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Bob Caddel (Bcaddel)
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Username: Bcaddel

Post Number: 1
Registered: 9-2008
Posted From: 75.15.221.31


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Posted on Sunday, September 28, 2008 - 11:31 pm:   

My parent rebuilt their 1971 MCI-7 about 10 years back and enjoyed it for a number of years. They have recently decided it is a little too much for them to head out on the open Road, now that they are 80. Actually they quit driving at around 76 years old but only admitted a few months back that they wouldn't be driving it anymore. Something we will all have to face someday I assume....

My wife and I purchased the bus from them and drove it from Texas to Reno, Nevada a couple of weeks ago. The 8V71 engine was rebuilt in 2000 and a rebuilt Allison 5 speed transmission was also installed at the same time. My concern is, that there is no tachometer on the dash. I have done quite a bit of reading on the board here and many of you seems to agree that a Tach may not be needed. We followed this advise and left it in 4th gear almost the whole trip, resulting in 60 mph (on level ground). 5th gear went up to almost 75 mph but we didn't do to much of that.

We averaged 6.9 mpg for the 1,600 mile trip. The engine runs great and we parked it in our drive way over a week ago and there isn't a drop of oil underneath the engine. I am very happy with how she preformed, but since I can't hear the engine revving up and I don't have a tach, I have no idea if I am over revving the engine or not.

Any advise, should I install a tach or is it safe to leave it in 4th and put the pedal to the metal?
niles steckbauer (Niles500)
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Username: Niles500

Post Number: 860
Registered: 11-2004
Posted From: 71.180.124.221

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Posted on Sunday, September 28, 2008 - 11:41 pm:   

The Allison should keep you in the right RPM's all the time - FWIW
Luvrbus (Luvrbus)
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Username: Luvrbus

Post Number: 544
Registered: 8-2006
Posted From: 74.33.57.23

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Posted on Monday, September 29, 2008 - 12:15 am:   

Bob a tach is nice even with the Allison I use mine for downshift points I don't like to wait for the transmission to down shift doing it before the downshift helps get over the hills.Buy you a tach a good investment
George M. Todd (George_mc6)
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Username: George_mc6

Post Number: 567
Registered: 8-2006
Posted From: 207.231.75.253

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Posted on Monday, September 29, 2008 - 1:37 am:   

Bob,
The engine is governed, so it will not over-rev in power. There is no reason to hold it in 4th gear, and reasons not to. The 71 series engines get their best fuel mileage between 1700 and 1800 rpm. Running it wide open in 4th will be about 2100 rpm, which is about normal max governed engine speed. Running it at part throttle in 5th would have produced better fuel mileage. 5th in a 754 Allison is direct drive, not overdrive, (neither here nor there.)
Welcome, and don't hesitate to ask!
George
Moe Hollow (Moehollow)
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Username: Moehollow

Post Number: 56
Registered: 12-2007
Posted From: 71.102.20.26

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Posted on Monday, September 29, 2008 - 5:30 pm:   

Just installed a tach. Absolutely not a necessity, but neither is the bus. I like it.
RJ Long (Rjlong)
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Username: Rjlong

Post Number: 1425
Registered: 12-2000
Posted From: 67.181.166.160


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Posted on Tuesday, September 30, 2008 - 12:17 am:   

Bob -

Welcome to the madness!!

"The 8V71 engine was rebuilt in 2000 and a rebuilt Allison 5 speed transmission was also installed at the same time."

I'm a little curious about the Allison in your coach. Does the shifter say "R-N-D-4-3-2-1" or does it say "R-N-D-3-2-1"? Some folk confuse the transmissions because the four-speed feels like a five speed when it shifts.

Now, to answer your question, in some regards, a tach is a toy. To others, it's an essential piece of instrumentation.

You can get by without one - how many thousands of highway and transit buses have pounded the pavement without one over the years - but having one is also nice.

Alternator-driven is the easiest to hook up - search the archives for lots of suggestions (one of the blessings of this board, btw.)

Read about shifting in the "Articles of Interest" section of this site, that, too, might be helpful.

Nice thing about this crazy hobby is that you can do it your way. . . It's your call.

FWIW & HTH. . .

:-)
Bob Caddel (Bcaddel)
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Username: Bcaddel

Post Number: 2
Registered: 9-2008
Posted From: 63.201.27.196


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Posted on Tuesday, September 30, 2008 - 11:27 pm:   

RJ
The transmission is a Allison MT 654 and the shifter says "R,N,1-5,1-4,1-3,1-2,1" so I am pretty sure it is a 5 speed. I really think running in 4th at 60 mph is about where I want to be, but I also think I would like to get a tach just to make sure I am running the RPM where it should be and in reading the board that may be my best chance at getting above 7 MPG.

