60 seires 515 hp

[terryweber]

getting 6.2 mpg told to drop hp to 435 could getup to 20% better ?????::confused:

[AmeriStar]

1997 brought the introduction of the DDEC IV engine, and further improvements in the design of the engine, notably a wastegate turbocharger and engine management improvements provided increased horsepower ratings up to 500 hp and increased torque outputs to 1,650 foot-pounds force. Prior to 97 the rated power for most of the 12.7's were at 430 horse power. Setting the 12.7 above 475 significantly reduces fuel mileage.
Our fleet of MCI motorcoaches used the 12.7 DD exclusively until 2007. We set the horsepower level at 470 and the top speed at 73 mph. Our fleet average is 7.8 mph.
500 horsepower sounds great, but the additional cost for fuel, not to mention the increase in operating temperature, is a huge negative.

[Jon Wehrenberg]

If you want to increase mileage substantially, for free, lift your right foot a little.

You only pay for the HP you use. It is that simple.

There are things you cannot control. You cannot do anything about the drivetrain efficiency, hills, quality of fuel, or the amount of HP produced per pound of fuel. When Mother Nature decides to blow strong headwinds at you there is no way to get her to stop them and make them a tailwind.

But you can drive slower. You can choose a lighter weight toad, you can reduce the weight of the bus by leaving a lot of stuff behind and not always filling the water tank before you drive. Save a little more fuel by never turning on the AC.

Or you can drive slower.

If improving your fuel mileage seems to be an issue do some math. Determine how much your fuel costs will be at your current level and based on the miles you drive annually. Then recalculate the cost at your target mileage figure. Then just to put that cost savings annually in perspective, determine your depreciation and the lost earnings on the capital invested in your coach. Kind of puts a quest for better mileage in perspective.

[jack14r]

I agree with Jon but there is something that we cannot change,as the coaches have gotten more slides and more marble/granite etc. they have gained as much as 8,000 pounds in weight,we must pay for that in fuel mileage no matter how much or little we use our right foot.I don't think that my coach will ever get the fuel mileage that Jon's coach will just because of the difference in weight.

[merle&louise]

There is a guy in Lufkin, TX who drills out the return fuel line orfice and increases the size of the opening from .008 to .009

Supposedly, this increases the fuel economy by 1 to 1.5 mpg!

A fellow POGGER told me about this. He has done it on his coach and now gets the improved fuel economy.

I was going to do it but the tech couldn't reach my return fuel orfice.

[johnklopp]

I agree with Jon. The only method to increase fuel mileage without emptying your coach is to get your foot out of it and slow down. Playing around with the fuel metering orifices puts your engine at risk. If it was that easy, the engine manufactures would have done it. Consider the consequences, a ruined engine 20K? or the EPA knocking at your door.

[travelite]

I'm trying to find the specs but my wife is pushing me out the door. I wanted to give the fuel pressure specs for idle, no load max rpm, and full load max power. Detroit Diesel is very specific about these fuel pressures. Opening the return fuel line orifice will certainly drop the pressures. Remember fuel is a lubricant and a coolant.

[merle&louise]

Kind of glad I didn't do it! Sounds like a bad deal. Ouch!

The good Lord must have been watching out for me.

[phorner]

If you are concerned about fuel economy, buy a Prius, not a bus.

There is absolutely nothing that's going to get your 50,000 pound vehicle, that's shaped like a brick, to sip fuel.

Just drive the darn thing and enjoy the ride :cool:

[terryweber]

If you want to increase mileage substantially, for free, lift your right foot a little.

You only pay for the HP you use. It is that simple.

There are things you cannot control. You cannot do anything about the drivetrain efficiency, hills, quality of fuel, or the amount of HP produced per pound of fuel. When Mother Nature decides to blow strong headwinds at you there is no way to get her to stop them and make them a tailwind.

But you can drive slower. You can choose a lighter weight toad, you can reduce the weight of the bus by leaving a lot of stuff behind and not always filling the water tank before you drive. Save a little more fuel by never turning on the AC.

Or you can drive slower.

If improving your fuel mileage seems to be an issue do some math. Determine how much your fuel costs will be at your current level and based on the miles you drive annually. Then recalculate the cost at your target mileage figure. Then just to put that cost savings annually in perspective, determine your depreciation and the lost earnings on the capital invested in your coach. Kind of puts a quest for better mileage in perspective.

thanks terry

[terryweber]

If you want to increase mileage substantially, for free, lift your right foot a little.

You only pay for the HP you use. It is that simple.

There are things you cannot control. You cannot do anything about the drivetrain efficiency, hills, quality of fuel, or the amount of HP produced per pound of fuel. When Mother Nature decides to blow strong headwinds at you there is no way to get her to stop them and make them a tailwind.

But you can drive slower. You can choose a lighter weight toad, you can reduce the weight of the bus by leaving a lot of stuff behind and not always filling the water tank before you drive. Save a little more fuel by never turning on the AC.

Or you can drive slower.

If improving your fuel mileage seems to be an issue do some math. Determine how much your fuel costs will be at your current level and based on the miles you drive annually. Then recalculate the cost at your target mileage figure. Then just to put that cost savings annually in perspective, determine your depreciation and the lost earnings on the capital invested in your coach. Kind of puts a quest for better mileage in perspective.

thanks terry

[terryweber]

I agree with Jon but there is something that we cannot change,as the coaches have gotten more slides and more marble/granite etc. they have gained as much as 8,000 pounds in weight,we must pay for that in fuel mileage no matter how much or little we use our right foot.I don't think that my coach will ever get the fuel mileage that Jon's coach will just because of the difference in weight.

thanks terry

[terryweber]

There is a guy in Lufkin, TX who drills out the return fuel line orfice and increases the size of the opening from .008 to .009

Supposedly, this increases the fuel economy by 1 to 1.5 mpg!

