Hello,
I did a short test of the fuel economy of my new Series 50 powered, 4.11 rear end gear ratio TMC "RTS" bus yesterday. I filled it at a truck stop, drove it 102.4 miles at 60 miles per hour, checking the speed every 15 seconds or so (that's work), and then filled it again at the same pump, with the bus oriented the same way. I used 9.524 gallons, for 10.75 miles per gallon. The bus is stripped, and only had the house batteries, some sheets of plywood and some empty water tanks on board.
The top speed is 75 miles per hour. I was able to go 62 miles per hour up a 1,000 foot grade that my old bus, a non-turbo 8V-71 powered MCI 5a, 35' x 96", could only take at 50 mph. My new RTS is 40' x 102" and has a turbo Series 50 engine that the computer says has only 6,000 miles on it. (Did I get a rebuilt engine, nobody knows...)
I am pretty pleased with the results of my test. I know I need to do a longer test for better accuracy, but this test should be pretty close for steady freeway driving at a moderate speed. The engine hardly seems to be working at 60 mph. The air conditioning worked fine - my first real test since I bought the bus in March. I could tell in 1 minute if I turned it off, as there is essentially no insulation in the bus right now, as I stripped the walls and ceiling of the factory insulation. Oh, I did turn the AC off during the fuel economy test, for the record, as I was trying to see the maximum economy I could get.
How much do you think the fuel economy will go down once I complete the conversion, if at all?
Thanks,
Kevin
San Francisco, CA
Your not going to make any friends getting 10 MPG. My DDEC 6V92 got 6 one time when the pump belt for the fan was loose. I hate you!
Quote from: NJT 5573 on May 07, 2007, 08:03:24 PM
Your not going to make any friends getting 10 MPG. My DDEC 6V92 got 6 one time when the pump belt for the fan was loose. I hate you!
Haa.. My 83 NJT (6575) got 7.7 running on veggie/mix and 5.5 on low sulphur diesel on return trip from Charlotte in January.
Pulling a 24 foot trailer. I get about 6 mpg normally. ( MUI engine )..
Kevin -
Keep your bus on a diet as you complete the interior.
Weight is a major culprit, both curb weight and that of right shoe.
Cruise control will help, Rostra or King. May even have one programmed into the DDEC on the S-50, just needs to be unlocked.
Any size tire (22.5 or 24.5) turning LESS than 495 revs per mile will help.
60 - 65 mph comfy cruise, when fully outfitted, should return overall average of 8 - 9.
All buses have the aerodynamics of a brick at speed - keep the silhouette as clean as possible for best results.
What transit property ran your RTS in revenue service? Golden Gate?
What's the VIN on your coach?
FWIW & HTH. . .
;)
Congrats, both on your mileage, and your Patience to drive 60.
The 6V92 turbo non DDEC, I run at 70 mpg gets about 6.7 mpg.
No bus air/conditioning running. I wonder as to how I would do at 60 MPG. Just never had the time it seems.
Maybe in retirement I will feel I have the time, but that is dependant on the housing slump another thread.
GP
PS TG for the spell check.
MUI is beating DDEC by 1.5 MPG or more. Stupid computers!
Quote from: Gary '79 5-C on May 08, 2007, 02:23:42 AM
Congrats, both on your mileage, and your Patience to drive 60.
The 6V92 turbo non DDEC, I run at 70 mpg gets about 6.7 mpg.
No bus air/conditioning running. I wonder as to how I would do at 60 MPG. Just never had the time it seems.
Maybe in retirement I will feel I have the time, but that is dependant on the housing slump another thread.
GP
PS TG for the spell check.
Gary,
As Curly use to say to Mo "I resemble that remark"I can remember when I was in my 20's I would drive home from Chicago to Wva in less than 7hrs now it's just over 8hrs. but that was back in the 70's when I think the speed limits were 70mph, and I know I was way over that speed lol. Now I find myself right on 60mph all the time in my car, man I hope it's not old age thats causing me to drive slower. I hope it just the arthritic foot I have LOL. At least that the story I'm going with.
WVaNative
I typically get around 8 mpg, give or take, 8V71 with standard crash box. Getting anything over that is only a dream. It all depends how heavy your foot is and how many hills you have to go up and what color your exhaust smoke is.
