| Author | Message | ||
| Dustin Bringham (Dmbringham)
Registered Member Username: Dmbringham Post Number: 20 Registered: 2-2009 Posted From: 98.162.236.45 Rating: N/A |
Anyone have an idea on the average MPG of what an MC-8 with an 8V71 Detroit & and Allison Auto should be getting? | ||
| David Lower (Dave_l)
Registered Member Username: Dave_l Post Number: 221 Registered: 11-2007 Posted From: 67.58.201.132  Rating: N/A |
Dustin is this with a fresh engine, 4 or 6 speed Allison? My MC7 with a 8V71 non turbo and a 4 speed Allison I figured it to be around 6mpg. You could try a serch of the past posts by hiting the serch button and put in fuel millage. Dave L I dont know if I greeted you when you signed up so welcome to the BNO site. | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1708 Registered: 12-2000 Posted From: 76.71.106.122  Rating: N/A |
In rough numbers, mine gets 6 mpg US at 70 mph and 7 mpg US at 60 mph. MC8. 8V71. HT740. 3.7 diff gear. still lightly loaded, no roof raise, two roof mounted air conditioners. happy coaching! buswarrior (Message edited by buswarrior on September 20, 2009) | ||
| Dustin Bringham (Dmbringham)
Registered Member Username: Dmbringham Post Number: 21 Registered: 2-2009 Posted From: 98.162.236.45 Rating: N/A |
Thanks for the greet! I'm on here often just don’t post a lot usually I can answer my own question by searching the archives. The 8V71 is not fresh, but in excellent shape; I don't know for sure but when I purchased the bus from a public school, I was told that there was approx 350k on the motor (Re-build). It's a 4 speed Allison auto trans. I am getting around 4 MPG on average, and that seems to be on the high side. That just seems a little low to me. Any ideas as to why & how I can improve?? | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1709 Registered: 12-2000 Posted From: 76.71.106.122 Rating: N/A |
How are you measuring your distance and is it accurate? How are you fueling the coach, same place, right to the lip? An inch or two of fuel will change the numbers dramatically on a tank by tank calculation. What kind of driving are you doing? Add in much city type driving, and the mileage takes a dive. My numbers are out on the highway, with only the on and off ramp mixed in, on high mileage transits to/from the south. you might not have a problem at your calculated 4 mpg. happy coaching! buswarrior | ||
| Dustin Bringham (Dmbringham)
Registered Member Username: Dmbringham Post Number: 22 Registered: 2-2009 Posted From: 98.162.236.45 Rating: N/A |
I am measuring my distance from the place I fuel up to my destination, and back to my fuel up point which is the exact same place. It is 90% HWY driving nothing above 70mph. I try to fill to the top every time or put in as much as I can. I guess I was looking for the 5-6mpg range on this bus, and just worried that there may be something wrong by not getting that higher number.... | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1640 Registered: 10-2003 Posted From: 71.58.71.157  Rating: N/A |
What is the coach's top speed? How close to it are you running? If the engine has standard timing and you are turning 2000 to 2100, it is not going to be very fuel efficient. Do you have a tachometer? Check your speedometer for accuracy with a GPS unit. Also check the odometer for accuracy with mile markers for about a 10 mile stretch. You can check this also with the GPS if you know how to do it. Pulling a trailer or large toad?.How much total does your coach weigh? | ||
| Dustin Bringham (Dmbringham)
Registered Member Username: Dmbringham Post Number: 23 Registered: 2-2009 Posted From: 98.162.236.45 Rating: N/A |
Top Speed according to the speedometer is 85 mph I try to keep the bus moving at 70 mph or below as much as possible; I will check it for accuracy next trip out. No Tach although I have plans on putting one in soon. No Trailer, I can get it weighed to find out total weight. | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1710 Registered: 12-2000 Posted From: 76.68.135.14 Rating: N/A |
oh boy! Perhaps a problem here? with a 3.7 differential, you need to turn the engine 2600 RPM to make 85 mph with a 3.36 diff, you need to turn the engine 2360 rpm to make 85 mph. I think your speedometer might be off? Any connected odometer will be off too. Reading too high would give you "better" than correct fuel economy, showing you traveling further than correct distances. let's keep going, we'll get to the bottom of this! happy coaching! buswarrior | ||
| Nellie Wilson (Vivianellie)
Registered Member Username: Vivianellie Post Number: 272 Registered: 11-2008 Posted From: 75.178.92.43  Rating: N/A |
