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Old 09-27-2012, 04:40 PM   #1
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yet more 7.3 idi questions

Hi all. new to the forums. crazy as a loon about getting a bus to haul motorcycles on vacation. I have located a good bus for my needs as far as size, condition, price. a 1991 international Thomas 22 1/2 ft 5 or 6 window bus with a 7.3 idi 5 sp manual and braun lift. only potential down side is the 7.3 idi? I have heard these are not just slow but remarkably so. And fuel mpg is not great. I know the engines are reliable,and mechanical injection is a plus for working on. simplicity. I don't have rear end ratio yet. But from what i have read, ratio is not going to correct fully the issues with these old 7.3s
I do plan on driving this bus everywhere i can, cross country, Mexico, Canada etc etc.

Question- first are they really as bad as i have heard, i e cresting hills @ 35. not being able to get out of way of semis going up mountain passes etc etc. yes i know i can put a turbo in it. but for 2500.00 maybe i should look for another bus? Trouble is everything else is perfect. Please lend an opinion, particularly those who have 1st hand experience. I cannot wait to get this project of the ground.

thanks
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Old 09-28-2012, 02:09 PM   #2
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Re: yet more 7.3 idi questions

You will be going slow, no doubt. You will go slow uphill with a pickup with that engine too. Weight and no turbo is the killer. I would try to find something else that you would be totally happy with. I wouldnt go any smaller than a 5.9 Cummins. That would be the lowest I would go as far as power.
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Old 09-28-2012, 04:44 PM   #3
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Re: yet more 7.3 idi questions

all depends on your gearing and how strong the motor is still.
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Old 09-28-2012, 05:32 PM   #4
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7.3 or 444cu in can go very fast

Most school buses are not designed to go fast. Spend about $3K and you can go fast. Most engines are very similar and there are no bad engines. Many folks evaluate engines before the experience. I once bought a bus with no working heater, for 2 days at a top speed of 52MPH. With a little money ande a gear change, the bus will go 80MPH.
A bus can be made to an owners wants/needs. Buses used in places with many hills have very low rear axle gears.
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Old 09-28-2012, 09:09 PM   #5
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Re: yet more 7.3 idi questions

Frank- Thanks you seem to be a respected contributor and i appreciate it. I know you can make a bus go fast, however at the loss of power, and at 185 hp and less than 400 ft lbs of torque i am imagining this motor will have a hard time pushing say @ 3.80 ratio. If i was to drive this thing in Florida i can see it. But if i get it to go fast i would doubt i would be able to cross say Eisenhower pass on 1 70 @ over say 20 mph. Correct? You live in Idaho, one of the mountainous states we have.so tell me could you take a 7.3 idi and make it a decent cross country rig? Its a school bus i realize, but after scouring the internet for hrs it seems that the consensus is this motor is one of the worst choices for a cross country vehicle. 70 would be good to be able to do. with cruising around 55- 60 but i really don't want to be going over passes having to pull over for loaded semis to pass. and getting over 10 mpg is what i am after.

thanks again
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Old 09-28-2012, 09:22 PM   #6
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Re: yet more 7.3 idi questions

Let me throw this in; I have a 250hp, 8.3 Cummins with a 4.10 rear. I pull big grades at 40-45mph and I pass trucks and RV's. I can pull any grade at that speed. My weight is 25,000. I live in MT and am constantly going up and down.
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Old 09-28-2012, 10:14 PM   #7
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Re: yet more 7.3 idi questions

Quote:
Originally Posted by opus
Let me throw this in; I have a 250hp, 8.3 Cummins with a 4.10 rear. I pull big grades at 40-45mph and I pass trucks and RV's. I can pull any grade at that speed. My weight is 25,000. I live in MT and am constantly going up and down.

