mpg to Florida

[artvonne]

BK has it figured out. Anything above 5 mpg is gravy so enjoy it. If you bought such a rig thinking it would save you money then you might need to check on your intake of meds again!!

  But it is nice to see that 5 mpg doesnt have to be the upper limit. I still remember when I was young, I asked a city bus driver what a city metro bus got for mileage. He said about 7. At first that sounded awful, but as reality sank in I began to see how awesome that actually was. A neighbor once gave me a 73 Buick 455 station wagon, that useless car never did better than 4 or 5 mpg. But gas wasnt $3 gallon yet either. That a giant city transit bus full of people could get better mileage than that stupid car still bothers me.

  It also appears that many here are pushing the later model 40 foot (and longer/wider/taller) buses, most are running rather heavy conversions approaching 40K pounds, and many have big power to make it move. That most are staying above 5 with those buggers is pretty remarkable. But wouldnt it be nicer to plan for 7 and never see it?

[RJ]

Art -

Oddball bits of info for you:

For more discussion about Detroit engines, try the Detroit Diesel group on Yahoo.

Stock 6V71 w/ a 4-valve head puts out 238 hp and 650 ft/lbs of torque with N60 injectors - same as an inline 6-71.  Incredibly "gutless" in a 40-foot bus, can barely get a Fishbowl up to 60 mph, even with the lower top speed transit gearing (4.56:1 or 5.33:1, compared to an MCIs 3.73:1).

A 6V71T puts out 275 hp and 801 ft/lbs with N75 injectors, whereas the inline 6-71T puts out 290/810.   

Stock 8V71 in "bus trim", like BW said, puts out 275 hp and 770 ft/lbs w/ N60s, 304 ("318") and 866 ft/lbs with N65s.

An 8V71T can be configured to either 350/990 or 375/1064 hp/torque, depending on injectors.

Stock 6V92T in "bus trim", again, 275 hp like the 8V NA, but with slightly more torque - 816 ft/lbs.

Play with the injectors (9G90s), and you can bump it to a reliable 350 hp with 1020 ft/lbs.

At altitude, the 350 hp 8V71T will out pull the 6V92T on long grades.  8V92TAs will easily outrun both.  BTDTHLB.

71 series can be set to 2300 or 2400 rpm (fire service) and still be reliable, 92s don't like more than 2100.

Either engine series, when freshly rebuilt, will last forever in RV service with good routine PM.  Your choice.


When I drove professionally, all of the MCIs in the fleet (8s, 9s, A3s) averaged 5 - 6.5 mpg, depending on where you were going and what you were doing.  Didn't seem to matter if it was a stick or auto, 8V71, 8V71T, 6V92TA or 8V92TA, overall mileage averages were the same.  These coaches have the aerodynamics of a brick, basically.

The 40-foot GMC Buffalos (none with the retractable tags) averaged 6 - 7.5 mpg.  All 8V71s with 4-spd manuals.  Lighter and "cleaner" aerodynamically than the MCIs.  Weight makes a difference!

The 4106s in the fleet were the mileage champs - they consistently got 8 - 9 mpg, regardless of how hard you drove them.  Driven conservatively, on flat ground, you can squeeze 10 out of an '06.  (Hard to do -  these aren't called the original "Sports Car of Buses" for nothing!  The RTS with a 4.10 rear axle is the second generation - right, Geoff?)

As most 4104 drivers will tell you, getting 9 - 11 mpg is pretty easy.  They're the "cleanest" aerodynamically (at least those that haven't been capped), and the 6-71 just chugs right along happily in it's "sweet spot" at 60 mph.

All of the above are mechanical engines, no DDECs.

I don't think anyone here will dispute the fact that running 75 mph can cost you somewhere between 1 - 2 mpg in fuel economy compared to running 65.   Simple physics - it take so much hp and torque to push these bricks thru the air at speed.

Make sense?

FWIW & HTH. . .

