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Old 06-03-2013, 07:10 PM   #15
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DatedD- you should be shopping for torque, not hp. 900 or greater torque or you'll be unhappy w/the performance. 900 is marginal IMO, but that will keep you out of the lower end rigs that have the Cummins ISB block engine. ISB is the same block (mostly) that comes in a Dodge pickup, and it has been used in a lot of lighter weight coaches, some rated at 275hp IIRC. ISC (8.3 liter) is the next step up, usually rated at 950 ft-lbs torque almost regardless of hp claim. Then comes ISL (8.9 liter) at 1250ish & 350-425 hp depending, but you'll never know the difference in the horsepower builds IMO. Cat engines have similar steps by engine displacement. Then if you are really going to have some fun, the ISM family weighs in at 11 liters IIRC, and I'm guessing ~1,500-1,600 torque. Fuel mileage is mildly inversely proportional to displacement, and substantially inversely proportional to lead footing.
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Old 06-03-2013, 07:22 PM   #16
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dated......Some of the info provided is not going to help you much in the year models you're looking at. The majority of those model years were just starting to get 350 HP engines. If you could find a 350 Cat C-7 in those years you listed, you would be satisfied with the performance. You would have to move into mid 2000 models to see 400HP engine.

Now someone will come along and say his 1995 Foretravel or other high end older brand had a big engine, but there won't be many of those around. The majority in the 90's are still small motors.
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Old 06-03-2013, 07:25 PM   #17
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The ISC 350 is always rated at 1050 ft lbs of torque. I installed a Banks kit, upping that to 435HP/1200 ft lbs. However it's not the maximum of the changes, but where it occurs. With the stock engine it was 1050 @ 1400 rpm and then went down. Now I never have less than 1050 until 2100 rpm and the 1200 ft lbs is spread from 1400 to just past 1700 rpm which is the prime highway cruising rpm.
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Old 06-03-2013, 07:30 PM   #18
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DatedD- you should be shopping for torque, not hp..
It is HORSEPOWER that gets you up a grade at speed, NOT TORQUE. Torque is nothing more than the twisting force on the crankshaft. But all the torque in the world means nothing unless you can spin the shaft fast enough to do some work. That is where HORSEPOWER comes into the picture. Horsepower is a measure of how FAST a given amount of work can be done.

SHOP FOR HORSEPOWER and let the torque fall where it may. I have the Cummins ISL 400 HP in a 35,000 pound coach and I'm very happy with its performance on grades. I can maintain 65 mph in 5th gear on a 4% grade. At that speed in 5th the engine is turning over right around 2,000 RPM...right on the HORSEPOWER peak. By keeping the RPM up there on the HP peak and shifting down to 4th if needed, I can hold 50 mph on a 6% grade.

A comment about csrrsr shifting at 1,500 RPM...
You are shifting WAY too early! You are not getting all the HORSEPOWER your engine is capable of by shifting at such a low RPM. I suspect that your performance on grades would improve quite a bit if you let the engine rev to 2,000 RPM before shifting.
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Old 06-03-2013, 08:10 PM   #19
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Originally Posted by Rich-n-Linda View Post

It is HORSEPOWER that gets you up a grade at speed, NOT TORQUE. Torque is nothing more than the twisting force on the crankshaft. But all the torque in the world means nothing unless you can spin the shaft fast enough to do some work. That is where HORSEPOWER comes into the picture. Horsepower is a measure of how FAST a given amount of work can be done.

SHOP FOR HORSEPOWER and let the torque fall where it may. I have the Cummins ISL 400 HP in a 35,000 pound coach and I'm very happy with its performance on grades. I can maintain 65 mph in 5th gear on a 4% grade. At that speed in 5th the engine is turning over right around 2,000 RPM...right on the HORSEPOWER peak. By keeping the RPM up there on the HP peak and shifting down to 4th if needed, I can hold 50 mph on a 6% grade.

