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Old 11-09-2016, 05:22 AM   #41
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Join Date: Sep 2014
Location: Eustis FLORIDA
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Year: 1999
Coachwork: Thomas
Chassis: Freighliner FS65
Engine: Cat 3126
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Quote:
Originally Posted by ElspethFlynn View Post
Hello!
I am new to this (and wondering if I have just wasted way too much money on a bus that will not work for me). I bought an auction bus for 2k.. while driving it home I blew out a tire (they all ended up needing replaced because they were capped and no good and cost around 1,100). On top of that, the bus would not go over 40 to 45 mph (the speedometer, when working, said 55, but my cousin followed me and confirmed I wasn't going over 45). Anyways, I made it back to TX (finally) and took the bus to shop #1... Shop number one did minor things like flushing fluids and replaced an axle seal, oil change, brakes, etc. (which cost about 800). They said the fuel injector module was bad and recommended another shop. So, shop #2 ended up replacing all of the injectors, fixing the wiring harness, and doing a couple other minor things (ended up costing 4,000). Sigh. So, now I have over 7,800 sunk into this bus and they tell me it won't go over 55 MPH. They lifted the governor to 70, but they said that it was not capable of going over 55 and the woman on the phone said that it was not built to go that fast because the engine would implode?!?! WTH? Has anyone ever heard of that? I am wondering if I should bail out now, or continue on and convert it and just deal with plodding along at 55 MPH, or if it is possible to get it moving a little faster... Thank you for any input!

Sincerely,
El
I've met folks who drive across the country at 55mph.
I'd say you have way too much money in it to quit now.

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Old 11-09-2016, 07:17 AM   #42
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Join Date: May 2009
Location: Columbus Ohio
Posts: 18,751
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
Ive driven 10,000 miles this year in my carpenter at 55 .. I say drive it and keep it... you probably have a wonderfully running T-444E now!.. you can always change the rear gears if you want ot run faster.. im assuming when you hit 55 your RPM is around 2600, 2700?
-Christopher
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Old 11-09-2016, 08:35 AM   #43
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Location: Houston, Texas
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Year: 1946
Coachwork: Chevrolet/Wayne
Chassis: 1- 1/2 ton
Engine: Cummins 4BT
Rated Cap: 15
We need some data to evaluate the situation...

1. Engine make & displacement
2. Transmission make & model
3. Rear axle make & gearing
4. Tire size (including actual height)

The engine will be limited by RPM.
The tranny will be limited to final output ratio
The rear gears will determine how fast the wheels turn in relation to the engine & trans
The tire diameter will determine the distance covered by each revolution

Together, these collectively dictate speed.

These numbers can be plotted on a gear calculator that will tell you exactly what speed to expect including with any mods to any of the above.

One such calculator is here...(I use the section at the bottom of the page)...

Engine RPM Calculator
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Old 11-09-2016, 12:39 PM   #44
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Join Date: May 2016
Location: Georgia
Posts: 2,264
Year: 2001
Coachwork: Blue Bird
Chassis: IH
Engine: T444E
Rated Cap: 14
Quote:
Originally Posted by ElspethFlynn View Post
Hello!
I am new to this (and wondering if I have just wasted way too much money on a bus that will not work for me). I bought an auction bus for 2k.. while driving it home I blew out a tire (they all ended up needing replaced because they were capped and no good and cost around 1,100). On top of that, the bus would not go over 40 to 45 mph (the speedometer, when working, said 55, but my cousin followed me and confirmed I wasn't going over 45). Anyways, I made it back to TX (finally) and took the bus to shop #1... Shop number one did minor things like flushing fluids and replaced an axle seal, oil change, brakes, etc. (which cost about 800). They said the fuel injector module was bad and recommended another shop. So, shop #2 ended up replacing all of the injectors, fixing the wiring harness, and doing a couple other minor things (ended up costing 4,000). Sigh. So, now I have over 7,800 sunk into this bus and they tell me it won't go over 55 MPH. They lifted the governor to 70, but they said that it was not capable of going over 55 and the woman on the phone said that it was not built to go that fast because the engine would implode?!?! WTH? Has anyone ever heard of that? I am wondering if I should bail out now, or continue on and convert it and just deal with plodding along at 55 MPH, or if it is possible to get it moving a little faster... Thank you for any input!

Sincerely,
El
I hate to be the one to say it, but doing some research ahead of time could have saved some grief.

We don't know what gear ratio your rear axle has, and that is probably one of the biggest limiting factors for your top speed. A ratio around 5.38 (and a 1:1 final drive in your transmission) will give you a top end somewhere around 55. Rear axle ratios of 6+ are not unheard of. An overdrive transmission could bump this up to about 65 (but I don't recall seeing you say which you have). The T444/7.3 (same thing) engine has a top speed of around 2600-2700 RPM.