 


Footnote:  Your city bus driver when you were a kid probably never filled the fuel tank, either.  IBME that transit buses, based on the nature of their operation, usually get between 2 - 4 mpg - even worse now with all the CNG-powered fleets to keep the environmental wackos happy.  They're getting the equivalent of 1.5 mpg.  Progress!

Oh, and as for that MCI w/ the broken engine?  500 bucks max.  It'll cost you more than than to have it towed home.  Keep looking, better bargains are out there!

 

[belfert]

I plan my trips based on getting at least 7 MPG.  I do usually overestimate the price of fuel though.  I planned on paying $3.50 a gallon average for my trip to Arcadia and I probably averaged around $3.20 a gallon.  I only paid $3.50 a gallon on my last fillup at home of around 30 gallons.

7 MPG would be great for a transit bus.  The city buses here average about 3.7 MPG per news reports.  I'm not sure if this is the average of all 885 buses that include city, suburban, and express routes, or just the average of the 40 foot transit buses.  The agency operates 45 foot MCIs, 40 foot transits, and 60 foot articulated transits.  I was shocked to hear how low the MPG is for city buses.

[buswarrior]

If we drove any of our coaches like a transit bus, we'd see the same dismal results.

Either full fuel, or full brakes, no cruising here, huge fuel burn to get that thing rolling, full horsepower use, torque converter unlocked, and in the lower gears, lots of spin for little movement.

That driver from your youth did not know of what he was speaking.

happy coaching!
buswarrior

[artvonne]

  Remember, that was almost 40 years ago and were talking a GMC fishbowl running genuine #2 fuel oil, if it makes any difference. Hey, im just the idiot asking questions lol. But several others said simular, FWIW. People do like to BS though... But they were the same people who told me 4104 would get 12 plus. Which back when we had good fuel was probably realistic if they can still hit 11 running the crap we have today.

  Right now I get between 6 and 8 pushing the bounder, usually with my foot mashed hard down on the floor. That supposedly makes 190 HP, so its apparently maxed out full pushing that sucker through the air at 65 to 70, yanking the Jeep along. Im at around 20K pounds right now with full tanks. I just dont see how I can do any worse with a Bus. If I could get the same economy shoving a 40 foot -9 down the highway, I win! If I can do better, its a win win. Weight, aerodynamics, speed, BTU of fuel, rolling resistance, driving habits and fuel efficiency all work together. Change any one, and you will effect fuel economy.

  RJ, in regards the broken motor Bus, I am rapidly losing interest before I even see it. Y'all are doin a good job convincing me. And I do appreciate it.

 

 

[Ed Hackenbruch]

I usually start looking for fuel when i have gone 700 miles. I figure that at 7mpg i have used 100 gallons and still have 44 in the tank. I got out my fuel log to see how i had done over the years.   As of the first week of Oct. (haven't gone anywhere since then)  in 6 & 1/2 years we have gone 32,106 miles, used 4343.2 gallons of fuel at a cost of $12,686, with an average price of $2.92 per gallon, and gotten 7.39 mpg. Have had a high of 8.2 and a low of 5.9 mpg during that time. This is in a 68 MCI 5A that  has gone from 27,450 lbs. to just over 29,000 lbs. over the years.

[Don Fairchild]

I run all over the west and to new Orleans and Bk's from time to time. My coach weighs in at 34,950 loaded and over 41,000 when I pull my truck. I pull the truck most of the time. When I leave Bakersfield I will climb a hill some of them only last a few minutes to over 15 minutes, like going to Seattle. I have  an 8V95TA set at 550HP and a 6Sp Allison. I run at 68 mph as much as possable. That is 1650 rpm. I average 8.4. When I don't have the truck on the back I get 8.9 any body can plug into the computer and see the fuel consumption. You can see for your self what I get.

Don

oh and the 8V71 set at 425 hp 1202ft lbs tq will get you up a hill.

