Another 13T Exhaust Build - 3" DIY (1 Viewer)

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Nov 12, 2003
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Truckee, CA
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.)
 
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pictures of the finished product?
 
it was 9pm when i finished it. Dark. Welding by touch. I'll shoot some picts after work.
 
looking forward to seeing them. sounds like a good project.
 
took something like 21 separate pieces (divided amount the four sections mentioned above). but, was cheaper then paying a shop... and mandrel bent. the two shops i had look at it before, didn't think they'd be able to fit 3" over the frame.
 
Did you turn up your fuel to get EGT's that high (+1200F)?
I assume you have your probe pre turbo.
My probe is post turbo but EGT's only go to 800-850F.
My exhuast pipe is approx 2.5 inch.
Be good to see pics of your install.

Cheers:beer:
 
Pump appears to be unfiddled with. I've heard many other 13BT owners express high EGT concern. The stock exhaust is silly how small it is.
 
Do you know what stock exhaust diameter is? Just want to know if mine is stock or after market.
Mine may have done 237000km's but I will never know what the real k's are. Its also got 33" tyres which has put the odometer out.
 
Certainly looking forward to the installed pics and any you have of the build up.
Thanks. Keep making that truck nicer, while I save up my pennies for it :)
 
Giffo, pics please. I'am running a straight through pipe of ± 2.5 ".

_cid_xhaust.jpg
 
sorry folks, I was backpacking for a few days. I'll snap some tonight. No really, I will!
 
I did something very similar to my 86 bj74 I am not sure if the lost of power from it how did it work for you do you feel more or less power.
 
The turbo creates enough back pressure on a dsl turbo, you will get better EGT's, faster spooling up of turbo and more power, not huge gains. Think of the stock xhuast and replacing it with a free-flow system. Or replacing your'e stock aircleaner with a K&N performance filter. The sound and the imagination make you believe you have at least 20 xtra horses. I say you gain a very small bit of hp, but there is no power loss IMHO.
 
well, I might not have gained any over all horsepower, but I definately shifted when I get that power. The turbo spools faster, and the 1500-2200 RPM range has way more power then before. Also, the EGT's were getting way too hot before this, now they are out of the danger zone. Also, remember... chicks dig it. Heh heh. Anyway, finally got some picts. Sorry about the camera-phone quality.

what I don't have a pict of, is connecting the 3" to the stock flange. I used 2.5" right at the flange, then necked it open to meet the 3" (and hammered the 3" a little to close the gaps)

three picts here:
down tube from turbo, through side-skirt.
along rocker panel
up and over frame (as seen from near the transfercase, looking backwards. notice the ball/socket joint here)
IMG00219.jpg
IMG00220.jpg
IMG00221.jpg
 
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more picts.

this is looking toward the transfer case, the pipe has already crossed over the frame, and is now traveling behind transfer case, before making a 90 degree toward back of truck
next picture is looking backwards, shot of the muffler in stock location
last is the tailpipe

exhaust is coded in 2000F paint because... well... just because.
IMG00222.jpg
IMG00223.jpg
IMG00224.jpg
 

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