What it is, is what it is.
It will change as you add more weight, so feel good now.
Happy Trails,
Paul
Dreamscape
Kevin, what transmission do you have in your RTS?
Do you have OD?
What are the trans and OD ratios?
I have a repowered MC9 with a series 50 and 3.73 gears and want to find some 4.11 gears to swap mine out. Currently have too much top end and could use a bit more get up and go from a dead stop. Power on hills is good now.
Thanks
With a fully converted RTS (32,000-34,000 lbs.), 350HP 6V92TA, 4:11 gears, running the diesel genset, I get 8mpg @ 62-65 mph.
That is a 11 year old post wonder how it is doing now on fuel with all the climate changes
Empty shells have lots of power and get great fuel mileage. Even our 4104 felt fast before conversion. Btw it had hv9 injectors and two valve head then, smoked like a locomotive but sure ran good. He will end up with 8 to 8 1/2 average, unless it is a minimal conversion.
Quote from: chessie4905 on February 23, 2018, 06:44:52 AM
Empty shells have lots of power and get great fuel mileage. Even our 4104 felt fast before conversion. Btw it had hv9 injectors and two valve head then, smoked like a locomotive but sure ran good. He will end up with 8 to 8 1/2 average, unless it is a minimal conversion.
Depends on the direction the wind is blowing too ;D figure on 5 to 6 mpg and enjoy the savings at Mac Donald's or Burger King
My old Crown Supercoach 40 foot 3 axle 10 wheeler ex school bus got around 10.5 mpg from Apple Valley CA to Cave Junction OR. VIN 37317.
About 60 mph tacking about 1500 rpm in tenth gear. 12Rx22.5 tires. 3.90 gears. .82 to one overdrive. Fuller RTO910. Small Cam 250 Cummings (sp?)
No turbo. Climbed the 6% and 7% grades at around 45 mph in 8th gear tacking about 1800 rpm. Slow. Curb weight then stripped was about 24500 pounds.
Long ago. CROWNS FOREVER! :)
The RTS was designed and tested in a wind tunnel for wind drag. It also stands at about 10 feet high with 20" bays. So great fuel mileage is not just being empty.
Surprising they went to all that trouble since they spent most of their life running 30 to 45 mph.
Quote from: chessie4905 on February 23, 2018, 04:32:45 PM
Surprising they went to all that trouble since they spent most of their life running 30 to 45 mph.
The RTS came in a variety of platforms and sizes. The suburban model came with overhead luggage racks and lower center isle, and was geared for highway speeds. The rear door was an option to be ADA compliant with a wheelchair lift. Wanna race?
I imagine they spent all that design money as a spin-off replacement for the 4905 design. Also there are similarities with the GMC motorhomes.
If only Allison had made a V740-it would have been perfect
A few years back, a guy named Teal put together a V730 with overdrive, using a planetary from a VS-2 transmission. I have the booklet he sold to modify the V730.
Bill Teal.
Bill Gerrie built one too. He will chime in...
Finding the donor parts is not easy, all that stuff had to survive too many waves of high scrap prices...
Happy coaching!
Buswarrior
Why in the world would you want 2 overdrives on a V730 they are already .875:1 in third,it's the 2nd gear to 3rd gear wide range that kills you on a V730 going from 1.121:1 to 0.875:1 is large gap to fill,I believe that is what TomC is referring to that since a 740 does not have that gap.The V730 is not much in the mountains
1600 rpm highway cruise in a V-drive?
Happy coaching!
Buswarrior
The V730 is .875 through all 3 gears. The angle drive is where it is overdriven. The gears are just like a 740 without a 1st gear. Since the tallest differential ratio is 4:12, it is like a MCI with 3:70. 4:12x.875 gives you 3:60 final drive. The torque converter used assists in takeoff since 1st is higher. The overdrive setup would lower cruising rpms at today's interstate speeds to 1750 to 1850 instead of 2300. Also with the penalty of the 315x80x22.5's slightly shorter tire would help compensate
Most common transmission with series 50 was the Voith...
