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Retarder Braking
Greetings:S
Do most all Prevost Coaches come with Retarder Braking Systems in some form? I have read Coach ads that state Jake Brakes, but not all ads will indicate retarder braking. Do I need to look specificly for a retarder braking in the “for sale” announcement on a Coach or do all come with some retarder braking. We will be using the Coach primilarly for travel from Green Bay Wi to Scottsdale, AZ. with a lot of side trips to the National Parks in the West. That means lots of Mountain Driving. Having driven the Rockie Mountains in a conversion van I now realize what the challenges are with a “big rig”. I have watched YouTube videos of Jake braking and am very impressed with the control one has going down hill with a truck and would assume that the same control would be there with a Prevost. I also realize that horsepower is needed to get up those mountains and while the standard 1 HP per hundred pounds of weight is standard do I need to look for more HP in a rig for those mountain climbs? What about turbocharging for high altitude; is that even offered or needed. Thanks for the insght, Cheers
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32 Replies
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I am not aware of any Prevost motor home conversion that does not offer a Jake or a retarder. I have had a Jake and a retarder and it is my opinion the retarder offers better braking and is more flexible with 6 levels of braking where the Jake has 2. The retarder may cause some heating issues with the transmission if you do not manage speed or temps, but if you anticipate the needs you can easily descend 6 and 8% grades without touching the brakes and without excessive heat.
A Jake doesn’t require any advance planning and has no consequences relating to its use, but it will not offer the braking force provided by the retarder.
All Prevost coaches, regardless of which engine is used has a turbo. Our coach weighs 53,000, I tow a 6700 pound Hummer H2 and while I am not capable of climbing every hill at the posted speed limit I am not the slowest vehicle up the hill. You can boost HP but if you cannot reject the heat that extra HP creates DDEC is going to derate the engine so the bottom line is when you need it the most you will not have it available. I would far rather have better fuel efficiency than added power because no matter where we live or drive we just are not spending enough time climbing hills to want the additional HP.
As a practical matter you likely have little control of your uphill speed with or without additional HP because it seems to me that when I try to storm up a hill someone is sure to pull out in front of me, and once my momentum is lost I’m stuck at a lower speed.
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Thank you for enlightening me. Your post was most helpful. Thank you very much
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If lots of mountain driving will be your norm, I would want a Jake as opposed to a Retarder. Out west in the big mountains, the Retarder will heat the tranny temp big time. My Liberty had the high temp light come on going west from the Eisenhower tunnel, even though I geared way down at the top and used a good speed for the downhill. It may have just been the nature of that bus, I know others don’t have that problem.
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The techique I have used successfully is when a long steep downhill is posted I drop my coach down to 50 MPH because I am going to use that as my target speed. I shift into 4th and set the retarder on the 2nd or 3rd position. I monitor the speed. Usually on a 6 to 8% grade the 2nd position is adequate, but if I notice speed building I drop it to the 3rd position. That usually slows me below the 50 MPH target so I drop to the 2nd position until speed approaches 55 MPH which is top speed for 4th.
I have done this technique multiple times out west and was able to easily control temps to below 230 which I arbitrarily chose to be my target max temp.
On those rare occasions when I was concerned about temps exceeding my target I applied the brakes firmly with the retarder master switch off and dropped back to 45. Then I reapplied the retarder and again went to the 3rd position. If you apply the brakes with the retarder on the retarder applies itself proportionally to the braking force so it does not allow temps to drop.
But fear not if you have a retarder and choose to use it agressively. The computer will limit its use if the coolant level gets too hot (around 300 degrees) so it will protect itself. I just did not want to get the temps up that high.
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I remember reading on a post a while back where someone wanted more horsepower to climb hills and one of the very knowledgeable members of this group made a comment that I will forever remember:
Torque gets you up the Hill…
Horsepower burns fuel.
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torque X RPM divided by 5,252 = horsepower
SO, by definition, increasing the horsepower at the same RPM will proportionally increase torque. The reality is that you increase torque at the same RPM, resulting in a higher horsepower calculation.
Horsepower is just a calculated number since you only really measure torque and RPM.
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The Series 60 torque curve is the problem.
We have our coaches programmed in economy mode as the default so upshifts will occur sooner at relatively low RPM and when starting up a hill the delay to downshift ends us dropping down to a lower gear and ending up with an RPM well below the torque peak.
