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Old 07-27-2016, 08:20 AM   #15
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Originally Posted by Rich-n-Linda View Post
LOL! I can assure you it's nothing personal. You give me far too much credit for having a good memory. I don't remember the other post at all. I think this coincidence took place because you may have made a similar statement about horsepower and torque in that other post. This is also an area of performance that interests me, so I've done a lot of reading and studying so I can fully understand it. Hopefully I can now fully explain it!

As I said earlier, horsepower is horsepower, no matter how it is produced. And it's not magic. HP is a function of both torque and RPM. An engine that produces tremendous amounts of torque at a low RPM, like a diesel, can produce lots of HP at a low RPM. By the same token, an engine that does not produce a lot of torque at low RPM simply has to turn over faster to produce more HP.

Torque is only half of the power equation. Think of it this way. If I have a shaft that is exerting 1,250 lb/ft of torque, but it is not turning, how many HP do I have? The answer? ZERO. The shaft is not turning, therefore no work is being performed, therefore no HP is being developed.

There are small, 4-cylinder engines in cars today that produce only 250 lb/ft of torque, but with turbo charging, nitrous and other performance tweaks they can develop well over 400 HP! And they will give a big, 400 cubic inch V8 a run for their money. But in order to produce that HP they have to spin at very high RPM. An engine that develops 250 lb/ft of torque turning over at 7,500 RPM will produce 357 HP. If I put that little engine in a motor home, and then geared it properly so that at 7,500 RPM in 5th gear I could go only 60-65 mph, that coach would go up a hill just as fast a coach with a 350 HP gas engine or a 350 HP diesel. The ONLY difference is the RPM that the engine is turning and the gearing required to gear down the higher RPM engine to normal road speeds.

I mention gearing because that subject is usually lost in these kinds of discussions, yet it is critically important. If I put that little 4-cylinder engine into a motor home with the same Allison transmission and rear end gears as used with an ISL diesel, that little engine would fall flat on its face. It would barely be able to move the coach because the diesel gearing is WAY too tall for that little engine.

However, if I put that little engine in a coach and followed it up with appropriate high-number rear end gear ratio to properly gear down the engine and match the high rpm engine to normal road speeds, it would then work just fine. The engine would make a lot of noise screaming at high RPM and likely wouldn't last very long as it is constantly being pushed to its limits, but while it was still running it would get the coach over the road at normal speeds.

Here are a few numbers to compare:
Cummins ISL: 900 lb/ft of Torque @ 2,100 RPM = 360 HP
Ford V-10: 450 lb/ft of Torque @ 4,200 RPM = 360 HP
Small 4-Cyl: 250 lb/ft of Torque @ 7,500 RPM = 357 HP

Note that the torque goes down, the RPM goes up, but the HORSEPOWER remains the same.

Horsepower is Horsepower, no matter what size or kind of engine is developing it. It's tough thing to get your head around. I hope I've explained it well enough so it's understandable.
Rich, I understand torque and horsepower, but I think you've lost sight of the OPs question which is "Was wondering what HP DP is equal in power to a V10." That's what I addressed in my response.

You've actually provided all the evidence he needs to understand that a diesel powered coach with the same horsepower as the V10 will not perform like the V10. Some engines, the 5.9 ISB may not perform as well as the V10 and others like the ISC may perform better.

In our coach, with a 33,500 max weight, the 350 HP Cummins is adequate and I don't think I'd want less engine in it.
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Old 07-27-2016, 09:06 AM   #16
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Originally Posted by barmcd View Post
Rich, I understand torque and horsepower, but I think you've lost sight of the OPs question which is "Was wondering what HP DP is equal in power to a V10." That's what I addressed in my response.

You've actually provided all the evidence he needs to understand that a diesel powered coach with the same horsepower as the V10 will not perform like the V10. Some engines, the 5.9 ISB may not perform as well as the V10 and others like the ISC may perform better.

In our coach, with a 33,500 max weight, the 350 HP Cummins is adequate and I don't think I'd want less engine in it.
I may have misunderstood the OP question. It is very simplistic. It is easy enough to determine what engine is equal but shortly thereafter both engines are placed in different coaches with different transmissions and gearing. While the engines performance on the stand may be equal the performance in the unit could be totally different.

