Engine brakes

[Dr4Film]

palehorse,

There is a throttle position sensor that the ECM monitors to tell the systems what to do.

Dr4Film ----- Richard

[palehorse89]

Originally Posted by Dr4Film

palehorse,

There is a throttle position sensor that the ECM monitors to tell the systems what to do.

Dr4Film ----- Richard

That is what I left out when I said "closed position" that a sensor is monitoring. Thanks Richard

[laj]

Originally Posted by Dr4Film

palehorse,

There is a throttle position sensor that the ECM monitors to tell the systems what to do.

Dr4Film ----- Richard

I understand that part. what I meant to ask is how the trans. knows to stay in 6th and not start shifting down on a downhill as opposed to shifting down as in coming up to a stop. just seems to me you could have it one way but not both. sorry for my confusion.

[palehorse89]

I took it to a Allison dealer and had the change the default downshift of 4th gear(from the factory) and change it to stay in 6th gear. In the program you can have them change it to what ever you want , 1st-6th gears.
All of this info. was posted in the beginning of this thread..........

[docj]

Originally Posted by Ray,IN

Dr.4film asked an important question, the two types are totally different. The engine brake is banned by local law in many cities, the exhaust brake may be used anywhere.

Unmuffled compression brakes are banned by lots of towns but you would have to be right behind me to hear mine. I use mine without any fears of being pulled over.

IMHO there is absolutely no comparison between an engine brake and an exhaust brake. When my Jake is in the full position, the engine creates more than 300 HP of stopping power.

[laj]

Originally Posted by palehorse89

I am not sure what you have so.......... if it has a Allison transmission take it to a Allison shop so they can connect to your transmission's ecm and they can reprogram it to stay in what ever gear you want, no more downshifting and sticking your teeth into your steering wheel. I had mine done to stay in 6th gear a couple of years ago and love it. Mine still downsgifts on it own whe coming to a stop like it did before, just no harsh downshift when I let off the pedel now. You came out of the same school I di and a couple of others on here, but you are going to hear a lt of different opinion's about this I think.

but how does it downshift like before when coming to a stop, but with the reprogramming you can keep it in sixth when going down a hill using the jake. this would be the best of both worlds. I'm jealous if you got both

[docj]

Originally Posted by palehorse89

I took it to a Allison dealer and had the change the default downshift of 4th gear(from the factory) and change it to stay in 6th gear. In the program you can have them change it to what ever you want , 1st-6th gears.

Something I think is worth noting is that if you have a true compression brake, the braking action is inversely proportional to how close to redline your engine is. To say it another way, the closer to redline you are the more braking action you will have. If you leave it in 6th gear you will have a slower turning engine until you manually downshift it. I like having maximum braking power the moment the Jake comes on. JMO

[laj]

but there are times all i need is to hold my speed to say 60 and with just letting it drift off on the jake I can maintain this and never touch the brakes. don't need or want it going to 5th or 4th automatically

[Dr4Film]

You can never have total control of your transmission. The Allison has been built smarter than the operator.

It will NEVER downshift at a speed that would damage the transmission. Even if you manually downshifted using the shift pad, it will NOT if you are traveling TOO fast.

With your Exhaust Brake or Engine Brake switched to OFF you WILL end up damaging your brakes, drums, disks, etc. and eventually losing your brakes altogether.

I don't understand what people want to do with their engine brake system. They were designed to reduce the amount of pedal braking in downhill grades.

If you have an Exhaust Brake System, whether built by PacBrake or Jake Brake, then there are specific ways to handle the system when doing grades. Know what you up-shift points are and most important, start down the grade no faster than what speed you want to maintain while descending. If you have a Jake Brake Compression Engine Brake, they are a two stage braking system with LOTS of braking horsepower. Those systems are great to leave off when not needed. But then when they ARE needed, by using a foot-switch to activate the system and using the 2-stage dash switch will allow you to choose how much braking you want while descending the grade.

Dr4Film ----- Richard

[laj]

that's what I do now. I have a 3 position jake and o just use the position for what braking I want. I'm just use to fullers where I have total control just no auto down shifting when coming up to a light. just thought I was missing something with the Allison by not having both.

[Steve Ownby]

Originally Posted by laj

I understand that part. what I meant to ask is how the trans. knows to stay in 6th and not start shifting down on a downhill as opposed to shifting down as in coming up to a stop. just seems to me you could have it one way but not both. sorry for my confusion.

The transmission reacts to electronic control inputs from the engine ECM/transmission TCM. If you have the Jake switch on and the throttle closes then the transmission downshifts. At the same time the Jake will act on either all the cylinders or some of the cylinders depending on the position of the high/low switch.

You can affect this operation when cresting a hill by either allowing the throttle to close which will activate the brake or " feather" the throttle so the ECM doesn't get the closed throttle signal and the Jake will not activate. If you decide you need the Jake, just let the throttle close & it will activate. If you then decide you are slowing too much, switch from high to low. If you then start too pick up speed to quickly, switch back to high.

You have complete control but it does require operator input and a knowledge on the part of the operator as to how the system works.

The first time you descend a grade successfully using the above technique without using the service brakes, you will feel like a driver rather than a passenger.

[palehorse89]

Originally Posted by laj

but how does it downshift like before when coming to a stop, but with the reprogramming you can keep it in sixth when going down a hill using the jake. this would be the best of both worlds. I'm jealous if you got both

Yes it just stays in 6th now, I can manually with the key pad downshift it if and when I need to. The Allison pre-programed downshift patterns did not change when coming to a stop from lets say 60 mph, the engine brake comes on and at 50 mph(on mine) it downshifts to 5th on its own (Allison programing) and then if I remember right at 45mph it downshifts to 4th gear and so on and so forth right down to 5mph(program set point for "off") and 1st gear following the program. Changing what gear it stays in when you let off the pedal does not affect the shift points from Allison. Hope this helps you out.

[laj]

thanks for the explanation. may go to Allison tomorrow to see about reprogramming mine.

[laj]

Originally Posted by Steve Ownby

The transmission reacts to electronic control inputs from the engine ECM/transmission TCM. If you have the Jake switch on and the throttle closes then the transmission downshifts. At the same time the Jake will act on either all the cylinders or some of the cylinders depending on the position of the high/low switch.

You can affect this operation when cresting a hill by either allowing the throttle to close which will activate the brake or " feather" the throttle so the ECM doesn't get the closed throttle signal and the Jake will not activate. If you decide you need the Jake, just let the throttle close & it will activate. If you then decide you are slowing too much, switch from high to low. If you then start too pick up speed to quickly, switch back to high.

You have complete control but it does require operator input and a knowledge on the part of the operator as to how the system works.

The first time you descend a grade successfully using the above technique without using the service brakes, you will feel like a driver rather than a passenger.

yes, I have ran lowboys out of the woods for yrs. so I have extensive experience and knowledge about how the jakes, or in my case retarder s work. thanks for your input. I enjoy reading everyone's opinions on what works for them. usually find something helpful out of every post.