[Ron]

Hi,we dont have a prevost but in my next life ? but we have a cc magna that is great,we have a 3 stage jake brake and wounder if i should use it when the road is wet,and chance of it sliding the rear tires. thanks Charles

[Archived]

Charles, wet is no problem. Ice, now that’s a whole nother story…….

[Larry & Diane]

Harry,

Just like service brakes, I turn the Jake on when I need it.

[glen]

I gotta remember to always let you drive ahead of me Per.

The Jake is a standby brake assist and when you need brakes the most, such as when the south end of a northbound semi-trailer is filling your windshield you are already too late when it comes to tuning on a switch.

If you only use it for control when descending hills controlling it manually is OK, but to think you are actually possessing the motor skills and reaction time to get the jake to assist you in an emergency stop you are kidding yourself because in a true panic stop you are standing on the brake pedal and with both hands you are pulling up on the steering wheel so your foot can really get on that pedal.

[Archived]

Jon,

If the south end of a northbound semi-trailer is filling your windshield, neither brake is going to do you any good, because you will be dead a split-second later. You have a retarder, so you have a different system, but for those with Jakes, the big difference is what gear you have the transmission go to when the Jake is engaged. If you have it programmed to not downshift at all, you will not get any worthwhile braking out of 6th gear until the coach slows down. You would have to manually downshift to get worthwhile braking. And I can hit the Jake switch as fast, or faster than anyone can manually downshift the transmission. Regardless, the Jake will have a delay either way, so it won’t help much in a true emergency. When I engage the Jake, I have maximum braking available as soon as it engages, and I can modulate the engagement with the throttle. Frankly, I consider my system to be much safer due getting maximum braking if I need it.

If I ever drive behind you, I will leave my Jake on, since your retarder is slightly more effective than the Jake.

[Jim/Chris]

Per,

Is the reason you don’t leave the Jake on all the time because of your decision to default to 2nd gear? Mine is never off and works in harmony with the cruise as well as the automatic downshifting of the transmission when slowing down.

[Andy]

Tru dat, Tom.

I got very used to that setup on my Affinity, and like it that way. When we are on the interstate nowhere near other cars, I see no need to leave the Jake on. As we go through downhills and uphills, I engage it as necessary. It makes it much easier in heavy traffic–going through Austin as an example. In heavy traffic, I leave it engaged, and the transmission will shift up when traffic speed increases, and when it slows, I lift my foot off the throttle, and get instant braking. Most of the time on the open road, the Jake stays off. If I leave it engaged on the highway, it will slow down when I don’t need slowdown–I let the coach coast downhill whenever I can, as long as speed does not exceed about 75 MPH.

[Per]

Admit it Per………….it is all about fuel economy.

[Jim/Chris]

Hi Jon,

When I first read your post about fuel economy I thought it was more of Jon’s humor on parade! Then I thought about when I’m in the car and using the transmission to slow down. I’ve not really thought of it from the fuel economy standpoint. But as you change the rpm of the engine you change the fuel used.

I didn’t think about it from the standpoint of the Jake either but what you’re saying the same principle is involved. My question is, is there any way to determine what the actual fuel difference is?

Or was Jon in fact using his hallmark humor and I fell for it?

Harry

[Archived]

Jon,

I’m still trying to get Prius mileage out of our coach! I guess you could call me a cheapskate, but my checkbook would definitely disagree with you after visits to Prevost, Marathon, Jeff, and American Fleet!

Harry, anytime you lift your foot off the throttle, you stop using fuel (except in cruise, of course), and if you have an instantaneous mileage readout, you will see fuel mileage go to 99.9 MPG. The more you can make that happen, the better mileage you get. Of course cruising at a lower speed is the best way to improve mileage. Our lifetime average on this coach for 30,800 miles is 6.73 cruising at 68 MPH, and Jon is just jealous!

[Archived]

Jealous Jon, I’ve heard of him… Doesn’t he reside right here on the forum? Yes I’m sure of it! Per I think you put your finger on it, I think it’s exactly that with a little paranoia and passive aggressive tendency thrown in! 🙂

Harry

[Per]

Adding an attempt to add 003 MPG to the coach performance by not allowing a retarder or jake to do the thing they do best may be OK, but when there is a discussion about how to best use those features without mentioning fuel economy as a consideration can be misleading to relatively new owners who are trying to figure out how to best use those features.

Unless I am wrong programming a jake to 2nd gear may have a neck snapping component to its operation as it drops into the next lowest gear on its way down to the second gear that has been programmed. It is not such a bad downshift when going from 6 to 5, but even when programmed to drop to 4th that can be a harsh downshift from 6th if the coach is just below the top speed for 4th because it will drop into the lower gear and instantly push the engine revs up close to the 2100 RPM limit. That’s tough on pasengers and all the mechanicals in the drivetrain. Remember in the upper gears the torque converter is locked so there is no cushion to downshifts.

[Andy]

Jon,

I woudn’t call it necck-snapping. It is a firm downshift, but unless you are a real tenderbutt, it is not that bad. I much prefer the safety of having max braking. As far as the drivetrain goes, remember these are million-mile buses, so I wouldn’t worry about the drivetrain. I think there is no reason to baby your coach. I’d much rather save on the service brakes and use the Jake like it was meant to.

[Archived]

Per, Per, Per, there isn’t a truck driver in the country that turns off his Jake except maybe for those signs you see in towns, No Engine Brakes.:) The intended use is full time braking assist.

[Per]

Tom, Tom, Tom, always putting something else into the mix. Why would a city post “No Engine Brakes”? Does it mess up the road or something like that, or noise? I don’t ever remember seeing that sign!