Never saw a Voith behind a series 50 in a RTS before interesting, I have seen plenty of ZF's and R V731 lol or is the R after the V731 I forgot
The RTS used a ZF transmission in their later years after GMC sold the assembly line.
I think the drop between 2nd and 3rd with the V730 automatic is the same as the 3rd to 4th gear percentage drop with the 740? About 37% or 38%?
About the same as a 13 speed manual shifted like a common 9 speed without using the splitter? The 7th to 8th gear percentage drop Takes torque.
If such a 37% rpm drop is horrible in a 35,000 Bus Conversion imagine how bad it must be in a 80,000 or less logging truck? Bad. Thus the needed splitter?
Here in Milwaukee, the MCTS had 150 RTS's built in 1980. All but 6 had the 8V-71/V730 and 6 had the 6V-92TA/V730.
Anyway, 2 of the 8V-71 versions were selected to receive a CUMMINS L10/VOITH combo an experimental program for a few years after which, they put the original powertrains back in.
So it may be safe to conclude that later RTS's could accept other trannys besides the stalwart V730.
My only bugaboo is why in the world did the V730 which were used in buses that normally didn't get above 45 on a regular basis need an overdrive while the 740 never had overdrive which would have made perfect sense in a MCI or PREVOST?
Quote from: CrabbyMilton on February 26, 2018, 04:39:58 AM... why in the world did the V730 which were used in buses that normally didn't get above 45 on a regular basis need an overdrive while the 740 never had overdrive which would have made perfect sense in a MCI or PREVOST?
As Geoff frequently points out, there's a difference in "highway/suburban" transit buses versus those that only run 40 mph urban routes. Maybe Milwaukee (and other users) felt the need for mixed-service buses that were at least capable of highway travel as part of their routes???
MCTS does operate what they call "Freeway Flyer" service so they'll need to go 50-60mph with that so I get that part so it may have been standardization with GM and the RTS which is a good thing
My point is that the 740 was never offered in overdrive which would have been logical. Later transit buses had the T drive and the ALLISON 747/748 which was based on the 740.
The design wasn't an actual "overdrive transmission in today's sense. They overdrive everything to provide a compact package that would work best with what they had as parameters, especially room to get it to fit.
There was no bus engine power that could pull an overdrive gear back then, and barely for the big truck engines.
Direct 1:1 was all you needed, and all you wanted.
The real "transit bus slow" stuff died with the 2 speed transmissions, last seen in the mid 70's.
Everything since then is capable of 60 mph or better.
If it wasn't for the internet interfering with busnut creativity, there would have been tons of capable high floor transit conversions built over the last 20 years. Great chassis, low profile and with good drivetrain, but into the scrap yard they went...
Happy coaching!
Buswarrior
The HT 70 Allison was found in buses with OD ,the MCI 7 had those problem was they were wet torque converters and leaked it was a good transmission for it's day with the over drive and being a 6 speed
Thanks for the perspective guys.
I remember the old GM NEW and OLD LOOK transits around here with the old 2 speeds. Sometimes I would wonder how they would get up some hill around here being that the 6V-71 with 170 HP straining for all it was worth then it finally shifted into 2 second.
Then going more than 35 or 40 in those seemed like you were about to take off from the sound of the engine. :)
Bill Gerrie and myself have a V730 with a Teal o-drive. I would NOT part with mine. I get 8.2 mpg since installing. I have a 6V92 with 9A90 injectors, 4 1/8 rear end and a power tech 8 kw 3 cyl isuzu gen that runs from the time I start the bus till I shut it off, plus all the time I am at the nascar races. usually 5 days. I run between 70 and 80 most of the time. Top speed ??? but I love it. I shift into o-drive at about 65 and out going up a hill at 70 mph. I can run at 60 in o-drive but I don't like the oil pressure at that low of a rpm. By the way I have a 4106. O-drive forever olebusman
How many miles have you put on it since installing? Have you had any issues? Are you using the VS2-8 planetary for overdrive or the planetary from the VS2-6? Thanks.
So what is the final drive with a extra O.D on a V730,the 0.875 is there no way to change it when the 2 planetary and sun gears are locked together as 1 unit that I know of anyways,you an change torque converters for stall ratios but it will not change the final ratio on a v730 or the HT 740.