A comment about csrrsr shifting at 1,500 RPM...
You are shifting WAY too early! You are not getting all the HORSEPOWER your engine is capable of by shifting at such a low RPM. I suspect that your performance on grades would improve quite a bit if you let the engine rev to 2,000 RPM before shifting.
When pulling big weights an engine that can deliver high torque numbers at low rpms is best. I had a truck with a series 60 Detroit rated at 500 hp and 1700lb/ft torque and another older one with a cat rated at 455hp and 1850 torque. Empty or just bob tailing around the Detroit was quicker. With a gross weight of 62,500kg or 137,500lbs the cat would put it to shame, up hills on the flat against the wind it didn't matter the cat would spank the Detroit.
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Old 06-03-2013, 08:32 PM   #20
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I'm looking at mid to late 90's diesel coaches and would like to know if the Cummins, CAT or Detroit engines which range between 275-350 HP have decent power to pull 6% or better grades pulling a 3000# toad. I'm asking those who have had experience with this combination to please share their comments.

My wife who was an over the road trucker for 25 years says we should be looking for no less than 400 HP, but pulling a 53 ft trailer weighing 80,000 # is different than a motorhome.

It seems that the majority of coaches I have looked at are in the 275-350 range.

Thanks!
datedd,
This thread has gotten a bit off topic, well sorta; HP/torque, blah-blah....grunt grunt.

No matter what you get, it will do its level best to please you.

My hope is that you find a sound, reliable rig, and, if so, I know it will get you over those few hills.

Find yer ride and enjoy it.
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Old 06-03-2013, 09:26 PM   #21
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Quote:
Originally Posted by Rich-n-Linda View Post

It is HORSEPOWER that gets you up a grade at speed, NOT TORQUE. Torque is nothing more than the twisting force on the crankshaft. But all the torque in the world means nothing's unless you can spin the shaft fast enough to do some work. That is where HORSEPOWER comes into the picture. Horsepower is a measure of how FAST a given amount of work can be done.

SHOP FOR HORSEPOWER and let the torque fall where it may. I have the Cummins ISL 400 HP in a 35,000 pound coach and I'm very happy with its performance on grades. I can maintain 65 mph in 5th gear on a 4% grade. At that speed in 5th the engine is turning over right around 2,000 RPM...right on the HORSEPOWER peak. By keeping the RPM up there on the HP peak and shifting down to 4th if needed, I can hold 50 mph on a 6% grade.

