Rookie DP Driver seeks advice

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oldryder

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Nov 8, 2017
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1st day on the road. 2005 Winnie Vectra 400hp cummins 6 spd allison.

Level at 65mph is 1600 rpm and 12.5 lbs of boost. short steep grades (overpasses) cause 25-30lbs of boost. engine temp was about 185; got to just under 200 on a long grade where I slowed down to 35 mph in 3rd gear.

Questions: what level of boost is OK for an extended period?

what is desirable range for engine RPM. Feels like 16 - 1900 is good; not sure about any higher rpm.

For engine brake: apply at crest of hill?

can trans be shifted while engine brake is engaged?

other question(s) I should be asking?

thx to anyone taking the time to offer advice.
 

donn

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What motor? Look up the specs for your motor and see what the torque curve looks like. You want to keep the RPM low to middle of the torque curve. That should get you good performance. As for boost? What ever it takes. Since you just bought this MH look at the radiator and cooling system closely.
 

thelazyl

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Molalla, Oregon
I didn't learn about my engine brake until our 2nd trip in our DP. I have it on almost exclusively now unless I am on a freeway (I don't want to slow down rapidly if I take it out of cruise control). It's a wonderful feature.
 

Ksouers

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My truck driving era was late 80's to mid 90's, Cummins NTC and STC, and Mack. This was just before the electronic engines. 9, 10 and 13 speed manual trannies.

Downhill Cummins was good to about 2100, it won't go any faster on it's own but will if you let it get away from you on a hill. Slower was better, but about 1700 to 1800 gave good braking. Uphill, shift at 1600, try to keep above 1700. Notice a pattern? You can't over boost, so don't worry about it.

Engine brake when you need it, avoid the service brakes if possible, but don't be afraid of them. Use them to slow down, don't keep feathering them to maintain speed. That's what your engine brake is for. Playing with the service brakes will heat them up and smoke.
You can use the engine and service brakes at the same time, so if you've got a long downhill, say Jellico or Monteagle, it's ok to use engine brakes full time and occasionally take a longish tap at the service brakes to slow down. Remember, you don't have to maintain a steady speed, just stay in a safe range.

I've fallen off those hills with 80,000 pounds more times than I care to remember. Your rig, a 400 Cummins and a Jake, should have little problem with those hills. Easy peasy. Just pay attention.


Hope it helps.

Kevin
 

Utclmjmpr

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You more than likely have the ISL engine and it's protected againsed all the concernes you have by the electronics,, don't worry about it..>>>Dan ( Do you actually have an engine brake or is it an exhaust brake?.)
 

docj

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I've driven ~70k miles in my Beaver powered by a humongous Cat C12. Instead of being fearful about your engine you should learn its strengths and limitations. Within reason, nothing you can do to it will hurt it. Depending on the weight of the MH and the power of the engine, driving DPs can vary quite a bit. On 2-lane roads going though rolling countryside at 55 mph I love to put mine in 4th and just enjoy driving it more like I would a car. That won't work for every MH but it sure is fun in mine.
 

SargeW

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The Cummins and Allison work well together and the built in electronics will not allow you to break something. For instance even if you try to downshift to 1st or 2nd gear at 60 mph, the trans just won't do it until the speed is low enough not to hurt the trans. Likewise, even going down a grade with the engine brake on, the trans WILL upshift to a higher gear if your speed gets to high for the one you are in.

Don't be afraid to take a slow steady pace going down a grade with the engine brake holding you back. There will always be someone behind you in a hurry and want to pass you. Let them. Stay to the right lane and relax. In time you will learn what speed is comfortable and safe for your rig. My personal preference is to always leave the engine brake engaged. In a panic stop situation, I promise you will not have the time to stop and think about finding the switch for your engine brake.

My Cummins ISL09 is newer than yours, but it is quite normal for my Cummins to hit 210 degrees when pulling a grade in summer. I will often downshift manually if I see a substantial grade coming up to bump the engine RPM about 200 RPM to assist with keeping the coolant moving quicker, and reduce the lag in downshifts and keep the speed up.
 

