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39 Diesel Rockit Update

Old 09-22-2012, 08:20 AM
  #31  
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Originally Posted by 7075T6
My 44 ft raceboat, with 2 x FPT 560, gets 1,43 mpg at 80 mph and 1,26 at WOT(85-88 mph depending on fuelload).
Never more than 1,65 mpg at any speed. Boat weighs 11000 lbs raceready, 220 gal of fuel, no crew.

http://www.offshoreonly.com/forums/g...ce-diesel.html
Even at lower speeds you don't get better economy? what about at 40 or 50 mph?
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Old 09-22-2012, 12:14 PM
  #32  
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Originally Posted by pstorti
I think your constants may be good for theory but off for the real world. my engines (315 hp each, 1.7-1.8 @ 53mph) are supposed to burn 16gph at wot but usually it is closer to 15. The Hustler has a more efficient hull than a regular boat the diesels may normally be installed in and they may not be 100% loaded at top speed. I don't know what they are using to measure the fuel rate maybe there is some error there as well. I have Maretron sensors that measure the supply and return rates along with temperature of the fuel to compensate for volume changes to get very exact numbers, unfortunately the stupid Garmin's only give me to tenths not hundredths, but if it is showing 1.7 to 1.8 I know the real number is closer to 1.75, as it rounds up and down.
In your case, your measured fuel rate is 1 - (15/16) = 6.6% lower.

In the case I presented, the claimed fuel economy is 2/1.35 = 48% higher!

The constants aren't off any where near that amount. For instance, diesel fuel may range from 6.9 to 7.1 pounds per gallon, and the BSFC range doesn't account for it either.

Michael
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Old 09-22-2012, 01:05 PM
  #33  
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Originally Posted by Michael1
In your case, your measured fuel rate is 1 - (15/16) = 6.6% lower.

In the case I presented, the claimed fuel economy is 2/1.35 = 48% higher!

The constants aren't off any where near that amount. For instance, diesel fuel may range from 6.9 to 7.1 pounds per gallon, and the BSFC range doesn't account for it either.

Michael
That's a good point, hopefully somebody from Hustler will chime in, we all know boat manufacturers tell it like it is with no exaggeration
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Old 09-22-2012, 01:40 PM
  #34  
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Originally Posted by pstorti
Even at lower speeds you don't get better economy? what about at 40 or 50 mph?
Looks like the hull is so much more efficient at higher speeds. Usually never run below 60-70 mph. Around 40 mph I usually go down to first gear not to loose turbopressure. And then the sea has to be big...

Last edited by 7075T6; 09-22-2012 at 02:30 PM.
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Old 09-23-2012, 12:46 AM
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Originally Posted by pstorti
That's a good point, hopefully somebody from Hustler will chime in, we all know boat manufacturers tell it like it is with no exaggeration
Joe at Hustler is defiantly the diesel guy, he loves the diesel boats.
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