Engine/Transmission (1998.5 - 2002) exhaust and pacbrake

[DMather]

Does anyone know if there is a source for a 4" Stainless Steel turbo back that is already set up to clamp onto the pacbrake prxb maxflow? (brake bolts right to turbo)



Went out to the shop this morning to put the brake on only to find that the exhaust is ready for replacement. Figure if I have to replace it maybe I can keep from cutting and welding a new part if it was available pre-made/modified.

 

[kurgan]

The PRXB Maxflow looks like it would take a downpipe from a 3rd gen truck. I'm not sure if a 3rd gen setup from somebody like MBRP or others would be a direct replacement for the 2nd gen trucks, I doubt it would. Another option is to get your hands on a 3rd gen downpipe to use with a 2nd gen exhaust. Sorry, I know none of this solves the problem with a one shot deal.

 

[AH64ID]

Don't the pacbrake's come with the exhaust adapter?



I doubt your going to find an exhaust specifically for the Pac. Just get the 4" of your choice and use the supplied adapter.



Might not be the easiest method, but probably easier on a new exhasust than an old one.

 

[DMather]

Yes, they come with a 3" adapter and I have the optional 4" adapter.

But, if a formed down pipe is available I would rather have it because A) I won't have a welded seam in the down pipe and B) I won't have to spend the time measuring, cutting, fitting and TIGing the adapter on the pipe.

 

[kurgan]

DMather,



While you're in this tread, i'd like to ask something. What made you decide on the Pacbrake? I'm still very torn between the Max Flow, and a BD remote mount. I don't think I want the turbo mount BD because (if i'm correct) the butterfly/outlet is only 3-3. 5 inches. If you do get it, I'd absolutely love to see some in cab video (with good sound) of it being used. I'm curious to know how it sounds in general, and as to whether it hisses or not.

 

[DMather]

Kurgan,



I already have the pacbrake. ($100 rebate until Mar 1) Here are some of the reasons I choose it:



1. the pacbrake replaces the turbo exhaust elbow - it's up, out of the elements and no inline pipe leaks



2. The pacbrake makes the outlet of the turbo 4" - perfect for my 4" exhaust - first photo shows the brake outlet and the second has the 4" header for the downpipe resting on it. (in the photos the brake is lying on it's "back")



3. There is no control module for the 02 - one wire to cab switch, one wire to ECM socket. (no idle switch needed)



4. uses pressure to actuate, not vacuum.



5. smoother exhaust flow with waste gate open to help keep temps in check. Third photo shows smooth wastegate path vs the 90 degree turn the gasses have to make and then remix with the exhaust stream... .



6. Brake vane closes completely and has a small valve in it so that back pressure is produced, even at idle.



There are only two things I am doing different for the install. 1) I am changing the mounting location of the compressor. It is supposed to mount next to the battery but I have a bypass oil filter located there. 2) I am adding an water drain solenoid to the tank. It will open for 1 second when the ignitions is turned off to blow out any moisture from the bottom of the tank.

 

[kurgan]

Doug,

Thanks for the pics and answers. Are those exhaust adapters that come with it stainless? Where were you thinking of mounting your compressor?

 

[DMather]

adapters are stainless. the 3" comes with... the 4" is "optional" ($$)

Compressor will probably go on top of engine by the APPS.

 

[AH64ID]

Compressor will probably go on top of engine by the APPS.

I have heard that's where it mounts on the 3rd gens, and are prone to failure from the vibration.

 

[DMather]

Well, it's installed. (couldn't find anyone near me that was willing to weld thin wall stainless so I had to buy a TIG, learn how and do it myself. Turned out really nice..... and I have either a $2000 exhaust or a $500 exhaust and a new tool/toy. :-laf



The full 4" outlet on the turbo feeding into the 4" exhaust dropped my egt by 75 degrees. 65mph holds 525 degrees and 2. 5 lbs boost when empty. Looking forward to loading it up to see if the improvement holds.



Just refilled the tank at 1402. 4 miles and it took 53. 2 gallons. (26. 36mpg)... . that was a pleasant surprise. Almost 2 mpg more.



Exhaust is quieter than what I had on before. (4" JCWhitney)... very slight drone at 75 but compared to before there is no drone. The sound is more of a ragged hiss at idle and growls when slowing from speed.

 

[kurgan]

I'd love to see how all this turned out with the install. Did you relocate the compressor like you said you were going to?

 

[DMather]

no, the pacbrake was installed per instructions with the exception of the intake air filter. I tossed it and ran the intake hose into the air cleaner box.

I relocated the bypass oil filter to the inside of the frame rail.

 

[DMather]

Well, with a couple thousand miles on it I am impressed.
The pacbrake works as I would expect for downhill speed control, etc.

But what is a surprise is that I seem to have picked up around 2 mpg overall, empty or pulling!..... and acceleration seems to be better. (unscientific measurement of "seat of the pants") The only thing I can think of that would cause this is the removal of the 3" section of exhaust pipe. The replacement of the turbine elbow with the brake and it's 4" outlet must smooth out a restriction.