5" Exhaust on IDI

[The Warden]

Hello!

I'm getting to the point where I need to start seriously work on wrapping up truck projects for the time being and getting the truck to a point where she's 100% operational...it looks like I'm going to be living in an apartment after June and may not have space to do any work at all on my truck, let alone anything major. One of the things I need to do is get some sort of exhaust system on the truck.

Prior to the head gasket/turbo job I did in '04, I had the opportunity to drive a truck that had a 7.3l with a Hypermax turbo and a 5" straight pipe. Some of you may remember this truck; it was a silver and red regular cab 4x4 that towcat got his hands on and stripped down last year (in fact, the tranny floor pan insert from that truck is now on my truck). To put it simply, I fell in love with how that truck sounded...very little rapping like you hear with a 4" pipe; just a loud rumble & turbo whine. Only thing is, that pipe exited in front of the rear wheel...something I don't really care for; it looks "off" IMHO and you have to deal with soot all over the rear wheel. When I did my head gasket project, I ditched the stock exhaust (figured there was no point in adapting down from the 3" downpipe to the itty-bitty 2 1/2" or 2 1/4" factory exhaust), so my exhaust has been exiting directly from the downpipe since 2004.

So, while I would like to do something similar to what that 7.3l IDI had, I'd rather get the pipe over the axle and behind the rear wheel. I talked with towcat about this a while back, and he was thinking that a 5" pipe wouldn't get over the axle and around the fuel tank and spare tire without bending so violently as to create a restriction on its own. But, he was thinking about this based on a 2WD truck, and we were considering the possibility that a 5" run over the axle might work better on a 4x4 with the extra ground clearance...but never came to a consensus (at least not that I can remember). With my school courseload building up to the point of overwhelming me last fall, I shelved this project...until now.

I suppose my question is this: Has anyone done a 5" behind-the-axle exhaust system on an IDI? If so, how did it work for you, and how did you go about it?

I searched around online, and it looks like a 5" kit exists for '94'-97 darkside rigs, but I couldn't tell from the picture how sharp the over-axle curves are...but this implies that it's at least possible if not exactly feasible. The price doesn't sound too ridiculous, although I think I'll wind up getting some lengths of pipe, a few elbows, clamps (can't weld ), and making something myself instead of buying and adapting that kit (broke college kid and the darkside kit comes with PSD-specific stuff I have no use for; I intend to go with a straight-pipe and I don't need the downpipe or the adapters for the kitty).

Also, does anyone know of a cheap 5" straight-through muffler available anywhere (that a piece of 5" pipe can go through so that it appears I have a muffler on the truck )?

Any thoughts would be greatly appreciated...thanks in advance!

 

[towcat]

tim-
if I were you, I'd quit screwing around hunting for pieces and buy the kit. You've seen the muffer on my carrier, it's a 4" straight thru and the part alone set me back $125. Install was another $30. Three key items in the kit...one, the tailpipe bends have already been worked out. You are going to waste alot of time trying to reinvent the wheel there. Two. the muffler. Its a straight thru design. Three. the adaptor pipe from your 3" DP to the 5". On the OBS trucks, the exhaust system is just like ours so there is almost no wasted parts as a result. Buy it. put it in. And be done with it. I got 4" on mime right now and the decel rap is gonna get me a ticket soon. Prolly will buy that kit too when time allows for me to be near the shop to wait for the ship.
added in edit.....
here's a pic of the pipe Tim was talking about.....

 

[f-two-fiddy]

After putting the 4" Autojet system, on my 85, I'd say getting a 5" pipe over the axle would be difficult at best. Not imposssible, but you'd have to have a GOOD shop bend that piece.

 

[reklund]

I'm runnning a 4" MBRP kit intended for a PSD on my 92 4WD, and the pipe BARELY clears the fuel tank. I even had to bend the lip of the pinch weld on the tank and skidplate a little for some clearance. When fully raised on the lift, the rear spring droops enought to contact the exhaust where it exits from under the truck and pull it down. I think a 5" would only be worse.

