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Drive your bus
Matching rpm and gear selection.. A complicated subject to some. Just simple put it in D and forget.. Maybe a good topic for Bill J at get together. The differance between a 2 stroke sweet spot and the 4 stroke. Climbing hills and manual down shift vs let the transmission do it for you. I found out with my 8V-92 and Allison I could manual downshift and maintain 1800rpm on a hill climb and stay cooler at the top(just a example).With the 2 stroke is runs much lower down to the 1200rpm range. After recent post on other boards it seams some are not getting info they need on available features and techniques pased on when purchasing their coaches. Driving hints as well.. Don’t be offended but learn or share what you have learned from your experiences.. LB just shared his observation of a H-45 driver taking down poles in a Walmart and injuring himself(on another board). Heck of a learning curve! When giving yourself plenty of room to stop at a red light=there will be a little car change lanes if front of you making it a panic stop=you hit it=your fault.. To the experienced guys dis reguard!! to others please be careful…
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6 Replies
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I prefer to shift the transmission when I want the transmission to shift. That means I am going to, occassionally, manually select the gear. This can be used well both while accellerating and while slowing and using the Jake to take some stress off the brakes. There is a weird power range around 55 MPH where the transmission can’t decide which gear it should be in so I select the lower gear and just let it run without issue. Dang, do you suppose I get 1/100 less MPG during this period? Oh well, it’s just money I would have given to Prevost at my next service stop anyway!
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I think one of the least understood practices regarding the operation of our coaches is power management. Not power managment as it relates to shore power but as it relates to moving 20 or 25 tons as efficiently as possible.
On level ground there is not much effort required of us as drivers, but as we get into hilly areas we have to participate to a certain extent. The easiest way to negotiate hilly terrain is to select the performance mode on the transmission, or go down to a lower gear. The circumstances will dictate what we do.
An 8V92 will perform better if the RPMs are kept relatively high. It has little power at lower RPM so without a performance mode on its transmission a driver needs to anticipate the need for power and go down a gear or two to maintain engine power.
The Series 60 was designed to operate fairly well at lower RPM, but it is not going to climb a hill as easily if the transmission is in economy mode because shifts will be delayed until the RPM is so low that hill climbing performance will be compromised. In anticipation of hills I am in performance mode which not only causes the transmission to down shift sooner to maintain engine RPM, but it also holds a gear to a higher RPM before upshifting. On a long steep hill I down shift manually before beginning the climb and I also increase my speed so I carry some energy into the hill to delay the drop in speed.
Managing energy also includes dealing with the downhill portion also. Our brakes are not designed to be “pumped” to keep them cool so we need to start a downhill run at a low speed and in a lower gear allowing the Jake brake or transmission retarder to control the buildup of speed. Out west on 6 to 8 percent grades I have slowed to below 55 MPH which is the top speed in my coach for 4th gear. I target 50 MPH as my desired downhill speed. As speed builds I either apply another step of the retarder, or if I had a Jake would go to the max level. If it continues to build, and before I hit 55 MPH I would make a fairly hard brake application to bring the coach to 45 MPH, and continue trying to maintain the speed with varying applications of retarder or Jake. If the speed built again, I would again reapply brakes to come back to the lower speed.
Once a coach is going fast it is very hard to stop, and the reverse is true when hill climbing in that once a coach gets too slow it is hard to build speed. We all have to work with our engines, transmissions and jake or retarder to maintain our speeds to the target range.
Or we can just sit and enjoy the view and let the engine and transmission do what they are supposed to do, but the results will not be as good as when we participate.
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My two cents. Since I’m well past the age where I’d be competing for a “Gold Medal” my practice is to be slow as I top the grade, get into a lower gear, put on the jake and stay in the truck lane. There is a reason for runaway ramps and I for one don’t need the definition. Slow and steady downhill will get you back to flat land safely.
Now going uphill, I work to keep the RPM’s in the 1,800 range and where possible I will pull out of the truck lane to pass a slower truck when the space is available to be taken. Going uphill I spend about half of the time glancing in the rearview.
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Ole man that I used to work with that was a mechanic of our Detroit’s 3 and 4 53 2 strokes told me they would last longer if you let them scream. Don’t know if this holds true on the 8 V’s but I sure like the sound. As far as jakes, I will play with the gears if needed when I’m stopping. Mine will not downshift and let the RPM’s get crazy if I push the wrong gear. That’s a good thing cause I’m always doing something wrong.
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I always go down the hill in 4th gear top is 55 mph easy to control bus as for going up performance mode for me , I will down shift on off ramp to help slow bus down with jakes and brakes very little to stop ! Just enjoy the ride , I doubt you can out think the computer let it do it’s thing what’s 15 mph slower or faster going to do!!!!!!
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It is said in Colorado a big rig can slowly go down a big hill time after time or you can go fast down hill maybe only once.
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