[luvrbus]

Don, you need to reduce it back to 500 hp buddy when you were getting 9+ the price of fuel today 300 hp is looking good just a little more time in saddle.
fwiw Art the 4104 with a 6-71 inline DDEC makes for a good setup 330 hp 11 to 14 mpg and that will get you over the hill too   


good luck

[Ed Hackenbruch]

Should have mentioned that i have an 8v71 that has just under 50,000 miles on a rebuild, no turbo, supposed to have been bumped up to 318 or 308 hp depending on who you are talking to. Also i have a MT 644 auto tranny.

[DMoedave]

New and Older Trailways buses. finally! Been trying to post this for 2 days. Sorry you gotta turn sideways. I think we would  be more areodynamic than the new one even with our door open lol.

[JohnEd]

Don,

What bus do you have?  Is your "TA" an air to air after cooler or the DD version of the air to water that sits under the blower?  My impression has always been that the DD would benefit greatly from an after-cooler that was positioned between the turbo and blower and I am curious as to your thoughts on that.

You seem to be getting exceptional efficiency.  I know the 6 speed Allison has a lot to do with that but it can't be the entire answer.  For those that don't know, and I do barely, you are in the business of rebuilding, designing and specing DD engines for all applications on land and sea.  You once told me that you could get some hellacious power from a two stroke but the problem was cooling it.  Boat motors have that cooling problem resolved, and as you pointed out, those 900 HP(?) tank motors had radiators that were 9 X 5 feet and were 20 core or so and I am making those dimensions up for the point.

I know you consult and you are paid for that service and I hope you are doing well in that regard.  An awful lot of this seems to be mix and match parts from all over and mainly from DD's tournament assortment of "stuff".  Can you share some of the info on what you do to make 550HP and get that kind of efficiency from an 8V92 without selling yourself out?

Seems sad to me that DD has that DDEC so locked up as to make it adjust proof.  What DDEC do you use and what injector model.  Is there a way around the constricting and inflexible DDEC programing?

Thanks,

John 

[Don Fairchild]

John, I run a CCTS liner that is highly modified from stock. They have liner ports that are angled in and tilted over at precise points to facilitate air movement. I run a stock 450 hp DDC injector that I had a co. Change tips from a 9-0058 to a 9-0062 and up the pop pressure. I run a stock DDEC III  ( parlor coach) program set at 475hp. I set my injectors at 1.484 ( stock is 1.520 valves at .014 and Jake's at .057 I will also tell you that when the heads were rebuilt I shimmed the valve springs to proper height and pressures.

On the engine dyno this combination shows 550HP at 1800rpm and 1550 ftlbstq at 1400rpm

We have long rod short piston combonation we are playing with that in early tests shows over 1700 ftlbs tq at 1400rpm and 600hp at 1750rpm. This is in an mui engine. we will be putting together a DDEC some time this summer to see how it will do.

As to some of you other questions. There are way around DDEC programing but it is all done after market.
Big Jim Done has a 4-71T CAC DDEC that he has mounted midship in a Toyota tuck. He runs at Bonnivile salt flats. It is putting out close to 600hp and turns over 3000 rpm.

I like the air to air cooling on a two-stroke engine. It has the same effect as on a four stroke.  As to the marine engines we are approved up to 700hp with the 12V71TI engines and you are correct with ocean as a radiator using With keel cooling and raw water intercoolers you can really put some hp into these engines with wonderful results.

Hope this answers you questions.

Don

[uncle ned]

I saw a set of Dons liners and pistons at BK's several years ago.  I have never seen better machine work on any engine part. Just wish I had met Don before I replaced my liners and pistons on my 6v.

uncle ned

PS he gave several ideas on a air to air cooler for "HUGGY" that is in the works. gathering up parts for the job.

[belfert]

The EPA is the main reason engine computers are locked down.  If the computer is programmed differently it might not pass pollution requirements anymore.