Gary RV_Wizard

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Agree with the others - it's pretty much bullet-proof and the Allison tranny, working with the engine computer, won't let you do anything dangerous to its health. Modern electronic control engines & trannies have largely done away with the concerns and manual intervention that old timers felt necessary on their diesel engines. Some owners think they can do a better job of engine & transmission management than the algoritms programmed into the computers by the powertrain engineers. They are almost always wrong, but they programming is designed to let them play if they wish.

Those temperatures are within normal range - the engine computer (ECM) manages cooling within a broad range.

The boost pressure algorithm is programmed into the engine computer at the factory. Boost increases to help meet horsepower demand. You don't have to do anything about it or worry either. High boost indicates the engine is producing near its max power.

You can leave the engine or exhaust brake enabled 99% of the time and it will engage as needed on downhills or when slowing. If you find its interventions annoying, turn it off except when you want it to help, e.g. at the top of a grade before starting downhill or if slowing to a stop from highway speeds. Note: many Cummins ISL engines have an engine brake built in, but some do not and there is an external exhaust brake instead. For practical purposes, you don't need to know the difference in how they work - the net result is the same.

Yes you can shift while the engine or exhaust brake is engaged, but it is pre-programmed to handle that by itself. Rarely, if ever, would you need to shift by yourself.

The Allison will work with the ECM to always attempt to operate in the peak horsepower & torque range, roughly 1600 rpms for a Cummins 400 ISL engine. Leave it in drive and push the go-pedal; the Allison will figure it out.
 

Larry N.

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can trans be shifted while engine brake is engaged?
When the engine brake is engaged, the electronics have already selected a lower gear (it may not have shifted yet), possibly lower than you would try yourself. On the Beaver I had, it selected 4th gear when engaged, but on my Ventana it selects 2nd. Yet the Beaver was more effective, due to being a more effective type.

You can leave the engine or exhaust brake enabled 99% of the time and it will engage as needed on downhills or when slowing.
With many units that is true, but the Beaver I had wouldn't let you have the brake on AND the cruise control engaged at the same time -- with my Ventana I can and do keep the brake on almost all the time.

Some owners think they can do a better job of engine & transmission management than the algoritms programmed into the computers by the powertrain engineers.
I'm probably one of those you refer to Gary, but while your statement is true in general, I've found that minor manual tweaks in certain situations can help a little. For instance when going from level ground to a steep climb you can manually anticipate the need for a downshift just a tad earlier than the electronics will do it, with the result (time and again) that you don't slow down quite as much so early thus losing less speed on the hill (up to a point, of course). Even on fairly long slopes it often means that my minimum speed at the top is 39 mph instead of 34 mph. Of course besides the shift, manually (pedally???) adding a bit more throttle than the cruise control would is another piece of that pie -- the two things together.

So what the engineer designed is pretty good, but occasionally could use a touch of fine tuning. But that fine tuning isn't required to get up the hill, it's just an enhancement, and I usually only find it worthwhile on rather steep hills, especially if they're long. The rest of the time auto works great.
 

SargeW

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That's known as the "human" part of the equation. I can see that long steep grade coming, but the drive train doesn't get notified until the speed is dropping and the RPM's are falling. Then it downshifts and starts playing "catch up". By anticipating the extra load, downshifting just to 5th from 6th gear gives you a head start on the grade. My temps and engine load is happier that way.
 

John From Detroit

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Davison Michigan
Every diesel has a optimum RPM that it works best at. Do a Google search to find out the RPM for your particular engine.

That is true of gas engines as well. My motorhome (a Gasser) liked 55-60 MPH. my Jeep 65 (have not tried it at 60)

And when it comes to engines you will find as many opinions as there are engines
But when it comes to Transmissions the sound of ALLISON drowns out all competition Even FORD admits that Allison is the best.. (Though they don't actually come out and say that but their latest and greatest is "The answer to the Allison".. or so they claim)..
 

oldryder

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Nov 8, 2017
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Many thanks for all the advice. I've got this pretty much figured out and I am VERY impressed with the 400hp Cummins/Allison driveline.

mark in MN
 

A Traveler

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...Some owners think they can do a better job of engine & transmission management than the algoritms programmed into the computers by the powertrain engineers. They are almost always wrong, but they programming is designed to let them play if they wish.
Well geez, I sure do appreciate being told I’m almost always wrong. You must be related to my wife. ;)

I KNOW I can do a better job than the computer, for one very important reason. I can anticipate something that is about to happen and act accordingly. The computer can only react to something that has already happened, and by then it’s too late.

