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Author Topic: How Much Horsepower?  (Read 1818 times)
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'60 PD4104-4355(sold) Now Freightliner Conversion

« on: August 04, 2013, 05:43:17 PM »

The subject keeps coming up about how much horsepower does it take to go a certain speed or how much fuel will I consume to go that speed.

Here is an interesting site that lets you calculate how much horsepower is required (at the rear wheels) to go a certain speed.  

Once you calculate this you can use the fuel consumption tables for your engine and determine what your fuel mileage will be.  Here is an article by Clarke Echols that will get you started.

Here's another.

A little research on Google or Bing will get you some more interesting info.

Have fun!

« Last Edit: August 04, 2013, 05:45:40 PM by usbusin » Logged

Gary D

USBUSIN was our 1960 PD4104 for 16 years Ustruckin' is our 2001 Freightliner truck conversion
Iceni John
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« Reply #1 on: August 04, 2013, 08:12:35 PM »

What's the typical Cd of a bus?   I suspect it's about 1.00 for most of ours, especially mine that is slab-fronted with the aerodynamics of a brick privy (unlike older Twinkie-shaped Crowns that are rounded front and rear).   A 1950s Hall-Scott-engined Crown achieved 103 MPH once on a racetrack, but there's no way a bus like mine would come close, even if it were geared high enough.

« Last Edit: August 04, 2013, 08:28:44 PM by Iceni John » Logged

1990 Crown 2R-40N-552 (the Super II):  6V92TAC / DDEC II / Jake,  HT740.     Hecho en Chino.
2kW of tiltable solar on the roof.
Behind the Orange Curtain, SoCal.
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« Reply #2 on: August 05, 2013, 06:17:28 AM »

   That doesn't take into account hills or grades. I think you can get a better estimate from other owner's reports. It's hard to lie about your numbers here, as you are going to be called out on unrealistic mpg's. A  fair variation will occur due to heavy foot, and how do you baby a coach on a grade? Get a run for it or let it lose momentum gradually and start holding up traffic. How many on here run their generators off the main fuel tank, skewing their figures? How much total weight do you carry. How much is from trying to fill up all those empty spaces in bays, etc. with everything for convenience, including an spare kitchen sink?

GMC h8h 649#028 (4905)
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1973 MCI MC-7 Combo


« Reply #3 on: August 05, 2013, 07:00:17 AM »

6.1mpg on the return to ct from Blytheville. No generator running. Just about what I was expecting. Running no faster than 65mph.


Bruce & Nancy Fagley
1973 MCI MC-7 Combo Freighter
450HP DD 8V-92T 2000 Reman
HT 740 Allison
Woodbury CT.
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1980 MCI MC-5C

« Reply #4 on: August 05, 2013, 07:22:24 AM »

I did the calc, got 160 hp at the rear wheels for 80 sq. Ft, 0.9 CF and 26K lbs.  Sound quite believable to me, that would correspond to maybe 220 at the crank.  For 80 mph it says 325 hp, so add 40 for accessories and 15%  for drive train that would be 416 hp.  I knew I couldn't run 80 anyway, but now I know.

« Last Edit: August 05, 2013, 07:28:59 AM by bevans6 » Logged

1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
Tatamagouche, Nova Scotia
HB of CJ
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« Reply #5 on: August 05, 2013, 09:58:33 PM »

Wow; FWIW, Crown Supercoaches must be more slick than imagined.  My old 1974 Crown 10-wheeler 40-ft ex-schoolie would max the speedo at an indicated 80-82 mph with just a RTO-910 Roadranger and a non turbo Small Cam 855 inch Cummins rated at only 250 hp.  Thanks again.  HB of CJ (old coot) now-buss-less Sad  Still LOVE this forum! Smiley Smiley
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« Reply #6 on: August 05, 2013, 10:28:29 PM »

Speed, MPG, weight & HP is always an interesting topic, Can assure you a proper 8V-92 with the RTO910, 3.73 on 11R24.5 will show 100+ on GPS, MPG who cares at that point?
At the other end of the game, my present setup ISM500, 4000R, 3.92, 275/80X22.5 will give you 9 mpg driving reasonable, low 60ish, but that is more nerve racking than the fuel cost at 70ish/7.5 mpg.  Its all the right foot.

MCI7 20+ Yrs
Foretravel w/ISM500
WG4T CW for ever.
Central Virginia
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« Reply #7 on: August 06, 2013, 04:52:50 AM »

LOL fall in behind Sonnie Grays Eagle with the 350hp Cat engine and 740 Allison it blows that theory all to hell
« Last Edit: August 06, 2013, 04:58:14 AM by luvrbus » Logged

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