black smoke up hills????

[pvcces]

Time, all diesels are governed; they would run away if they weren't. If the governor is functioning, you can't hurt them by flooring the accelerator while sitting still. This is called high idle speed on bulldozers, for example.

On the other hand, many of these engines are equipped with a fast idle which is not the same thing. Fast idle is used to maintain something around double normal idle speed to maintain air conditioning in a coach while at a short or meal stop.

High RPM can and will use more fuel, so keeping them at governed speed does not do much for fuel economy. The more efficient engines of today are normally running under 1500 RPM.

For what it's worth.

Tom Caffrey

[RJ]

By the way did I mention I don't know nothing about diesel engines.

what do you mean by running the gears.   I was taught to high of rpm will blow a motor.

Time -

Keep asking questions, and you'll learn all about diesels both here and on various other message boards.

Diesels are not like gas engines - they generate most of their power between idle and around 2100 rpm, which is usually where the governor is set.

Your average gas auto engine will happily rev to 6000 or more, depending on the make/model.

The stock 8V71 in your coach was normally set up for revenue service with N60 injectors and governed at 2100/2150.  This combination gives about 275 hp and around 775 ft/lbs of torque, but also returns decent (for a bus) fuel economy.  Something to consider at $5/gallon.

You can run a Detroit two-stroke like your 8V71 all day long on the governor at 2100 rpm and it won't hurt it at all, other than burn a lot of fuel.

"Running the gears" means exactly what HBofCJ said - you take the engine all the way to the governor in each gear before you shift up to the next one.  It won't hurt this engine at all - as a matter of fact, you'll find, as a newbie, that the whole coach will seem to perform better if you do.

It's also important with the powertrain you've got, which is typical of most stick-shift highway coaches.  With only four speeds in the manual gearbox, you need to use the full rpm range of the engine for best performance.  If you have the automatic in your Buffalo, it's even more important that you shift it manually for best performance, especially when it comes to downshifting.  Re-read that link I posted earlier regarding this.  If nothing else, when running around town with a V-730 automatic, leave it in 2nd.  When you hit the freeway, then shift to 3rd/D.  BTDT, well worth the effort.

FWIW & HTH. . .

[Tenor]

Hey guys,
Much of the advice for shifting here is missing an important point - Time to Go's bus has an automatic tranny.  Or maybe I'm missing the point and that you can do all of the discussed manual shifting with an automatic?  I've only driven 4 Speeds. 

Glenn

[HB of CJ]

"Running the gears" is easy.  What it means is that in a Bus Conversion with a 4 or 5 speed MANUAL tranny, and with the older 2-stroke Detroit Diesel engine, you rev up your mighty Detroit until it  1)...sounds like it is going to explode!, 2) If you have a tack, to anywhere from 2000 to 2300-2400 rpm, or, 3) if you are shifting by the speedometer (most common) you have a memorized speed range for each forward gear.  Very easy actually.  Like driving the older VW bugs.

An example.  A lot of the older 35 foot MCI coaches had only 4 speed trannys.  The gear ratios worked out to a corresponding mph speed range.  1st gear was good up to around 15 mph.  2nd gear from around 10mph up to 30mph.  3rd was good from about 25mph up to around 50mph and 4th gear was good from around 50 mph all the way up to the top speed of the bus.  Normally you DID NOT stay in high gear at a low road speed pulling power from the mill.

Once you get used to it, it comes naturally.  Obviously there are exceptions to the rule, like "drifting" down a very slight down grade at a moderate speed, you could (I know I got lazy and did soss.) leave it in high gear and just let the coach coast.  The other way also is done, like climbing a steep long grade where the engine is really working.  Instead of keeping your foot on the floor, you "backed out of it" slightly and kept high rpm, but with partial throttle.  Detroits love this.  They hate "lugging"  Good luck. 

[RJ]

Hey guys,
Much of the advice for shifting here is missing an important point - Time to Go's bus has an automatic tranny.  Or maybe I'm missing the point and that you can do all of the discussed manual shifting with an automatic?  I've only driven 4 Speeds. 

Glenn

Glenn -

For most busnuts that frequent this and the other message boards, because of the vintage of our vehicles, a lot of the info related to shifting a manual gearbox does, in some respects, apply to the most common automatic found in them, the HT-740.  (The V-730 is basically the same gearbox with one less gear in it.)

If you want to maximize the performance, you shift it manually.  If you don't really care, just put it in "D" and go.  Which is really fine for 99.9% of most busnut's driving situations.

BUT -

It's still important that you know the maximum road speed in each of the lower gears, because:

1.  When climbing hills, you need to downshift it manually, otherwise it will shift too late on it's own, and then you're ready for another downshift, which it will again do too late.  Good way to overheat the beast, btw, especially MCIs.  The BNO article talks about how to do this smoothly.

2.  When descending hills, knowing that the HT-740 will still upshift to protect itself when you exceed the maximum road speed in a lower gear, well, it could not only save you an expensive engine rebuild from over-revving, but it also could prevent a runaway bus because you're now going too fast for the hill (non-Jake brake equipped vehicles here).

So, yes, some of the manual shifting advice is valid for automatics, too.

FWIW & HTH. . .

[Tenor]

RJ,
Thank You!  Thats the explanation that newbies need!  So in comparison to hot rod car auto tranny's, most of the automatics in busses have a manual valve body that allows you to manually shift or just leave it in drive.

Glenn