I know 5" is cool and all, but honestly it's overkill for these trucks. We simply cant/dont run enough boost to generate enough exhaust to necessitate a 5" exhaust. Shoot, the 4" is probably too much, but it looks cool and fits fine!

PM Me and I'll share the installation details if you want...

Ryan

 

[The Warden]

if I were you, I'd quit screwing around hunting for pieces and buy the kit.

You're right as always...I really should just shell out the $$. Even as I was typing up my first post, part of me was thinking that I should just go for the kit and quit trying to skimp and Mickey-Mouse something. I just have to make sure I can afford it...$400 is a good chunk of change, but the price does seem reasonable all things considering, and will save quite a bit of headache in the long run. I'm not sure I want to know what shipping's going to be. I just have to make sure that I didn't trash the stock hangers too badly when I pulled the old exhaust

I'm runnning a 4" MBRP kit intended for a PSD on my 92 4WD, and the pipe BARELY clears the fuel tank. I even had to bend the lip of the pinch weld on the tank and skidplate a little for some clearance. When fully raised on the lift, the rear spring droops enought to contact the exhaust where it exits from under the truck and pull it down. I think a 5" would only be worse.

I know 5" is cool and all, but honestly it's overkill for these trucks. We simply cant/dont run enough boost to generate enough exhaust to necessitate a 5" exhaust. Shoot, the 4" is probably too much, but it looks cool and fits fine!

PM Me and I'll share the installation details if you want...

I know the 5" is overkill actually, someone posted an article recently that concluded that anything bigger than 4" on ANY pickup diesel, while not harming the engine at all, isn't helping things...so it's just for the factor.

Actually, regarding your install...not trying to put you on the spot or anything but I wonder if it might be worthwhile to post it here? I imagine that I'm not the only one who could get some good tips out of it.

Do you have any pictures of your setup? IIRC, issues with the springs and rear tank skidplate were what towcat was worried about when we talked abotu this before, and it's a bit worrying that your kit has that problem (especially since you also have a 4x4)...but, it seems to me like if that were such a problem, why would a 5" kit even be available? Not doubting you or anything; just wondering how they addressed this (or if they did). Or are they expecting people to take a BFH to the tank?

 

[f-two-fiddy]

Considering that the consensus that 4" is plentygood for our rigs. Why not just get the Autojet system? It's economical and fits great.

 

[typ4]

Bought a 4" stainless muffler on ebay for 50 bucks including shipping, t&j perf in cali I think, it looks exactly like a magnaflow. the steel one is fine too, I just put one an a motorhome worked great nice tone with a 6bta.

 

[aaklingler]

I have the kit in your link, but haven't gotten to install it yet. Its definitly has some pretty nasty bends and seems to lean out over the axle pretty far and there is a seem in the tailpipes over the axle.

 

[towcat]

I have the kit in your link, but haven't gotten to install it yet. Its definitly has some pretty nasty bends and seems to lean out over the axle pretty far and there is a seem in the tailpipes over the axle.

pics?

 

[The Warden]

Where are the pics?

 

[aaklingler]

I would but I don't have a digital camera, sorry.

 

[aaklingler]

Also, the 89 in my sig currently has 5" exhaust exiting behind the tire and it is pretty much a straight piece of pipe from the downpipe to the bend to the side behind the axle, but it has a dent in it from the rear end hitting it.

 

[Agnem]

One thing is for sure, 5" is very expensive. I hope you got the bucks for it. For the money, 3.5" is by far a better deal. But of course this coming from a guy with 4" stacks on one truck and 4" sidepipes on another. ;p

 

[NapaBavarian]

Now you got me thinking, I was going to go 4" straight pipe when I get a turbo on my monster, but more bark dosn't suck so now I gotta find a turbo

 

[highest_vision]

Tim, I hope I am not replying to this too late (only online once a week ) but someone somewhere else installed a 5 incher from this guy. I think it was Joe Mc but I don't really remember. Apparently in worked Exhaust from a 99-03 truck I believe.
James