I can get a rear axle module refurbished with a new gearset (with the ratio of my choice) for about $850, and with a transmission jack and a few hours of labor I could swap it myself. This would probably be the most cost effective (for me) way to boost my top end. Will I do it? Well, that sort of depend on my planned use for my bus. I may build it into a food truck, and for that use, top speed really won't be a concern (as long as I don't make any extended road trips with it - which I probably won't.) I may build it into a party-wagon, and again, it'll primarily see local service so top end is again a low priority. If I build it into a living quarters or road-trip vehicle, then top speed becomes a priority. (I'm unlikely to set it up for long trips, mostly because the 9 Liter engine is becoming something of a rare breed, and if/when I break down somewhere, getting parts and road service could become a big challenge. To that end, I'd prefer a T444 or DT466, which are very common and very easy to get parts for).
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Old 03-01-2017, 09:50 AM   #45
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Join Date: Oct 2016
Location: Essex, MD
Posts: 3,738
Year: 1999
Coachwork: Blue Bird
Chassis: Blue Bird TC RE 3904, Flat Nose, 40', 277" wh base
Engine: 8.3L Cummins ISC 260hp, MT643, 4.44 rear
Rated Cap: 84 pax or 1 RV; 33,000lbs
Quote:
Originally Posted by Geo Jeff View Post
There is always to much of good thing. I build high MPG vehicles. I have my own that I use to race in the eco fuel races. Its gets 68mpg real average. I use it for every thing it has trailer hitch on it now. i get 35mpg with a 1500 to 2k lb load.

But I have it all mapped out on the dyno and built just for that mapping. If i put a tire on it that's just 1" taller it loses 20 mpg. Virtually takes away every thing I have done to the car from weight reduction to engine mods.

When you want more MPG you have to build more Hp and lower the torque curve. Look at the car manufactures they add more hp every year to the cars and trucks and they keep getting better MPG. I have to build full race engine at wot at 6rpm produces twice the stock engines HP so i can idle that super efficient engine around down low in the rpm to get a bit better fuel burn out of every drop of gas. If you use 100 hp to go down the road and you want it to get actual better MPG you need that 100 hp to show up sooner at lower rpm. So raising that gear ratio or knowing what it will do for you is as easy as trip to the dyno shop to see where your engine is peaking at its shift point rpm. The do the math where the new rpm shift point wil be and then look at your dyno sheet and see how much power you need to have the torque right there. This is when you see your just a few like 50 hp off from ideal. So you take it in and ask the good man to set the engine to that rpm with that hp. No matter how much you move the rpm around you can never get away from the fact it has a camshaft and that's what determines the driving compression and your cruise rpm. Those lobes open and close at a certain time depending on how long there open and peak compression on when they shut both valves and re open them. not to get to complicated but your running compression is what pushes you down the road and the cam shaft shape is how the energy pushes on those pistons and for how long.

You may just need a different cam shaft as i suspect we all do. When i use to work for VW /benz most people don't realize a gas German engine is the same as a diesel is with just a different head. For instance the rabbit diesels until they got to TDI had the same cam as the gas engine. No one cared and was looking for more power. Take 1.9 cam profile and stick in a old 1.5 rabbit and you can feel a difference. So don't over look actual performance because its your friend when you need more HP and more MPG there one in the same.

having your cam reground is cheap and you don't have to know cams at all just go a new modern day style like from a 1996 VW tdi Canadain model. Tacoma cam grinders can do one in week return mail.

Running a rv cam (same as your chevy truck) profile in a non turbo diesel is a great way to go as well. so if you have NA 3208 cat in a old beast this would be a great upgrade. helping you make that tall rear end gear really work for you. I use to do this to the 4cyl benz non turbo and rabbit.

what i don't understand is why my 6 speed 350 hp c7 cat in my 40ft RV only gets 6 mph. i need to check those gears because this thing might beat a small import honda racing around town its brutally fast on the tae off and holds the pass at any speed you want but never gets better or worse than 6 mpg. I may drive it off a mountain pass soon and see if i can get a bit more MPG in free fall. I just had it scanned and dynoed and they say its 100% at 70k miles.
Quote:
Originally Posted by GreyCoyote View Post
In a DT466, dont bother messing with the cam or compression. These are tricks for gassers and NA diesels . Regrinding is fruitless (many tractor pullers use the stock cam) unless you are radically changing the operatingrange of the engine. And the engine simply cant use any more compression.

The DT engine is already capable of breathing far beyond the amount of fuel you can throw at it. Need more flow? Add PSI and more intercooler.