The Allison will work with the ECM to always attempt to operate in the peak horsepower & torque range, roughly 1600 rpms for a Cummins 400 ISL engine. Leave it in drive and push the go-pedal; the Allison will figure it out.
I strongly disagree with this. These vehicles are not cars! They don’t have 20 to 30 pounds per horsepower, like a car. If we’re lucky, we’ll have a 100 pounds of vehicle for every horsepower in the engine, and maybe more! You cannot put these heavy, underpowered vehicles in DRIVE, push the go pedal and watch the scenery go by. If that truly was their intent, the manufacturers would not have provided a way to override the computer.

Attempting to keep the RPM at only 1,600 (Cummins ISL) while climbing a long grade is a sure-fire recipe for an overheat situation. The horsepower peak for the ISL is at 2,100 RPM. And it is horsepower that gets you up a hill at good speed, not torque. Climbing a grade in a gear that allows me to run at 1,900 to 2,100 RPM gets me:
  • Max Horsepower
  • Max Engine Cooling Fan Speed
  • Max Water Pump Speed
...all of which are desirable things. The computer, if left to just automatically do its thing, will not do that.
 

billwild

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What was not mentioned is you may want to turn off the exhaust brake on your Vectra in cities and small towns. Very often there will be signs to remind you to turn them off, because of the noise they make. City bylaws.
 

A Traveler

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An exhaust brake doesn't make any noise.

And most of the coaches with true compression brakes ("Jake" brakes) make very little noise because the variable geometry turbo muffles the sound. My Jake Brake makes almost no noise at all.

I pay no attention to those local restrictions because they are all based on noise...and my coach doesn't make any noise when the Jake is engaged.
 

SeilerBird

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St Cloud Florida USA
I KNOW I can do a better job than the computer, for one very important reason. I can anticipate something that is about to happen and act accordingly. The computer can only react to something that has already happened, and by then it’s too late.
I'd put my money on the computer. Computers have been programmed to anticipate for decades. Ever hear of a hurricane warning in Florida?
 

Larry N.

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An exhaust brake doesn't make any noise.

And most of the coaches with true compression brakes ("Jake" brakes) make very little noise because the variable geometry turbo muffles the sound. My Jake Brake makes almost no noise at all.

I pay no attention to those local restrictions because they are all based on noise...and my coach doesn't make any noise when the Jake is engaged.
What kind is your rig? Are you listening to it from outside? My 2007 Beaver made a huge racket when the brake was active, while my 2016 Ventana is much quieter but still makes a moderate amount of noise. I heard (hear) very little noise inside, but if it's active when going through a tunnel or, often, under an underpass, I can hear reflected noise from outside. Even gas engines make noise on decelration, though they tend to be so well muffled (except some trucks) that the noise is minimal.
 

A Traveler

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I'd put my money on the computer. Computers have been programmed to anticipate for decades. Ever hear of a hurricane warning in Florida?
You're kidding, right? That is a completely different thing. Weather computers can see a hurricane coming for days. The computer in your coach can't see a foot in front of you! It cannot see a grade coming, nor can it downshift at the bottom of the grade because it doesn't even know it's on a grade yet.

What kind is your rig?
Cummins 400 HP ISL and an Allison 3000...the same power train as in thousands of other coaches on the road today.

Are you listening to it from outside?
I have listened to my coach as another person drove it by me with the Jake Brake engaged. The noise of the Jake was about the same as the exhaust sound when under power. The sound is different, but not loud.

My 2007 Beaver made a huge racket when the brake was active, while my 2016 Ventana is much quieter but still makes a moderate amount of noise. I heard (hear) very little noise inside, but if it's active when going through a tunnel or, often, under an underpass, I can hear reflected noise from outside. Even gas engines make noise on decelration, though they tend to be so well muffled (except some trucks) that the noise is minimal.
I'm sure there are differences among different coaches with different engines, turbos and exhaust systems. I have a friend whose Jake Brake on his motor home sounds just like the big trucks, with that terribly loud "Braaap" sound when decelerating. But my coach, and a lot of others that use the variable geometry turbo, just don't make much noise.


Yeap! Your wife sounds like a smart women. ;) ;) ;)
LOL!
I've got to show her this thread.
 
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