2 stage exhaust brake?

[weighit]

About to pick up a 2016 Tiffin Bus that has a 2 stage exhaust brake. Never had one before, so the question is, stage 1 or 2 is best for the motor when in use? My Tiffin now has just a exhaust brake and I drive with it on all the time.

[wjohnson913]

You will have an engine brake, commonly referred to as a Jake brake. I use low most of the time and put it in high when descending steep grades. Depending how your transmission is programmed high engine brake will most likely select second gear and will slow until it can shift into second.
You will see or more accurately feel a big difference between an exhaust brake and engine brake. They are very reassuring on steep grades.

[Pigman1]

Bill is correct, however some additional things to think about. The engine/trans system will not allow the brake and trans gear it's calling for to overspeed the engine, so even though your shift panel is calling for second gear your trans may be as high as 5th, depending on your road speed. Don't get concerned if you see as high as 2400RPM when going downhill. The trans will automatically upshift when needed to keep from an actual engine rpm overspeed. Also, as you engage the engine brake, especially at high road speeds, the brake becomes less effective. Engine RPM's will not let the trans downshift as it WOULD cause an engine overspeed if it did. Just use a good firm application of service brakes to get you slowed down to where the engine brake can get you into 3rd or 4th and you'll be pleased as to how well it works. BTW, DW drives too and doesn't even turn a hair. These rigs are FUN to drive after you get a bit of practice.


Picking 1 or 2 gets to be a game after you get a bit of experience. It depends on your weight (heavier means more momentum so more brake needed), road speed, road steepness (grade), and your comfort speed based on things like road lanes, width, turns, etc. Play with it, A LOT, until you start to get comfortable. After a while you'll crest a rise, look down the hill and slow to the speed you need with service brakes or letting off the throttle, select the range, 1 or 2, and cruise down the hill with your feet flat on the floor. It's a very comfortable system. We regularly drive the Alaska highway with road grades as steep as 10% and the Bus at max gross pulling a toad weighing 7800 pounds. Long hills too, up to 3-5 miles.

[Ljwt330]

Both posts, above, are spot on.

One more thing to add since you are moving from an exhaust brake to an engine brake. I found that the exhaust brake activates and slows more quickly than the engine brake. Release of he accelerator pedal led to nearly immediate slowing and rapid down-shift. With the engine brake, the slowing is more gradual at the onset, then proceeds to a stronger deceleration, due to the design as mentioned in the above posts.

This was my observation from having the exhaust brake on a Freightliner and now a two stage engine brake on my Alpine. I usually drive with the brake on low, then use high on steeper grades. Of course, the brake is off when on wet roads.

[wolfe10]

The smallest engine Cummins fit with an engine compression brake/Jake brake is the ISL.


Please confirm that you have that engine.


Smaller engines (B and C engines) will have exhaust brake or more likely a variable vane turbo that functions similar to an exhaust brake.


Switch labeling alone may not tell the whole story.

[Pigman1]

Thanks Brett. I believe that all 2016 Buses were on Powerglide chassis with ISL's. Wouldn't bet the farm on that, but that was what I was told. By 2013 when we watched our Bus being built at Tiffin I didn't see any Spartan or Freightliner chassis in the yard waiting for the Allegro Bus coaches to be added, but that could have just been a production schedule and delivery issue. How about we ask? I'm curious to know.



Anyone out there have a Tiffin Allegro Bus 2013 or later WITHOUT A POWERGLIDE CHASSIS and/or A CUMMINS ISL ? ?

[firedoc]

Originally Posted by Pigman1

Thanks Brett. I believe that all 2016 Buses were on Powerglide chassis with ISL's. Wouldn't bet the farm on that, but that was what I was told. By 2013 when we watched our Bus being built at Tiffin I didn't see any Spartan or Freightliner chassis in the yard waiting for the Allegro Bus coaches to be added, but that could have just been a production schedule and delivery issue. How about we ask? I'm curious to know.



Anyone out there have a Tiffin Allegro Bus 2013 or later WITHOUT A POWERGLIDE CHASSIS and/or A CUMMINS ISL ? ?

I can only dream!

[96 Wideglide]

Originally Posted by wolfe10

Smaller engines (B and C engines) will have exhaust brake or more likely a variable vane turbo that functions similar to an exhaust brake.


Switch labeling alone may not tell the whole story.

Don't believe either of those exhaust brakes came with anything more than a on / off switch though.