And you think your Rv gets poor fuel economy

[MandysMom]

Mel and I are watching a tractor pull show on tv. They said those monster tractors get 20 feet per gallon or 264 gallons per mile!!!!!

[Queen]

Holy cow! Sounds like a plane or huge boat.

[MelissaD]

Pulling hills in my semi, my dash said I was getting 0.2 mpg (ie that's 5 gallons per mile). Maybe that's why I carried 240 gallons of fuel

When I worked at the utility. The backup diesel generators at work (Marine Size V10 twin turbos, the size of a room) burned 256 gallons per hour at full load 5.2 MW (5,200 KW) We had 3 of them. When the 4 gas turbine generators (basically a jet engine hooked to a generator) lite off on a hot day we had a 3 million gallon fuel tank. To keep from running out, a local company had a contract to deliver 10,000 gallons of fuel per hour as long as the turbine ran to ensure we did not run out of fuel.

I found this interesting....

* One dragster's 500-inch Hemi makes more horsepower then the first 8 rows at Daytona.

* Under full throttle, a dragster engine consumes 1 1/2 gallons of nitro per second, the same rate of fuel consumption as a fully loaded 747 but with 4 times the energy volume.

* The supercharger takes more power to drive than a stock hemi makes.

* Even with nearly 3000 CFM of air being rammed in by the supercharger on overdrive, the fuel mixture is compressed into nearly-solid form before ignition. Cylinders run on the verge of hydraulic lock.

* Dual magnetos apply 44 amps to each spark plug. This is the output of an arc welder in each cylinder.

* At stoichiometric (exact) 1.7:1 air/fuel mixture (for nitro), the flame front of nitromethane measures 7050 degrees F.

* Nitromethane burns yellow. The spectacular white flame seen above the stacks at night is raw burning hydrogen, dissociated from atmospheric water vapor by the searing exhaust gases.

* Spark plug electrodes are totally consumed during a pass. After 1/2 way, the engine is dieseling from compression-plus the glow of exhaust valves at 1400 degrees F. The engine can only be shut down by cutting off its fuel flow.

* If spark momentarily fails early in the run, unburned nitro builds up in those cylinders and then explodes with a force that can blow cylinder heads off the block in pieces or blow the block in half.

* Dragsters twist the crank (torsionally) so far (20 degrees in the big end of the track) that sometimes cam lobes are ground offset from front to rear to re-phase the valve timing somewhere closer to synchronization with the pistons.

* To exceed 300mph in 4.5 seconds dragsters must accelerate at an average of over 4G's. But in reaching 200 mph well before 1/2 track, launch acceleration is closer to 8G's.

* If all the equipment is paid off, the crew worked for free, and for once NOTHING BLOWS UP, each run costs $1000.00 per second.

* Dragsters reach over 300 miles per hour before you have read this sentence.

Did you know …

… that the nitromethane-powered engines of NHRA Top Fuel dragsters and Funny Cars produce approximately 7,000 horsepower, about 37 times that of the average street car?

… that one cylinder of the eight cylinders of a Top Fuel dragster or a Funny Car produces 750 horsepower, equaling the entire horsepower output of a NASCAR engine?

… that the gasoline-powered engines of NHRA Pro Stock cars produce about 1,200 horsepower, about eight times that of the average street car?

… that an NHRA Top Fuel dragster accelerates from 0 to 100 mph in less than .8-second, almost 11 seconds quicker than it takes a production Porsche 911 Turbo to reach the same speed?

… that an NHRA Top Fuel dragster leaves the starting line with a force nearly five times that of gravity, the same force of the space shuttle when it leaves the launching pad at Cape Canaveral?

… that an NHRA Funny Car is slowed by a reverse force more than seven times that of gravity when both parachutes deploy simultaneously?

… that NHRA Top Fuel dragsters and Funny Cars consume between four and five gallons of fuel during a quarter-mile run, which is equivalent to between 16 and 20 gallons per mile?

… that NHRA Top Fuel dragsters and Funny Cars use between 10 and 12 gallons of fuel for a complete pass, including the burnout, backup to the starting line, and quarter-mile run?

… that NHRA Top Fuel dragsters and Funny Cars travel the length of more than four football fields in less than five seconds?

… that NHRA Top Fuel dragsters can exceed 280 mph in just 660 feet?

… that from a standing start, NHRA Top Fuel dragsters accelerate faster than a jumbo jet, a fighter jet, and a Formula One race car?

… that a fuel pump for an NHRA Top Fuel dragster and Funny Car delivers 65 gallons of fuel per minute, equivalent to eight bathroom showers running at the same time?

… that the fuel-line pressure for NHRA Top Fuel dragsters and Funny Cars is between 400 and 500 pounds, about 20 times greater than the pressure on passenger-car fuel pumps?

… that depending on size and angle, the large rear wing on an NHRA Top Fuel dragster develops between 4,000 and 8,000 pounds of downforce?

… that the 17-inch rear tires used on NHRA Top Fuel dragsters and Funny Cars wear out after four to six runs, or about two miles? Some brands of passenger-car tires are guaranteed for 80,000 miles.

… that it takes just 15/100ths of a second for all 7,000 horsepower of an NHRA Top Fuel dragster engine to reach the rear wheels?

… that it's desirable for an NHRA Top Fuel dragster to race with its front wheels inches off the ground for about the first 200 feet of the run? This ensures proper weight transfer to the rear wheels, a crucial part of a good launch and quick run.

