Exhaust brake

[Leeland]

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Any one running one, if so did you just install or did you up grade valve springs?

 

[laserjock]

Subscribed. I bought one. Wondered the same thing. If you search around there is a table on BW's site that tells you acceptable back pressure on a stock engine.

 

[Leeland]

I know newer Pac's have a bypass valve in them to prevent over pressurization. Just don't want to hang one and have it hang a exhaust valve open too long and have it kiss a piston. Already kicking around 910's, just curious if it'll make them necessary

 

[LCAM-01XA]

Got a Pacbrake meant for a DT530 or something, running fine with factory valve springs. It's the older style without the self-adjusting valve, it's just a simple butterfly with a factory hole drilled into it to allow pressure bleed-off. Seems to be most effective till about as low as 1000 RPMs, given enough distance it can slow the truck down from interstate speed to under 10mph, after we change the ZF gears it can possibly go even lower.

How do ya'll plan on controlling those things? If you're gonna be turning the brake off just before downshift then reengaging it till it's time to downshift again you really wanna think long and hard where you gonna put the switch for it...

 

[laserjock]

Got a Pacbrake meant for a DT530 or something, running fine with factory valve springs. It's the older style without the self-adjusting valve, it's just a simple butterfly with a factory hole drilled into it to allow pressure bleed-off. Seems to be most effective till about as low as 1000 RPMs, given enough distance it can slow the truck down from interstate speed to under 10mph, after we change the ZF gears it can possibly go even lower.

How do ya'll plan on controlling those things? If you're gonna be turning the brake off just before downshift then reengaging it till it's time to downshift again you really wanna think long and hard where you gonna put the switch for it...

This is what I bought new military surplus. Glad to see there is presidence for it working. I have been thinking about it. I'll get back to you. I think it can be done with simple switches, but I'm also reading up on Arduino. I think it might just be the slick way to do it. Its a simple process controller that is fairly bulletproof. I use similar things at work frequently. No crashes. They just work. It would be nice to be able to add delays and so forth to smooth things out. Even put a warm-up feature on the thing to close for faster warmup in the morning. It may be that a tie into the tach sensor to kill it at a certain RPM is just what is needed. If it dies off at 1000 RPM, then set the brake to kick out at 1100 or so for the downshift maybe.

Lots of possibilites.

 

[LCAM-01XA]

Eww, extra electronics! IMHO there really is no need for them in this application tho, I mean you certainly can, but there is a much cleaner solution if you don't mind working a thumb out a bit. The way ours are set up (we have two), is we use Eaton RoadRanger shift valves (shifter knob for a big truck with built-in air switch) - take your ZF shift knob off, weld a 1/2" bolt to the shifter, thread the RR valve onto that, run one air line from your tank to the RR valve and the other from the RR valve to the exhaust brake. Those shift valves are technically speaking supposed to only see 60psi in their proper application, but we run ours unregulated 140psi and they work just fine. Besides, depending on what spring you got in the PacBrake, 60psi is about as low as you can go and still be ale to operate the brake - any less and at least our air cylinders don't push hard enough to overcome the snap-open spring of the brake's butterfly...

Btw for RR valves there are like 1500 versions, you need one with a single air switch so your most common choices would be the straight-10 with a range paddle on the front and a Super-10 with a splitter slide on the side. Either will work, but the straight 10 valve would put your the brake-on position down and the brake-off is up, kinda awkward to shift that on and off quick and often (at least to me it was). Super-10 valve on the other hand is brake-on forward and brake-off towards the back, simple thumb operation, much more ergonomic for frequent use (makes sense since that is how it's designed to be used when controlling an splitter). I personally really hate the Super-10 transmission itself, but I gotta give it to it its shift valve makes an excellent exhaust brake control interface

 

[laserjock]

So did you check the back pressure or you just went ahead and set the thing to max pressure? I suspect with it being for a bigger engine, the chances of too much back pressure is fairly low. I would guess the hole is sized larger. Does that size work well?

 

[riotwarrior]

Watching this thread..once get a bit more done electrically on big truck I will work and see if the exhaust brake on it is functioning. For now the electrical components are disconnected while I revamp the truck back to a stock configuration.

 

[typ4]

If the engine is accessible change the springs, valve float is bad. and the brake will be more effective at the higher available pressure.

 

[LCAM-01XA]

So did you check the back pressure or you just went ahead and set the thing to max pressure? I suspect with it being for a bigger engine, the chances of too much back pressure is fairly low. I would guess the hole is sized larger. Does that size work well?

Ours are non-adjustable, butterfly is either open or closed, there are no in-between positions. Well, suppose some can be had by varying the pressure in the air cylinder, but we haven't done that, as there was no need.

But no, never measured the backpressure, actually been meaning to throw a gauge on there for like forever now, but still haven't got around to it... I seem to recall seeing somewhere some listings of the max backpressure allowed before valve float becomes a concern for a variety of engines, and then some fluid dynamics voodoo handled by someone way smarter than I can ever be suggested it should be okay to use the DT 530 brake on the IDI. That said, i don't remember the diameter of the pressure relief orifice in the butterfly, so what you got may or may not be the same as what we got...

But yeah, listen to what Typ4 says - if there is easy access to them, replace the valve springs with better ones, better safe than sorry when you forget to watch your engine speed and hit the brake at 3000+ rpms

 

[Leeland]

Good to know Russ.

 

[Koch13351]

On controlling it:
Why not have a primary 'On' switch for the system, and put a pressure switch as a secondary control on the clutch pedal assembly? Kind of like the brake light pressure switch on the brake pedal. That way it will cut out as soon as you start to push the clutch in for a downshift, and reactivates once the clutch pedal is fully released. Kind of idiot proof that way I'd think.

 

[laserjock]

If the engine is accessible change the springs, valve float is bad. and the brake will be more effective at the higher available pressure.

So what do you recommend for valve spring upgrades? I know it's been discussed that you don't really recommend upgrading valve springs for the torque cam. I've seen people say the Comp 910's fit. As I'm doing a custom reman, are valve springs cheap insurance?

To the adjustment of backpressure point, there are two ways to adjust it as far as I can tell. The BW brakes adjust I believe just on air pressure. These PAC brakes I would think could adjust the same way but if memory serves, there is an adjustable stop on it to set how far it closes. I've actually considered putting a permanent backpressure gauge in the system because it's not going to be real convenient around here to load the truck heave and take to the top of the steepest hill around and brake it. Much bigger hills and probably bigger loads out there.

 

[typ4]

Its not that I dont recommend it, for the torque cam new stock springs are fine. It I was doing an exh brake I would use stiffer springs.

 

[laserjock]

So the Comp 910's then? That's the only other spring I've seen profered as an alternative.