Downhill Speed Control - Proper Gear Selection vs Retarder

Topic: Downhill Speed Control - Proper Gear Selection vs Retarder (Read 5141 times) previous topic - next topic

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #25 – May 04, 2018, 11:53:56 pm

Quote from: Tom Lang – May 04, 2018, 11:12:09 pm

I'm content with the present setup.

Whenever I take my foot of the throttle with the retarder active, the retarder does apply braking force, slowing the rig down more than merely coasting would, hence the need for brake lights.If I don't want or need that amount of braking, I can push the joystick forward or apply slight throttle.

Anyone with a 2003 should have the same setup as I do.

Tom I have an 2003, can guarantee mine does not apply any brake lights when retarder on with stick on any position. If your brake lights stay on any time retarder [on stick], does not seem a good idea. If retarder on, and you need to stop quickly with brake pedal, brake light would already be on because you are on retard, so no indication of you braking hard. I am not talking about braking ability, I am talking about the guy behind me, and if he can tell the difference between me slowing slightly on retard, or jamming on the brakes for a emergency. Cannot imagine DOT approving a brake light system that is disabled just because the lever is in the first position, [ in my coach, 42000 lbs], 1st position is just barely slowing down coach, only slightly better slowing, than coast down. It is fine running retarder in city to slow down between throttle use if you think it necessary, but personally would not want brake light on, any time retarder is on. Rather have it when I step on the brake. To each his own.

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #26 – May 05, 2018, 12:04:18 am

Mine is how it came from the factory. Is yours?

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #27 – May 05, 2018, 12:27:55 am

Quote from: Tom Lang – May 05, 2018, 12:04:18 am

Mine is how it came from the factory. Is yours?

Yes, if I look at 12 volt wiring, and air brake diagram, [mine anyway] brake light pressure switch is on foot brake air line, nothing connected to retarder electrical circuit. If your brake light is connected to retarder, would love to see schematic, maybe Foretravel made mine differently.

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #28 – May 05, 2018, 12:42:40 am

This has been discussed before. A long time before

Brake lights with retarder activity (split from Retarder Operation)

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #29 – May 05, 2018, 12:48:01 am

Quote from: craneman – May 05, 2018, 12:42:40 am

This has been discussed before. A long time before

Brake lights with retarder activity (split from Retarder Operation)

Thanks.

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #30 – May 05, 2018, 07:44:07 am

Our 95 didn't come with the joystick option, so I added it a couple of years ago, plug and play installation. I didn't add the brake light relay option so there is no brake light operation when just using the joystick, only when service brake is applied. Because I only use the retarder joystick on long downhill grades, I don't feel its necessary to have the brake lights on in that situation. Not much different than using engine braking in my opinion.
The retarder with the joystick is a great option, wouldn't want to be without it while in the mountains. Just keep a close watch on the tranny temp and engine RPM. Not difficult to find a stick position and gear that keeps all things in check.

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #31 – May 05, 2018, 10:39:54 am

I've seen this dog fight before. Everyone is entitled to their opinion. Mine is if I am going down a steep grade and there are vehicles behind me, when I pull the retarder stick and start slowing down the lights will inform them. As far as the lights staying on going down a grade, they are brake lights and any new vehicles will think I am riding the brakes. I don't care what they think and they will just have to get over it.

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #32 – May 05, 2018, 11:23:59 am

I feel the same way, when the retarder is being used, I am braking, therefore the brake lights are on. Anyone behind me hopefully will see my lights and they will slow down also.

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #33 – May 05, 2018, 11:37:55 am

We added the relay, but with a dash switch can decide when and if to have brake lights on with retarder. Mostly drive with retard not activating brake lights. Relay is next to our two air brake switches mounted on forward top of metal wall in our street side forward compartment. This arrangement also keep our Jeep tow brake from activating with retarder.
Now if I only knew if the brake lights come on when we are driving the Jeep on the highway, and Adaptive Cruise Control or Emergency Braking systems automatically slows down the Jeep.

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #34 – May 05, 2018, 12:09:39 pm

1) The city buses in St Paul have a center rear light that is green if the bus is accelerating or at steady speed, yellow if no throttle and no brake and pulsing red if braking.

2) Choose what works best for you going down hill, your comfort level and safety comes first. I use Gears, Retarder, Service Brakes in that order. Works for me.

3) Add one of these clever programmable timers to your retarder activated brake light circuit and it will let you set the brake lights to flash in any pattern or groups of patterns in any timing you want. Regular brake activation will override the pulse patterns.

You can make your regular brake lights do something too like flash three or four times and then be steady, sort of like the EMT vehicles do.

Universal Brake Light Flasher/Strober - M1 model [FLSHR_M1] - .95 : 3rd...

Or just use them for any timing function. Want something to turn off or on in say five minutes? Like your porch light? Or water pump? These will do that. They have one that switches power and another that switches ground.

If you can think of it there is probably a solution out there to make it so.

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #35 – May 05, 2018, 12:27:26 pm

Another reason I'm happy FT wired the brake lights to come on with the retarder is that pulling full back on the joystick does apply some serious braking. This is how I initially slow at off ramps and coming to stop signs and lights, followed by either backing off the retarder or using the brake pedal, as needed.

Letting the car behind me know I'm slowing or stopping is a good thing.

The retarder is after all a braking system.

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #36 – May 05, 2018, 05:23:32 pm

My only concern about the retarder activating the brake lights is that I believe it also activates the toad brakes through the RoadMaster InvisiBrake. It worries me that I am wearing out the brakes on my toad. Am I understanding this correctly?

