. Go from there.
__________________
2007 Triple E - Empress Elite - Freightliner
WH 22 owner for 7 years
JCM is offline   Reply With Quote
Old 05-04-2013, 12:30 PM   #23
Senior Member
 
Craigls2's Avatar
 
Fleetwood Owners Club
Freightliner Owners Club
Join Date: Sep 2012
Location: WI
Posts: 271
Quote:
Originally Posted by Diplomat Don View Post
Everybody likes what they have, but my opinion is that the Cummins 400 (ISL) is probably one of the best RV engines ever made. It's one of the most popular, it's a rocket in small to medium coaches. It's got the umph to move a large coach and when driven with a soft foot will get great mileage for an RV.

There was a small group of ISL's (about a 6 month build date) that had a wrist pin issue, but other than that, you rarely hear of any issues with them.

The 350 Cat would probably be my second choice for a very reliable engine.
I read somewhere that Cummins is streamlining their product line and discontinuing the ISC and making the ISL the "standard" engine. Could be a rumor.
__________________
2013 Fleetwood Discovery 40G / 2012 GMC Acadia
Craigls2 is offline   Reply With Quote
Old 05-04-2013, 03:29 PM   #24
Senior Member
 
Join Date: Oct 2009
Posts: 248
If you do go for the ISC Cummins then I can strongly recommend an upgrade to the Banks kit if you find yourself needing extra power.

I ran a 38' Beaver with an ISC for a year and then picked up a brand new Banks kit on eBay for $700 - installation was another $400 and took less than a day.

It made a huge difference to hill climbing - and I spent a long time pulling the grades in the Rockies with a Jeep GC toad. Prior to the upgrade I would pull Vale, CO at 25mph - afterwards I was far happier at 35-40mph.

It has a safety factor built in by measuring the EGT and limiting boost at anything > 1250F.

Of course I hate to think how many gallons of diesel I used on that climb!
__________________
steveclv is offline   Reply With Quote
Old 05-04-2013, 04:07 PM   #25
Senior Member
 
CJ7ole's Avatar
 
Winnebago Owners Club
Ford Super Duty Owner
Join Date: Mar 2009
Posts: 968
Ask any automotive engineer and you will get the answer horsepower is the measure of how fast an engine will get you up the hill. More torque will allow an engine to run slower, so you get the feeling of more power because you aren't reving the engine to get your rated horsepower. Remember, one of the original definitions of horsepower is the work needed to raise 33,000 pounds one foot in one minute. Whether a draft horse could ever really do that is questionable.

So if you can transmit 300 horsepower to your rear wheels, and there are no other friction losses, that engine will allow a 33,000 pound coach to go up the mountain 300 vertical feet in one minute, or up a 5% grade at 68 mph (one minute to travel 6000 feet). That of course shows how many other friction factors including resistance from the tires, the transmission and bearings are involved. If you are burning 150 horsepower at 68 mph on a flat highway, you are left with only 150 hp to work on gaining elevation as you head up the mountain. No I am not an automotive engineer, nor did I stay at a Holiday Inn Express. It is a basic high school physics story problem.

I don't have a diesel as you can see by my signature, but I usually pass loaded big rigs going up the mountain because I have one quarter the weight, but half the horsepower. And that is without screaming at 4500 rpms where I am maxing out the horsepower, but maintaining about 3600 rpm. Yes that is where the motor is at the peak of the torque curve, a good compromise between noise and horsepower. Yes I do sometimes envy the DP's but when I some day get a newer rig, I will probably stay with a gasser.
__________________
Ole and Anne Anderson, Highland, Michigan
'02 Adventurer 32V, Ford F-53, ours since 4/08,Goodyears, Konis, SeeLevel, CHF
'84 CJ-7 , 5.3 Chevy, 3" lift, 33's, Detroit Locker, Fiberglas tub, winch, hi-lift
CJ7ole is offline   Reply With Quote
Old 05-04-2013, 05:07 PM   #26
HHg
Registered User
 
Join Date: Nov 2010
Location: Austin, Texas
Posts: 413
Sure there is....figure out what you need and what you can live with and what you can afford.

Hhg
__________________
HHg is offline   Reply With Quote
Old 05-04-2013, 05:46 PM   #27
Senior Member
 
Alan24601's Avatar
 
Fleetwood Owners Club
Join Date: Jun 2011
Posts: 498
My Banks kit shows EGT but it only turns the display red and warns when I exceed 1350 degrees. It would desirable if it automatically controlled EGT. I was surprised to see there is a version that does that. Are you sure it derates the motor based on EGT?
__________________
Alan24601 is offline   Reply With Quote
Old 05-04-2013, 06:01 PM   #28
Senior Member
 
Join Date: Oct 2009
Posts: 248
My kit was about 4 years old with the Ottomind - and yes, it derated the boost as it exceeded 1250

Mine didn't illuminate the gauge so I suspect you may have a newer version and things may have changed although 1250F was always considered to be the max safe temp.
__________________

__________________
steveclv is offline   Reply With Quote
Reply



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Virginia Campgrounds

Reviews provided by


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 10:35 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.