Repower - a retrospective

[Brian Diehl]

I recently reached a pretty important milestone with my conversion.  Two weeks ago I completed putting on as many miles on my repower as I had put on the old motor (since buying the bus) before it died.  I had put 26500 miles on the old engine and now have 27000+ miles on the repower project.  Here are some basic facts:

Old Engine = 4,144 gallons burned
New Engine = 3139 gallons burned

Old Engine = 6.39 mpg
New Engine = 8.44 mpg

The new engine gets 32% better fuel economy.

I have saved 1,005.5 gallons with the new engine compared to the old engine.  This is about $3,000 or so of avoided diesel costs.  This is 1/5th of my repower cost.

One thing about the old engine fuel mileage ... I got substantially better mileage in the early days of my conversion since it was so much lighter.  If the old engine had pushed around the current weight the entire 26,500 miles the average mileage would have been lower and hence the % improvement a bit better.  I have also towed my Grand Cherokee a substantial amount of the repower miles driven.  I only towed the TOAD once or twice with the old engine.  Again, this would push up the repower mileage by a tick or two again showing the % improvement to be better still.

Hopefully these facts help guide anyone down the path of a repower versus overhaul decision.


If I had it to do again, would I?  YES!  I am absolutely amazed at how much nicer it is to drive this bus with the amount of power this engine has.  The benefits of the repower are enjoyed every time I take it out.

[Lonnie time to go]

Thank you for the info brian.

Lonnie

[DMoedave]

Hey Brian, what was the before and after engines? Do you have the same trans? Those are some great numbers. It is way too early for me to post numbers we have only put 5400 miles on ours since we got it from the repower last August.
Our take is pretty much the same. I would do it again. My wife and I are in our mid 50's and trying to plan for the future, which includes our bus. It has more power now, gets 7.5- 10.5 mpg; can now pull a toad; we can go over 60 if we want(and we arent such a menace to the road ways); we can travel more comfortably with less stress; climb hills at a better speed; and its FUN to drive.
We went from a wore out 4-71 with a clark 4 speed, 4.10 rear gears to a  Rebuilt 6V-71, Allison 654, and 3.70 gearing.
The down side is we took out a home equity loan (which we couldent get now!) and are paying it off. And i still dont have the rear bedroom rebuilt yet!

[Brian Diehl]

The old engine was a 6v92 with a HT754 CR tranny spinning a 3:33 diff.  The new engine is a Cummins ISM with a Eaton Gen 1 Autoshift and the same diff.

Here is my story about the conversion: http://home.earthlink.net/%7Ediehls0792_1/BusSection10.html

[plyonsMC9]

Great information!  Thank you for sharing guys.   One of these days, I'd like to repower our 6v92 mechanical / Allison 740.  It is "tired".  But for now, very sturdy.   

Kind Regards, Phil

[RoyJ]

The old engine was a 6v92 with a HT754 CR tranny spinning a 3:33 diff.  The new engine is a Cummins ISM with a Eaton Gen 1 Autoshift and the same diff.

Here is my story about the conversion: http://home.earthlink.net/%7Ediehls0792_1/BusSection10.html

Well, I guess some things, like power, driveability, and desireability, are mastercard priceless 

Did you end up tuning the engine to 450hp?

[Brian Diehl]

The old engine was a 6v92 with a HT754 CR tranny spinning a 3:33 diff.  The new engine is a Cummins ISM with a Eaton Gen 1 Autoshift and the same diff.

Here is my story about the conversion: http://home.earthlink.net/%7Ediehls0792_1/BusSection10.html

Well, I guess some things, like power, driveability, and desireability, are mastercard priceless 

Did you end up tuning the engine to 450hp?

Roy, I did not ever have it reprogrammed to 450HP.  I've found 400 to be more than adequate and couldn't justify the money to have it reprogrammed.

Yes, this thing is much better to drive and is worth the effort I put into the conversion instead of a straight overhaul to the existing engine.  The fact that I get better mileage is a bonus, not "the" reason to do the repower.

[Busted Knuckle]

The old engine was a 6v92 with a HT754 CR tranny spinning a 3:33 diff.  The new engine is a Cummins ISM with a Eaton Gen 1 Autoshift and the same diff.

Here is my story about the conversion: http://home.earthlink.net/%7Ediehls0792_1/BusSection10.html

Well, I guess some things, like power, driveability, and desireability, are mastercard priceless 
Did you end up tuning the engine to 450hp?

No using the small Cummins out of a Dodge PU in a bus would make a mastercard priceless for the future tow/repair bills.

Sorry Roy, I'm not bashing you. And I have always thought that the Dodge/Cummins was an awesome set up!
But I feel it's too small to be pushing a full size fully converted OTR coach down the road very far without troubles!
I understand that they work great in "schoolies" but a schoolie don't weigh near as much.
And I do in fact have proof that one in a heavier coach will cause problems.
I had a customer that bought a "Party bus" that was an ex-military bus with one in it. He then had it "professionally" converted to a "party bus" by a company up in OH (I don't know the company) but they did a nice job of converting it to his specifications which used a ton of granite and lots of extra stuff and it broke down on the way back to Paducah, KY from OH and was towed into the Frieghtliner dealer in Calvert City, KY.
Once their RV/Bus shop repaired it he started chartering it. About once a month something else broke and it was again towed to CC. Once when I was there dropping it off I asked the guy in charge of the RV/Bus shop "Man this guy sure bought a worn out lemon, huh?"
And he replied "No the bus was/is in really very good shape. The military took excellent care of it. It's just all this extra weight they put in it converting it and then putting 30 people and a bunch of booze in it, is more than it was designed to haul!
They pulled that engine out and put a CAT engine in it and he still runs it today! Last I heard he has only had one failure in 7 yrs compared to 9 in one yr with the old engine.
FWIW
  BK