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #37 – May 05, 2018, 06:29:32 pm

Probably. I have SMI AirForce One brakes for the toad, proportional with the coach air brakes.
I notice the retarder braking is not as effective with the toad as without. But the service brakes, aided by the retarder and toad brakes, really kick in on hard braking.

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #38 – May 05, 2018, 09:33:55 pm

I guess it depends on your individual driving habits, I use the service brakes for braking and only use the Joystick function of the retarder for maintaining safe speed on downhill grades. Yes if you were to full throttle back on the joystick then it would be prudent to have the brake lights on to warn anyone behind you that you are rapidly decelerating. Not sure how this affects the toad brakes as we don't (as of now) have a towed vehicle. But it would be a concern, obviously would not want the toad brakes to be activated unless service brakes are applied.

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #39 – May 06, 2018, 07:54:48 am

The attached seminar PDF from the folks at VMSpc provided me with an interesting perspective in regard to this topic. Probably relevant with or without VMSpc but certainly showing the advantages of having VMSpc data available.

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #40 – May 06, 2018, 11:14:35 pm

I don't know if our coach is heavier than others but we had to manage things very carefully if we didn't want to build a lot of transmission heat. This means higher rpm and lower gears. One of the more annoying things about descending is that the maximum rpm off load (using the retarder) is a bit higher than maximum rpm under power. This means that if you ride down at a higher rpm, you have to continue to decelerate to get the engine to a safe speed to apply power, and you have to apply power before it will upshift. I mean lets be serious here, it's like a dream come true driving this vs other things I've driven. Just a minor nitpick.

We got passed by so many trucks and rvs down steep grades it made me wonder if I couldn't just pick it up to normal highway speed and be okay. When it said "truck speed 25mph". We did 25mph.

We also were fairly slow up the hills. I made sure to keep engine temps under 200F when I know the engine can take something like 220. For us, this actually meant pulling over and cooling off during our climb of echo summit, but never had to any other time.

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #41 – May 06, 2018, 11:32:20 pm

Quote

you have to continue to decelerate to get the engine to a safe speed to apply power, and you have to apply power before it will upshift.

That has always bugged me too.
jor

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #42 – May 07, 2018, 08:36:03 am

Quote from: Mark D – May 06, 2018, 11:14:35 pm

One of the more annoying things about descending is that the maximum rpm off load (using the retarder) is a bit higher than maximum rpm under power.

YES, most engines do have a higher RPM off load than governed RPM under load.

Here are numbers for a 2003 Cummins ISL:

Idle speed: 600-800. Peak Torque 1200 lb-ft @1300RPM. Peak HP (400) @2100. Governed RPM 2330. Overspeed 2600.

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #43 – May 07, 2018, 10:51:12 am

When descending above governed rpm, doesn't a tap on the throttle trigger an up shift? I seem to recall it doing so.

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #44 – May 07, 2018, 10:55:08 am

Quote from: Tom Lang – May 07, 2018, 10:51:12 am

When descending above governed rpm, doesn't a tap on the throttle trigger an up shift? I seem to recall it doing so.

Two answers:

Whether you touch the throttle or not, when the RPM reaches "overspeed" it will upshift.

If you touch the throttle (even just barely touching it) the transmission will upshift even if well below governed RPM (think of it as a "normal light throttle upshift".

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #45 – May 07, 2018, 12:33:47 pm

Quote

Whether you touch the throttle or not, when the RPM reaches "overspeed" it will upshift.

Looks like we have two threads going on this one. Anyhow, I use the tap the throttle method as I have always been afraid to let the engine wind up to the overspeed limit. Does anyone do that and just let the Allison upshift?
jor

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #46 – May 07, 2018, 12:50:05 pm

On our trip down the West Coast from Washington State we used the retarder to slow for curves and down hills. Coming down the very steep and long pass in Death Valley I apparently let the retarder do too much of the work and got a trans hot red light. Downshifting did not really work so I just used the air brakes instead of the retarder and then took a break to let things cool down - the light wen out in less than a minute. No drama, smoke or anything like that and everything worked fine across the rest of the USA. The setup in our 36' 1997 U270 makes for a very good drivers machine with lots of feedback and control...this coming from a former tour bus driver in Alaska driving the robust MCI motorcoaches with 8V92 Detroits on some of the more challenging dirt highways in the USA.

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #47 – May 07, 2018, 01:20:40 pm

Quote from: jor – May 07, 2018, 12:33:47 pm

Looks like we have two threads going on this one. Anyhow, I use the tap the throttle method as I have always been afraid to let the engine wind up to the overspeed limit. Does anyone do that and just let the Allison upshift?
jor

I am with you, I initiate the up-shift. Think of the Allison's automatic upshift as the "fail-safe".

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #48 – May 07, 2018, 02:21:34 pm

Tom and Ron [red tractor], I talked to Aubrey Lee [ex Foretravel Electrical guy] when at MOT this morning and he confirms you were right, and Foretravel did install a connection that activated the brake lights when the Joystick retarder became standard. He said they did it because DOT or some other gov. agency required it. I guess a PO disabled it on my coach. If anyone knows where this connection is, would appreciate the info. Would probably hook it up again, and install a switch so I could defeat it when necessary.

Re: Downhill Speed Control - Proper Gear Selection vs Retarder

Reply #49 – May 07, 2018, 04:47:34 pm

I'd look in the schematics. I suspect you will find a relay.

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