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Old 07-19-2021, 11:24 PM   #1
Join Date: Aug 2020
Location: Colorado
Posts: 19
Year: 2001
Chassis: Bluebird TC 2000
Cummins 5.9 ISB help

I have a Blue Bird 2001 tc 2000. It has the 5.9 ISB with the Alison AT545. It is a retired city bus and appears to be governed to 2300 rpm which brings it to a top speed of 58mph. Does anyone know if this sounds reasonable? Is this bus governed or does it come with the rpm limited to 2300? I brought it to a bus service center that was supposed to be an authorized Cummins shop. They refused to put it on the computer and said it was gear locked and there is no way to electronically alter the rpm settings. They also said that my engine was not electronic? Is this accurate? It has a 9 pin connector so I am assuming it is an electronic engine. I know the 12 valve motors have actual govoner springs. Is this the case for mine? Kind of disappointed with the fact that I went through the time and expense of having "Cummins" look at this bus and say there is nothing they can do. Any direction would be appreciated.

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Old 07-20-2021, 08:31 AM   #2
Bus Geek
Join Date: May 2014
Location: West Ohio
Posts: 3,710
Year: 1984
Coachwork: Bluebird
Chassis: International 1753
Engine: 6.9 International
Rated Cap: 65
Your rated rpm and governed rpm depends on the power rating of the engine. The isb came with a handful of different ratings, depending on what it was ordered with and what it was installed in. Being that it's a 5.9 ISB, it is definitely electronic, and your rpms are controlled 100% by the ecm.

You might have a top speed of 58 might be because it's gear locked/bound. The only way to tell is by connecting the computer, but to do that it would have cost you an hour of diagnostic, which is 100+ bucks. Even if they did remove a speed limiter in the ecm, with you being at 2300, you're likely not going to gain much in the way of top speed. You'll have to regear the rear axle, or install a transmission with OD to go any faster.

The shop likely said there is nothing they can do, because they don't want to do it, or incur any liability from them doing it. Things can be done to get it to go faster, but realize with your at545, you're already flirting with reliability issues. More speed/power will only hasten it's demise.
My build: The Silver Bullet
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