Green_Machine

Hey everyone.

I had the opportunity to drive a newer dodge with the integrated exhaust brake. What a difference from my setup. (BD with BD controller).

My ebrake itself works great, but the control leaves a lot to be desired.

I'm pretty Dodge knock off the Exbrake based on rpm, rather than speed. This means the exhaust brake will still work in the lower gears, rather than being useless below 60k or so.

Also, the Dodge converter clutch lockup is instant and never fails to lockup, unlike my BD controller. The BD controller will hold a lockup the truck pcm initiates, but will not initiate one itself. This means I have to play with the brakes and feathering the throttle off to try to get it to engage. It's distracting especially when I'm hauling a big load.

So, I'm thinking of building myself one which will work better.

I will have to tap into the rpm signal, the pedal signal (for 0 throttle), transmission signals etc.

I thought I'd raise a thread to update my progress.


Chay

Green_Machine

It seems the tricky part so far is finding an rpm signal. From what I've seen, the cam and crank sensors go into the ecm, and the tach guage reads off a data bus.

I thought about clipping onto the injector drivers, but with multiple events per fire this will be too unweildy.

I've read stories about tapping into the cam sensor for alarms. It screws with the signal to the ecm. If I keep the input impedance high enough it could work though.

So depending on the cam signal (I'll check it out) I may have to create a rpm reference to run the box.

The rest of the signals look pretty straight forward.

More to come.


Chay

Green_Machine

I'm learning more about this 'throttle application' requirement to engage the tcc clutch. The ATS Copilot info states:

"It is important to apply throttle pressure during the 4-3 downshift to synchronize the convertor clutch to the engine"

I guess the idea is that the tcc clutch would wear if it had to spool the engine up to the road speed in whatever gear you're in. It would be similar to downshifting in a standard I guess.

Perhaps some who are using the mystery switch with a exbrake could chime in? If you downshifted then flicked the mystery switch on this is what you'd be doing.

The trouble with my BD is that it's easy to feather in 4th or 2nd and get the ecm to engage the tcc clutch, but in 3rd it's a ***** and I want to use it a lot in 3rd.

So, I could go with the throttle bump requirement after a shift, but then lock it up with the controller rather than waiting for the pcm to do it if it's really necessary. Otherwise I'll just get it to lock in and replace the tc clutch sometime (?) in the future if it's actually hard on it.


Chay

Green_Machine

I've been continuing along my path here, learning more about the operation of the tranny etc.

I've come up with a possible solution which is an intermediate fix for those running BD Autoloc electronics with their exbrakes.

My major ***** with this box is that the TCC doesn't always lock up when the exbrake comes on, and so I get no braking. I'm sick of playing with the throttle when I should be paying attention to what's going on in front of me.

Anyway, I think I've found a solution. Essentially I want to make an automated mystery switch.

The DFIV module controls when the 'brake solenoid' turns on, then the Autoloc controlls the TCC solenoid, etc. How it works is if the TCC is locked already, then the Autoloc keeps it locked until the brake is done. If it's not in, then it doesn't come in (Crap!). So, if I can fake out the Autoloc, it will do a decent job of keeping the TCC in.

So, I'm going to use a device which gives me a 1.5 second pulse output when it's input goes true.

The coil for the device will drive off the brake solenoid power wire, so each time the brake turns on it will pulse the output.

The output is a contact closure. This contact will connect the yellow wire of the Autoloc to ground. This simulates the ecm trying to lock up the tcc solenoid. If I'm right, the Autoloc will sense this, and latch the TCC in every time the exhaust brake is turned on.

Also, when the brake tuns off (IE: you applied power), the relay output drops immediately. This will return control of the tcc to the Autoloc/ECM.


MAYBE (a big maybe-testing will prove this) a person could just use a relay instead of the 1.5 second pulsed contact. This depends on whether the Autoloc will suspend it's tcc lock output, even when the ecm tcc lock input is true (grounded). If it will, then you could just use a relay.

I think there is a good chance the Autoloc doesn't do this though.

As part of the 'mystery switch' mod, I will be jumpering the transmission relay contact, terminals 30 (+12) to 87 (Load). It took me a while to figure this out, but essentially it enables control of the overdrive solenoid, the tcc solenoid, and the pressure solenoid at all times. Enough people have done it that I doubt it will kill my batteries!

Chay

Jim O

I am glad I bought a Stick and installed a Jacobs exhaust brake.
Jim O

dadwolf2

I'm glad I bought a stick and a Pacbrake!

Green_Machine

I'm willing to bet you don't have a 12k boat and a wife who pulls it out regularly with no stress.

Autos have their place! You just have to deal with a bit of complication on the other end of things.


Chay

Green_Machine

A quick update from over the weekend:


A couple of changes from the original plan:

1) The DFIV outputs whenever the throttle pedal is at idle. This is not the right output to use. With the autoloc, it's used as an input, but doesn't control the exbrake directly.

The DFIV is all you need for a manual, but not an Auto. Now that I think of it, that's why I got the Autoloc to begin with.


Ok, so in my configuration, the Autoloc controls the exhaust brake application and cutt off (low speed)to avoid low speed transmission shudder.

The exbrake on/off is hooked up to the Autoloc'Brake' output. It goes to
12V when the speed is high enough, and the throttle is at idle. This was the perfect input for my pulse generator.

The output remained wired the same....


The result is that I get good braking anytime the exbrake is on. If I'm doing 110k in overdrive, then I brake down to 90k, I hit the overdrive off switch and tap the throttle, it locks into drive and exbrake with TCC on immediately, then down to 75k, pull it down to 2nd and tap the pedal again, it locks in right away down to 45k and kicks off. Wonderfull!!!!!

My exbrake switch will be in the "on" position much more than it used to be!!!


Chay

Reelay

Ditto!!

DodgeChallenger

Glad I am a stick shaker with a Pacbrake. Stops better than the 6.7 6spd I drove. No slush boxes for me.