Hi Dustin - Don't know about the automatic, but mine - 8V71 (318) with 4-speed and 3.3 diff - gets from 8 to about 10.5 MPG. On this last leg, from Virginia to NC, got 10.8. BUT it was flat, flat, flat. Also no roof A/Cs, no toad, no tag axle. And hardly any weight - empty tanks (except fuel) and no gen as yet. For the most part, kept revs between 1650-1800 and ran between 50-60 MPH. Optimal condiions and that's the best I've ever gotten; doubt it will happen very often but gives me something to shoot for. Like BusWarrior mentions, speed dramatically increases my fuel consumption - as do hills and traffic. But, hey, when you drive a bus, the cost of motels and restaurants drastically DEcreases, right? I guess life's just one big happy trade-off. Nellie | ||
| John MC9 (John_mc9)
Registered Member Username: John_mc9 Post Number: 982 Registered: 7-2006 Posted From: 74.162.93.80  Rating: N/A |
Dustin - A decent GPS unit will provide the most accurate speed display. Differential ratio, and speed, will make the most difference in MPG. If your bus was built for "local line work", high highway speeds will drain the fuel pretty quick. With a city bus going over 60 mph, I would expect 4 mpg.. | ||
| Jack Conrad (Jackconrad)
Registered Member Username: Jackconrad Post Number: 1163 Registered: 12-2000 Posted From: 68.26.36.135  Rating: N/A |
Best to figure your mileage over many fill-ups, not just 1 or 2. When we started our conversion (MC-8 with 8V71/Allison 740), we were getting 7.0-7.2 MPG with our empty shell (approx. 25,000#). With the finished conversion (approx 35,000#) and our engine getting "tired", our mileage dropped to 5.3-5.5 MPG. With our "new" engine, we are averaging 6.4-6.6. Jack | ||
| Dustin Bringham (Dmbringham)
Registered Member Username: Dmbringham Post Number: 24 Registered: 2-2009 Posted From: 98.162.236.45 Rating: |
OK So here is more info: checked the speedometer, and it is working properly. I still have not weighed it but have plans to do so this week. Not sure on diff ratio, but will find out this week also. | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1662 Registered: 10-2003 Posted From: 71.58.71.157 Rating: N/A |
The rpm the engine is running at during your "cruising speed" is going to be necessary. | ||
| Josh McElhiney (Zcommanager)
Registered Member Username: Zcommanager Post Number: 47 Registered: 1-2009 Posted From: 75.187.41.177 Rating: N/A |
Dustin - I have a 35' GMC with a 6-71 DD and 4 speed spicer and averaged slightly over 8 mpg on a cross-country trip last summer. Now that did drop to around 5 or 5.5 going through the Guadalupe Mtns in New Mexico, but the rest of the trip we were back up to 8 or 8.5. So given that you have an extra 5 feet in length, 2 more cylinders and an auto tranny, you may not be too far off...although, 4 seems a tad low. Welcome to the board...better late than never!!! Josh | ||
| Dustin Bringham (Dmbringham)
Registered Member Username: Dmbringham Post Number: 25 Registered: 2-2009 Posted From: 98.162.236.45 Rating: N/A |
I took my bus in and had it serviced last week, I had them put new fuel filters on, air cleaner etc. That seemed to help, but I added a gallon of Lucas additive to it right before a long trip, got home last night, and figured just over 6mpg. I was pretty happy with that, considering I started around 4mpg before the additive, and service. | ||
| Greg Roberts (Eagle 20) (Gregeagle20)
Registered Member Username: Gregeagle20 Post Number: 275 Registered: 4-2002 Posted From: 66.18.167.76 Rating: N/A |
Wow that is impressive. How much and did you just add it to the crankcase or also to other lubricants? Is this proven safe for the detroit 2-cycle engines? That is a huge increase. Has anyone else had this sort of result? | ||
| Dustin Bringham (Dmbringham)
Registered Member Username: Dmbringham Post Number: 26 Registered: 2-2009 Posted From: 98.162.236.45 Rating: N/A |
I have always added the oil additive to all my engines gas or diesel, and have had great luck with it. I just started adding the fuel additive to my pickup, and talked to a few people that have busses/trucks, and they were telling me to add the fuel treatment to the bus. I did, and I am sold. I added a gallon to the fuel tank (full), and I noticed a huge difference. I always add a full gallon to my oil when I get the bus serviced, I have asked a few mechanics, and they have all told me Lucas makes a great product, and will work fine in a 2 stroke Detroit. I don’t attribute everything on the fuel mileage to the Lucas as I said before I had it serviced, and changed the fuel filters, and air cleaner. I would recommend trying the fuel treatment to see what you get. | ||
| David Guglielmetti (Daveg)
Registered Member Username: Daveg Post Number: 110 Registered: 2-2009 Posted From: 70.130.69.119  Rating: N/A |
My bets are on the air cleaner element. Although before that I would have wagered on gearing/RPM at cruising speed. Skip the fuel treatment for a couple of tanks full and tell us what happens. |
