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Author Topic: How to increase speed  (Read 3719 times)
Eric
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« on: April 25, 2010, 05:26:55 PM »

Hello again! We are on our trip out west and thanks to all your suggestions the bus can now climb hills and isn't getting blown around! However there is this pesky 60mph deal that is driving me crazy! We are a transit bus with a 6v92ta non ddec and an atec v731 trans...what trans/rear end swapping would it take to give me a bit more top end and say a passing gear? Could my current trans be reprogramed to any benifit?

« Last Edit: April 25, 2010, 05:50:16 PM by ekhedge » Logged
Sean
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« Reply #1 on: April 25, 2010, 05:55:16 PM »

"Reprogramming" is not going to do it -- you'd need different gears, or a different rear end.

You can get some more top speed at the expense of low-end power by going to a larger diameter tire.  If you already have 12R22.5 or 315/80R22.5, there's not a lot further you can go, but changing to 24" wheels would give you some higher-RPM options.

The non-highway gearing is the single biggest drawback to selecting a transit as a conversion shell.

We have a similar issue, with a very low ratio diff (4.3).  We solve it by staying off the Interstate, which suits us better anyway.  Even when we are on the slab, we keep it to 55-60, even though our top speed is north of 70 (with the Detroit screaming).

FWIW.

-Sean
http://OurOdyssey.BlogSpot.com
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Eric
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« Reply #2 on: April 25, 2010, 05:59:13 PM »

I was figuring as such! I'm with you i prefer to stay off the interstate however time constraints don't allow it! And sometimes 55-60 you can be a hazard when the limit is 75!
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Barn Owl
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« Reply #3 on: April 25, 2010, 08:34:21 PM »

Quote
We solve it by staying off the Interstate, which suits us better anyway.  Even when we are on the slab, we keep it to 55-60, even though our top speed is north of 70 (with the Detroit screaming).


I couldn't agree more with Sean. Slow and steady wins the race and you have a better time doing it. If you need to drive over 60mph much, then you have fuel money to burn. That few mph difference adds up to hundreds of dollars over time, and the more money you spend on extra fuel, divided by small amount of time you save, is a lot of $$ per hour.


This is one of my favorite post by Buswarrier:

Quote below from: Topic: Tire inflation: MPG versus comfort

Quote
So, for your 2340 mile trip:

36 hours at 65 mph
39 hours at 60 mph

Question needs to be: How much fuel did it cost extra to save the 3 hours?

Perhaps the single biggest issue that lets the fuel companies empty our wallets, car companies sell us powerful SUV's and who knows how many collisions happen... is the inability of the human mind to get its head around the relationship between time, speed and distance.

If just one vehicle passes us, we "feel" we are being left behind. Which bothers that other head that periodically thinks it is in charge....

We are the most educated masses in recorded history, yet we still can't stand it when others pass us on the highway, and feel we are being left behind. And we let ourselves get fleeced at every automotive related turn because of it. anyhow....

My coach gets 6 mpg at 70 mph and gets 7 mpg at 60 mph.

MC8, 8V71 at the 270 hp settings, HT740, 3.7:1 diff gear.

To travel down for Jack's party:

For fuel costs, we'll use my preferred cheapest-fuel-on-the-trip stopping point, the Flying J at Wytheville VA, where fuel this afternoon is said to be selling for the low price of $2.019 a gallon....
(where did $4.50 go?)

1500 miles

70 mph = 21.5 hours = 250 gallons = $504.75
60 mph = 25 hours = 214.3 gallons = $432.67

so, saving 3.5 hours costs us 35.7 gallons/ $72.08 one way.

(At $4.50 a gallon diesel, the savings would be $160.65)

If there was a way to earn more than $20.60 per hour for those saved 3.5 hours, then the economics of driving faster and burning more fuel works.

I can choose to spend some of those savings on "back home beverages" for the ex-patriots and snowbirds.

Of course, in any road trip, and making these kinds of calculations, we need to consider that the whole trip is not made at the calculated speeds, any city driving will negatively effect fuel economy as will all the accelerating to highway cruise speed. The actual driving time is longer than our math.