… that the nitromethane used to power the engines of NHRA Top Fuel dragsters and Funny Cars costs about $30 per gallon?

Sources: NHRA Communications and Technical Departments, NHRA race teams, motorsports equipment manufacturers (and boostedpimp)

[Cudedog]

Interesting thread.

What kind of average mpg do A`s, B's and C's get?

Thanks.

Anne.

[snowball]

I'm not any of those but my diesel pulling a 36 foot 5th wheel gets around 10-11 mpg
not towing get about 18
when we towed a 24 foot tt with our fan got a whole 8-10 one reason I will stay with a diesel
sheila

[MandysMom]

My Sprinter chassis Leisure Travel van, a 2005 ( had it since new picked up at factory), 22 ft long 2500 series chassis, I get around 16 to 18 mpg diesel in town and short haul. On the road I usually get around 22 to 25 mpg, but in 2010 we went over the Sierras from Sacramento to head south to,visit friends in Az. On the first leg of the trip I filled up in Sacramento then again south of Carson City NV . When I calculated the mpg, I kept thinking I was making a mistake ESP since we had just climbed over the Sierras. I kept getting 28 mpg. Had Mel calculate it and he got same!! Conclusion, my Sprinter diesel is finally getting broken in! Only has 23,000 on it. I hope we can travel more once Mel recovers from all this mess.
The Sprinter is class B and is full motor home with toilet, wet bath, stove, microwave, and fridge plus king size bed. Newer Sprinters based RV's are often on the 3500 rear dual wheel chassis and get quite a bit fewer mpg than mine I hear. We are conservative on speed, rarely hitting 70 mph and mostly travel at 55 to 60 on trips which helps mpg.
Our 76 GMC 40 ft bus, with it's big Detroit diesel often averages 5 to 7 mpg if we are lucky! It's a class A but not typical due to its being nearly 40 years old original engine!
Velda

[gingerK]

I'm thinking so far with Angel (20' class c) I get 11mpg. But I could have mis-figured this so I will pay closer attention next time I go and fill up. My TC, Pony I get about 10mpg. Not because Pony's too heavy but because I have a 360 and the rear end is set up for pulling, not fuel economy. Without Pony on I get around 12 mpg. Pulling my horse trailer (16' steel stock combo) I get about 9.

[Acadianmom]

I get 10 mpg with my 23' Coach House, 11 mpg with a tail wind. It's on an E-450 chassis. The 1992 27' Class C I had on an E-350 only got 8 mpg. This past week I got gas for $1.95. I can't remember the last time gas was that low.

Martha

[MelissaD]

The "fleet average" for many trucking companies I've driven for is 6.5 mpg. Some trucks get a little better and some get a little worse but it's a pretty good average. Also used for reporting fuel taxes for IFTA. (Trucks pay fuel tax based on fleet average mpg times the miles driven in that state.) So the trucking companies take the fleet average number seriously.

The aerodynamics, engine, transmission type (9 speed vs say a 18 speed with double overdrives) and gear ratios of the rear axle(s) greatly affects mpg. Most semi's are geared and match to the torque curves of the engine to produce their best performance around mpg about 63 mph. Odd thing is unlike the old manual engines setting a governor on the new computer engines actually decreases the mpg's but old habits in management are hard to break.

Many class A DP use engines and drive lines similar to semis and busses so their mileage will be very similar but a little better due to running a lighter gross weight.

In my pick up I get 10-11 mpg towing my 12,000# 5er and around 17 mpg highway. Since I have a 4:10 rear end (drive shaft turns 4.1 times for every wheel/tire turn) I'm geared for power(towing) not mpgs. The F450 has a 4:30 rear end so it gets worse mileage but tows better (ie climbs hills better). Most new trucks come with a 3.73:1 rear end so they get better mpg's and make up for the towing power due to the higher engine torque ratings. A gain of 2 mpg due to the change in gear ratios.

Many new pickups loving called "grocery getters" have rear ends with 3.33:1 or higher like 3.08:1 (called "tall Gear") which makes them go faster for the same engine rpm, get better mpgs but they lack towing power. The Fed's pushing for higher mpgs is forcing this. Another reason "Tow Haul" was invent. Allows the truck to get better mileage to make the Fed's happy but you can put it back to the towing beast you bought it for by putting it in Tow Haul. It's also why Tow Haul drops out when you turn the truck off.

Since RV's and trailers are big boxes in the wind, aerodynamics for most units is out the window. Wind drag is probably the biggest killer of mileage. The B's have the advantage that the van builder spent some money designing it's aerodynamics and the conversion people don't normally muck it up, unlike the C's. Sprinter has done a lot of engineering to make a van that is economical to operate from a fleet perspective and the class B's reap that benefit. Mileage wise the class B's will rule on mpg's.

[Acadianmom]

I don't know anything about rear end ratios and all that but know about the performance of the ones I have had. In the 80's I had a 24' Class C with a Chevrolet engine that didn't have enough power for the weight. That thing was a bear to drive, it wandered all over the road. My husband had a truck one time that did that. I went out West to the Grand Canyon and the mountains and it had a hard time getting up the mountains. I don't know that I would buy a Class C with the E-350 if I was planning on going to the Rockies. Maybe they would have enough power. The E-450 I have now has plenty of power. I went from Louisiana to Seattle and didn't have any problems with the passes.

Martha

[Colliemom]

I average about 13-14 pulling my trailer but less in really hilly areas such as out west in WY where grades were steeper. In town driving it gest around 21.

[Liz]

It is what it is....fill 'er up, lol.