Just another thread about exhaust for a BJ74. The 13BT runs pretty high EGT's, even with the boost comp valve turned up a little (running about 12-13 PSI of boost). The truck has always been... sluggish. So, I finally motivated and built myself some new exhaust. It's not hard, but it's time consuming. I used a porta band to cut the pipes. i suggest using blue masking tape as a guide when cutting... it's the best way I've found to ensure a straight cut. I also often used the masking tape to quickly hold two pieces together while I test fit them under the car.
The exhaust was made in four sections following the stock routing.
-from the turbo, down, out through the fender, straight back between rocker panel. this section ends at the flex joint (it's just clamped together).
-from the flex joint, up and over the frame... ending at a ball-socket
-from the ball socket, basically above the frame rail, straight across back of transfercase, ending a the muffler
-from the muffler out to tailpipe location by rear wheel.
I don't much like welding upside down under the truck, so all welding was done on the table. So, I'd test fit something with either masking tape, or a spot weld holding it together, then fully weld it.
The only welding down under the truck was the last section (tail pipe) to the muffler.
I used a couple of these J-bends:
Dynomax 42323
I used this Muffler:
http://www.summitracing.com/parts/SUM-638230/
I used some Pep boys exhaust hangers.
I used one of these ball/socket connectors (sold in pairs, I used the other one for my HDJ80):
Flowmaster 15930
I also used a 3" flex joint (can't find it on Jegs right now)
I found this cool exhaust tool... but I don't remember paying this much (I think I got a knock off brand): Walker Exhaust 35273 - Walker Exhaust Hand & Other Tools – SummitRacing.com
Honestly... I didn't really need it.
I know that 3" is overkill... 2.75, or even 2.5" would probably suffice. But, I had to do some 3" work on my HDJ80, and keeping everything 3" made for less things I had to buy. And... if I'm going to go through the trouble, I wanted to go as big as I can.
The result: It's quieter then before. To be fair...the stock muffler had already been removed, and the stock 2" (less, actually) was riddled with cracks and holes.
It's cooler. I'd say about 200F cooler at cruising. Also, I used to be able to hit 1200F easily, and I could keep it climbing. Now, I can't get it to 1200F... 1150 seems the hottest I can get it (all pre-turbo).
the best part: It's way more responsive. I mean... way more. The turbo starts boosting about 700RPM sooner then before. It really starts to pull at 1500; before I didn't get much untill 2000. So, i'm shifting sooner now, not winding the engine out. (I'll be honest, I'm a California driver... I like to accelerate). It is a joy to drive now... It pulls like a 13BT ought to.
Anyway, I would highly recommend this to anyone with a 13BT engine. There are many arguments that say you don't need 3"... I don't disagree... but I wanted 3". (besides... (Chicks dig it.)
The exhaust was made in four sections following the stock routing.
-from the turbo, down, out through the fender, straight back between rocker panel. this section ends at the flex joint (it's just clamped together).
-from the flex joint, up and over the frame... ending at a ball-socket
-from the ball socket, basically above the frame rail, straight across back of transfercase, ending a the muffler
-from the muffler out to tailpipe location by rear wheel.
I don't much like welding upside down under the truck, so all welding was done on the table. So, I'd test fit something with either masking tape, or a spot weld holding it together, then fully weld it.
The only welding down under the truck was the last section (tail pipe) to the muffler.
I used a couple of these J-bends:
Dynomax 42323
I used this Muffler:
http://www.summitracing.com/parts/SUM-638230/
I used some Pep boys exhaust hangers.
I used one of these ball/socket connectors (sold in pairs, I used the other one for my HDJ80):
Flowmaster 15930
I also used a 3" flex joint (can't find it on Jegs right now)
I found this cool exhaust tool... but I don't remember paying this much (I think I got a knock off brand): Walker Exhaust 35273 - Walker Exhaust Hand & Other Tools – SummitRacing.com
Honestly... I didn't really need it.
I know that 3" is overkill... 2.75, or even 2.5" would probably suffice. But, I had to do some 3" work on my HDJ80, and keeping everything 3" made for less things I had to buy. And... if I'm going to go through the trouble, I wanted to go as big as I can.
The result: It's quieter then before. To be fair...the stock muffler had already been removed, and the stock 2" (less, actually) was riddled with cracks and holes.
It's cooler. I'd say about 200F cooler at cruising. Also, I used to be able to hit 1200F easily, and I could keep it climbing. Now, I can't get it to 1200F... 1150 seems the hottest I can get it (all pre-turbo).
the best part: It's way more responsive. I mean... way more. The turbo starts boosting about 700RPM sooner then before. It really starts to pull at 1500; before I didn't get much untill 2000. So, i'm shifting sooner now, not winding the engine out. (I'll be honest, I'm a California driver... I like to accelerate). It is a joy to drive now... It pulls like a 13BT ought to.
Anyway, I would highly recommend this to anyone with a 13BT engine. There are many arguments that say you don't need 3"... I don't disagree... but I wanted 3". (besides... (Chicks dig it.)
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