It makes the final overall ratio 3:60 instead of 4:12. Of course the first and second gear are also lower numerically, instead of the second and third ratios of the 740 because the angle drive years are overdrive to .875.
Quote from: chessie4905 on February 26, 2018, 02:10:49 PM
It makes the final overall ratio 3:60 instead of 4:12. Of course the first and second gear are also lower numerically, instead of the second and third ratios of the 740 because the angle drive years are overdrive to .875.
That transmission (V730) if Allison could have made it as durable as a 740 it would have probably been ok,but man they give a lot of problems,they did make it easy to remove though ;)
Hey Bill, Did any of these guys see that your tranny, on ebay, was built for odrive? oldebusman
Quote from: chessie4905 on February 26, 2018, 10:36:14 AM
How many miles have you put on it since installing? Have you had any issues? Are you using the VS2-8 planetary for overdrive or the planetary from the VS2-6? Thanks.
If you're asking the OP he hasn't been active for over four years so you'll likely never get a reply from him.
I asked him about that last week when I noticed the fittings on the bell. I wanted to know if he had the rest of the od parts. He said only the trans. He has had the od in his transit for several years. Works great with no issues.
Howdy
I would be very interested in the VS-2 parts list and details, if someone has them on offer.
I run a lot on a stretch of freeway that is 120kph (75mph). My RTS (1994/S50/Vr730r) maxes at 90kph with me running against the limiter the whole time. The one benefit is that I have done better than 22l/100km (about 11mpg) - was a shoulder season trip, so don't know if I was running winter or summer blend. On highway I always get better than 10mpg.
The RTS is so stable and comfortable at speed that I would like to be able to run about 70-75 without the roughness that comes with banging off the limiter.
cheers
Ken
Have you been into your engine computer to be sure you aren't at the mercy of the transit company's governor setting???
90 kph sounds exactly like it is held back.
As for your experience at the governor, that sounds strange?
Should accelerate to governor setting and then just cruise there?
happy coaching!
buswarrior
If I could keep my speed down to 56 mph in my RTS, I'm sure I could get 10 mpg. But I can go 80.
I puttered along this winter around 63 for 120 miles each way. Got 6.7 mpg or so... was kind a bummed. Winter fuel?
Quote from: neoneddy on April 16, 2018, 10:02:10 PMI puttered along this winter around 63 for 120 miles each way. Got 6.7 mpg or so... was kind a bummed. Winter fuel? [\quote]
Yeah, winter fuel surely doesn't help. But just about everything is against us in the winter -- very small things like tire flexibility, lubricant viscosity, even air drag all build up to make a difference. Winter fuel is blended to a formula that's set by the petro companies -- it's based on month of the year and location; the November fuel baseline in Florida very different from that in Minnesota and, of course, the baseline in Minnesota is lower in February than Florida. (And California rules make it impossible to buy anything but the most expensive fuel.) Add to that the the refiners/distributors/jobbers have to be sure that there's a margin plus they take every advantage to cheapen their fuel in the process, even if it makes for poorer fuel consumption.
You might want to try that run again when it's 82 degrees out and see if it makes a difference. (My guess is that you'll see an effect, just not a lot.)
Quote from: neoneddy on April 16, 2018, 10:02:10 PM
I puttered along this winter around 63 for 120 miles each way. Got 6.7 mpg or so... was kind a bummed. Winter fuel?
How did you measure this fuel economy?
120 miles each way? How many trips to the pump?
One extra pull on the pump handle changes the calculation by how much?
Don't beat up the coach or the fuel if the scientific methods are suspect?
happy coaching!
buswarrior
Quote from: buswarrior on April 17, 2018, 07:12:35 AM
How did you measure this fuel economy?
120 miles each way? How many trips to the pump?
One extra pull on the pump handle changes the calculation by how much?
Don't beat up the coach or the fuel if the scientific methods are suspect?
happy coaching!
buswarrior
I kind of wondered the same thing. It dawned on me it is quite difficult to get an accurate MPG calc off my MC8, particularly when running the generator that is connected to the primary engine fuel supply. The upside is I'm likely getting better mpg than I had calculated. Net net though as the credit card seems the same amount. LOL