Mountain passes

[0533]

As I recall at POG 4, Bill Jenson from Prevost said that performance mode added 200 rpm to the shift cycle.

200 RPM will make a substantial difference in the power, as I am often too late on the hill climb waiting for the economy mode to sense the hill and make the shift.

Mango, you should replace your Avatar with a changing mugshot showing your mustache rebirth, it would be an interesting progression or is it too late?

[Jon Wehrenberg]

Bruce, in the upper RH corner of the display it should read "mode" when you are in performance mode. It shows nothing when you are in the default economy mode. I think this is reversed for Tuga's coach.

I wouldn't bet about adding 200 RPM. I think under the exact same pedal pressure it may do that, but I have found I can do a full power acceleration in my coach and wind out each gear to max RPMs something not even close to possible in economy mode.

When you are climbing a steep hill you want the engine wound as tight as possible for maximum HP. I manually downshift to prevent the transmission from upshifting if required.

[bluevost]

Not all modes are created equal. In my CC, when mode is on, I am in economy. When mode is off, I am in performance.

Ken

[0533]

Bruce, in the upper RH corner of the display it should read "mode" when you are in performance mode. It shows nothing when you are in the default economy mode. I think this is reversed for Tuga's coach.

I wouldn't bet about adding 200 RPM. I think under the exact same pedal pressure it may do that, but I have found I can do a full power acceleration in my coach and wind out each gear to max RPMs something not even close to possible in economy mode.

When you are climbing a steep hill you want the engine wound as tight as possible for maximum HP. I manually downshift to prevent the transmission from upshifting if required.

Thanks Jon and Ken for the info. I will make this part of my driving habits from now on. I did learn about keeping my foot on the floor for hill climbing but missed the page on Economy verses performance.

[MangoMike]

Perhaps I mispoke.

Shifting is delayed for an extra 200 rpm. The engine does gain an extra 200.

Mike

[Jon Wehrenberg]

Ken brings up an excellent point.

For our coaches the default mode was economy. It has smoother shifts and delivers the best fuel mileage at the expense of some hill climbing ability if left to shift on its own.

Prevost cannot change the default. Ken's coach was either ordered with the transmission set to use performance mode as the default, or an Allison dealer reset the default. Allison dealers are the only folks who can change the default mode.

This according to Bill Jensen of Prevost.

[Coloradobus]

Well, everyone drives differently. We use the "mode" button most of the time, with and without the cruise control.
When we were east a few years ago on the piedmont, I let the coach run in "economy." All other times, the mode "sport" button is on.
We have put 50,000 miles on this coach in 3 1/2 years, and the bulk of this mileage has been done with the transmission in "Sport: mode.
When we were running with "Orange County Gang" last April to Kerrville, we had a "RPM Check" Everyone but us was running around 1450 rpm at 62 mph in 6th gear. We were at 1800 rpm is 5th. If we are going less than 68 mph, our tranny is in 5th gear.
So, everyone's preference is different for various reason. Our mileage useage is not significantly different whether in Sport or Economy>

[Jon Wehrenberg]

Within certain limits the gear a bus is in and the RPM are not an absolute indicator of horsepower produced or fuel consumed.

The fuel we consume is directly proportional to the HP produced. If we lug a coach up a hill in a higher gear at a given speed we are likely to consume the same amount of fuel as a free revving engine going up the same hill at the same speed in a lower gear. As Jim and Chris point out their use of a lower gear does not impact their fuel mileage appreciably.

There is an engine operating range in which the engine is producing near maximum HP and torque. Above or below that range of RPM you give up either mileage or pulling power.

[dale farley]

I've noticed that my RPMs will sometimes go to 2200 if my Jake is in the "High" setting and I let off on the accelerator. Is this unusual or damaging?

[Jon Wehrenberg]

That is good Dale.

A jake works best at higher RPM, and your DDEC is controlling things to optimize your engine, transmission and Jake combination.