engine size vs vehicle weight

[tmac]

This forum is fantastic! Have spent over 13-hours trying to educate myself with the knowledge, experience, and experiences of other members. My problem is I'm not a very good note taker.

Somewhere - someone - provided a simple formula for calculating minimum diesel engine size (in horsepower) versus vehicle weight (VCWR?). Before I spend any more time looking for this formula, maybe someone can help me out?

Thanks,

Tom

 

[Ned]

The rule of thumb is 1 HP/100 lbs of GCVWR.

 

[Ron]

One Horse power for every hunderd pounds.  32000 =  at least 320 HP recommended.

 

[MonacoMoe]

Ron,

I believe that you mean 3200 lbs for a 320 HP engine....

 

[Ned]

3200 lbs and 320 hp would win at the drag strip   32000 lbs and 320 hp is correct.

 

[Gary RV_Wizard]

The torque vs RPM curve is probably of more significance than the HP anyway. The lower the RPMs at which the power is generated, te better overall performance you will enjoy in a heavy vehicle.  But torque and HP go hand in hand, so more of one yields more of the other as well.

And how much is "enough" depends to a large extent on your personal criteria for acceptable performance. With a suitable transmission and rear axle, a 1 HP engine will drag you up any and all hills. You may just have to shift a lot (or listen when the automatic shifts).    :  More HP & torque means you stay in higher gears more of the time.

 

[John From Detroit]

One of the things I love about my Workhorse,, CGVWR, 27000, Actuall 26000 by scale, HP 335 with peak torque rather low on the RPM curve.. In short, it goes well with lots of room between my foot and the floorboards

 

[tmac]

Thanks for all the replies fellas.

 

[John From Detroit]

In reading the article it appears that the fact it occured in an RV park was incidental

And i do agree that Justice seems to have been served.  Anyone who would refer to children as "Piggies" (Other than in a political context) deserves what the convict got.

(The one political reference was actually a comment on the children's father, not the children themselves, but that is a long story, and as it happens I think the old man was a pig too, never did like him, and he was my boss! or rather my bosses boss)

 

[psiegert]

Living in the Colorado Rockies, we believe extra HP is necessary at the high altitude.  But I am not familiar with the torque ratios.  I am considering purchasing a used RV (2003 Safari Zanzibar with 370hp) with 1200 lb/ft at max net 1300 rpm.  Is this good or bad?

 

[Carl L]

Living in the Colorado Rockies, we believe extra HP is necessary at the high altitude.

Yup, gotta discount HP at the rate of 3% per 1000 feet of elevation for a normally aspirated engine (ie not turbocharged).  I suspect torque diminishes by the same factor.

 

[John From Detroit]

Living in the Colorado Rockies, we believe extra HP is necessary at the high altitude.  But I am not familiar with the torque ratios.  I am considering purchasing a used RV (2003 Safari Zanzibar with 370hp) with 1200 lb/ft at max net 1300 rpm.  Is this good or bad?

What is the CGVW rating of that horse? (By rating it should be able to haul around 37000 lbs where I am, likely about 34-35 where you are, if that is the rest of the drive train can take it)

 

[psiegert]

The CGVW rating is 40,500.  It is a Cummins 370 HP 540ci/8.8L; Allison 3000 MP 6 Speed Electronic Transmission and 4.30:1 Axel Ratio.

Do you know anything about the 2003 Safari Zanzibar?

 

[BernieD]

Living in the Colorado Rockies, we believe extra HP is necessary at the high altitude.  But I am not familiar with the torque ratios.  I am considering purchasing a used RV (2003 Safari Zanzibar with 370hp) with 1200 lb/ft at max net 1300 rpm.  Is this good or bad?

I have the same engine but with 400hp. I've done a lot of climbing in and thru the Rockies and have not had any significant prolblems. Our coach weighs 30k#s in travel mode and I tow a 4,300# car. The 370hp engine does not lose that much, go for it.