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Discussion Starter #1
A while back I ordered a new 4" exhaust system /w down pipe to help add a little more power. While installing the system I found out that a 4" tailpipe is a VERY tight fit between the fuel tank and the rear shock, I mean about 1/4" on each side:eek: . So in my wisdom;) I thought heck just dump it in front of the rear axel:grd: . I go to get a new insception sticker, and it fails because the exhaust doesn't exit from under the BlazerCensored . So I use more of my wisdom and make a reducer from 4" to the OEM 2.5" tail pipe, and life is good again with a new sticker.

But wait... here's the deal with the 4" pipe dumped EGT @ 65-70MPH are around 500-550 @ 1-2PSI boost. Same MPH, and boost 700-750 with the system reduced down from 4" to 2.5" at the muffle and what about the back pessure that has to be there. Don't worry the dump is back on now:D . So in short open that Exhaust up, it will save you later.:ro)
 

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my 4 inch system also had very tight clearances but it exits behind the rear duallies. midas installed it. pricey but i no longer have a clunk when i go over speed bumps so it's worth it. can't begin to guess how many times i crawled under there looking for the cause. i now know it was the stock exhaust
 

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Ditto on the tight clearance at rear shock and fuel tank. I angled my tail pipe up so that it fits.

Interesting with your egt's. I did my exhaust before installing any gauges.
 

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Discussion Starter #4
Interesting with your egt's.
Yea I know. I didn't install my gauges until after the 4" was put on, so I really don't know what it was before:confused: . I messed with the home made TM until I found the sweet spot between boost and EGT and haven't thought about until I put the the OEM tailpipe back on.

But keep in mind I've done a few thing to the Blazer since installing the gauges, so really this is a good example of why it VERY IMPORTANT to install gauges before doing alot of upgrades, like adding fuel, chips, or programs, etc... Oh yea the turbo isn't as loud as it was:(
 

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what kinda boost pressure are you running. i have a 4 inch system and my home made tm will hold 10 lbs under full throttle and backs down to 3-4 lbs under flat highway cruising. gotta sell some more pet life jackets on ebay to finance an egt.
 

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Discussion Starter #6
Ed,

My boost is about the same 10psi @ WOT, and backs down to about 1-2psi while cruising. I think some of it has to do with going from3" downpipe to 4" pipe then way down to 2.5" pipe making it hard for the exhaust to exit. Verses going from 3" down pipe to 4" pipe out the truck.
BTW I need to edit those numbers... after driving around some more last night and coming to work today I've only seen about 100-125* EGT increase, not 200* increase, but the EGT's do seen to raise faster now than before.
 

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John Kennedy and other say that with the 6.5TD a 3 1/2 inch system is all you need even if you add a lot of mods. You might try reducing to 3 1/2 inch where you went back to stock and that would give you more clearence and all the pipe need and a drop in back pressure.
 

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Discussion Starter #8
That's what I'm thinking about doing now, is just getting a 3.5" tailpipe made for it. But I'm kinda old school and like knowing it's dumped :ro) and loud but I'll just have to get over it:( . anyways thanks for reading my :rant:
 

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I think flowmaster sells a large O.D. tailpipe for our trucks, iirc. That way you don't have to get a whole kit.
 

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Discussion Starter #10
Cool thanks Guy, I'll check it out.
 

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if you go to a muffler shop or can get someone on here to give it up the dmax factory exhaust will fit with few mods and it is 3 and some odd inches big and made out of better pipe then your get from a shop.
 

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Discussion Starter #12
Good call Chevy Man, looks like it's time for my Dad to upgrade his exhaust...):h
 

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I got a Dmax exhaust under my burb. It's 3-1/2" ID (or OD? can't recall for certain).
 

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Discussion Starter #14
Wade,
Where's the fuel tank on your burb? On my Blazer the tank is in the back between the rear tires so to speak. So once I fished the 4"pipe between the rear shock and fuel tank there was only about a 1/4 inch on each side, and that didn't make me feel to good about it being that close. I know 3.5" will give me more room between the shock and tank so that is most likely what I'll do.
 

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My tank is between the frame rails, behind the rear axle. I think that's the same place you describe yours to be.

There's a foot of room between the tank and the shock on my burb, so getting the exhaust thru there is no problem. My shock must be in a different place than yours.
 

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The fuel tank sits further back in a Suburban than in a Tahoe. So the clearance issue with the tank isn't likely to be a problem in a Suburban.

You notice the tank placement difference sitting in the third row of both trucks - in a Tahoe, the floor is higher in the third row due to the fuel tank sitting beneath it there. In a Suburban, the floor is lower in the third row, as the indentation for the fuel tank starts further back beneath the third row seat.
 

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I'll be darned... You're right Stingray. There is a "footwell" for the third row in my burb, but not in my Tahoe. I never do any wrenching on the Tahoe (a 99 1/2tn 350 w/ 70,000 miles doesn't require nearly the amount of my attention as my burb does), so I never really noticed it before.

Learned something new today.
 

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Yeah, I only noticed it when I sat in the third row of my cousin's Yukon. My knees were practically in my face, and I was thinking, hmmmm, my Suburban's 3rd row isn't like this! What is different here? Then I realized it was the floor height.
 

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Discussion Starter #19
Update...

Got the inspection today done:ro) and can you believe that tailpipe just fell off...:confused: ;)
 
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