If you want more power/mileage, look at the injectors, turbo, fuel timing, etc. The only real difference between a 180 HP and a 350 HP DT466 is the ECM, the injectors/pump and the turbo. (And pistons, but only in the material used. The higher HP variants use a 2-piece cast iron piston. Lower HP variants use a 1-piece forged aluminum design. Both have the same cup and quench design). These components are the areas where huge gains can be made if you have the time and budget.

I'd also be remiss if I didnt point out the DT530. Its nothing more than a DT466 with an extra half-inch of stroke. A 530 would build big power at 1900-2000 revs and could seriously use the gears you are contemplating. Dunno if the MT643 would survive the experience, but hey...
I'm thinking we need to find a bus and a garage with a locking door. We throw these two in there and they don't come out until we get a skoolie that can keep up with the coaches while getting 30mpg.
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Old 05-05-2017, 01:11 AM   #46
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Originally Posted by EastCoastCB View Post
Internationals' are adjustable. no need for any new parts.
How do you adjust an international? I will need to do this on my bus.
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Old 05-05-2017, 01:36 AM   #47
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Using a dyno is a great idea if you have access to one.

Back in the day of gas engines when people asked about re-gearing, OD's, and more gears I always told them to first install a manifold vacuum gauge.

Depending upon where you were on the scale would determine how much more gearing you could go. If you were already below 10" you were getting into the "don't bother" range.

The fundamental thing to remember about most school buses is they are purchased to provide to/from transportation that requires a lot of stops and rarely speeds in excess of 35 MPH.

I know of one school district in the Seattle area that ordered many Thomas West-Coast-ER's with Cat 3126/C7 250 HP engines with the MD3060 with 6th gear locked out. Top speed gearing was 60 MPH, and that was with 5th gear OD. It also meant it scooted up any hill it came to and when the light turned green it could beat just about any car or light truck off the line. Loaded.

Those buses could be re-geared very successfully or have the 6th gear unlocked and they would easily cruise at the highway speeds of flyover country.

On the other side of the coin, I had a Loadstar chassis 11-row Blue Bird bus with the 6.9L and AT540. It was geared to a top speed of 47 MPH. At this late date I can't remember what HP rating the engine had but I would guess it was probably down around 160 or 180 HP. Even with a top speed of 47 MPH it was pretty pokey. I used it on a shuttle route where the speed limit for most of the route was under 25 MPH so it worked out great for us. I never even considered changing the rear gear set because I doubted the engine had enough get up and go to handle faster gears.

There is no free lunch when trying to go faster. It requires more torque to get you there and more HP to keep you going faster. More torque and HP means upgrades to the engine. It also then requires upgrades to the cooling system as you will need much more cooling capacity.

Which is why I always tell people to find a bus with the power package and gearing you really want, even it if means shelling out considerably more $$$$ to get what you want. If you settle for something less the cost of re-powering and re-gearing will quickly mount up and end up costing you more $$$$ than if you had purchased the bus with more HP and speed in the first place.
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Old 05-05-2017, 03:17 AM   #48
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Join Date: May 2009
Location: Columbus Ohio
Posts: 18,751
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
Quote:
Originally Posted by oswaltadventures View Post
How do you adjust an international? I will need to do this on my bus.
The mechanical dt466 and dt360 you can alter the rpm governorsceasily in the pump as well as the fuel rate, navistar factory limits my dt360 to 2700 rpm load and 2900 no llad( floored in neutral). The max safe rpm as listed in the books is 3200 loaded, with the caveat they say you shorten its expected life span.
You can safely spin out the fuel screws to get more fuel and horsepower but again at a likely shortened lifespan.

Like cowlirz says speed costs money, I've built hotrods for years , some real hot ones.. the hotter the rod the more I spent and the more stuff I busted too..

Also on these older engines that have spent 20 plus years at a certain max rpm and fuel, turning them up to me is risky..

There are lots of go fast busses put there, they cost more, or you can just slow down and enjoy your road trip..
Christopher
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Old 05-05-2017, 08:40 AM   #49
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Join Date: Oct 2016
Location: Essex, MD
Posts: 3,738
Year: 1999
Coachwork: Blue Bird
Chassis: Blue Bird TC RE 3904, Flat Nose, 40', 277" wh base
Engine: 8.3L Cummins ISC 260hp, MT643, 4.44 rear
Rated Cap: 84 pax or 1 RV; 33,000lbs
Quote:
Originally Posted by cadillackid View Post
There are lots of go fast busses put there, they cost more, or you can just slow down and enjoy your road trip..
Christopher
I neeed me an MD3060. LincolnEcho got an 8.3L with an MD3060 ion his '99 Blue Bird. Mine has the MT643. So whatever sensors and input the MD3060 needs were available in '99.

His tranny and my rear end and I've got a 106mph bus. I might not be able to climb a speed bump but downhill... LOOK OUT!!
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