Jacobsen exhaust brake adjustments?

[wfernau]

The Dodge dealer recently installed a Jacobson exhaust brake on my 2001 six speed.



I am disappointed in the minimal braking power and long lag time before the brake activates. "Too little, too late", sums it up.



Has anyone found a way to increase braking power? The Chrysler manual says that maximum braking power develops at 3100 RPM. I usually need the braking power at 2200 RPM. Can the Jacobs unit be adjusted to deliver better braking power at lower RPMs?



Also, is there a way to reduce the lag time before brake activation? Mine activates about four seconds after I release the accelerator. This is about twice as long as Dodge describes in their manual. Can this be adjusted? Better yet, can the automatic lag time be eliminated all together with a gear shift mounted manual switch? I'd like to activate the brake when I want to; not when Dodge wants to!



Any ideas?



Thanks.



Bill

 

[Bob Cochran]

Bill ~ The lag time is provided by the ECM I believe and unless it is adjustable electronically I am not aware it can be changed. Mine does start about a couple of seconds after letting off the the go pedal. As I recall you can disconnect the wire from the ECM I think goes to pin 20 (someone correct me if I am wrong) and you can activate the brake when you want using that wire and a switch where ever you want to mount it. At least I think so!!!



Cannot increase breaking power that I am aware. I think most exhaust brakes work better at higher RPM's. Some do have better exhaust brakeing at lower RPMs as they close of more than the Jacobs.



As to 2200 RPM vrs 3100 and 2 seconds to 4. Please don't take this wrong. The intent of the exhaust brake is to help slow the truck on down hill grades. In this case 2 seconds or 4 makes no diff. if you turn it on as we should. Gearing down easily gets you up to 3100 RPM. So it is actually doing the job. If you use it to help extend the life of service brakes then the 3100 is to high and 4 seconds is a very long time. :--)



Hope this helps some at least.

 

[monkfarm]

Jake brake

I have the Jake brake also. I have learned to live with it just like Bob was saying. I am sure there is faster, more efficient brands (which weren't around (except for the pac-brake which I don't believe is any better_) when I had mine installed right after I bought the truck new in '99. 85,000 later, haven't turned the Jake off much, and I haven't had to replace my brakes yet. (although I think I'm headed for a new set of brakes soon. ) I would also be interested in adjusting mine up, although I think Bob is right that it isn't possible. I don't really see the point in putting the switch on the gearshift like some do, I just leave it on most of the time, except when I'm parked idling and I want to quiet that whirring noise you hear when it's on.

 

[TowPro]

For others reading this thinking about buying an exhaust brake, these reasons are why I went with the BD. It has more brake power at the lower RPM's that I drive at. (Well drove at, I don't have on my new auto truck )



Some suggestions.



Does pin 20 on the ECM apply 12V or ground when the brake should come on? You have a couple ways to change this delay



1-Buy the switch and bracket from BD works off the throttle peddle. And use this source instead of the ECM connection to turn on the brake. Just wire the switch to switch - or +, which ever one pin 20 switches.



2-Use the Blue wire from the Trailer Brake controller Connector under the dash (instead of the ECM) to turn on the exhaust brake. This wire applies positive when the brake pedal is depressed. (This will work if the ECM switches +, if the ECM switches neg, this will still work, but you will have to change the way the brake relay is wired)



I used this method along with the BD switch so the fuel had to be off, and the brakes had to be on for the E-brake to come on.

I always felt when I am going down a hill on the highway and I let off the fuel pedal, it was a waist to have the exhaust brake to come on. I only wanted it on when brakes were applied. Even a light touch to the brake pedal (enough to turn on the brake lights) would make the brake come on.



3- If the ECM is APPLYING POSITIVE VOLTAGE, using 2 diodes, you can splice a diode into the wire between the ECM and the Brake, then splice the blue wire from the brake controller connector, through a diode into the E-brake wire between the e-brake and the diode that is installed in that line.



