mc5 fuel economy - yic

Damn Yankee · January 27, 2009, 07:34:44 AM

I only drove it twice last year and I'm not positive on the shift points but I think it shifts to 2nd at 15 mph, 3rd at 25 mph and 4th at 45 mph. not sure of the rpm's but I rarely get to 2100. The PO didn't set the governer to specs, I have had it up to 80 mph at 2500 rpm (down hill & daydreaming) Going up hill it will upshift on it's own at 45 mph. problems with detent cable adjustments or trans governor are common.

johns4104s · January 27, 2009, 10:26:38 AM

Gracius Amgo Viento,

Sounds like blocked fuel filters, Thow the old ones away, buy new ones say for $25.00 then whos the hero you,

Olay

John

Fredward · January 27, 2009, 07:40:45 PM

My -5A with 8V71 and 4 speed has N70 injectors and it gets between 5 and 7 depending on if i'm towing the car and if i'm keeping it at 2000 - 2100 rpm which is where it seems to like to run. That produces about 72 to 75 mph according to GPS. It also starts immediately down to about 50. From 40-50 its bump and run. Below 40 it takes ether. I have two group 31 start batteries and i run straight 40.

I had the rack run last winter and it took about an hour and the mechanic charged about $70.00. Of course I had the engine on a dolly, not installed in the cave. It made ahuge difference on how it sounds, and how much blue/white smoke it produces when started. Running the rack is simple if you know what you're doing and have the Detroit issue curved wrenches. Otherwise, pay to have it done becuase its touchy.

Definitely replace fuel filters and check air filter before spending any money.

I don't know how anybody gets more than 75 mph out of a spicer equipped MC-5 unless they have the RPMs turned way up.

FRED

Barn Owl · January 27, 2009, 09:56:45 PM

Wow, I have seen so many outrageous claims on mpg I thought there was something seriously wrong with my bus. I also have N70 injectors with my 8v71 and V730 and am happy if I get 7mpg. Up and down these mountains it is more like 6 to 6.5. I plan on having my rack run as soon as I can find someone locally that I feel good about. I hope that helps with my starting because mine is difficult unless warm and seems to have injectors that have difficulty waking up the first few seconds. I don't have any blue smoke but too much black if I get into it. Thanks for sharing Fred.

johns4104s · January 28, 2009, 05:27:45 AM

Fred,

I had /have a 4104/671 which was always hard to start cold until I found out that the one way valve holding the prime in the head was allowing the fuel to drop back,not holding the prime good enough. Once I change out the valve no problem.

John

zubzub · January 28, 2009, 10:41:02 AM

Quote from: johns4104s on January 28, 2009, 05:27:45 AM
Fred,

I had /have a 4104/671 which was always hard to start cold until I found out that the one way valve holding the prime in the head was allowing the fuel to drop back,not holding the prime good enough. Once I change out the valve no problem.

John

Hi Johns4104s. I hadn't noticed there was a one way holding prime in my 671, is it under the valve cover? Need to look at da book again I suppose.

TomC · January 28, 2009, 04:37:38 PM

If you have a mechanical 6-71, 8V-71, 6V-92, or 8V-92, a trick to starting the engine in cold weather is to start it from the back by the engine. What you do is to turn on the ignition, then hold the stop lever on the governor shut with your fingers. Then start turning over the engine-after a count to five slowly release the lever over the next 5 seconds, and the engine should start. This works because, first you're turning the engine over without fuel preheating it, and the shut off lever on the governor retards the timing to make starting in cold weather easier. I've done this several times both in the past with my truck with the 8V-92 and my bus with 8V-71. So far, I've only used ether when the weather was below 0. Good Luck, TomC

Lin · January 28, 2009, 06:08:11 PM

Tom,

I am a little confused. Are you saying to reach around or in the middle of the fan belt to hold the fuel lever shut? I am really shy of getting near that belt when it is moving. If I aired up with the electric compressor first, would holding the rear stop button do the same thing?

steve5B · January 28, 2009, 06:27:41 PM

Tom C,

Your last post is some real good info on starting in real cold weather. I'll try it next time I fire the old girl up. Our temps here

in Indiana rarely get extreme as others around the country, but here of late, we've had our share. Back to the post. my 5B

has a 8v-92 and it sips fuel at 75-80 for what reason I can not explain. May be the gear ratio? at those speeds the engine

seems like it's hardly running!

Steve 5B.....

Fredward · January 28, 2009, 07:54:15 PM

Steve - how in the world does an 8V92 fit in the hole an 8V71 fits into with about 2" of clearance? After personally removing and re-installing my 8V71 i can't imagine how that mill would fit. And secondarily, how does it stay cool? I have to drive with the temp gauge when the weather is above 80 degrees. Did you install that mill? Can you send pictures of the motor mounts/rails?
Fred

steve5B · January 29, 2009, 06:51:58 AM

Fred,

I have that question ask all the time, when I bought my bus out of Canada from Trailways they re powered their units from the

71's to the 92's natural. If I knew how to download pic's of it I would. As mentioned the fuel mileage is fantastic, power is

awesome. It fits in there without any problem. I guess because it doesn't have the turbo. The only thing that is noticeable

is that it seems to have larger heads from what I can tell. Never had a heating problem!

Steve 5B....

Tom Y · January 29, 2009, 09:50:19 AM

Steve 5B, What does sipping fuel equal in MPG? Thanks Tom Y

steve5B · January 29, 2009, 08:42:55 PM

Tom,

What I will state, and have no reason to fabricate the truth, she will get 10-11 MPG. I use special products in the engine,

Trans, and the rearend. There will be a lot of controversies over this statement but that is the truth. I have mentioned

this in previous post. One being the higher CETANE of the fuel the better the performance and fuel economy for starters.

As for the heating issue as formentioned, I use pluronic 60 mixed in the radiators. Cuts heat by 25plus degrees.

Steve 5B....

Lin · January 29, 2009, 09:48:24 PM

Steve,

I tried to see what you were talking about and came up with pluronic L61 and a product called Kwick Kool. Is that what you are using? Do you know of any independent lab work on these things?

TomC · January 29, 2009, 10:32:55 PM

Lin- I have a V drive with no belts (everything is gear driven) so I can access my governor without getting near anything spinning.
The 8V-71 and the 8V-92 are exactly the same dimensions externally, except for the addition of the vibration damper (what looks like a small flywheel) behind the crank pulley. As to cooling, the 8V-92TA is THEE hardest engine to cool-except if you had an even larger 12V-71 or 12V-92. This is why, converting to a 4 stroke with air to air intercooler will be less strenuous on the cooling system. Good Luck, TomC