I really like the looks of this tach (digital) but dont exactly understand how it gets RPM from installing a transducer on the fuel injector line?
http://www.tinytach.com/tinytach/diesel.php#
I think I will take your advise and search the archives to see what others are doing about tach before I actually purchase one. Thanks for your input
Luvrbus (Luvrbus)
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Username: Luvrbus

Post Number: 546
Registered: 8-2006
Posted From: 74.33.57.23

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Posted on Tuesday, September 30, 2008 - 11:39 pm:   

Bob, that will not work on a 2 stroke it is made for a rail fuel system check these people in Phoenix for a good tach www.precisionspeed.com

(Message edited by luvrbus on October 01, 2008)
RJ Long (Rjlong)
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Username: Rjlong

Post Number: 1426
Registered: 12-2000
Posted From: 67.181.166.160


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Posted on Wednesday, October 01, 2008 - 2:48 am:   

Bob -

I'm sort of surprised it's an MT-654, usually you'll find an HT-754 in the full-size coaches. The MT's are a little lighter duty, but will hold up fine in RV service. But double-check - look on the driver's side of the transmission, above the oil pan, there should be a plate with the ID info on it.

Also, I looked at the photos of the coach through the link you provided in your profile. From that I can tell that you've got a late production MC-7 - the dashboard is the same as those found on the MC-8s, which came out in early '73. (That's a "good thing" - the original 7's dash is UGLY, IMHO.) The "1" and "2" black-on-white number stickers in the dashboard & switch panel photos tell me that this coach is an ex-Greyhound unit. (I suggest that you remove those number stickers, btw, for reasons you can probably figure out.)

Now, reality check: I spent 25+ years in the bus industry, several of which were pounding I-80 over Donner Summit into your neck of the woods. Drove GMCs, Eagles and MCIs. AT-equipped MCIs and Eagles averaged 5.5 - 6.5 mpg all the time, seemingly regardless of which two-stroke was in the tail. Stick shift GMs got around 7 - 8, but they're also 8,000 lbs lighter to begin with.

The point I'm making is that the mileage you're getting is typical for a 40-foot, 3-axle coach, and there's not a whole lot of room for improvement, as long as you're running the two-stroke Detroit.

Fifth gear @ 60 - 62 mph will give you better fuel mileage than 4th for one simple reason - the engine's turning about 250-300 rpm LESS in fifth at the same road speed, yet is still within the power curve (albeit at the low end). Less rpm = less fuel burned. Simple. (Question: What size tires are on the drive axle?)

Take your coach for a drive and find out what the maximum road speed is in each of the lower gears, 1 - 4. Make a mark on the speedo (if it's working) at each maximum. Now you've got the range for each gear to operate in, w/o a tach! Plus you've got your marks as to when to downshift while pulling Donner! Now how easy was that, eh?

You will get better performance out of the coach if you shift it manually, but skip first unless you're wiggling into a campsite or something similar. Use "1-2" to get started, then work your way up.

When up-shifting manually, and for best performance, drive it like a stick shift - run it to the governor, then shift. Or let it shift itself, easing up slightly at each shift point to smooth it out.

Bottom Line: Put it in "1-5" and go. Downshift manually, at the appropriate time, as marked on the speedo, when pulling grades, otherwise, leave it in "1-5". (You can leave it in "1-3" around town if you don't want the tranny to hunt back and forth between gears all the time.)

FWIW & HTH. . .

:-)



PS: Check your profile's emailbox.
Bob Caddel (Bcaddel)
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Username: Bcaddel

Post Number: 3
Registered: 9-2008
Posted From: 63.201.27.196


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Posted on Wednesday, October 01, 2008 - 9:23 am:   

RJ
I have the work order from AZ Transmission exchange in Pheonix on the transmission install $9,754. My folks had told me they were under the impression it was the best choice for their application, but I would imagine you are correct about it being not as heavy duty as most. That would have been a chunck of money for my dad back then so I bet he could have easily been talked into a lighter duty transmission if he felt it would do the job.

The reason I kind of like running in 4th gear up against the govenor is when I shift into 5th I am constantly varying my speed from 60 up to over 70. My day to day auto is a F-350 and have no problems keeping a steady speed on the highway even when I'm pulling a horse trailer but the bus seems to be a little harder to keep right on a certain speed without really concentrating. Keeping it in 4th I just put my food down and forget about it. I was able to average 6.9 mpg on our maiden voyage from Texas to Reno so as you mentioned thats on the high side of expected MPG.

I had read several of your post (and many others) before we went to pick up the bus and use many of your tips on the trip home. This board is great for that reason. I was very concerned that at my age (60)this would be too much of a project for me but with all the knowledge posted here, I am able to find many answers to questions I dont even know I have until I read the answers....

