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Old 05-09-2013, 07:08 AM   #43
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Here is a very good discussion about what climbs the hill. Note the parasitic load of the cooling fan as a function of RPM. The engine is cooled not by cubic ft/min across the radiator but mass flow.
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Old 05-09-2013, 07:50 AM   #44
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Quote:
Originally Posted by szy View Post
Some ISC do have a Jake brake , JFYI
This is technically true. Out in the used coach market it would be rare to run across one. A very few manufacturers in a narrow range of years had this option. Gulf Stream sticks in my head, but there is all sorts of worthless trivia rattling around in there.
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Old 05-10-2013, 11:43 PM   #45
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Thanks to everyone for your very valued input!
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Old 05-10-2013, 11:50 PM   #46
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I was going to add that torque is more important than HP. 2 motors with the same HP can have much different torque ratings. The engine manufacturers will list what the torques are for each motor. Pick the one with the highest torque rating.
Actually the spread of that torque is just as important as the maximum amount.
The green line is the stock ISC 350, the black line is the stock 400 ISL, the red line is the ISC 350 w/Banks Power Pack.
The Banks ISC shows better power in almost all areas over even the ISL 400.
I have the dyno readouts for the ISL 450 that I should add to this chart someday.
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Old 05-11-2013, 12:03 AM   #47
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I'm going to agree with Alan on this one. If you don't drive in the mountains or don't care about going 15 mph on a long, steep pull then it doesn't matter. Last summer we left Estes Park for Moab and hit the long, steep climbs on I70 west of Denver. We were in a 2004 Excursion (27,000 lbs, 4000lb toad, 350hp ISC max torque 1050) and went up the mountain at 35mph. Our friends in a 1999 American Eagle (~34,000 lbs, 5,000 lb toad, 330hp ISC I think and max torque around 850 ft/lbs) could only maintain 20-25mph. Dividing the max torque by the max weight of the coach is about the fairest way to compare pulling power between different rigs, in my opinion. We can argue if it's HP or torque that gets you up the hill but my money is on torque.
I just looked it up, the ISC 330 has 950 ft lbs of torque
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Old 05-11-2013, 12:10 AM   #48
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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?
Yes, the ISC Banks Power Pack OttoMind for the older (before 2003 as I remember) does just that. They no longer make kits for that application. Too old and not enough demand, plus the OttoMind manufacturer went out of business.
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Old 05-11-2013, 12:15 AM   #49
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BTW: a dyno ONLY measures torque and rpm, the horsepower is derived from those two figures and those only. So without torque you have no horsepower.
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Old 05-11-2013, 07:18 AM   #50
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I have been following this thread and wish cat had a proven vendor like banks that could boost the power on my 3126e. I have researched the mp8 and the bully dog product. Does anyone have any input as to reliability after install?
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Old 05-11-2013, 12:41 PM   #51
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I'm glad we got the right answer to what hp does and what torque does. Torque is what moves a vehicle, hp is a measure of how fast the vehicle will go. We have 1350 ft-lbs of torque going through a 4.10 rear end. If you have a 4.88 rear end; transmissions being equal, an engine with 1134 ft-lb will have the same torque at the rear wheel as ours.
A diesel engine compresses the air let in during the intake stroke on the power stroke. When the piston reaches the top, fuel is injected, and the piston is forced back down, producing power. If no fuel is injected, the energy used to compress the air is mostly recovered as the piston moves back to the bottom of the power stroke. If the Jake brake is on, the air is let out by the exhaust valve at the top of the stroke, and the piston is now pulling a vacuum going back down. Thus the energy used to compress the air is added to the energy used to pull a vacuum. This is why braking hp with a Jake brake is almost equal to the hp at full power. Our 350 hp engine has a bit over 300hp braking power. With an exhaust brake, you are putting a potato in the tail pipe!

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Old 05-11-2013, 04:47 PM   #52
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If you plan on keeping the M/H for any length of time, I say go with the biggest and best you can afford. Trust me, 5 years from now, you'll be kicking yourself for not getting the big motor. 40 foot is a heavy coach. There's no substitute for cubic inches!
Try driving the different coaches with the different engines, then make your decision.
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Old 05-11-2013, 05:48 PM   #53
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My Cummins produces a meager 215 hp which is about as far as I feel like modifying it, after all it started out as 190. But, where I live and where I routinely go presents no problem in maintaining interstate speeds or passing when necessary. The rig is lite by today's standards even when pulling a toad using a dolly. Bottom line, I don't need to be first at the hilltop, I just want to get there.
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Old 05-11-2013, 07:18 PM   #54
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Yes it is torque that pushes you up a hill, BUT it is horsepower that determines how fast you go up the hill.

Let me give a simple example. Remember the thing at the circuis where the pony walks around a center pole attached to a long arm? Lets say that the arm is 20 feet long. Even at my age I could push with 50 pounds force for 10 minuites or so developing 1000 ft/ lb of torque.

Now how fast do you think I could move a 30,000 lb motorhome up a hill?

Horsepower is RPM x Torque. I could develop the 1000 FT lb but my rpm would be my RPM would be very low, perhaps 0.5.

Gas engines can produce 350 horsepower but at 4,000 plus RPM. So while you diesel is humming along producing 350 HP at 2000 RPM, the gas engine will be sereaming along at 4000 RPM.

Also remember that a transmission can increse or decrease the torque to the rear wheels, but it can not change the horsepower available to the rear wheels.

Okay, I'm braced for the rebutal
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Old 05-11-2013, 09:30 PM   #55
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No rebuttal from me, pardner! You've got it RIGHT. By the way, 1,000 foot-pounds of torque at .5 RPM is .09 horsepower.

This is a perfect illustration of how torque is only HALF the picture. Thousands of foot-pounds of torque mean NOTHING if you can't spin the shaft fast enough! It is the torque AND the RPM the tell the tale and add up to HORSEPOWER. And that is what gets you up the hill at speed.
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Old 05-12-2013, 10:00 AM   #56
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My observation is when one is shopping for RV's the most obvious in your face engine specification is HP, emblems and brochures listing it everywhere but torque must be looked up in a spec sheet. Not every 350 Hp motor has the same capability to move a big MH up a hill. Both Hp and torque need to be considered.
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