1HDFT 3" Exhaust Questions (1 Viewer)

[Dork]

So, a short bit of backstory.

Truck is a 95 HDJ81, exhaust is new(er) 3" from the cat back, and was put on in Japan before I got the vehicle here. The section from the turbo dump to the cat is still the old 2.5". In the "two birds with one stone" school of thought, I'm getting rid of the cat, and replacing that small section with 3" pipe in order to make some extra room for a slider mounting leg. Easy, right?

My questions are:

1 - That 3-bolt flange that comes off the turbo does not seem to match up with the holes on a standard 3" 3-bolt flange. The old small pipe also seems to be pushed into the turbo flange somewhat inefficiently, but that's not important. What did anyone else do with that connection? Did you take off the original flange, cut the old smaller pipe out, try to clean it up really good, and then weld new pipe to the outside face of it? Or take a new flange, massage the bolt holes a bit to just make it work and jam a gasket in there?

2 - When doing exhausts, everyone just says "buy a pre-bent mandrel U and cut it up as needed" which sounded really simple. As I was starting to figure things out, I slid one of the flanges over the pipe in order to make a measurement, as that seemed like a really good way to make a perfect square line around the pipe to cut along. At that point I realized that the mandrel bend is NOT perfectly round all the way, and there is a fairly significant gap on one edge of the flange. I see this as a problem, for example, if I were to cut a 30-ish bend, and then try to mate a straight section to that, the straight round bit won't match up with my not perfectly round bent piece. What do people do with that? Just pinch the pipe in a vice or something to round it up a bit and make it fit better? Is my Dynomax pre-bent piece of exhaust pipe just a piece of ill-manufactured garbage?

Thanks in advance for any insight y'all may have.

 

[mudgudgeon]

Hdj81 had no cat AFAIK.
Turbo has a cast dump pipe. Turbo flange is 4 bolts, i think the dump has a 3 bolt flange. for best result, go 3" all the way from the turbo, the cast dump pipe is less than 3" outlet from memory.
IMO you'll get a more durable fillet weld if the pipe is inside the flange rather than butted to it
make sure you use a decent length braided flex between the down pipe and the first exhaust hanger on the chassis.

All the mandrel bent elbows i have used have been pretty truly circular when cut anywhere around the bend. I've mostly used 90 bends. You'll get at least a couple of cuts from each. I've done a few exhausts this way, including full set of V8 headers for a race car. make sure your cut is done on a radial line, ie 30 degrees needs to be 30 degrees from centre point of the bend's radius. if your cut is on the piss, the cut end will not be circular. I've found that joins once tacked might need just a little tweeking with a G cramp or large welders vice grips to get the two pieces aligned

 

[Dork]

Thanks for the response. Indeed the cast dump is a wee bit smaller, looks like it's around 2 3/4" or something like that. I may have to pull off that cast fitting tonight and either try to cut a flange for it, or just live with it for now.

I keep hearing that these have no cats, but here's what I pulled off last night. I'm guessing it's a 95-97 only thing, along with the EGR system that's on the motor?

And here's the deformation of the pipe I'm talking about. I'm guess the 180s are just worse for it, and a 90 would be better to work with.

 

[IanB]

I'm guessing that's more of a resonator than a cat, just from the look of the exterior casing.

X2 on 3" dump pipe, the system will only flow as well as the bottleneck, you don't want that point to be right at the turbo or everything behind it is a waste. It's a tight fit, but my ATEB 3" system is run inside the frame rail, leaving LOTS of room for slider mounting, that would be my other recommendation, even if it means cutting up and modifying your existing 3" system.

 

[Dork]

Resonator, Catalytic converter... Whatever it actually is, it's a big clunky doohicky that's in the way. It's got a Toyota/Futaba stamp on the bottom of it, so I figured it was a stock part. Maybe it isn't?

This whole little bit of work with the exhaust was just supposed to be a quick, cheap and easy stopgap for now to accommodate the slider installation with intentions of re-doing the entire exhaust a year or so later on. The pricing on stainless steel exhaust parts in Canada is a bit tough to swallow at the moment. As always, simple little projects quickly spiral out of control.

Running down the inside of the frame rail does seem to make sense, as far as reducing bends go. Have you noticed any issues with it there, just looking at it it looks like it would be REALLY tight by the front driveshaft and transfer case?

Maybe those two pipelines that the feds approved yesterday will have a trickle down effect to help the wallet breathe better next year, and then the truck can breathe better at the same time. One can hope anyway...

 

[IanB]

If it's stamped "Toyota", it's a factory part, no question.

It is really tight to run inside the frame rail, the only issue I had was a vibration at idle where one of the flanges was contacting the belly plate just in front of the transfer case, I "clearanced" the belly plate and no further issues. Stainless isn't required, as regular exhaust tubing doesn't rust the same way with a diesel as it does with a gasser, although I'm not the guy to give you the scientific reasons for this, I think there's less moisture in the exhaust or something like that.

Embrace the spiral! Ride the wave of torque!

 

[mudgudgeon]

Resonator, Catalytic converter... Whatever it actually is, it's a big clunky doohicky that's in the way. It's got a Toyota/Futaba stamp on the bottom of it, so I figured it was a stock part. Maybe it isn't?