Nice new Hobby for the wife and I.
Bob Caddel (Bcaddel)
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Username: Bcaddel

Post Number: 4
Registered: 9-2008
Posted From: 63.201.27.196


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Posted on Wednesday, October 01, 2008 - 9:30 am:   

RJ
I have the work order from AZ Transmission exchange in Pheonix on the transmission install $9,754. My folks had told me they were under the impression it was the best choice for their application, but I would imagine you are correct about it being not as heavy duty as most. That would have been a chunck of money for my dad back then so I bet he could have easily been talked into a lighter duty transmission if he felt it would do the job.

The reason I kind of like running in 4th gear up against the govenor is when I shift into 5th I am constantly varying my speed from 60 up to over 70. My day to day auto is a F-350 and have no problems keeping a steady speed on the highway even when I'm pulling a horse trailer but the bus seems to be a little harder to keep right on a certain speed without really concentrating. Keeping it in 4th I just put my food down and forget about it. I was able to average 6.9 mpg on our maiden voyage from Texas to Reno so as you mentioned thats on the high side of expected MPG.

I had read several of your post (and many others) before we went to pick up the bus and use many of your tips on the trip home. This board is great for that reason. I was very concerned that at my age (60)this would be too much of a project for me but with all the knowledge posted here, I am able to find many answers to questions I dont even know I have until I read the answers....

Nice new Hobby for the wife and I.
Tom Christman (Tchristman)
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Username: Tchristman

Post Number: 23
Registered: 1-2006
Posted From: 66.218.33.156

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Posted on Wednesday, October 01, 2008 - 11:10 am:   

You should just put it in D and go. If it shifts into 5th, the transmission says it is OK. Lower RPM equals better fuel mileage-no matter what the engine. If it starts to lug to much the transmission will down shift for you (if it is adjusted correctly). I have a V730 and installed a tachometer about a year ago. I installed a tach generator on the tach drive off the blower. I really enjoy having it, and makes it possible to run at a better rpm. Now I cruise at 58 which is right at 1800rpm. Good Luck, TomC
Jim Wilke (Jim Bob) (Pd41044039)
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Username: Pd41044039

Post Number: 312
Registered: 2-2001
Posted From: 69.77.156.190

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Posted on Wednesday, October 01, 2008 - 2:48 pm:   

I used to have the fast/slow problem on my bus & it has a stick shift. My solution was to install a cruise control. It will keep the bus where you set the speed. It is also GREAT to not have a tired throttle leg!

You will also notice as you get used to your bus that you will be able to tell by feel & by ear about what speed you are running at. I used to be able to tell my wife how fast she was going within about 2-3 mph when I was lying down on the couch.
Tom Caffrey (Pvcces)
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Username: Pvcces

Post Number: 1226
Registered: 5-2001
Posted From: 65.74.65.209

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Posted on Wednesday, October 01, 2008 - 9:55 pm:   

Bob, one way to look at the right RPM to run the engine is to realize that it is the best speed for serious work. When running along with a light engine load, lower RPM is fine and will save you some fuel.

If you have the C60 injectors with standard timing, you have a VERY wide powerband. If you have the N65 injectors with advanced timing, then you have more power but your powerband is quite a bit narrower. Narrower means more gears.

This is why the truckers with ten speeds or more used the latter configuration, but standard shift buses did not.

The rated horsepower was about 270 and 304, respectively. The 304 was known as a 318, but that rating comes from using different standards.

For what it's worth.

Tom Caffrey PD4106-2576
Suncatcher
Ketchikan, Alaska
Mike Eades (Mike4905)
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Username: Mike4905

Post Number: 171
Registered: 12-2000
Posted From: 68.200.183.92

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Posted on Friday, October 03, 2008 - 4:16 am:   

Bob I have 4905 with 65 injectors and advanced timing. I pull a 24 foot box trailer and I average about 5.25 mpg. I am happy with that. No tach and I haven't found a need for one. I also drive road coaches for a large company. Our new coaches have tachs. They are used to set the computer. The drivers almost never use them. Maybe on a hill run off, so we can tell if the jake is working. We new mci's, prevost's,and setra's all us ethe same type of setup. For the most part that is what our tach's do.
FAST FRED (Fast_fred)
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Username: Fast_fred

Post Number: 485
Registered: 10-2006
Posted From: 208.100.193.159

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Posted on Friday, October 03, 2008 - 7:09 am:   

"Bob, one way to look at the right RPM to run the engine is to realize that it is the best speed for serious work. When running along with a light engine load, lower RPM is fine and will save you some fuel."


To continue this concept , most folks feel it is necessary to use 60% or more of the rated HP from a DD 2 stroke .

That's why the fuel consumption usually goes up with "big" injectors , even when driven modestly.

Our N60 Sportscar delivers 9+ and on RARE! times 10 MPG.

At 70mph 9 mpg translates to about 8GPH.

Since a DD will create only about 16 HP per gallon ,128 or so HP is being used.

On the chassis dyno at purchase the engine pulled 195 HP at the rear wheels..

So we are using a reasonable percentage of the power produced , therefore acceptable fuel mileage.

FF

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