If the family is inspired to get in and get out when we stop, the "tortoise and the hare" story can easily be told again. It would be pretty easy for the people on the "faster" coach to burn through 3.5 hours of sitting still during two long days of road travel. If you haven't done it, try running a log book like the commercial drivers do, you'd be amazed at how time can get burned up sitting still while you are on the road, and, relatively how little the slower moving traffic through an urban setting slows your pace across the nation.

On your bus, the differences in tire pressures you are considering will not make a difference you can accurately measure at the fuel pump with your odometer. (Hot fuel will do more to you, I might suggest) Too many other variables in operation and driver behaviour, especially when you are thinking harder about fuel consumption now.

THINK versus FEEL....

only a few will get it, the rest will subsidize?

happy coaching!
buswarrior






« Last Edit: April 25, 2010, 08:43:59 PM by Barn Owl » Logged

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John316
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« Reply #4 on: April 26, 2010, 05:07:25 AM »

I am with Ek on this one. At this point, when we travel, we can't take it leisurely. We usually run the speed limit (and chaff when we go through Illannoyance 55mph). There are some places out west that are 80mph, and that is nice.

But, if we weren't on a schedule...that would be different. From what I have seen, Ekhedge has a point. I think that driving 55 on a 75mph zone is a bit slow and unsafe.

God bless,

John
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robertglines1
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« Reply #5 on: April 26, 2010, 05:33:49 AM »

it is nice to have option..not necessarily use it....2 yrs ago my wife mother passed away ...we made it home from 650 miles away...1 hr before she passed..my wife got to say goodbye...at 70 plus....I don't normally drive that fast but the option is there...many other bus nuts are transit savvy..I would ask  these questions...is engine set at max governed speed for 6v92 ,would running faster effect my ride or speed,is it worth the 1 to 2 grand to change gear ratio,and last is the most of my driving flat land or hills??-----Yes we could have taken toad home;I don't think it would have been faster (old jeep)..air was out of question..got news at 5:30 pm far from a major airport....happy safe bussing..Bob
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JackConrad
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« Reply #6 on: April 26, 2010, 05:36:54 AM »

   We made a rather drastic change in our driving style after retiring. When we were still working, we used whatever was the fastest route (usually the interstate) and drove faster, because we always had a limited time before we had to be back to work.
   Since retiring, we do not set any schedule and take our time, mostly staying off the interstates and taking time too 'smell the roses". We rarely drive more than 200-250 milkes per day. In our bus, 60-62 MPH is a comfortable speed.  Just our way YMMV  Jack
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wal1809
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« Reply #7 on: April 26, 2010, 06:34:48 AM »

My comfortable driving speed is right at 60 MPH.  I have to be careful because the bus's drivng speed is a lot higher than that.  It will get to 80 in a heartbeat and that is too fast in my brain for safety.  I am not sure what that speed would do for my fuel economy but I am positive it is not good.  What kills me are the hills.  I can push it but I can see the results in the temp. from throwing fuel on the piston heads.  I learned this weekend just to give up the 10 miles per hour and leave my foot locked in one position on the pedal. Hit the hill at 65 and let it back itself down to 55 as you go over.  I read that on Tejas website and I am was surpirsed I could see it in the temp guage.
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buswarrior
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« Reply #8 on: April 26, 2010, 06:40:35 AM »

What differential gear do you have now?

Which tires do you have now?

Is you speed measuring device accurate? Maybe not 60?

What no-load RPM is the 6V92 set at now? Using what device to measure?

Gotta know where we are, so we'll know whether we can get someplace different?

Thanks Barn Owl!

happy coaching!
buswarrior

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« Reply #9 on: April 26, 2010, 07:08:52 AM »

My RTS top ends at 63 on flat ground (6V92TA w/V730).  I tend to drive 55 most of the time with an average mpg of 7-7.5.  Personally, I am fine with that speed.  Two years ago I made the trip to Arcadia at top speed (I was late getting going each of the two days).  My mileage fell to 5.5mpg.

