My expectations of bus 5.9 cummins

[AraS]

I think that is what they are trying to say, the engine is ok for a skoolie as long as I don't force it. What I like about it is the suppose fuel "economy".

[Stuntmanmitch]

Originally Posted by cowlitzcoach

The Cummins 6BT/ISB has gone through a progression of changes and improvements over the years.

The first mechanical versions were 5.9L and had 12-valves in the head.

The next significant change was going to a 24-valve head with electronics.

The last significant change was upping the displacement to 6.7L.

Of course, the 6.7L version with 24-valves is going to perform very differently from the 5.9L with 12-vavles.

I think I have the 12 valve, its a 97'. I pulled a early 90's mercury cougar on a trailer across some moderate grades with almost no noticeable difference (MT643). My bus has a chair lift in the back if that is of any significance. It tops out at 62 on flat land, that's fast enough for me in something that big. Not as powerful as others but MPGs were also a consideration for me.

I'm definitely about to google twin turbo busses anyway though

[Stuntmanmitch]

It's apples and oranges to compare that motor in a truck compared to a bus that weighs 3-4x's as much. The 5.9 is fine for getting up and down the road if you're not in a hurry

Another thing I got from this site; "never be in a hurry in your bus"

Originally Posted by AraS

I think that is what they are trying to say, the engine is ok for a skoolie as long as I don't force it. What I like about it is the suppose fuel "economy".

Bingo

[Ronnie]

stupid question , how do I put a photo in? it asks for a url?

[TrailLifeBill]

Top row to right of smiley is attachments (paper clip). Then navigate to image on your computer.

[Ronnie]

5.9 cummins with a light load.... 25,000lbs
My bus is just over 17,000lbs

[Ronnie]

Thanks, just tried it, adding a photo

[cowlitzcoach]

Originally Posted by Ronnie

5.9 cummins with a light load.... 25,000lbs
My bus is just over 17,000lbs

While the 5.9L 6BT in a bus is basically the same engine that was put into a Dodge pickup the ratings of the engine are very different.

In a school bus the highest HP rating I can remember seeing in a 5.9L 12-valve mechanical was 210 HP. Moving up to the 24-valve I saw some 250 HP versions.

At the same time in Dodge pickups the HP rating was over 300 and going up all the time.

So while a Dodge 1-ton with a Cummins diesel is a very capable truck for hauling insanely large loads a bus of the same vintage is going to need some serious upgrades in order to haul the same insanely large loads.

[Ronnie]

I am sure you are correct that the buses did not get the same HP. But.. it is clear these engine are capable of so much more. And reasonable amounts more are had by tuning the injection pump. If you want BIG power then yes more mods are needed, like turbos upgrades.

My truck is rated at 215hp, and I have not changed it, still stock with 360,000 miles

[Tango]

Below are the notes I got from one of the really savvy tuners over on 4BTSwaps.Com.

Note that these tweaks apply specifically to all mechanical, P-Pump Cummins B Series engines...

If you haven't already, install a 3000 RPM governor spring. Although you won't be running that speed, it helps with gear shifts. Second, consider changing the torque plate in the pump to a #10. That one has decent manors and can provide a significant power increase when needed. Third, adjust the timing to 16 deg. No higher or you risk blowing a head gasket. That will help with power and may improve fuel mileage as well. Last thing is possibly change the fuel overflow valve in the pump. Those things have a spring that gets weaker over time and can cause a loss of power. There are aftermarket items which are vast improvements over the stock unit. All of these changes are not expensive and can be done with the pump in place. A turbo boost elbow would also be advisable to help tune the boost level to take advantage of the new power. Your 130 HP engine can quickly become 200 HP without any bad effects on the engine or sacrifice of fuel economy. You'd basically be making the engine more efficient. And of course the power can go up even further. About 250 HP would be the limits for a stock turbo and injectors. After that point you'd be looking at other mods and don't think you're looking in that direction. A solid 200 HP would feel like you had a big block gas engine in there.
Of all the changes I mentioned, the timing adjustment would probably the hardest. That one requires loosening the the nut on the pump gear and a few special tools to accomplish the job. The governor spring would be #1 in order of importance. Then the torque plate and boost elbow. The change in timing would probably be one of the last things, but can have a huge impact on performance. Changing the overflow valve can be done in a very short time. It's also the cheapest. All the changes may be done for around $300 in part cost, depending on how well you shop. Probably the most bang for the buck on a P pump engine.

[Ronnie]

Just a quick note on governor springs, sometimes you can get lucky and not change the spring but adjust the max engine speed screw and get 3200 rpm max. This gives power through 3000 rpm's before defueling, with a total limit of 3200.