Unlike the Volvo engine which develops max torque early and holds an almost flat line at max torque up through almost all of the rev range, the Series 60 develops max torque at a higher RPM and then falls off pretty quickly. So climing a hill in a Series 60 is best done by shifting manually and holding the gears almost to the 2100 RPM limit so when you upshift you hit the torque peak as closely as possible in the next gear.
In other words, drive it like you stole it. It helps if you leave the cruise control on because with DDEC you get a little more power than if you have it off.
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I will have to keep an eye on trans temps as I don’t have a trans temp gauge per se, I have a gauge built-in the computer read-out that I can toggle to get it on the screen.
In my other thread (New Build of a 2015 Liberty), I had mentioned about the brake lights not coming on with the retarder activated. Since this thread is about retarder braking I thought I would pop in here with the answer that I asked Ft. Worth Prevost.
I had noticed that our brake lights were not coming on during retarder activation. Personally, I thought it would be a good idea to have the brake lights on while ‘retarding’ so others would know that I was slowing. There have been pro’s and con’s on the idea of brake lights.
The Prevost people say that mine should activate with the retarder. There is a remote possibility that I noticed it incorrectly and will give it another try. I’m really now at 50/50 on wanting it or not. Jon mentioned that people would think that I am constantly putting my brakes on is a good point. I need to digest this info and think about what I want.
The folks here at Prevost Ft. Worth are very nice and accommodating. I came in for a fog light replacement and threw a couple of other things at them to check, they were so kind to work me in. Thanks Jason A.!
Mark
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My 1991 has a jake system I use all the time. Pull a 2013 Ford Super crew and it helps big time with the stopping. Don’t know about the retarders that work off the trans and they sound in big hill situations might heat things up in a hurry but they have been around a while and work also.
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I too have had both the Jake and a Retarder and the retarder in my coach has never heated the transmission fluid above 225 degrees,I have come down Black mountain with a stacker trailer grossing 71,000 and never touched the brakes .The retarder will generate 500 brake horse power which is IMHO much greater than the jake that I had.
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My bus came new with a Jake AND a Retarder. Never seen another one like that. But, mine was ordered new with a stacker, so maybe that was the reason. I use the Retarder most of the time, and have never overheated the trans.
In regards to activating the brake lights when the retarder is on, I prefer mine NOT to do that, so that when low amounts of Retarder are used, the brake lights are not constantly coming on and off. But the main reason is, when I’m towing a trailer with electric brakes, It does not activate the trailer brakes every time the Retarder comes on and off.
If I’m using the retarder to maintain a speed limit going down a hill, why does everyone else need to know I’m using it, or think I’m getting on the brakes, and I’m not slowing down below the speed limit.
I use the Decel switch to activate brake lights as needed if I need to show my brake lights without getting on the manual brakes.
Just my 2 cents.
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I agree Jerry I pull trailer all over and I get it into 4 th gear and go down hills I have never had it over heat I like the retarder I have had both I like the first one best , I go all over the USA and Canada pulling a trailer hope that helps
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Jerry, you should have your brake controller set up differently with a switch on the brake pedal so it is only applied when you actually have a foot on the pedal, not just when the controller “see’s a brake light”.
Anyways, I have both Jakes and Retarder, there is no comparison the retarder has amazing slowing power.
With proper use, and watching temps and using Transynd in the Allison temps are not an issue. Depending on hills I like to use a mix of the Jake and retarder and manually applying some trailer brakes too.
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Mark,
I think you can monitor the transmission temp at your message center. Since your coach is a multiplex coach you might have to leave your coach the way it was set up because your system is constantly monitoring what it sees as normal. I’m not even sure you have relays for your stop lights because a lot of the circuit breakers, fuses, rellays and wiring that is on non-multiplex coaches may not be present on yours which makes extensive use of modules that handle all the switching and circuit protection.
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Yes, you are right, I can monitor the tranny temp at the message center. It takes a couple of toggle moves to get there.
I think I’m just going to leave the brake situation as it is (I don’t think they come on with the retarder). As long as I know how I’m set up ‘now’, I can apply the brake pedal slightly as I’m using the retarder if I feel like I need the brake lights to be activated.
Mark
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