With this setup, when you let off the fuel, the E-brake will come on with a delay like it does not, but if you hit the brake pedal (just enough that the brake lights come on) the E-Brake will come on instantly.





The reason for the diodes is so the brake lights do not apply positive to the ECM when you hit the brakes (first diode) and so when the ECM turns on the E-brake, it will not turn on the brake lights (2nd diode). Again, this would work if the ECM is applying 12V positive to turn on the E-brake. I would have to draw it out to remember which way to put in the diodes. (It’s been a while)

 

[Bob Cochran]

TowPro is exactly right. The BD offers more adjustment while the Jacobs can be dealer installed and "NO" warrantly guestions!!! In his method you have the delay when taking foot of go pedal and instant when using the brakes. Gosh what a pain it would be if on mine when I shifted the exhaust brake worked. I wish I knew if it was -12 or +12 volt on pin 20. Anybody else help on this or made changes as TowPro said and can add here to help out.



To add to what monkfarm said is the reason for the switch on gear shift is people don't like the load of the exhaust brake on engine when idling or for long time in a traffice jam. I don't run mine all the time because on mine it gunks up the AIT or is that IAT I never get it right!!! That has been talked about here a lot. At least for me it did get gunked and ran much better after cleaning so now I don't use exhaust brake all the time as I was. Removing and cleaning this thing is not hard but I think a pain in the a$$!!



Hope this all proves productive.

 

[CFAR]

http://www.klenger.net/dodge/ecm-ebrake/index.html



The link above shows pin 20 as ecm output.



It also shows that a grnd is supplied to the solenoid already, so I would ASSume that there is a 12v signal from the ecm, of course I could go out with the multimeter and check, but its so much more fun to ASSume.



Mine seems to kick in with a 2sec lag.



I have found that braking power is adequate, I leave it on most of the time.



I have Bob V's super shifter and will be hooking up to the yellow wire comming off of the toggle switch, with the appropriate diodes to isolate the ecm from my own 12v source, don't want to feed 12v? back into the ecm. Otherwise I would have to remember to always turn off toggle switch and use it as isolation.



The delay allows for shifting, if you have no delay you would be trying to accelerate into the brake. I would also like to be able to instantly turn it off or on.



Like driving in stop and go, or pulling away from a light.



Simply turn off the toggle switch and use the shifter mounted switch to engage or disengage brake.



I would probably still use the ecm on the highway as I find the 2sec delay about right for most traffic.

 

[Briman]

I have the Jacobs brake and it's been on the truck since new. I have 110K on the ticker and still have the original brakes (although I have new pads, pins, and anti rattle clips in stock) The amount of braking provided has been consistent from new till now. I am quite used to the delay and drive accordingly. I'll let my foot off the gas a couple of seconds prior to when I want the brake to activate. I would like a shifter mounted switch to shut it off at stop lights and other times I'm sitting still with the engine running. The exhaust brake is truly wonderful with a 30' travel trailer on the rear while descending a mountain pass. Like between Durango and Silverton. I feel the braking is totally adequate and using it allot is better for the operating mechanism than having it off most the time.

 

[wfernau]

Jacobsen Exhaust Brake

Is this a great site or what!!!



Bob Cochran, monkfarm, TowPro, CFAR, and Briman:



Thanks for all the excellent suggestions for switching the brake.



With your help, I have plenty to work with. As I experiment with your ideas I will post the set up that I find works for me.



Can't tell you all how much I appreciate your input.



Bill

 

[Bob Cochran]

Bill your welcome just hope something works for you. Oo.

 

[BillH]

Why not leave the toggle switch on all the time and wire the black wire, in series, to a shifter mounted switch which would turn the E-Brake on and off?



Would this be workable or not?