[Ronnie]

Not being picky but I always do the overflow valve first

[Rivetboy]

Originally Posted by Twigg

You can't go much higher than around 210 hp with that transmission.

If you do you run the risk of exceeding the input torque limit and that could get expensive.

ALLISON AT 545 SPECIFICATIONS
General Purpose Truck and Motorhome Rating
Net input power 235 hp (175 kW)
Net input torque 445 lb-ft (603 N·m)
Vehicle weight Up to 30,000 lbs (13,608 kg) GVW or GC

These are the specs that I have seen most everywhere. That rating is for up to 30000 lbs gross weight . My feelings are if you are 10000 lbs lighter than the gross weight rating and with additional dedicated transmission cooling than those HP and Torque figures are very conservative.
Time will tell good thing a rebuilt AT 545 is only $1200 bucks.

[Twigg]

Originally Posted by Rivetboy

ALLISON AT 545 SPECIFICATIONS
General Purpose Truck and Motorhome Rating
Net input power 235 hp (175 kW)
Net input torque 445 lb-ft (603 N·m)
Vehicle weight Up to 30,000 lbs (13,608 kg) GVW or GC

These are the specs that I have seen most everywhere. That rating is for up to 30000 lbs gross weight . My feelings are if you are 10000 lbs lighter than the gross weight rating and with additional dedicated transmission cooling than those HP and Torque figures are very conservative.
Time will tell good thing a rebuilt AT 545 is only $1200 bucks.

It's the input torque you have to watch. That's the one that will hurt you if you go over.

You rarely run maximum power, but the engine produces maximum torque every time it hits the right rpm.

[Ronnie]

a 5.9 at 215 hp is right there at 440ft lbs torque. so anything less and you have room within factory specs to go up to this.

[EastCoastCB]

Originally Posted by Rivetboy

ALLISON AT 545 SPECIFICATIONS
General Purpose Truck and Motorhome Rating
Net input power 235 hp (175 kW)
Net input torque 445 lb-ft (603 N·m)
Vehicle weight Up to 30,000 lbs (13,608 kg) GVW or GC

These are the specs that I have seen most everywhere. That rating is for up to 30000 lbs gross weight . My feelings are if you are 10000 lbs lighter than the gross weight rating and with additional dedicated transmission cooling than those HP and Torque figures are very conservative.
Time will tell good thing a rebuilt AT 545 is only $1200 bucks.

A used takeout 545 is cheap or even free!
If I were gonna have to spend $1200 on a 545 I'd pony up and spend the extra $ to upgrade to a 643 or even a 2000 maybe.

[Rivetboy]

Originally Posted by EastCoastCB

A used takeout 545 is cheap or even free!
If I were gonna have to spend $1200 on a 545 I'd pony up and spend the extra $ to upgrade to a 643 or even a 2000 maybe.

That would mean possibly redrilling the bellhosing for runout. What a pain So the the plan is down the road is to buy a donor bus with a lock up trans and have my way with the engine and then swap them out. But thats a ways out as I am still putting this one back in.

[Tango]

Definitely need to know what SAE bolt pattern you have on your engine before diving into a new tranny. From what I understand, the vast majority of mechanical Cummins engines are SAE 3...but...you need to know for sure. There are a number of aftermarket adapters for some combinations that are fairly cheap. If you have to have a "one-off" made...that's gonna be expensive.

For the record...my old 4BT is SAE 3 and the new Allison 2200MH is also SAE 3.

[cadillackid]

Originally Posted by Tango

Definitely need to know what SAE bolt pattern you have on your engine before diving into a new tranny. From what I understand, the vast majority of mechanical Cummins engines are SAE 3...but...you need to know for sure. There are a number of aftermarket adapters for some combinations that are fairly cheap. If you have to have a "one-off" made...that's gonna be expensive.

For the record...my old 4BT is SAE 3 and the new Allison 2200MH is also SAE 3.

the allison 1000 / 2000 have removeable bells and can be built with either..

the AT545 bell is part of the case and is SAE 3
the MT643 bell is part of the case and is SAE 2


-Christopher

[Versatile]

Originally Posted by Stuntmanmitch

I think I have the 12 valve, its a 97'. I pulled a early 90's mercury cougar on a trailer across some moderate grades with almost no noticeable difference (MT643). My bus has a chair lift in the back if that is of any significance. It tops out at 62 on flat land, that's fast enough for me in something that big. Not as powerful as others but MPGs were also a consideration for me.

I'm definitely about to google twin turbo busses anyway though

Sounds like my bus.