best way to "downsize" a bus engine?

for an Asian procurement, I'm looking at a stripped Toyota Coaster bus as the starting point to convert into a relocate-able office. I use the term "relocate-able" rather than "mobile" because there will never be a need to go faster than 25 mph. The thing won't be more than once a week or so.

That being the case, the OEM 4.0 Liter diesel engine seems like significant overkill and wasteful.

Is there any feasible way to strip out the motor from a factory-delivered chassis, replace it with a smaller motor, than sell the 4.0 to a coachbuilder or bus-repair guy?

Reply to
dances_with_barkadas
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Not familiar with your app but, I have never seen a situation like yours with limited use where the economic aspects of the project are not prohibitive. For a low mileage application, it would take many years to realize a return on investment from fuel savings. Maintenance expense is not likely to be much different. It is not likely that the salvage value of the old engine is going to be anywhere near enough to cover the cost of the replacement components and, by the time you add in the labor cost for the project, there is just not much probability that the project is feasable on a low useage application.

Lugnut

Reply to
lugnut

Lugnut makes some very good points. It could be done, sure. But the cost of acquiring a good motor and fitting it to the existing bus willl be high. Mating the engine to the rest of the drive train will be a challenge too. Since you will be downsizing the powerplant you may have to find a way to offset the reduced power available to push that big bus around. Replacing a lower geared transmission, adding a brownie box or dropping the rear end gearing are all expensive possibilities for giving your bus enough power to negotiate hills at

25mph and do something as simple as pull out of a rut or back out of a ditch.

If you plan on leaving the motor running to supply power to the mobile office when parked you might look into adding a separate motor-generator unit as used in motor homes.

You need to do a cost-benefit analysis before proceeding I think. Compute the difference in actual fuel usage, difference in maintenance costs (likely minimal) for five years. Then subtract the cost of a conversion. I think you will end up with a very large negative number.

Reply to
John S.

Keep in mind that a diesel engine is far more efficient at part throttle operation than a gasoline (Otto cycle) engine. You may not be wasting as much as you think.

Reply to
stauffer

Remember that the engine will still need to do the same amount of work to move the same amount of weight. As long as you don't leave the engine idling for long periods I doubt you'd ever see any kind of savings swapping out to a smaller motor.

4 litres doesn't seem large for a bus engine, BTW.

Your money would be better spent simply making sure that the tires were well inflated and that the motor was tuned up.

If cash is a real concern then use a real trailer and just use a truck to move it when necessary.

Reply to
Noozer

Wrong economic reasoning.

Who cares about the wastefulness of a one minute operation that happens once a week?

Do you think that the few drops of fluid that you save over the remaining lifetime of the bus will ever recover the cost of the engine conversion?

DOH!

Reply to
Kaz Kylheku

So its overkill. If its going to be so rarely used, the lifetime cost of feeding the bigger engine a little more fuel would NEVER be more than the cost of trying to replace it. Why bother???

Reply to
Steve

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