Engine/Transmission (1994 - 1998) Exhaust brake idea...

[tp0d]

Dunno if this has been attempted before, but I have an idea for a manual, cable style pull exhaust brake. Take the exhaust elbow, drill a straight thru set of holes to mount an SS rod and paddle (25/50% constriction) for the braking action. Return spring, mounting, and other hardware are still being thought of. . Momentary button would be mounted in center of pull handle to engage TC.



Which brings me to my next q. . Would this exh elbow for a 2000 auto fit my truck?



http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=7950537305&fromMakeTrack=true



i have a 96 auto, hx35. . havent really looked hard at my existing elbow, but I dont want to use that as a gineau pig. .



If that wont fit, does anyone have a stock HX-35 elbow they'd be willing to part with? PM me plz. .



tnx



-jerry

 

[JAmos]

I could be wrong but it seems that most exhaust brakes are between 80-90 percent restrictive-someone correct me if im wrong. Good luck on the tinkering/inventing. Keep us posted on progress.



Jordan

 

[Turbo Tim 1]

The biggest problem I see with you idea is exhaust leakage where the rod goes through. You don't want to be having a fire. I have thought about doing something like that but I was going to make it under the truck as part of the exhaust piping.



Here is what I am working on for a low budget exhaust brake that will probably cost me more in the end. Recently I aquired two brand new Jacobs exhaust brakes for a C Series Cummins, they use pressure instead of vacuum to actuate and also are 4 inches in diameter. If a person has a 4 inch exhaust you can get exhaust sleeves from jacobs to make the brake an inline model. or if you have a turbo with a 4 inch outlet (HX40) and the room to mount it you can do direct mount. My though is to put stacks on my truck so I will probably use both of them and have them mounted in the bed of my truck away from the road grime. I bought them for $130 each off of ebay and they came with mounting clamps and actuation solenoids. I am keeping my eyes open right now for a 100% duty cycle 12 volt air compressor and I am going to put an air tank in the box too for actuation. Right now they just sit on my shelf but I'll get to it when the warm weather comes back around.

 

[JAmos]

Yea forgot bout the sealing issue. If that could be figured out easy enough then the rest might not be too hard?



Jordan

 

[tp0d]

Sealing isnt too much of an issue. . I can get 1/4" compression by ips fittings and tap them into the elbow for the rotators, then pack the compression end with refractory wool (2000°+) A little dry graphite in the wool for lube, and its sealed. . I`m just wondering how much force it would take to actuate the valve manually. . hmmmmm What are those inline valves rated at Tim? (psi) I`ve yet to find a good number on how restrictive a closed brake is. . keep on lookin tho heh



-j

 

[radixr]

If you have too much restriction, the back pressure will build high enough to cause valve float and then... :{ :{ :{

 

[Turbo Tim 1]

I've heard numbers of 65 psi of backpressure, I am going to find out for sure and then I will monitor that and see what I have. Since these brakes are the same only larger than the one made for a ISB Dodge I don't think it will be any problem.

 

[CumminsPower98]

My BD brake is supposed to be adjusted to 25 psi at idle when the 60# exhaust valve springs are installed. I have no idea what the pressure is during use.

 

[RustyJC]

My though is to put stacks on my truck so I will probably use both of them and have them mounted in the bed of my truck away from the road grime.

An exhaust brake essentially turns the engine into an air compressor - that parasitic load is where the engine braking comes from. Like any compressor, its efficiency is a function of the fixed clearance (or volume) that the piston is pumping against. By having the engine pumping against all the volume in the exhaust system between the turbocharger and the bed of the truck up to your brake locations in the stacks, the fixed clearance will be extremely large. Therefore, the engine braking effect you will achieve will be reduced significantly.



Rusty

 

[Turbo Tim 1]

RustyJC, with that thought in mind wouldn't it make sense that it may take a little longer to feel the full effect of the brake but that after the full volume of the exhaust system is up to pressure that outcome would be the same. Much like an air compressor with a 5 gallon tank or a 50 gallon tank, they will both get to the same pressure it'll just take the larger tank longer to fill. Prove me wrong so I don't do a whole bunch of work for nothing but wouldn't the braking effect be the same but just take longer to get there.

 

[RustyJC]

If you're familiar with reciprocating compressors, you know that one way to control capacity is with a volume unloader. This is often a chamber with a plug valve to either seal it off from the working volume of a compressor end or to open the unloader volume to the compressor end. With the volume unloader actuated, the additional volume means that the piston must travel farther in its stroke until the gas (at suction pressure at the start of the stroke) is compressed up to discharge pressure. This means that the compression line on the PV (pressure/volume) diagram has a flatter slope. Since gas horsepower is a function of the area within the PV diagram, a flatter compression line means less area within the PV curve, thus less horsepower consumed and (since the discharge valve opens later in the cycle) less gas compressed. The additional clearance also flattens the re-expansion line on the PV diagram, but we'll ignore that for simplicity.



The same thing holds true with an exhaust brake. As you move the brake(s) farther and farther away from the engine, you're increasing the volume the engine's pistons are working against on the exhaust stroke, right? Also remember - the exhaust brake is not a positive sealing valve, so pressure is always leaking off. Therefore, you have a compressor system that's flowing gas, and you've added fixed clearance. That reduces the engine braking horsepower because the area within each cylinder's PV curve during its exhaust event when the exhaust brake is activiated is less than it would be if the same brake were mounted at the turbocharger outlet flange where the "compressor system" would be operating with much less fixed clearance (i. e. , the incremental volume of the exhaust system).



Rusty