Usuable Fuel Gallons from fuel tank

[bcaddel]

Thanks RJ for your responce, it appears I definitely do not have the aux tank so I only have a total of 144 gallon capacity.  As Cody mentioned we don't want to run the tank on the bottom 1/4 tank normally but I feel we need to know what is available for those times when we might need it.

Before Pilot purchased the Flying J's we would always try to stop at a Flying J so we had access to propane, dump station and cheap fuel price. Sometimes that would cause us to stretch our milage to get to the next "J". It appears the Flying J's are changing their pricing strategy now so they most likely won't be the cheapest price anymore but they are still RV friendly, so we will still use them and sometimes we have to dig down a little deeper into the fuel tank to get there. My fuel gauge seems to be right on so I will rely on it and my milage (and 144 tank capacity) to see if I can make it to the closest "J".

Buswarrior
Do you run in the same gear when driving at 60 vs 70. We have a MT645 "5" speed transmission and when I want to drive at 60 I shift into 4th and run at 2300 rpm. It seems to run cooler and holds right at 59/60 mph. If I shift into 5th it wants to run up around 65 to 67 at 1800 rpm but it runs a little hotter and I assume burns a little more fuel but I havent been able to define that since I do both during each fill up.

bob

[luvrbus]

Bob, it is a good idea to run all the fuel out and drain the tanks I do it about every 3 years even living in the desert doing this I don't change fuel filters till around 25,000 mile mark and they are still good



good luck

[bcaddel]

Clifford, I agree with you on the filters. I think I will bring the coach home almost empty next time and drain the tanks to see what might still be in there.

Our bus had been sitting for about 4 years when we purchased it. The filters plugged up out on the highway in the mountains of Colorado. We drove at 20 mph for about an hour to get to a truckstop to purchase new filters and change them. We always carry spares now.

The bus started running rough about 7000 miles later and I pulled over and put on the spare set  and it cleared up right away so I might have some gunk down in the bottom of the tank.

[luvrbus]

Bob, you will use less fuel at 1800 rpm than at 2300 if the heat goes up a little increase your speed sounds like your dad had the bus setup for 70mph some guys would love 70 mph at around 1900 rpm and I would not worry about the heat if it stays under 200 degrees 



good luck

[buswarrior]

Mine has 4 gears, so same 4th gear for 60 or 70 mph.

I turn governed speed of 2100 rpm at 70 mph. Engine turns somewhere 1850 rpm to make 60 mph.

I agree with luvrbus, you'll see some good fuel mileage if you stay in top gear at 60 mph.

The 8V71 is better at fuel consumption in the 1750 to 1950 rpm range than up high.

Temperature wise, it sounds like you are seeing it running against the thermostats turning 2300 rpm in 4th gear, the fans and water pump are shedding all the heat and then some.

What kind of temps are you seeing in 5th at 60 mph?

You may have some hidden economy in your gear choice!

happy coaching!
buswarrior

[bcaddel]

buswarrior (thanks for asking)

I would like to give some history prior to giving the temp numbers. We drove from Texas to Nevada last September and took a 7500 mile trip around the country the whole month of May this year, plus several trips around Nevada this summer.

The engine seemed to stay in the 185 range during all of this travel and in the past I have not had the temp go much above 190 at anytime except when I would be driving up a mountain grade. I have misters and I turn them on if I get close to 200 and keep them on until I crest the mountain top then turn them off. I am usually around 180 when I turn them off at the top of the mountain.

Last weekend we drove from Reno to Salt Lake, it was only about 88 degrees outside. We were traveling on level ground, in 5th gear running between 1800 to 2000 rpm's (no cruise control) and around 65 mph. The temperature hit 200 after about 2 hours of driving on level ground. We turned on the misters and it cooled right off, but when we turned the misters off it started going back above 190 and crept up to 200 degrees (misters off) which had only happend once before in Texas last year but it was 104 degrees outside then.

The misters always cool it down but as you know there are problems with using the misters too much on the radiator so we try not to use them. On the way back home from Salt Lake we ran in 4th gear and 2300 rpm and it never went above 190 even on the hills. We left Salt Lake at 6:00 in the morning and was back in Reno by 3:00 in the afternoon so the outside temp was 10 to 20 degrees cooler than when we had the problem.

Nothing has changed with the bus so I am a little concerned about the 15 degree rise in engine temperature. I have an almost new engine and the radiators were taken out and redone about 20,000 miles ago and really look good. The cowling is all sealed up and I don't think there are many if any air leaks and I don't loose any coolant so I am just a little worried about what I might face next summer.

I would appreciate any suggestions or comments on what could be causing this problem. The temp guage on the dash match the temp guage in the engine compartment plus I carry a Temperature gun that confirmed the temperature when I pointed it toward the thermostat area.

