Size of Engine

[GOLDWINGER2]

Originally Posted by Mike Canter

Sorry you missed it. It is torque that pulls/accelerates the MH from a standstill and it is horsepower that lets you maintain a steady speed to climb a steep grade. Like I have said before if you think it is torque that will get you up a steep grade then just try holding your engine rpm at the max torque rpm and see if you can maintain a speed. No way. To maintain speed on a steep grade you have to hold the motor at the rpm specified for peak horsepower. If you don't believe that then I am more than glad to demonstrate that with a 846 cubic inch Detroit Series 60 with peak torque of 1650 ft lbs at 1100 rpm and 525 HP at 1800 rpm that I cannot maintain or climb a steep grade holding the motor at peak torque at 1100 rpm. It just will not do it and will overheat. It has to be at 1800 rpm to climb or maintain speed going up a steep 6%+ grade. If it gets to 7 or 8% then I have to downshift will maintaining that 1800 rpm. If my motorhome drops to 1100 rpm I am in deep trouble. If you still think it is torque then you either do not know where you peak HP occurs at or you have never climbed a steep grade.

I run 4000-4200 on the big grades, good enough.
J

[lonestarace]

Originally Posted by Coached

Nuff said on this subject you think?

NO! Please tell us how gear ratio and torque multiplication figures into this. Please?

[Coached]

Originally Posted by GOLDWINGER2

I run 4000-4200 on the big grades, good enough.
J

This sums it up for me ... Mike is dead on .. my point is that, as he sez, running at 1800 rpm he has the motor in that "sweet spot" where hp and torque work together the best ... he's got a big, big block that produces gobs of power and it is located more than 40' behind him, a small diesel motor may just get it done, period ... We have a "test hill" around here that our local Dealer sends customer to in order to experience difference for themselves ... I've been in a 40' Discovery with an ISB (about 3 years ago) Cummins making about 290 hp and around 550 pounds pushing the rig up the hill - it was pathetic ... and a big block gas motor would be screaming to come even close to this kind of performance and it's right between you and your passenger in most cases. Not sure what you mean by "torque multipliers", and gear ratios will affect all motors the same way? Get a gear low enough to give you max. acceleration by getting hp to peak quickly will also mean a screaming engine at plain old highway speeds as well? To the OP - drive a gas, a small diesel and a big diesel and see for yourself??

[Mike Canter]

I am so lucky that my engine is so far back and the rpm is so low that I just don't hear it unless my drivers window is open then I can hear it off the Detroit barriers. I can hear that turbo whine. I have a monster turbo because I can make 42 lbs of boost with such a large engine at such a low rpm so it really is big. Look at the turbo size in this picture. As a reference to how big it is look at my DW behind it.

[DRL1950]

Wow, after reading some of these posts I really feel inadequate!!!

[Tsronco]

Originally Posted by DRL1950

Wow, after reading some of these posts I really feel inadequate!!!

Haha ditto!!!

[Mike Canter]

Sorry, didn't mean to do that.

[Tha_Rooster]

Size torque and Hp matters what I use to be able to do in a 2004 v10 in first flat out I can do in third just a chugging along and carrying a lot more weight.

[DRL1950]

Originally Posted by Mike Canter

Sorry, didn't mean to do that.

Not at all Mike, just confirms what we already knew, there are lots of smart people in RV's these days!!

[JimM68]

back to the original question...

Is bigger better? Heck yes it is.
But... not at the expense of a shower you cannot get into because the glass door hits the toilet (floorplan)

And the biggie is, for the most part, we really don't have a choice. The coach has the motor it has, that's just how it is. This ain't the 60's and that ain't a Chevelle, and you just can't option anything from a 6 banger to a 454 and 6 choices in between.

Course there are always exceptions. As a Monaco guy, I know for example, that the only difference bewteen a late model knight and a diplomat is the dip's side radiator ISL, and about $40 grand.

Look at a lot of coaches from several manufacturers. This is a big decision. Take your time do your homework.

[Mike Canter]

I can't resist this....bigger is better. My new motor is on its way.

[Triker56]

I've been in a 40' Discovery with an ISB (about 3 years ago) Cummins making about 290 hp and around 550 pounds pushing the rig up the hill - it was pathetic

The Discovery never had a 550 ft lb ISB put in any of them.
They all had at least 275 HP & 660 lb ft and the newer(08-09-10) 6.7L ISB 750 lb ft at 350 HP. In 2011 the D went to a ISC 8.3L with 1050 lb ft engine.

All Discovery's made since 1997 have also had a Allison 6 speed in them.

I love my ISB with Banks Powerpack with turbo 33-34 PSI and the average of 10.283 MPG.
Bigger engines can pass me if they want going up hills. But I will pass them while they are taking on more diesel.

I can run the speed limit + of 55 MPH pulling a toad, going from bottom of I75 Mounteagle to the top with no problem, while never going over 2,100 RPM of the available 24-2500.

[bachler]

What I see, when talking to people at club/chapter meetings, They are happy with what they own. Mostly gas. However If you have ever owned an adaquite powered diesel You will never go back to a gas, Unless for Finantual reasons. The diesel 300 HP = 900 FT LBS torque the gas 400 HP = 300 FT LBS torque. (appx) Torque gets you up the hill.. Enough said;; OOPS the diesel costs maybe $25000.00 more when you buy.

[Mike Canter]

Bachler, sorry, but I see you missed the results of this whole thread. It is torque that accelarates you from a standstill and it is horsepower that lets you maintain a constant speed going up a steep grade.