What you have is what all buses should have but it's a big difference from an IDI 7.3 engine. That 7.3 is OK in a pickup but I wouldn't want it in my bus.
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Old 09-29-2012, 03:13 PM   #8
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Re: yet more 7.3 idi questions

Opus thanks for that but if i the bus had an 8.3 this thread would not exist. a 7.3 idi is pretty different.
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Old 09-29-2012, 05:06 PM   #9
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Re: yet more 7.3 idi questions

Quote:
Originally Posted by bustoff
Opus thanks for that but if i the bus had an 8.3 this thread would not exist. a 7.3 idi is pretty different.
You missed my point. You were talking about mountain passes, wondering how you would climb them. I told you how I climb them with a considerably larger engine. So, with that statement, you can be pretty sure that you will be climbing passes pretty dog gone slow, with a non-turbo'd, 7.3 engine.
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Old 09-29-2012, 07:04 PM   #10
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Re: yet more 7.3 idi questions

my shuttle with the 7.3 does just fine on highways with 4:10's. i loose speed in the hills but not as much as semi's do etc. only sitting at about 10k lbs though.


in the end its really what the owner wants. if you dont feel a 7.3 is big enough, go bigger. bigger engine isnt necessarily worse. its all about the power to weight ratio.
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Old 09-30-2012, 02:17 PM   #11
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Re: yet more 7.3 idi questions

Opus- yes i am sorry i did miss your point. And it was quite valid. It could have been read one of two ways, i read it wrong. Thanks
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Old 09-30-2012, 02:34 PM   #12
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Re: yet more 7.3 idi questions

Ha, no problem. The joy of communicating like this.
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Old 09-30-2012, 06:49 PM   #13
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Re: yet more 7.3 idi questions

i have owned several buses, and i would be scared to have a 7.3 liter in a full size skoolie.

I agree with the above poster that the cummins 5.9 is a much better choice.

The difference in price between a bus with an underpowered engine or a bus with what many consider a great engine is negligible. It's all about finding a bus when you want one.

I prefer to contact many school districts and ask when they are planning to auction off the buses. Direct from the school district is the best way to get a bus in my opinion. They tend to do excellent maintenance.
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Old 10-01-2012, 02:25 PM   #14
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Re: yet more 7.3 idi questions

While my build isn't finished yet, I have had T444E out on some decent hills. I've got a spicer 5-speed manual with a 1-1 top gear transmission and a 5.82 rear, and I can get the bus up to 65 at about 2700RPM. I can also climb most of the steep hills here in fifth gear without dropping below 45 mph.

The 45 mph mark is important, because it would mean shifting down to fourth. SO even with really low gearing you can still make hills. Granted, with a bigger engine, I'm sure I'd be pulling hills at 50, but it's what came with the bus and it runs fine ...

ETA: Oh, and it looks like I'm getting 10-12 mpg with that ...
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Old 10-01-2012, 04:30 PM   #15
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Re: yet more 7.3 idi questions

Quote:
Originally Posted by Hex
While my build isn't finished yet, I have had T444E out on some decent hills. I've got a spicer 5-speed manual with a 1-1 top gear transmission and a 5.82 rear, and I can get the bus up to 65 at about 2700RPM. I can also climb most of the steep hills here in fifth gear without dropping below 45 mph.

The 45 mph mark is important, because it would mean shifting down to fourth. SO even with really low gearing you can still make hills. Granted, with a bigger engine, I'm sure I'd be pulling hills at 50, but it's what came with the bus and it runs fine ...

ETA: Oh, and it looks like I'm getting 10-12 mpg with that ...
Even though the 444e is the same displacement as the 7.3 IDI, it's a different animal.
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Old 10-01-2012, 05:00 PM   #16
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Re: yet more 7.3 idi questions

Yep if it had a dt444e it would be in my driveway now. idi is non turbo mechanical injection. dt444e is turbo and electronic controlled. huge difference especially in torque.
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Old 10-01-2012, 05:03 PM   #17
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Re: yet more 7.3 idi questions

Huge difference in repair costs too. ;)
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Old 10-01-2012, 09:19 PM   #18
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Re: yet more 7.3 idi questions

Injectors for the 444e run about $250 each.
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Old 10-02-2012, 10:31 AM   #19
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Re: yet more 7.3 idi questions

Ahh, fair enough. I know just enough about the engines to be dangerous.
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