Suggestions?

[buswarrior]

I would be highly suspicious that air is getting past the fan door seals, or otherwise around the radiators instead of through them.

On installing new-to-me rads in my MC8, heretic that I am, I used a can of spray foam to seal around the rads, using the tired shards of rubber seal to act as a base for my foaming. Sealed up tight and easily chewed out the next time rads have to come out.

What shape are those seals in?

For the fan door, run the engine on fast idle, get a ladder, and check around the door for evidence of air sucking past. Smokers may blow smoke, others may use tissues or whatever, look for it sucking air in where it shouldn't.

If you get some wind through there, fear not, I continue to use duct tape around the door in the appropriate colour to seal mine until I get around to improving the situation. I am dissatisfied with how small the stock seal contact surface is, I want to do an upgrade to bigger stuff.

Any corrosion opened up the ceiling or floor of the fan compartment? 

Some chunk of rubber blocking at least some of the gap that the fan belt goes up there through?

Air getting past is guilty until proven innocent, before I'd move on to more complicated diagnosis.

happy coaching!
buswarrior

[gfcgfc1]

Hello all , o.k. i just got into my flame proof suit.  I getWAT better fuel mileage than 6.5 unless I'm climbing big hills.BUT...The bus I beleive has hi highway gearing i.e. low numerically. The coach is not heavy currently gutted but the 6.5 is worse then the worst mileage I've ever gotten keepin SCRUPULOUS track of miles gallons fuel used etc....OK go ahead flame suit is intact and fully functional LOL

[bcaddel]

gfcgfc1
OK, I will bite, what kind of fuel milage do you get?

I would also be interested in what RPM & speed do you usually run?

What temperature does your engine operate at when running down the highway?

and last but not least how many gallons do you have and what do you consider your range on a full tank.

Thanks for info
Bob

[bcaddel]

Buswarrior

You gave me some great ideas on the air flow. I have not checked the area where the fan belt goes up to the fan, or the fan door. Looking at the radiators from the outside, it has been sealed with that spray foam stuff so I assumed it was sealed everywhere but I haven't confirmed (or even looked) at the inside area.

Bob

[gfcgfc1]

Hello , Bob , my MC-7 has 179 gallons fuel capacity.6.8 is the worst mileage I have gotten. That is thru the mountains in NewMexico headed west . 7.5 average up to a high of 9plus all highway . 4 speed Spicer Manual trans. I stay under 70mph.The Tachometer is inop. now so I cant tell RPM's.not very  high tho by ear.The bus is not a jack rabbit or hot rod .Engine runs very strong and smooth almost no smoke except under HARD acceleration and big hills out west NewMex and Northern Arizona. I havent checked the gears in the differential ,  is there a 3.3xx ratio available for the rear end? That is what I think /suspect it has.OK FLAME away! LOL!!    GFC

[luvrbus]

Gf, I don't think a 3:33 is available for a MCI 7 Richard on the board here cut the center section out and installed a different one to get taller gears on his 7.
No body here is going to flame you about your post on your mileage first liar here doesn't stand a chance according to John Ed       LOL 
PS I believe you I have a 05 Eagle with that set up that gets great fuel mileage   



good luck

[bcaddel]

gfcgfc1,

Congratulations, that sounds pretty darn good to me. I am fairly certain that I have the 3.7 rear end. My speeds and rpm's & tires match that setup so I am fairly confident. I have never got over 7 mpg but have got close on one or two fill ups, but that is probably mostly from possibly not getting it topped off each time.

How slow do you get when going up some of those long 6% grades? I seldom drop below 30mph but I have a couple of times on some on the longer grades. I just turn on the flashers and give thanks for the passing lanes.

[gfcgfc1]

Hello all , Bob I have been thru 2nd gear and into 1st gear scared and praying till the top.Then all gleeful and triumphant , like I did something,LOL!!
The temps normally 185 - 190 Than sometimes my shutterstadts act backwards and close when hot urghhhh! Temps come right down tho . This bus is geared for the highway with no hills .But I live in the Rockies! What is lhe lowest numerically available gear set for this differential, 'cause I'm confident that I have it. If 3.3xx isn't available what is close to that, that comes in a MC-7?3.5xx?Love the mileage hate the gear in the hills.Maybe more gears in the tranny would help.Roadranger ten speed would that help cut the hill?

[buswarrior]

stick shift 4 speed will get better fuel mileage than an automatic.

In revenue service, it was considered that the auto lost 1 mpg over the stick shift.

Did the MC7 have a different axle from the MC8/9?

I'd have thought the same Rockwell limitation of stuffing a 3.36 or whatever it is into that axle would work on the '7, same as the newer ones.

Educate us, please!

happy coaching!
buswarrior