A fellow POGGER told me about this. He has done it on his coach and now gets the improved fuel economy.

I was going to do it but the tech couldn't reach my return fuel orfice.

thanks terry

[terryweber]

There is a guy in Lufkin, TX who drills out the return fuel line orfice and increases the size of the opening from .008 to .009

Supposedly, this increases the fuel economy by 1 to 1.5 mpg!

A fellow POGGER told me about this. He has done it on his coach and now gets the improved fuel economy.

I was going to do it but the tech couldn't reach my return fuel orfice.

thanks terry

[terryweber]

If you are concerned about fuel economy, buy a Prius, not a bus.

There is absolutely nothing that's going to get your 50,000 pound vehicle, that's shaped like a brick, to sip fuel.

Just drive the darn thing and enjoy the ride :cool:

thanks terry

[Jon Wehrenberg]

From time to time we have gotten into discussions on fuel mileage. We offer all kinds of comments such as what has been posted above. Discussing mileage alone is only recognizing part of the equation when considering direct operating expenses.

If we cannot improve mileage beyond a certain level, we still have ways to reduce fuel costs. It's no secret I am an advoicate of long range fuel. If you have never had it the desire to have it is likely much less than mine. But once you have experienced the benefits of long range fuel it becomes very difficult to give it up. For me there are two reasons in favor of long range fuel. First, it significantly reduces my need to visit truck stops. As we are now equipped with 298 gallons capacity very few of our trips require a fuel stop except when we get home and can use our local Pilot.

But having long range fuel is also an opportunity to buy the least expensive fuel. With a computer anyone can plot their route, look at fuel costs along the way and plan fuel stops to only buy the least expensive fuel. In our case I don't even need a computer. I just keep track of fuel costs as we travel, and if there is a really cheap price along our route that I see on the outbound leg, when we are returning home I just top off there and save a dime or more per gallon. The savings we can enjoy may not be significant, but it is the equivalent of increasing the MPG.

There is nothing you can do to add additional fuel capacity to your bus, but if you are looking for a newer coach there are those with long ranbge fuel out there in the marketplace. Currently Prevost does not offer long range fuel on new shells, but I suspect if the converters and owners wanted long range fuel it would be made available as an option.

[merle&louise]

Jon,

Knowing that you are considering a new or newer coach, which would you choose slides or extra fuel range? I don't think that both options could be incorporated in a new coach because of the weight factor.

I think (correct me if I'm wrong) that the fuel capacity on the newer Prevosts is around 208 gallons. So you carry an additional 90 gallons, and that 90 gallons weighs about 720 #. I think that the slides weigh about 800# to 1100# each depending on the length of the slide. In your opinion, could a converter deliver both extended range tanks and slides?

[Jon Wehrenberg]

The motorhome shells have kept pace with the market. Maybe not as fast as some would like, but as the market has asked for slides and other weight adding features Prevost has increased the gross and axle weights of the coach. If you were to buy a new X3 (used to be an XLII) you would note the front axle is going to have a 19,000 pound capacity.

Having said that however and despite the fact Di wants the mass of the H2, I am opposed to weight. If I do buy a new shell and conversion I am going to get slides and I have decided I am going to get long range fuel even if it is not listed as an option. I want the slides because if we are going to the expense of a new coach it has to be a significant step up from what we have. That means I gain features I want, and give up nothing I have and wish to retain.

But because the empty weight of the shell will increase with slides and extra fuel, me and the converter are going to have to be very much aware of weight and balance. That might rule out things like granite floors and a lot of batteries, but we will just have to work around stuff like that. Diesel fuel weight is related to temprature, but for rough planning purposes I wil just use 7 pounds per gallon (it is less) for a weight of about 630 pounds for long range fuel. Yes a converter can deliver a coach with long range fuel and slides, but with the new wheelbase the challenge is going to be gettin the weights for each axle within the limits and still leave capacity for the owner's personal efects.

[Kenneth Brewer]

I agree with Jon. The only method to increase fuel mileage without emptying your coach is to get your foot out of it and slow down. Playing around with the fuel metering orifices puts your engine at risk. If it was that easy, the engine manufactures would have done it. Consider the consequences, a ruined engine 20K? or the EPA knocking at your door.

What he said. Thank you.

[merle&louise]

The motorhome shells have kept pace with the market. Maybe not as fast as some would like, but as the market has asked for slides and other weight adding features Prevost has increased the gross and axle weights of the coach. If you were to buy a new X3 (used to be an XLII) you would note the front axle is going to have a 19,000 pound capacity.

Having said that however and despite the fact Di wants the mass of the H2, I am opposed to weight. If I do buy a new shell and conversion I am going to get slides and I have decided I am going to get long range fuel even if it is not listed as an option. I want the slides because if we are going to the expense of a new coach it has to be a significant step up from what we have. That means I gain features I want, and give up nothing I have and wish to retain.

But because the empty weight of the shell will increase with slides and extra fuel, me and the converter are going to have to be very much aware of weight and balance. That might rule out things like granite floors and a lot of batteries, but we will just have to work around stuff like that. Diesel fuel weight is related to temprature, but for rough planning purposes I wil just use 7 pounds per gallon (it is less) for a weight of about 630 pounds for long range fuel. Yes a converter can deliver a coach with long range fuel and slides, but with the new wheelbase the challenge is going to be gettin the weights for each axle within the limits and still leave capacity for the owner's personal efects.

Jon, it sounds like you are going to build a fine Liberty. That bad boy will be really nice with long range fuel and slides. If anybody can engineer a coach like that I know you can. Enjoy building it - we're all pulling for you!

[Jon Wehrenberg]

It's a long way from happening and we have some hoops to jump through first.