This whole little bit of work with the exhaust was just supposed to be a quick, cheap and easy stopgap for now to accommodate the slider installation with intentions of re-doing the entire exhaust a year or so later on. The pricing on stainless steel exhaust parts in Canada is a bit tough to swallow at the moment. As always, simple little projects quickly spiral out of control.

Running down the inside of the frame rail does seem to make sense, as far as reducing bends go. Have you noticed any issues with it there, just looking at it it looks like it would be REALLY tight by the front driveshaft and transfer case?

Maybe those two pipelines that the feds approved yesterday will have a trickle down effect to help the wallet breathe better next year, and then the truck can breathe better at the same time. One can hope anyway...

I also ran 3" inside the frame rail. I used 4" pipe from the turbo for the dump pipe (2x 75-80-ish degree bends) hard mounted to the gear box bell housing and transfer case. reduced to 3" at the gearbox cross member, slight offset to clear the transfer case, long braided flex, 45 bends up over the rear diff, 45 bend into a larger full flow 3" muffler, the exited at the rear. Mine had 3/8 clearance to the transfer, had no rattles, no bends over 45 degrees after the dump pipe.

I will do more or less the same with my 105series at some point, but I'll jam two mufflers into the system.

I've put pictures of my dump pipe up on mud before

 

[mudgudgeon]

while your at it, I'd use v-band type joints for less clearance issues, and far easier fitting.

 

[Dork]

All good info, thanks. I think im going to end up just slapping this together for now as a learning experience and to get the truck drivable. At the same time though, I'm going to take some measurements of that cast dump and then take my time to work on building a new one to put in it's place when i don't have any sort of self imposed deadline looming over me.

 

[AussieHJCruza]

That thing pictured is the first of the 2 mufflers.

X whatever on running inside chassis, nice and easy until the rear axle, and then it's interesting, but that's more pipe size than routing. Lose the cast part and start the 3" right from the back of the turbo, I can get some pics of my setup if you like

 

[MonsterCruiser]

I've put pictures of my dump pipe up on mud before

Found them

3 inch exhaust elbow on CT26

 

[mudgudgeon]

Thats it.

That is bright. mild steel pipe. about 18/24 months old. surface rust on the outside, a nice coat of soot inside. and oil from dead turbo

 

[Dork]

So, based on the awful experience i had pulling the cast flange off last night, that can't have been fun at all to bolt back in with the whole length of pipe being in place. So your flex piece was after the end of that and bolted in between that dump pipe and what follows?

Looks like www.bicperformance.com/products.htm sells a flange already cut and ready to go for only $30us. Might be worthwhile to save some headache.

Anyone know of a Canadian source?

 

[MonsterCruiser]

Looks like www.bicperformance.com/products.htm sells a flange already cut and ready to go for only $30us. Might be worthwhile to save some headache.

Anyone know of a Canadian source?

Pricing is in USD, but I believe (based on that other thread) BIC is based out of Langley, BC.

 

[mudgudgeon]

So, based on the awful experience i had pulling the cast flange off last night, that can't have been fun at all to bolt back in with the whole length of pipe being in place. So your flex piece was after the end of that and bolted in between that dump pipe and what follows?

Looks like www.bicperformance.com/products.htm sells a flange already cut and ready to go for only $30us. Might be worthwhile to save some headache.

Anyone know of a Canadian source?

Yep. The piece pictured finished near the back of the transfer case, and i had a 12" long flex after that. That down pipe was bolted rigid at the gearbox, and to the transfer case. the rest of it hung from the standard mounts on the chassis. the flex was between the rigid engine mounted pipe, and the chassis mounted pipe. I used the longest flex i could find as the engines shudder a lot on shut down, and shift a bit under torque.

 

[Dork]

So, just to give this thread a little bit of finality, I got it done.

And it's a piece of

It fits OK, and it'll work fine, but I don't like it. Gotta add some sort of a hanger in the middle section there too if it's going to stay for very long. As a bonus, it was my first time welding anything more serious than just doing simple tacks, and from what people have said about how difficult welding exhaust pipe can be, I think I did not too bad. So, I guess yay for learning.

For now, I have something that works in the meantime so I can continue on with the slider project, and order up everything I need to do it properly, in stainless, inside of the frame rail, as suggested.

Anyway, here's some pictures of junk.

 

[AussieHJCruza]

Straight pipe sounds Phat doesn't it!

 

[Jentuh]

doesn't look too bad at all! I just finished my 3" stainless exhaust. First time welding with electrode's. Went better then expected.

 

[CruiserGord]

I got rid of the 3 bolt flange and the actual elbow that mates up with the turbo. Bought a turbo exhaust flange made of mild steel from a supra enthusiast retailer and then had it remade out of stainless steel. Took said flange and a aero turbine 3030XL muffler to Unobtanium Welding and had them fab me a up a sexy exhaust system. The free flow also caused my worn out turbo to detonate as well. And now I'm broke.

 

[Dork]

I got rid of the 3 bolt flange and the actual elbow that mates up with the turbo. Bought a turbo exhaust flange made of mild steel from a supra enthusiast retailer and then had it remade out of stainless steel. Took said flange and a aero turbine 3030XL muffler to Unobtanium Welding and had them fab me a up a sexy exhaust system. The free flow also caused my worn out turbo to detonate as well. And now I'm broke.


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That is extremely shiny