The answer to the OP question would be more relevant if a gas or diesel engine was an option in the same coach (unless the OP is planning to swap a diesel into a gas chassis).
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Old 07-27-2016, 12:54 PM   #17
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Sorry, I was not trying to make a big issue for everyone about my post. I was simply trying to understand the power difference between a V10 gasser and diesel pusher. I have a F53 now and it was the only option in a gas class A motor home with the floor plan we liked. Driving over a few mountains I now know how it handles them. I have found a great floor plan in a DP that is available in several different models and they each have a different sized Cummings engines and of course different prices as well. I was trying to understand what sized DP would react the same as a gas coach so I could stay away from making a bad purchase. I have not yet drove a DP and was hoping to learn from others what sized engines would do the job for me. I see many different HP ratings being promoted out there up 600 HP. Without winning the powerball I need to balance all the variables the price, brand, age and engine size to make the best decision but it must do better than the V-10 and be less expensive than a coach with 600 HP. So what should I not consider.
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Old 07-27-2016, 01:12 PM   #18
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Sorry, I was not trying to make a big issue for everyone about my post. I was simply trying to understand the power difference between a V10 gasser and diesel pusher. I have a F53 now and it was the only option in a gas class A motor home with the floor plan we liked. Driving over a few mountains I now know how it handles them. I have found a great floor plan in a DP that is available in several different models and they each have a different sized Cummings engines and of course different prices as well. I was trying to understand what sized DP would react the same as a gas coach so I could stay away from making a bad purchase. I have not yet drove a DP and was hoping to learn from others what sized engines would do the job for me. I see many different HP ratings being promoted out there up 600 HP. Without winning the powerball I need to balance all the variables the price, brand, age and engine size to make the best decision but it must do better than the V-10 and be less expensive than a coach with 600 HP. So what should I not consider.
My opinion is to get the biggest engine you can afford. The difference between engines is the Cummins family is pretty pronounced from a performance stand point. I think all the engines in a family get around the same miles per gallon regardless of how they are set up. I get 7.5 in my coach with an 350 hp ISC and those with a 300 HP ISC seem to get close to the same.

ISB tops out around 900 lb/ft of torque and 380 hp.
The ISC 1050 ft/lb and 360 hp
ISL 1250 ft/lb and 450 hp
ISX 1950 ft/lb and 600 hp.

Rich gave a pretty good explanation of the how horsepower and torque work and affect the way a gas engine and diesel engine feel when you are driving them. The biggest surprise for me when I bought my first diesel pickup was that acceleration picked up after the transmission shifted unlike a gas engined truck which is just the opposite. That's because max torque in a diesel is at lower rpm and max torque in a gas engine is at higher rpm. I feel the same effect in my coach, though it's not as pronounced.
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Old 07-27-2016, 01:18 PM   #19
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I have now a V 10 and 24000 coach it pulls very well with the 38 to 40 foot pushers with 350 horsepower such as a C7 isc but there are the 30,000 class coach. If were me I would go to an ISL 1200 foot pounds torque 400 horsepower or in the early ones 370 horsepower for a 38 to 42 foot coach. But I guess it's just my educated opinion having driven several ISB 36', ISC, ISL, C7, c9 in 40'. The ISB for smaller coachs is OK , but not in the 38-40. One can quote torque and horsepower figures for ever but until you put them with the weight there's no comparison.

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Old 07-27-2016, 02:22 PM   #20
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Sorry, I was not trying to make a big issue for everyone about my post. I was simply trying to understand the power difference between a V10 gasser and diesel pusher. I have a F53 now and it was the only option in a gas class A motor home with the floor plan we liked. Driving over a few mountains I now know how it handles them. I have found a great floor plan in a DP that is available in several different models and they each have a different sized Cummings engines and of course different prices as well. I was trying to understand what sized DP would react the same as a gas coach so I could stay away from making a bad purchase. I have not yet drove a DP and was hoping to learn from others what sized engines would do the job for me. I see many different HP ratings being promoted out there up 600 HP. Without winning the powerball I need to balance all the variables the price, brand, age and engine size to make the best decision but it must do better than the V-10 and be less expensive than a coach with 600 HP. So what should I not consider.
It would probably be more helpful if people knew what you were looking at. I can tell you that at 350hp and just over 1000lb/ft of torque my 38ft coach goes just fine towing a car that weights about 4500lbs. Going longer than 38ft I certainly would want at least 350+, more likely 400-500. I wouldn't mind having more power myself, but i don't feel what my coach has is inadequate. I just want more.

Unless you're looking at a very small DP I wouldn't expect to see the ISB engine spec'd in one. Usually the ISC for the 36-40ft and then on to the ISL and ISX. On long, steep grades you're going to slow down, that's just the nature of the beast. I have a 3.5 mile, winding, 6-7* grade to get to my house, that tops out close to 9* at the last 1/8th mile. I usually crest it doing just under 40mph. Doesn't matter if I'm towing a car or not. It's not uncommon to see freight trucks pulled over on the way up this climb or just after it. Usually when I get passed by another MH on a climb it's either a small class C or a big bus conversion. Nothing like being in the middle of a long grade and having a 45ft bus conversion with a match painted stacker trailer come flying by you.

Really, you only have a handful of chassis manufacturers out there, mostly Spartan and Freightliner, unless you go with a company that "builds their own"; usually by purchasing front and rear ends from Freightliner.

I would personally look for a floor plan I liked, then take it for a drive and see how it handled. A coach with a great motor and a crap floorplan isn't going to make you happy. Meanwhile, unless the coach you're looking at was built to appease more to budget than anything else, it should have enough motor. We'd all want more power, and if you can find a coach that ticks all the boxes for you and has more motor than the competitors then I'd say go for it.