Bill

 

[CFAR]

It would work but you would still have the 2 sec delay

 

[wfernau]

Jacobsen Exhaust Brake Adjustment

Gents:



The two second/four second delay is what I want to eliminate with the switch. Leaving the toggle on and switching the brake activator will do the job except for the delay.



What will switching from post 20 turn on and off? Will post 20 eliminate the delay?



I have seen two switches on a single gear shift knob. How would one of these fit into the instant on exhaust brake?



We are getting closer.



Thanks.



Bill

 

[Bob Cochran]

Bill I think switching post 20 will cut out the delay. The question is do you need to put a voltage on pin 20, ground or exactly what? That part I don't know perhaps others can help.

 

[CFAR]

http://www.klenger.net/dodge/ecm-ebrake/index.html



Sorry I wasn't clearer, hope this does more good than bad but here goes.



I assume by post 20 you mean pin 20 on the ecm?

If you look at the schematic in the above link you will note that there is a 12vdc signal comming from the ecm when there is no "throttle" being applied, it also says the 12vdc prvides pwr for the vacuum solenoid. And it you look at the green wire comming off of the toggle switch you will see its already grounded, it provides a ground for the solenoid and the light in the toggle switch. There is also a 10 amp fuse in the red wire comming from the ecm, while the solenoid only pulls less than an amp, while the solenoid pulls about . 83 amps.



If you want to cut out the delay simply hook up your shifter mounted (you have to supply) switch between a 12vdc (ignition on) source and the yellow wire comming off of your toggle switch. This is the simplest way I know of to have "instant on" capabilities. This will also allow you to isolate the ecm (turn off the toggle switch) from the 12vdc source connected to your switch. I don't know if applying 12v to the ecm via pin 20 will damage anything, but I would not want to take the chance.



Or you can simply disconnect the red wire from pin 20, I would heat shrink the end and tie it up some where and then do the above, no need to worry about ecm damage.



If you do either of these you will have to turn off the brake manually.



Hope this helps



CFAR

 

[klenger]

A variation on CFAR's recommendation would be to run 12 vdc through a shifter mounted switch and connect it to pin 20 output of the ECM using two diodes to provide isolation between the ECM output and the manual switch. Then, either the ECM or shifter mounted switch would activate the brake.



Very crude drawing of diode isolation.



IMHO, the 2 sec. delay is not a problem. The e-brakes are not intended to be used for panic stops, but to retard speed while decending long grades. If the 2 sec. delay is too long for you, then (again IMHO) you were driving to fast to begin with.



I love it when I would decend into Dillon CO down I-70 from the tunnel watching all the cars with their brake lights flashing on and off as I am decending under full control with a 10K 5er behind me coasting in 5th gear and never touch the brakes.

 

[Roger rodbolt]

wfernau,



I used the factory Jacobs brake for a while and also disliked the ECM delay. Now I use the "inline" or "remote" BD brake which is activated by a micro switch on the accelerator pedal. I also use a shifter mounted switch for the off/on feature. You can adapt your Jacobs brake to the micro switch system which, in my opinion is better then maually turning the brake on when you need it.



Regarding the lack of braking power, I would get the Jacobs brake checked out, maybe the valve isn't seating properly or you have an exhaust leak between the e-brake and the engine. Certainly the BD brake can be adjusted and has more braking power but the Jacobs brake works well in all the trucks that I've driven. Good luck, Larry

 

[wfernau]

Jacobs brake

Once again, I truly appreciate all the excellent help.



Next week end is taken, but the following will incorporate some wiring. I'll let you know how the brake works.



I am amazed at the expertise contributing to this thread. THANKS!



Bill

 

[CFAR]

Expertise?? Who's that?









All kidding aside, I hope what little we do know helps, I know this site has helped me.



And a big thank you to Klenger who lets me repeatedly borrow and post the ecm/ebrake stuff from his website. Its a lot easier than scanning it out of my ebrake manual. But I have to remember to put it back when I'm done. I did honest.

 

[klenger]