One thing you'll find with every commercial exhaust brake that I know of is that they have a mechanism to deactivate them as soon as the accelerator pedal is touched. Some catastrophic pressures and temperatures could result otherwise. Those contemplating manual cable actuation might consider the possibility that sometime, somewhere someone might get back on the long, skinny pedal without pushing the cable back in!

Rusty

 

That is an excellent point. And you know that sooner or later it will happen. I wonder how much manifold pressure is developed under normal use? If compression is about 450 psi, the exhaust manifold pressure could get up around, maybe, 300 or so. Wow.

Wetspirit

 

As I mentioned [in several posts] there's only one thing that was holding me back: could not find out what size bleed orifice or bypass to use to prevent damage from over-pressure. I got all the info I could but that one piece of info was missing.

Got the answer! Stumbled onto a page at BD about a Banks exhaust brake for a Ford diesel and they inadvertently posted the info!

http://www.bd-power.com/ford/exhaustbrakes.php

That's about as close to 20% of total area as you can get, so that's the safety zone. Hope it helps you other guys too....

 

All I saw was the 5/8" hole comment. Is that what you are refering to? It seems like some sort of relief valve would be the hot setup. Then it could be tight to work well and blow open if I stepped on the loud pedal. All mechanical.

Wetspirit

 

I hadn't seen the replies regading acclerator pedal disconnect before I posted. That sure is something to think about! That could get a little technical to solve.

Mine's a 4BT out of a stepvan and I used the donor truck's accelerator pedal and cable assembly. It was a Grumann/Olsen with GM TH400, before I swapped in the Dodge NV4500. Well, the pedal assembly has an adjustable switch for tranny kickdown/passing gear. Could probably adjust that back and connect to a solenoid release mechanism whenever throttle is depressed.

Yes, the 5/8" hole is what I was talking about, and the ex-brake ID was something like 3.125" or somesuch. The ratio comes out to about 20% give or take.

 

Yeah,that ought to work..all you need is something to flip it off...it would have to automaticaly reset,but that should not be a problem

 

Ha ha, kinda funny. Fell asleep last nite thinking about the switching and didn't realize 'til I read this post that I never finsished figuring it out!

Could be done similar to a 2-way lite switch, like the ones on either end of the room for switching the same lite, but that gets too complicated. A simple microswitch that gets tripped as some part of pedal or accelerator hardware passes by is probably easiest. Might have to figure out some sort of latching mechanism on solenoid or ram used to engage brake where the mocroswitch unlatches it by interrupting signal. It would have to discoonect power to the solenoid.

 

The commercial e-brakes that use a microswitch at the accelerator pedal just use it to disable the e-brake whenever the accelerator is off-idle. In other words, power is sent to the e-brake actuator only when the accelerator position is at idle.

Rusty

 

That makes sense!

 

No worries stepping on the loud pedal while the exhaust brake is active. The thing is with the e-brake on exhaust flow is seriously restricted, when you step on the go pedal fuel is intoduced but the turbo can't spool because there is no place for the expanding gasses to go (quickly anyway). What results is a quickly climbing EGT level and a large cloud of black smoke emitting from your tail pipe.
You won't blow your motor up due to pressure, you may however melt a piston if you laid into it for 10 minutes straight

 

You'd obviously notice right away that the brake was still on but I wonder how much exhaust manifold pressure would build up instantly. Some engines that were not designed for exhaust brakes might blow a manifold gasket or blow open the exhaust valves. I just like the simplicity of a handle on the dash that can be pulled out for braking, then pushed in for normal operation. All mechanical. I'm just thinking of using it while four wheeling or a long downgrade on a diesel Samurai. Not on a day to day driver.



Wetspirit