To get a completely reversed view on this subject, you can check out this video, where they went from DP to gas. They compare driving in the hills in a gas coach to what they experienced in their Fleetwood DP.
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Old 07-27-2016, 02:36 PM   #21
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Old 07-27-2016, 04:10 PM   #22
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I disagree. Horsepower is horsepower, no matter how it is produced. This IS an apples to apples comparison.

The only difference between the Ford V-10 and the typical diesel is the RPM at which the horsepower is produced. The diesel will hit its HP peak somewhere around 2,000 RPM, while you'll have to spin that Ford up to about 4,500 RPM to get maximum HP out of it. But HP is HP, and that 362 HP V-10 will perform just as well as a 360 HP diesel, if it is driven correctly.
What you say is true! The speed the engine spins = wear
The slower the spin - less wear
That's is one reason diesels last longer.
Longer lasting means more expensive.

Gas versus Diesel is all about how much a person wants to spend!!
Not to mention a few thousand things that I have not mentioned
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Old 07-27-2016, 04:13 PM   #23
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Do like I did find a dealer that will let you try out both!
Once you make up your mind let us know what you found.
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Old 07-27-2016, 07:31 PM   #24
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I have now a V 10 and 24000 coach it pulls very well with the 38 to 40 foot pushers with 350 horsepower such as a C7 isc but there are the 30,000 class coach. If were me I would go to an ISL 1200 foot pounds torque 400 horsepower or in the early ones 370 horsepower for a 38 to 42 foot coach. But I guess it's just my educated opinion having driven several ISB 36', ISC, ISL, C7, c9 in 40'. The ISB for smaller coachs is OK , but not in the 38-40. One can quote torque and horsepower figures for ever but until you put them with the weight there's no comparison.

LEN
Len, it depends on what age of coach you're looking at. Some pretty large late 1990 and early 2000 coaches came with the 5.9 ISB.
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Old 07-27-2016, 08:43 PM   #25
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I have no dog in this fight but I do have some experience I can share. Last October I sold My 362 HP, 37 foot coach with a gas motor and bought a 340 HP 39 foot coach with a diesel motor. I don't think here is much difference in performance at all between the 2 I have owned. My shifting and the factory gearing make the performance great for me as most of my driving is 67 MPH highway and some mountains 5000 feet or less.
In the gasser I was 22,000 lbs. plus 4,000 towed, the diesel is 26,000 lbs. with 5000 towed. Gas 6.0 MPG, Diesel 9.3 MPG
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Old 07-27-2016, 09:21 PM   #26
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We have a 41`6" with the 400 ISL Cummins with 1250 ft. lbs. of torque. The 425 ISL also has 1250 ft. LBS of torque. Ours does not have the DPF or DEf engine. It was built in December 2006. In 2007 they came out with the DPF. I think around 2010 they came out with the DEF.
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Old 07-27-2016, 10:10 PM   #27
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Rich, I understand torque and horsepower, but I think you've lost sight of the OPs question which is "Was wondering what HP DP is equal in power to a V10." That's what I addressed in my response.

You've actually provided all the evidence he needs to understand that a diesel powered coach with the same horsepower as the V10 will not perform like the V10...

NO! My point is exactly the opposite. A 350 HP gasoline engine will provide the exact same level of performance as a 350 HP diesel. The difference is that you'll have to rev the gas engine to over 4,000 RPM to get that HP.

I just watched the Wynn's video clip a few posts above this one. In the clip he said that he didn't notice much difference in speed on the hills between this gas coach and their former diesel. Exactly...HP is HP.

However, if our coach rattled like theirs it would drive me crazy!
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Old 07-29-2016, 01:05 AM   #28
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You're trying to compare apple and oranges. Diesel engines don't deliver power like a gas engine so there can be no direct comparison horse power for horsepower. Also, all very heavy coaches are diesel powered. I pulled the same trailer with a 270 hp gas powered truck and 250 hp diesel truck and the difference was night and day with the diesel performing much better in all areas. Diesel engines tend to put out massive amounts of torque with their horse power so they tend to tow and haul better at lower rpm than a gas engine. Gas engines tend to put out similar horse power and torque numbers making them a little better in acceleration. For what its worth, we have a 31,500 lb DP with a 350 hp Cummins and it's more than adequate. I think a gas coach might feel more lively accelerating, but generally won't perform as well in other areas. I think I wouldn't like anything less than 350 hp/1050 ft/lbs of torque in a 40' coach.
I have the same only my GCW with toad is 35,500 lbs. I had my 350 ISL ECM reflashed to bring the HP up to 400 and the torque to 1200 ft/lbs. It's a fire breathing dragon that climbs passes of 6 and 7% in cruise control and never drops below 55 mph. I am getting 8 to 9 mpg and it doesn't even know it's towing a 4500 lbs pickup behind it. It cost me $400 and was done by a Cummins shop with software provided by Cummins so it's box stock.
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