[JohnEd]

I run a CCTS liner that is highly modified from stock.

Do you run the CCTS, and I am going to take a WAG and assume that that isn't a DD part, because it is easier to mod?

They have liner ports that are angled in and tilted over at precise points to facilitate air movement.

Did you get blank liners and "install" your own port dimensions and orientation?  Shades of my 2 cycle dirt bike days our "special" transfer port mods.  And Holy crap did we get more power.


 I run a stock 450 hp DDC injector that I had a co. Change tips from a 9-0058 to a 9-0062

The injectors I have seen have a ceramic head that has the hole shaped to shape the pattern for best atomization.  Am I right in assuming that the 58 and 62 numbers relate to the jet diameter?

up the pop pressure.

Is this the fuel pressure in the rail?  I didn't ask the pressure cause I think that might be classified.

I run a stock DDEC III  ( parlor coach) program set at 475hp.

So there is no mod to the DDEC?

I set my injectors at 1.484 ( stock is 1.520

Showing my ignorance:  I thought only the MUII had a cam pushing on the injector.  In that case reducing the gap would increase the duration of the open period and dump more fuel.  So in the DDEC III the same theory applies and there is a similar adjustment?  I did admit to being stupid on this topic.

valves at .014 and Jake's at .057

I ran my valves ad a reduced gap to max the air flow and I guess you have the same motive.  In readings here I have gathered that the Jake is very sensitive to "gap" and will fall off dramatically if the gap is to large.

I will also tell you that when the heads were rebuilt I shimmed the valve springs to proper height and pressures.

Maybe that was a test?  Shimming the springs won't change the valve height as the shims I have seen go under the spring between the head and spring.  I guess the top of the spring would be altered if the shim was installed between the spring retainer and the top of the spring but putting it there would add to the valve mass(effective) and promote came wear and yield nothing in valve lift..  I must be missing something.  At any rate you are getting in top what I call "blueprinting" the head and changing the geometry.  I also had to test for spring bind after shimming but I eventually went with brand new springs and changed them out to get a hand select match across the head.  Do you also check the valves for equal and proper lift after a micro check of the cam?  Do you do a three angle grind on the valve seat or do you make more passes?  Do you port or polish the heads or pistons?

We have long rod short piston combination we are playing with that in early tests shows over 1700 ftlbs tq at 1400rpm and 600hp at 1750rpm.

That sounds like you are changing the compression ratio.  I am clueless as to all the details and reasons for it but I recall people that upgraded to a turbo installed "two piece pistons" and I think that was for better piston cooling.  You don't sound like you are doing that and I wonder about all the "stuff" I have read over the years.  Nice HP numbers, by the way.

As to some of you other questions. There are way around DDEC programing but it is all done after market.
Big Jim Done has a 4-71T CAC DDEC that he has mounted midship in a Toyota tuck. He runs at Bonnivile salt flats. It is putting out close to 600hp and turns over 3000 rpm.

I like the air to air cooling on a two-stroke engine. It has the same effect as on a four stroke. 

I follow that.  I was talking about having the air to air after the turbo...as usual, and keeping the water to air under the blower to help get rid of the heat generated by the blower.  I read a long time ago that the water to air stock after cooler was "very" restrictive and you got a power boost from deleting the thing.  I didn't believe that but I sure can't do much but ask questions in this arena.


 As to the marine engines we are approved up to 700hp with the 12V71TI engines and you are correct with ocean as a radiator using With keel cooling and raw water intercoolers you can really put some hp into these engines with wonderful results.

Hope this answers you questions.



Even if I could fully comprehend all your answers I don't think it is possible to answer all the questions.  Each answer begets two more questions and "begets" indicates how old that wisdom truly is.

Thank you for the kindness you have shown in answering, Don.  I will make every effort to visit your shop when I next go south.  Don't worry, you have a LOT of time for prep or evasion.

John