A comment about csrrsr shifting at 1,500 RPM...
You are shifting WAY too early! You are not getting all the HORSEPOWER your engine is capable of by shifting at such a low RPM. I suspect that your performance on grades would improve quite a bit if you let the engine rev to 2,000 RPM before shifting.
IMHO CSRRSR meant that he down shifts at 1500 rpm when the rpm drops that low while pulling a grade to get the rpm back up, not that he shifts while accelerating at 1500. At least that's the way I read it.
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Old 06-03-2013, 09:47 PM   #22
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Rich-n-Linda.....These discussions always get into HP vs Torque and many jump in and say run at max HP. Next time you're out, try climbing some of the grades at about 1700 -1800 rpm. This is close to where the ISL crosses over HP and Torque. My coach weighs about the same as yours and I never climb at 2000 rpm. The only time I see that number is when the exhaust brake is on. I'm also doing 5+ mph more than what you're getting on a 5% grade. I climb 5% grades at 55 with cruise on and maybe dropping to 5th. Not trying to argue, just give it try.....you don't need to wring the ISL's neck to make it work. Theory is always great, but often doesn't work in practice.
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Old 06-03-2013, 10:06 PM   #23
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Horsepower is only a calculated measure of torque and RPM. No dyno actually measures horsepower, they only measure RPM and torque, then the HP is calculated from that.
HP was invented to sell the new fangled steam engines to mine owners who wanted to know how many horses could be replaced by the engine. Also, it favors high rpm engines.
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Old 06-03-2013, 10:25 PM   #24
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I have to agree with those that said you will be glad if you get at least 400 HP, if that fits your budget, IMHO. Having said that I also think you can't have too much HP, IMO. I like having good acceleration when you need it, being able to jump out in the fast lane and pass when I want to, and not hold up the whole line while climbing a grade. We're very happy with our coach. The 400 C9 cat is just fine, but if and when we ever trade I will try to have more power.
I often wonder about these motors in terms of how they are set up for RVs. I, like others on these threads, I drove the big trucks for several years. My MO weighs about the same as an empty semi but those motors would out pull these of greater HP. I think they have the computers set on RVs so it is harder for an inexperienced driver to harm the motor. I would look into something like a Banks kit for my cat but A) I'm pretty happy already, B) I'm sure it wouldn't be cheap, and C) I'm not sure I wouldn't have an over heating problem with the side mounted radiator. Maybe sometime I'll go to the Cat dealer and talk to them about resetting the computer for more power, what we used to call "turning it up".
I also think everybody should do what makes them happy and try not to worry too much about what others do. If it makes you happy to set the cruise at 62 and only drive 200 miles a day I think that's great. I admire that kind of patience. If you want to do the speed limit plus 5 up the Grapevine pulling an enclosed stacker with two hot rods and a Harley inside I think that's great too. I think the one having the most fun is winning either way.
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Old 06-03-2013, 11:11 PM   #25
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Our engine has 350HP and 1,350 ft-lbs of torque pulling about a 34,000 pound coach and a 3,500 pound car. Today I had a couple of 18-wheelers on my tail that wanted to go a bit faster than my 63MPH on 95 in Nevada close to Fallon. On the first long hill they fell way back--we slowed down to about 55MPH. Don't think we slowed down to less than 45MPH towing a car on hills.
BTW, on the comment:
"A comment about csrrsr shifting at 1,500 RPM... You are shifting WAY too early! You are not getting all the HORSEPOWER your engine is capable of by shifting at such a low RPM. I suspect that your performance on grades would improve quite a bit if you let the engine rev to 2,000 RPM before shifting."

Our max HP is at 1,600 RPM!
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Old 06-04-2013, 12:09 AM   #26
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........It seems that the majority of coaches I have looked at are in the 275-350 range.
Thanks!
As someone pointed out - you are likely seeing the 275-350 range due to the year models you're looking at. If you look at newer units with higher HP/TQ you will find price going up and longer / heavier units - then tag axels and longer, pricier still.

As others have also said - you can pay for bolt on performance - and make improvements at the margins. But nothing is free.

I do not have a lot of grade experience because I don't live in a mountain area. I have and will travel again in grade areas and get along fine with 325 HP. If you live in and will always be in a mountain zone - then I guess you need to listen to the others. But our decision was based on this worst case assumption - If 49% of US is mountain territory and 51% is not - I would be happy more than half the time the way we travel. Well - it's not 49% mountains - don't live in mountains - so I'm happy plenty. We plan to go full time and will be here and there - but not on grade even 30% of the time - and we will be happy to be wherever we are.

Check your budget - check your ratio of time on grade - check your floor plan etc and get as much of everything you can for your dollars including power. But if budget is whats got you in the '90's - it's going to take some looking to get above 325-350.

Now if DW had the breaks on the dollars and can ease off the pressure - take her shopping. If you're like us - budget mattered and we found the happy place for us at 325.

Good luck in the hunt.
Steve and Annie
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Old 06-04-2013, 12:43 AM   #27
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My rig has the ISB with a 300/660 rating but does fine, since it is a 21,000 pound chassis. Loaded with the car and trailer, it is about 27,000 pounds and does fine on grades of 6%. More power would be nice, but, at the cost of MPG. Right now, without the trailer, I have seen 13 MPG and towing, about 10.5 which I think is pretty good. It is all about balance, I suppose and where you plan to travel.
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Old 06-04-2013, 01:05 AM   #28
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Thanks folks for the replies; they are MUCH appreciated!
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