With an RTS you can get a 4.10 rear end that will take you up around 70.  But that change done by itself will reduce acceleration and hill climbing power.  Later model RTS's came with the option of 50 series and ZF transmission.  Maybe the ZF would be an option to get more gears in combination with the 4.10 rear end to help maintain acceleration and hill climbing options.
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« Reply #10 on: April 26, 2010, 07:57:55 AM »

When we went to Ponca City Oklahoma on a pheasant hunt I filled up the bus until I could see the fuel in the nec of the fill tube.  When we stopped again I filled it to the same spot.  We did our cyphering and figured it at 7.8 miles per gallon.  From Oklahoma City to Ponca we were only ablt to drive 50 to 55 miles per hour because of the stuck fuel throttle.  Any faster than that and I could not shut her down.  So we had to go really slow in some spots.
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TomC
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« Reply #11 on: April 26, 2010, 09:11:32 AM »

You probably have 5.55 rear end ratio which would give you a top speed of 60mph (with 12R-22.5 tires) at 2,300rpm (which is not good for a 92 series).  I changed mine to 4.56 and changed the tires to 11R-24.5 (from 485rpm to 476rpm).  I cruise at 1850rpm which is 58mph.  2100rpm is 66mph and my top 2400rpm (which doesn't hurt a 71 series) is 75mph (but uses alot more fuel).  I am pleased with the 4.56 ratio since I live in California, am also subjected to hill climbing and serious mountains.  You could go with 4.1 ratio (which is the highest ratio you can go with the V drive).  But then some of your startability would be sacrificed. But, if you're also going to bump your engine hp to 350hp, you'd be alright.  With 12R-22.5 tires and the 4.1 ratio, you'd have a comfortable 1800rpm cruise at 61mph with a 2100rpm top speed at 72mph.  Increasing to 11R-24.5 tires and the 4.1 ratio, you'd have a comfortable 1800rpm cruise at 63mph with a 2100rpm top speed at 74mph.  Good Luck, TomC
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Eric
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« Reply #12 on: April 27, 2010, 08:53:44 PM »

Well thanks everyone! it seems my best interest may be n finding an OTR coach. Sometimes our time constraints doesn't allow us the 55 mph time table. Sad Anybody have a shell that needs a silver 6v92 I could transplant? Wink
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buswarrior
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« Reply #13 on: April 27, 2010, 09:35:06 PM »

Time constraints?

I'll mention these things only because other impressionable folks are watching this thread...

Please, do a little math and tell us how much money you are going to spend for a new coach, to go how much faster, to burn how much more fuel, to save how much time, over what distance?

Where's the confirmation of your current coach set-up to be sure you are getting everything out of it you can? How do you know you don't have 200 more RPM stifled in it from the previous owner's wild ideas of engine settings?

Depending on the length and style of your typical trip, lingering at a dinner stop, wandering through the store, will more than cancel out the thou$and$ you seem prepared to spend to "save" time.

Now, if this is a just a tip-of-the-iceberg dissatisfaction with your current coach and you just want to sell yourself on something else, well, seek out a busnut with a coach to sell and help them out!

But if this is all that is wrong with your coach, you don't really have much wrong, except a conditioned perception that the auto industry marketers have taken advantage of for ever:

Faster isn't as fast as you think it is

To cover 100 miles at these constant speeds:

55 mph - 109 minutes
60 mph - 100 minutes
65 mph - 92 minutes
70 mph - 86 minutes
75 mph - 80 minutes

It is very hard to cross the continent in a coach at an average trip speed higher than the speed limit, due to stops, terrain, traffic, slowing and accelerating, not to mention the numb and restless bums on board!

happy coaching!
buswarrior



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Ed Hackenbruch
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« Reply #14 on: April 28, 2010, 07:23:03 AM »

I usually figure that i am going to average 50 miles an hour wherever i go. Doesn't matter if i can go 75 or 80 mph, sooner or later traffic, hills, towns, construction, accidents, fuel stops, lunch stops or something else will slow me down and by the end of the day i will have only gone 50 miles for each hour driven. I usually guess how long it is going to take to get from point A to B, and using the 50 miles each hour rule i am pretty close if not exactly on my estimated arrival time. Grin
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1968 MCI 5A with 8V71 and Allison MT644 transmission.  Western USA
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